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Ted Rook
07-02-2006, 03:55 AM
Hi Alan,

I'm curious to find out the type of relay you use in your development tool kit for switching between crossovers at speaker power level. The reason is that I created a little project recently, a pair of polarity inversion relays, and I am dismayed to find that the octal 10A relays I chose have a degrading effect on the stereo image. Now I am not a tweaker, I'm the last person to believe unscientific claims about connection wizardry, but, the thing I was trying to hear disappeared. I find absolute polarity to be close to the limit of detectability and then only with pure stereo mic recordings. So, I need a relay that doesn't impact the stereo image. What do you use? As you may recall I'm in the US but some relay types are generic. An RS or Farnell part number would be handy :-)

Best Regards

Ted Rook LS5/12 and now M30

PS congratulations for the resurrected forum. I wonder if I'm the only one who doesn't like being titled junior member!!!?

A.S.
07-02-2006, 08:24 AM
Hi Alan,

I'm curious to find out the type of relay you use in your development tool kit for switching between crossovers at speaker power level. .... So, I need a relay that doesn't impact the stereo image. What do you use? As you may recall I'm in the US but some relay types are generic. An RS or Farnell part number would be handy :-)

I grabbed whatever was convenient. I don't recall if they were fancy, but I suppose given a choice I'd go for mercury contacts. Or gold. Or silver. Or just about anything with a low contact resistance ... down in the thousandths of an ohm range. Put that into perspective: a typical speaker cable could introduce 500-1000 times more resistance.

For a really good 'snap' action, use the full voltage specified for the relay (AC or DC, as specified) and select one with spare contacts that can be wired through an LED which give a positive, visual confirmation that the contacts have truly changed over. You don't want to go to all that bother and then kid yourself do you?

As for stereo image changes - I'm baffled. There *must* be some other reason: logic says that a relay can't impair image. It doesn't have a brain, so it doesn't know about such things.

Ted Rook
07-02-2006, 07:50 PM
Thank you Alan.
Since posting my question I learned a little more about relay science and I found this paragraph particularly relevant......seems I was careless in my selection of silver contact relays for this application

quote from potter Brumfield application note http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf

Also, an interface voltage of several tenths of a volt can result
with fine silver contacts because of the sulfide film. This film has been
known to capture and imbed airborne dirt. Breaking through this film
generates electrical noise. Because of this, fine silver contacts are not
used for low-level switching, such as audio circuits. Rather, fine silver
and silver alloy contacts are for use in circuits of 12 volts, 0.4 ampere, or
more.

"Back to the drawing board"

Ted

A.S.
07-02-2006, 09:05 PM
Thank you Alan.
Since posting my question I learned a little more about relay science a....
"Back to the drawing board"

Ted
Er, I really don't think so Ted. It's all a matter of proportion. It's so easy in audio to lose that sense of proportionality.

I'd be willing to bet you that regardless of whatever caveats you read in that report concerning contact materials, that *all* that matters for the purpose of your speaker-switcher is a fairly low resistance - say a quarter of an ohm or so. Anything better than that isn't worth the bother. But I anticipate that you'll not believe me until you've spent serious time and effort: I find that time after time in this crazy industry.

Why do we chase after a degree of perfection that simply isn't achievable - or worthwhile - or even necessary? No wonder women are not attracted to this industry!!!

Ted Rook
07-02-2006, 11:57 PM
Alan,

you are being very generous with your time thank you.

What you wrote is exactly the down to earth common sense reply that we need in audio. I bought a relay with "quarter ohm contact resistance" That demonstrates my devotion to common sense too.

There's only one problem, it obscures low level detail, you would hear it too if I could bring it to you and you would be as amazed as I am.

...........that *all* that matters for the purpose of your speaker-switcher is a fairly low resistance - say a quarter of an ohm or so. Anything better than that isn't worth the bother............

Relay makers go to great lengths to get the contact material appropriate to the varieties of end use: type of load, power rating, and I find, minimum values for current and voltage.

I now see I made an error in using the maximum power rating (10 Amps) to select the device for this application. I should have used the minimum signal as the defining characteristic, milliVolts and microAmps, and I am confident that there I will find the superior contact behavior required.

Ted

A.S.
08-02-2006, 11:25 AM
Alan,

What you wrote is exactly the down to earth common sense reply that we need in audio. I bought a relay with "quarter ohm contact resistance" That demonstrates my devotion to common sense too.

There's only one problem, it obscures low level detail, you would hear it too if I could bring it to you and you would be as amazed as I am. ... Relay makers go to great lengths to get the contact material appropriate to the varieties of end use: type of load, power rating, and I find, minimum values for current and voltage ...
Ted

Maybe Ted, maybe.

I still don't believe that after the countless millions of solder joints, semiconductor joints, metal film resistors, capacitors and the like in the signal path from the mics to your speakers that right at the very final hurdle a bit of contact resistance (oxide or whatever) can make an audible difference!

Ted Rook
09-02-2006, 03:26 AM
I too subscribe to the robust principal where the audio signal is concerned. It traverses millions of solder joints as you rightly say. If you did not have more important calls on your time I would send you the set-up for you to hear for yourself, maybe I should? You would need a quiet listening space, a CD made using pure coincident stereo mic technique and ten minutes to set up. I'm continuing with the project and I'll let you know what transpires.

Please do not think I have been taken over by some malevolent high-end audio energy, my feet are still firmly on (technical) ground :D

Ted

A.S.
09-02-2006, 08:23 AM
I too subscribe to the robust principal where the audio signal is concerned. It traverses millions of solder joints as you rightly say. ...
Ted

Well you know Ted, I've just remembered how I coped with a conceptually similar situation when I built a change-over box to test in-line cables (CD to amp for example) about 20 years ago. In-line signals are, of course, much smaller that those fed to the speaker so, presumably, more vulnerable to contact issues?

What I did was to buy reasonable quality relays with many contacts that changed over. When energised, some opened, and some closed but with a momentary overlap, so there was no break at all in the signal. No gap. No silence.

Under those conditions, it was not possible to hear, see, smell, feel or in any other way deduce the change over. All cables tested passed this test as sonicly identical in every way. However, using conventional break-before-make relays, which introduced a small silent gap as they flicked over, there were "definite differences".

John Parkyn
12-02-2006, 01:30 AM
Alan:

There is a fair amount of talk about "Radial".

What is "Radial" and what is so great about it?

Are there plans to use "Radial" in all Harbeth models ... I could be wrong but I didn't see mention of "Radial" when I scanned the Monitor 40 and HL P3ES-2 pages on the (main) Harbeth website.

Thank you,

John

A.S.
12-02-2006, 10:35 AM
What is "Radial" and what is so great about it?... I could be wrong but I didn't see mention of "Radial" when I scanned the Monitor 40 and HL P3ES-2 pages on the (main) Harbeth website.
John
Research And Development Into Advanced Loudspeakers (RADIAL) is the Harbeth patented and exclusive cone material that resulted from a Harbeth inspired, British Government co-funded project. This Govt. incentive scheme was set up about 1990 as a helping hand to get engineering graduates into industry. The so called 'Teaching Company Scheme' was conceived to bring those latent skills to SME's (small-medium businesses) just like Harbeth.

It was underpinned by the ongoing project management (at the local University/Poly, head of dept. Dr./Professor level). The deal was that Harbeth would fund 50% of the three graduates salaries and sundry costs for the three years and 0% of the equipment budget. At the end of the project all the equipment would be inherited by the University. As some ?150,000 of taxpayers money was being spent, the Govt. inspectors attended the quarterly Review meetings at the University and grilled us all on progress through formal presentations before further funds were released.

The darkest moment was about 18 months in when we realised that the petrochemical companies were never going to support us with the supply of custom made plastic film (to enable us to vacuum form cones) because our lifetime usage was, in their scale of thinking, pitifully small. That forced us to think laterally - to vacuum forming - which, due to the vastly higher set-up (tooling) costs the Govt. people eventually agreed to co-fund. It was the spark that revolutionised the whole project.

So, RADIAL is an advance polymeric cone, using a blend of chemicals with just the right acoustic properties. I have started the write-up here but it is not complete: http://www.harbeth.co.uk/designersnotebook/chapter4/chapter4-1/index.php (http://www.harbeth.co.uk/usergroup/../designersnotebook/chapter4/chapter4-1/index.php)

Someone did ask once if this was an appropriate use of taxpayers money. First, the Govt. has received back in import savings, export earnings, payroll tax, corporation tax and VAT many times what they invested in us so for the taxpayer it was a spectacularly successful deal. E.K., our team leader is now a senior figure in the design of MRI scanners, so mankind daily benefits from his contribution. His success is offset by sadness: it's such a pity that Jane, one of the original team was killed in a car accident as I discovered when I needed to make a second large batch (500kg+) of RADIAL in 2004. Jane was the young process engineer who with her sleeves rolled up and wielding a huge spanner frequently dived into the extrusion moulder when the prototype RADIAL plastic mixes went 'off the boil'. Her tenacity and gritty, willing determination to tease into bonding materials that were on the theoretical edge of combinability (for reasons of temperature and density) was absolutely invaluable. We got there in the end.

One of the great benefits of a thoroughly peer-reviewed project is proper documentation - and E.K. and I were able to pick-up Jane's excellent and detailed notes (and especially those literally in the margins of her reports) and regenerate the ratios, pressures and temperatures exactly. RADIAL lives on.

The RADIAL cone is used in the M40's midrange driver. Picture here of the chopped RADIAL granules (which are naturally white) still warm out of the granuliser.

mou
13-02-2006, 09:26 AM
I've found controversial information both from local dealers and the 'net. Some says it needs a long burn in period, some others says a few hours or even minutes, and, to make it all worse, some say that all units are burnt in prior to leaving the factory.
Where do you stand here and what's your opinion about the significance of run in time or burn in time on a loudspeaker unit?

A.S.
13-02-2006, 09:46 AM
I've found controversial information both from local dealers and the 'net. Some says it needs a long burn in period, some others says a few hours or even minutes, and, to make it all worse, some say that all units are burnt in prior to leaving the factory.
Where do you stand here and what's your opinion about the significance of run in time or burn in time on a loudspeaker unit?
Um. You do know that this and many other questions are covered in the main website's FAQ don't you?! We update that regularly so please do check there from time to time.

http://www.harbeth.co.uk/faq/index.php#16

Burn-in is another one of those minor technical issues masquerading as a universe of misunderstanding and folklore. The only things that can age (hence, burn-in) are the suspension and the ferrofluid in the tweeter's magnetic circuit. The suspension reaches it's final value after a few hours 'working' (or even minutes if the signal is bass-heavy and/or quite loud: beware) and the ferrofluid become optimally runny after a few seconds or so.

After that, the only thing that changes is ..... YOU!

A.S.
28-03-2006, 04:17 PM
Regarding cone movement and the harbeth grille frame .... there is a balance between how far the frame has to protrude from the front of the cabinet (which could look rather inelegant) and the danger of the cone (softly) brushing against the cloth. So, recently I made some experiments to see how much power I needed to push into my speaker to touch the cloth.

The mximum linear excusrion of a woofer is defined (approximately) by the thickness of the magnet top plate, which is what you would see under the corrugated 'spider' if it and the cone were transparent. It is solely resfponsible for folding the magnetic fiend into a narrow gap, and hence onto the voice coil. The voice coil is 12mm long, and the top plate is 6mm thick, so at rest, there is 3mm of coil sitting above the top plate and 3mm below. (This is all approximate due to fringing effects etc.).

So that means that is the bass unit (and of course it's voice coil) move more than 3mm towards you from the resp position or 3mm backwards into the cabinet from rest, the voice coil has partially left the linear magnetic field. So, plus and minus 3mm of linear movement is barely any motion at all, yet it will produce a good loud sound, so by definition, a fore/aft excursion that has the bass unit flailing about must be beyond ?3mm - hence with rising distortion, reduced power handling etc. etc.. Under such extreme excursions the contact with the cloth actually acts as a last-stop break.

Should you think that this is some peculiar limitation of Harbeth speakers I can assure you that the industry standard is 6mm thickness for top plates, so this would be an identical situation right across the (quality) speaker industry.

Summary: if the voice coil is not fully and continuously immersed in the magnetic field at all times, the magnet can not control the motion of the cone, and technical and subjective performance will degrade.

danrubin
28-03-2006, 06:51 PM
That is the theory and specification. My experience was this: I was taking frequency response measurements of my system using the Rives Audio CD. At the low end (20Hz up to about 50Hz), I heard loud and distinct noise from the grille (buzzing, "rattle"). The woofer surround was making contact. This was at volume levels of about 75db at 1KHz, down 10-25 db at the lower frequencies.

So, I removed the grilles and listened to the Harbeths "naked" for the first time. It fixed the noise problem. Moreover, though perhaps a touch bright, I find I am preferring the sound. And thinking back on earlier exposure to Harbeth (CES 2004, where I heard them for the first time) and the great sound I heard from them at the Denver show last September, I believe the grilles were always off. Doesn't look as good, however.

In designing the SHL5, is the speaker "voiced" with the grilles on? If so, how "off" do you feel the sound becomes when the grilles are removed?

Another issue is finding a fix for the problem.

-Dan

A.S.
28-03-2006, 08:42 PM
That is the theory and specification... There are two factors here: first, are you sure at those low frequencies that it wasn't the port sucking the cloth as opposed to driver contacting the cloth?

I should have added that the frequncy response of the Harbeth SuperGrille is extremely flat - I'd hesitate to say the best in the speaker industry for a grille when most are just sheets of wood with an aperture (or two) chopped in them, covered with cloth and slapped onto the front of the speaker. However, part of the sonic excellence of the Harbeth solution is that the cloth is close to the drivers. As with all things there has to be some sort of balance between forces.

danrubin
29-03-2006, 09:09 PM
are you sure at those low frequencies that it wasn't the port sucking the cloth as opposed to driver contacting the cloth?
I'm fairly sure, but I will re-run the exercise in the next few days and post again. My impression is that the driver was contacting the crossbar of the grill in addition to, or rather than, the cloth. I'll observe closely and report back.

Gary DiChiara
29-03-2006, 11:45 PM
I have experienced a similar noise on my M40s (only when using a test CD and only at a certain frequency around 60hz) and upon closer examination I determined the noise was actually eminating from the grille cloth slapping the front of the crossbar. A few little pieces of blueTack between the grille cloth and the crossbar eliminated the noise completely. with musical programme, it was never a problem. Hope this helps.

Ned Mast
30-03-2006, 08:25 PM
Apart from the wonderful manner in which my SHL5's reproduce recorded music, I am also quite impressed with the fine cabnetry (in my case, cherry-wood). Do you recommend that any type of wood preservative (some kind of oil?) be used (sparingly, of course) to maintain the fine finish of the cabinets?

With thanks,

Ned Mast

kevint
23-05-2006, 08:25 AM
Hi Alan,
You mentioned the standard BBC stand is made from tubular Speedframe, would like to know more details about the usual BBC way on setting up monitor.
Do they use any spike for level adjusting or floor the stand?
Anything to interface the monitor to stand? Without any thing in between, it is often hard to get perfectly flat top stand to rest the monitor on.
Is the room carpeted?

You also mentioned Monitor series is designed for well-lagged environment, can you suggest ways to make domestic room more lagged?
Thanks!

Kevin

A.S.
24-05-2006, 10:06 AM
Good question, but I think you would be surprised at the reality. In a professional sound organsation there is zero time and zero interest in tweaking and tuning. The speakers are tools to do a job; they are installed, and almost certainly never adjusted from the moment they are installed to the moment they end their life many long years later. They are not even given a dusting! So, forget all about spikes, cups, fancy cables etc. etc.! All that matters to the BBC engineers is that the sound from the speakers is sufficiently neutral and characterless that they don't have to get up from the mixing desk and make their way down into the studio (perhaps 100m away) to check that they can believe what the speakers are telling them.

Yes, the BBC control rooms (or cubicles as they are known) are very well lagged: thick 300mm absorbing panels on the walls; good quality carpets with good quality underlay (most important), double or triple glazed, and with absorbing ceiling tiles.

Of all these, I would say the easiest and best to aim for at home are ...

1. A really good quality (wool) carpet with the best quality fibre backed with rubber crumb underlay you can afford. Do not save money on the underlay: it is a false economy.

2. The thickest, softest lines curtains you can afford, floor to ceiling on the side walls. You can arrange these such that you can slide them open when you want to listen, and open them when you don't.

3. Book cases. As many as possible - and ideally (although very inconvenient) with the spines against the case and the open pages facing into the room.

4. If you have your own den where cosmetics are not important, then consider lining the walls with top quality fibre-on-rubber crumb underlay with the crumb against the wall. The SHL5 was designed in a small 4 x 5m room using just that on the walls and it works extremely well - although does make the room look dark.

Thorsten Rock
11-07-2006, 09:59 AM
Hi Alan,

I still have two old 8" woofers by Harbeth which I bought in the late 1980s. They are marked LF8MkIII and bear a golden star (probably for matching?).

Now I suspect these are the drivers which were sold in Germany without consent of Harbeth (you said something about those in the old forum - yes, they were advertised as genuine Harbeth drivers) - but they still look very similar to those used in the H.L. Monitor Mk III (I hope these are real Harbeths at least).

Do you still have the cabinet (and port) dimensions and the schematics for the crossover? I know that there's much more to speaker design than putting the parts into some home-made box, but as I still have the drivers here I hope it will make a very decent low-budget speaker at least - even if it won't equal the quality of your current products.

Thank you very much,
with kind regards,
Thorsten

kevint
29-09-2006, 08:45 AM
Hi Alan,
Curious to know how ready Harbeth speaker is on RoHS compliance regards. I learnt from a magazine that a UK speaker manufacturer has to move some of production processes offshore in order to use typical lead solder on their crossover board which the manufacturer thinks sounds better than lead-free solder.

What kind of solder does Harbeth use? Does it matter?

Kevin

A.S.
29-09-2006, 11:48 AM
I think you're kidding me about the sound of solder! How on earth can there be any difference? Marketing - merely marketing talk (IMHO).

We regrettably ceased using leaded solder a few months ago. It's a pity - the visual quality of solder joints was better but mechanically and electrically, we are assured that there are no differences.

Vangelis
09-10-2006, 02:45 PM
Hi Alan, A while back I ordered a pair SHL5s in tiger ebony. I needed a darker finsh so I ordered them sight unseen. I'm excited about the speakers and I was wondering if you have any photos of Harbeths in the Tiger Ebony? A photo would help ease my wait. Thanks.

macolive
10-10-2006, 01:19 PM
Hi Vangelis,

Allow me to post a picture of my SHL5 Ebony. Just in case Alan is too busy.

http://i8.photobucket.com/albums/a16/mac-olive/harbethuncovered.jpg

Vangelis
10-10-2006, 01:48 PM
Macolive, Wow, what a great photo. Its the first image I've seen of the Tiger Ebony that I ordered. It will be worth the wait. Thanks Again.

macolive
10-10-2006, 01:56 PM
I forgot to say congratulations! You will definitely not be disappointed. It's a glorious sound coming out from a gorgeous speaker.

Jeff Day
28-11-2006, 03:18 AM
Hi Alan,

The grills on my new Super HL5 are a very tight fit and I was wondering if you have a recommended method for removing the grills that doesn't put the cabinets' veneer at risk from a nick or scuff, as I want to photograph them with the grills off (the Tiger Ebony is beautiful by the way).

Kind regards,

Jeff

A.S.
28-11-2006, 08:01 AM
Jeff - that's a very good question, and one we were discussing in the office recently as we studied a customer's picture which clearly showed that a screwdriver (or similar) had been used to lever-off the grille.

We are planning to make a little video, but in the meantime I'd say pinch some cloth between thumb and first finger and give the grille a really good tug. Yes, sometimes they are tight, but that's a better than loose and buzzing and as you may know, I recommend that the grilles are left fitted for listening - counter-intuitive maybe but the response is actually smoother with them on so effective is the grille design.

By the way, here in the UK we say "grille" not "grill".

Jeff Day
28-11-2006, 01:54 PM
Thanks for the tip Alan - appreciated. I tried pulling it off with my fingers as you recommended but couldn't get a firm grip on the edge, so I covered a pair of round-nose pliers with masking tape to protect the cloth and veneer from the metal of the pliers. The pliers allowed me to grip the edge of the frame & cloth tightly and easily & neatly extract the 'grille' without any damage to the cloth or veneer.

Best,

Jeff

Shutterbox
29-11-2006, 02:28 AM
Alan, how about fixing/stapling a short piece of fabric to the side of the frame of the grill, on both sides of the grill.

So that when the user holds both the short pieces of fabric(short so as not to affect the looks of the speaker, if thats a concern at all), and grill can be remove w/o warping the grill frame.

A.S.
29-11-2006, 08:53 AM
That's a very good idea. I'll talk it over with the grille maker ladies. I guess it's going to rely entirely on the strength of the glue.

KT88
09-12-2006, 01:00 AM
Hello,all. I have the opposite problem with my Compact 7ES-2's. The grilles seem to be too loose in their channels and will buzz/vibrate at certain lower frequencies. Any suggestions for a fix on this? Thanks. Bob LaBarca

A.S.
09-12-2006, 10:07 AM
Ah - steel and wood each with their own unique characteristics. This is quite easy: remove grilles, apply a little outward bias on both long sides and refit.

James Beltran
09-02-2007, 03:33 AM
Alan,
Being a contented owner of numerous models over the years( and still hanging on to them) I am happy to say that if it is time to change my SHL 5 it's going to be the M40 for me. For that I need to buy another house.But in the meanwhile, I am wondering if I should attempt to tighten the screws on the front and rear panels as they may be lose after years of use and is there any advice on the level of tightness which allows the speakers to perform at it's best.
Best Regards
James Beltran
Malaysia

oferab
13-04-2007, 05:31 AM
Hi dear harberth designers
I have a question about active vs. passive loudspeakers design,
regarding the benefit of active loudspeakers design, among them are better crossover, more efficienty, better amplifier matching, more control on the frequency response and more, why don't Harbeth produce more active loudspeakers, and only have one model which is active, is it because the audiophile market is not mature enough for Active loudspeakers, or are there other reasons
Regards
Ofer

A.S.
14-04-2007, 08:47 AM
... better crossover, more efficiency, better amplifier matching, more control on the frequency response and moreInteresting question. Actually, the sonic advantages of Active are really small compared with passive. It is not true to say that an Active crossover is necessarily better - it is certainly much more complicated.

In my opinion the correct way to design a speaker system is this:

1. Design and optimise passive version. This then becomes the template for the active filter circuits.

2. Design the active filters from the passive filter template.

3. Adjust time delay etc. in the active if desired.

Commercially, the hifi user wants maximum choice. This speaker + that amp. If he buys active he has no choice of amp. Not ideal for him. In the studio what they will pay for is convenience - they are not much interested in the active v. passive arguments which they really don't understand.

leekb
14-04-2007, 10:50 AM
I brought home a brand new S-SHL5 yesterday. The grille fits so tightly I do not think I will ever be able to remove the grille to catch a glimpse of the drivers. Alan, how's the little video coming along? It will be useful for those who have problems removing the grille, including me.

A.S.
15-04-2007, 09:40 AM
Could you email me privately with the serial numbers so I can investigate this please? Can you also tell me your room temperature now?

Since I'm not aware of any really tight grille/cabinets here I think expansion of the grille frame (steel) or cabinet due to temperature is a factor.

The video - yes, I will talk to our PR man about that next week.

Jeff Day
15-04-2007, 03:53 PM
Hi Alan,

I've had the same problem with my grilles being too tight. In fact after my 6Moons article went live I was demoing the speakers for visitors and ended up tearing the grill fabric on one of the grilles while removing them. Any chance I can get it recovered?

Kind regards,

Jeff

Hu
15-04-2007, 04:03 PM
I cannot remove the grilles too, too tight!

A.S.
15-04-2007, 06:39 PM
Not so. The grilles went on so they will come off. But, as I noted before, thermal expansion on the frame means that they can be very tight.

Please remember that we recommend all listening is with the grilles on because, maybe surprisingly, the frequency response is flatter with the SuperGrill on, not off.

There is absolutely no need to remove the grilles - ever.

leekb
16-04-2007, 12:22 PM
Alan, I have PM'ed you the info you requested. Thanks.

oferab
16-04-2007, 03:24 PM
Thanks for your detailed replay
I think that with active system, you get get a better integration of the components, where all the system is tuned in one place,
also you save the cost of the cases, and the cables
on the other hand, you need a pre amp, instead of an integrated amp
pepole who are using pre amp and seperate amp, will not have a problem
but the Audiophile market is not ready for that kind of solution, for myself,
I think it is better get a complete and tuned system, without having to search for the right amplifier

A.S.
17-04-2007, 08:08 AM
... I think that with active system, you get get a better integration of the components, where all the system is tuned in one place ...I think that may be true but it is not necessarily true.

There are many very cheap active systems available (for the home musician market) which have cheap electronics, cheap drive units and cheap cabinets. They are acceptable to that market but not for our market. So, you can not assume that 'active solutions are always good' - it depends upon the details of the design and how much money is available for the designer to spend on components etc. etc..

We should again try and understand "what was in the mind of the designer" - perfection or profit?

leekb
26-04-2007, 07:15 AM
I have finally managed to remove the grille, with some tools, and no damage.

extracted from - http://www.6moons.com/audioreviews/leben2/system_2.html -

There is no way I could pull off the grills by pinching them between my fingers and I have strong and grippy guitarist fingers. I had to resort to using a pair of pliers (which I covered with masking tape to protect the grille cloth and veneer in case of a slip up on my part). The trick is to grip the metal frame firmly with pliers -- be careful because the stretchy grill cloth will slip on the metal frame's surface -- and pull it straight out towards you. This will dislodge one corner of the grille, generally, and then you can pull the rest of the grille frame out of its groove by hand. Be very careful with the pliers so you don't damage any veneer and whatever you do, do not use a screwdriver to try and pry off the grill. The grill frame goes too deep into the wood to be able to get any leverage on it and all you will accomplish is damaging the wood of the speaker around the grille.

A.S.
26-04-2007, 03:57 PM
... I was wondering if you have a recommended method for removing the grilles ...We have been preparing to make a video to explain the grille removal situation.

In talking this through with production today it seems that we have always rolled the speakers onto their face (on our perfectly clean workbench) as we are turning them over to fit the polythene bag ready for final packing. It could be that although this operation is very brief - lasting just a second or so - that on the heavier speakers such as the SHL5 that this depresses the grille fully into the recess. That's a good thing acoustically but may well make them harder to remove.

With effect from today we are rotating the speaker 180 degrees so that we roll them briefly onto their backs before packing.

Chayro
26-05-2007, 04:48 PM
Why is it that some speakers have the woofers mounted on the front of the baffle (HL5) and some inside (M30)? I would imagine that inside mounting may serve to be a bit more protection in a hostile studio invironment, but are there other sonic reasons?

A.S.
27-05-2007, 06:34 PM
The issue is not of extra protection at all. It concerns the most workable phase relationship between the bass unit and tweeter given all the other considerations of the design. Let's suppose we had to describe in precise words (not pictures) to someone on the phone the arrangement of the drive units on the speaker's baffle. Visualise the complete speaker cabinet suspended in the air on a hanging chain without the grille so we can clearly see the drive units; now we can talk about the position of those the two (or three) drive units in 3D space according to the X, Y, Z principal.

Imagine as you look at the speakers from the face (the baffle) the position of the voice coil of the tweeter and voice coil of the bass/mid unit. The X plane describes the position of these voice coils on a line drawn from left to right: in the the case of all Harbeth speakers the two voice coils are at the same position in the X plane, intentionally. The Y plane describes a line drawn through the middle of the cabinet from top to bottom: as the tweeter is above the woofer it has a higher number in the Y scale.

Now, there is another plane to consider: the Z plane. As you face the speaker this describes the position of the voice coils of the drivers as distance away from you. Clearly, the tweeter is nearer to you than the bass/midrange unit and although this distance is small (say, 5cms) it is quite an appreciable distance acoustically because sound waves travel so very slowly.

So, at the design stage I have to adjust the crossover and/or physical mounting of the woofer (I can't change the position of the tweeter, it must always be nearest to you) to compensate for the positional differences between the drivers. Shuffling the position of the bass/mid driver (relative to a fixed tweeter position) by even 1cm or so (i.e. 20%) can give an extra degree of design flexibility.

Rear mounting does slow down production though which increases cost and selling price.

Ned Mast
29-05-2007, 12:18 AM
Alan,

Do you think that putting a fuse in the speaker line degrades the sound of the Harbeths? I ask because a problem I had with a pre-amp sent a bad signal to my amp and my M40s, resulting in a most loud and awful noise. Fortunately, the fuse to the power of my amp blew before damage was done to the M40s. I've sent the pre-amp for repairs, but would hate to lose a speaker due to such a problem. I'm wondering if I can rely upon the amp fuse to always protect the speakers from such 'rogue' signals.

Ned

A.S.
29-05-2007, 10:14 AM
That's a good question.

OK - here is my opinion. The fuse seems to be (and conceptually is) a very simple device. It is a length of wire of a certain thickness stretched or twisted between metal end caps and securely soldered into place. Sounds very simple doesn't it. They are all designed to 'blow' when the thin wire becomes so hot that it burns through and how quickly this occurs needs some careful investigation. There are large companies who make nothing more than fuses of every type and size. They are experts at creating a fuse exactly according to the customer's specification. Most fuses protect mains powered equipment at the (predictable) point of power in to the equipment.

The problem we have when trying to protect a music signal with a fuse - such as in in-line fuse to a speaker - is that no two pieces of music have the same heating effect on the fuse wire. The 1812 Overture with its canons and huge dynamic range would heat the fuse quite quickly because a large current will be flowing through the fuse to the speaker. Conversely, a violin sonata with its light delicate tone will need very little current so the fuse will barely heat-up if at all.

The problem we have is of choosing one fuse that will protect our speaker on all types of music at all listening levels. Tricky. We really don't want to have the fuse blow somewhere during the last minutes of the 1812 yet we do want to protect the speaker. How can we balance the inconvenience with the protection? Only by trial and error, and different customers would select different fuse ratings according to their listening level and musical tastes. They would have to err on the side of the fuse blowing which would introduce some irritation to their listening pleasure.

I think you'll agree that this would create more after-care problems than it solves. As for changing the sound quality, well it is possible (since we don't really know what materials have been used inside the fuse) but I wouldn't expect there to be any audible degradation unless the fuse had a very low A rating hence very fine wire with high resistance. In which case it would be regularly blowing.

Ned Mast
30-05-2007, 01:35 AM
Alan,

Thank you for your response to my question about fusing. I can see that choosing the correct value fuse would be a trial and error process and perhaps be quite a nuisance. I shall await the diagnosis of the problem afflicting my pre-amp, and if I'm assured that the problem can be - and will be - cured, I'll consider the fusing measures unnecessary at this time.

Best, Ned

A.S.
30-05-2007, 09:35 AM
... I can see that choosing the correct value fuse would be a trial and error process and perhaps be quite a nuisance ...Yes, I think so too. It would be a fine line between having a fuse that is over-rated and never blows and an under-rated fuse that frequently (and irritatingly) blows.

I forgot to mention that not only is the fuse rating dependent upon loudness and music type, but also on the type of speaker. For example, the Monitor 40 and the Compact 7 (just to pick two models at random) would need different fuse ratings even on the same music.

I think that there are so many variables that we can all see why in-line fuses to the speaker never caught on despite their protective possibilities!

nfnc
07-06-2007, 03:20 PM
Chapter 5 of the Designer's notebook mentions that one of the four functions of the "crossover network" inside a Harbeth cabinet would be:

"Function #4: Time alignment. Another whole saga in itself!"

Are the Harbeths designed to be time aligned and/or phase coherent speakers?

Thanks.

A.S.
07-06-2007, 04:31 PM
This is a broad-ranging question. The function of a properly designed crossover, as used in all Harbeth speakers is to perfectly integrate the drivers by control of frequency response and phase over as wide a listening arc as possible. As the tweeter is always physically in front of the woofer its sound waves will, unless steps are taken in the crossover design, arrive before that of the woofer the listener's ear. This would not be acceptable to me.

One of the many function of our crossover is to compensate for this time difference to bring the tweeter back into acoustic alignment with the bass/mid unit difference - you can think of this as time alignment. This part of the crossover design is the most challenging, and where 50% of the design time is taken. It is possible to align the drivers only at specific points in space - for example on the reference axis.

The real difficulties lie in the area of the limited tricks and techniques the designer has available to him for this 'time alignment'. Solutions that look as if they will work very effectively in theory, on paper, so often sound dreadful.

eelekim
24-11-2007, 07:26 AM
Should the screws been tightened regularly? Thx!

A.S.
03-12-2007, 08:14 PM
Good question. There is no harm in tightening the screws occasionally but please use the correct screwdriver (http://www.harbeth.co.uk/sales/servicingandspares/images/Harbeth-screwdriver-O.jpg). I suggest a very slight tightening once a year is enough by hand, not using an electric screwdriver.

kevint
06-12-2007, 02:59 AM
Does it also applies to back drive mounting model like M30 or M40? I found it is not possible to tighten the screws from the front.


Good question. There is no harm in tightening the screws occasionally but please use the correct screwdriver (http://www.harbeth.co.uk/sales/servicingandspares/images/Harbeth-screwdriver-O.jpg). I suggest a very slight tightening once a year is enough by hand, not using an electric screwdriver.

A.S.
06-12-2007, 09:07 PM
Good point! Actually, those baffle screws for the M20 or M30 bass unit (and M40 midrange unit) are held in place by nylock nuts. They never need tightening. Please don't try and tighten those screws as you will simply 'mash' the heads - very ugly.

midwoofer
12-02-2008, 10:04 AM
Hi Alan,
what about the video?
I have the same problem by removing the grilles. Impossible so far.
I don?t like to force it because I could damage the cloth and the wood.
Thanks.

Jmohd
17-02-2008, 08:51 AM
Good question. There is no harm in tightening the screws occasionally but please use the correct screwdriver (http://www.harbeth.co.uk/sales/servicingandspares/images/Harbeth-screwdriver-O.jpg). I suggest a very slight tightening once a year is enough by hand, not using an electric screwdriver.

Alan,
How do we know when to tighten the cabinet screws?
Is there any set torque?
Is there any tightening sequence?

Rgds

A.S.
17-02-2008, 02:10 PM
Hello,

I'd suggest perhaps testing the screws for hand-tightness ever year or two. You should not be concerned about this issue at all. No torque recommendation but I would not use an electric screwdriver. Use a good quality screwdriver of the correct type (see link above) and bit size. There is no sequence, just go round in order in case you miss one.

Remember - in a thin-wall cabinet such as these onse, the concept of screw-tightness is not important.

keithwwk
17-02-2008, 03:43 PM
Hi Alan,
May I know what is the screw driver size should I use? Are both old C7 and new SHL5 shared the same screws size? I think I may need to tighten my old C7's screws now.

choykw
13-05-2008, 02:54 AM
Dear Sir,

I am a proud owner of the Harbeth Super 5 HLS 30th anniversary model. I just want to know how I can safely remove the front grille of the speakers. It is quite difficult and challenging; I do not want to damage the cabinet nor the grille. Thanks.

Best regards,
choykw

Jeff Day
13-05-2008, 03:58 PM
Dear Sir,

I am a proud owner of the Harbeth Super 5 HLS 30th anniversary model. I just want to know how I can safely remove the front grille of the speakers. It is quite difficult and challenging; I do not want to damage the cabinet nor the grille. Thanks.

Best regards,
choykw
Hi,

I recommend that you leave your grille cloths in place, as Alan has voiced the speakers to be used that way. Also, it is nearly impossible to remove them without damaging the cabinet or the grill cloth itself.

I removed mine without damage to cabinet wood by covering a pair of pliers with masking tape. I then 'pinched' the metal frame with the pliers and pulled it straight out. The grille is held very snugly so you have to work your way around the frame pulling it out a little at a time until it comes loose enough to pull off.

I don't recommend you do this as the chances are about 95% that the grill cloth will be damaged by doing this. I removed mine just so I could photograph it sans grilles for magazine articles, but in the process I damaged the fabric, and now I will have to replace my grilles one of these days.

Best,

Jeff

Gan CK
13-05-2008, 04:10 PM
Hi,

I recommend that you leave your grille cloths in place, as Alan has voiced the speakers to be used that way. Also, it is nearly impossible to remove them without damaging the cabinet or the grill cloth itself.

I removed mine without damage to cabinet wood by covering a pair of pliers with masking tape. I then 'pinched' the metal frame with the pliers and pulled it straight out. The grille is held very snugly so you have to work your way around the frame pulling it out a little at a time until it comes loose enough to pull off.

I don't recommend you do this as the chances are about 95% that the grill cloth will be damaged by doing this. I removed mine just so I could photograph it sans grilles for magazine articles, but in the process I damaged the fabric, and now I will have to replace my grilles one of these days.

Best,

Jeff


Hi Jeff, that was also how i removed the grille on my SHL-5 & in the course of it, damaged the fabric slightly. However, i prefer to run my SHL-5s naked. I find that they sound more transparent & open in this way. I guess it all boils down to preference at the end of the day.

Btw Jeff, your review on the Leben CS600 with SHL-5 was excellent. Read it a few times actually. Just out of curiosity, besides the CS600, have you heard your SHL-5 driven by other amps such as Lavardin or LFD?

Jeff Day
13-05-2008, 04:33 PM
Hi Jeff, that was also how i removed the grille on my SHL-5 & in the course of it, damaged the fabric slightly. However, i prefer to run my SHL-5s naked. I find that they sound more transparent & open in this way. I guess it all boils down to preference at the end of the day.

Btw Jeff, your review on the Leben CS600 with SHL-5 was excellent. Read it a few times actually. Just out of curiosity, besides the CS600, have you heard your SHL-5 driven by other amps such as Lavardin or LFD?
Hi Gan,

Yes, I agree, I too like the way they sound (and look!) without the grills.

For amps I have tried the Shindo Cortese, the Leben CS600, the Leben CS300X, the Leben CS660P, the Pass XA30.5, the de Havilaand (sp?) 845 amp, and some I'm probably forgetting. Not the ones you mention though, but I'd like to try them as I've heard good things about them. The Cortese is a very nice amp, but not a good match for the 5's for my tastes. My favorites were the Leben amps and the 845 de Havilland amp, All very nice. The 845 in particular gives a huge sense of space and is very nice to listen too.

Best,

Jeff

Gan CK
13-05-2008, 04:45 PM
Hi Gan,

Yes, I agree, I too like the way they sound (and look!) without the grills.

For amps I have tried the Shindo Cortese, the Leben CS600, the Leben CS300X, the Leben CS660P, the Pass XA30.5, the de Havilaand (sp?) 845 amp, and some I'm probably forgetting. Not the ones you mention though, but I'd like to try them as I've heard good things about them. The Cortese is a very nice amp, but not a good match for the 5's for my tastes. My favorites were the Leben amps and the 845 de Havilland amp, All very nice. The 845 in particular gives a huge sense of space and is very nice to listen too.

Best,

Jeff

Thks for sharing Jeff, i reckon a good 845 amp like Unison Research S8 will sound wonderfully sweet & musical on SHL-5s. Guess you have read Sam Tellig's superb review of the LFD Zero Integrated LE MK3 on stereophile. So, any chance you'll be covering LFD in the near future? Would like to hear what you think of them, especially with the SHL-5s.

Regards

Gan

choykw
14-05-2008, 03:09 AM
Hi,

I recommend that you leave your grille cloths in place, as Alan has voiced the speakers to be used that way. Also, it is nearly impossible to remove them without damaging the cabinet or the grill cloth itself.

I removed mine without damage to cabinet wood by covering a pair of pliers with masking tape. I then 'pinched' the metal frame with the pliers and pulled it straight out. The grille is held very snugly so you have to work your way around the frame pulling it out a little at a time until it comes loose enough to pull off.

I don't recommend you do this as the chances are about 95% that the grill cloth will be damaged by doing this. I removed mine just so I could photograph it sans grilles for magazine articles, but in the process I damaged the fabric, and now I will have to replace my grilles one of these days.

Best,

Jeff
Hi Jeff,
Thanks for the advice. I read somewhere in the forum that Harbeth had some kind of video clip about how to remove the grille without any damage. Has anyone gotten hold of the video clip? Also I read about the article in 6-moon on Leben CS 600 driving the 5SHL. Is that the best combination in terms of value for money? Thanks.

choykw

denjo
14-05-2008, 05:05 AM
The Harbeth SHL5 and Leben CS-600 is a very synergistic match (Thanks Jeff for the recommendation) which has brought my musical enjoyment to a totally new plane!

Best Regards
Dennis

Soundbyte
14-05-2008, 05:10 AM
Hi Jeff,
Thanks for the advice. I read somewhere in the forum that Harbeth had some kind of video clip about how to remove the grille without any damage. Has anyone gotten hold of the video clip? Also I read about the article in 6-moon on Leben CS 600 driving the 5SHL. Is that the best combination in terms of value for money? Thanks.

choykw

Hi choykw,
If you have gotten your Harbeth from Jimmy, ask him for assistance... he have develop a tool for removing the Harbeth Grille safely.

Cheers.

Gan CK
14-05-2008, 06:23 AM
Hi Jeff,

Also I read about the article in 6-moon on Leben CS 600 driving the 5SHL. Is that the best combination in terms of value for money? Thanks.

choykw

Well, at this price point, i would suggest that you also listen to LFD MI100 with SHL-5. I have not heard the CS600 with SHL-5, so can't say how good it is but at this moment & at around S$7K price point, the LFD MI100 is my reference in terms of musicality, tonal purity & sophistication. I believe at this price point, only the Leben CS600 & LFD MI100 are worth considering. Of course, you might also want to have a listen to Naim supernait. I heard the supernait driving some Roksan spks at absolute sound & it was quite disappointing. Perhaps the other amp to try is the Creek Destiny if on a tighter budget.

choykw
14-05-2008, 09:06 AM
Hi,
Thanks. Do you know how the tool looks like or describe how I can make one and the appropriate applications?
Best regards,
choykw

Jeff Day
14-05-2008, 01:58 PM
Hi Jeff,
Thanks for the advice. I read somewhere in the forum that Harbeth had some kind of video clip about how to remove the grille without any damage. Has anyone gotten hold of the video clip? Also I read about the article in 6-moon on Leben CS 600 driving the 5SHL. Is that the best combination in terms of value for money? Thanks.

choykw
Hi Choykw,

I don't believe the video was ever posted.

Just about any competantly designed amplifier works well with the Super 5's, but having said that, I am particularly fond of the match with the Leben CS600 integrated. The Leben pre & CS660P combination is also extremely good, but not nearly as cost effective.

Kind regards,

Jeff

Gan CK
14-05-2008, 03:43 PM
Hi,
Thanks. Do you know how the tool looks like or describe how I can make one and the appropriate applications?
Best regards,
choykw

Hi Choykw, basically its a paper clip bent to make it look like a hook on one end & a handle for you to get a grip on the other end. You insert the hook into the gap at any corner of the grille, get a hold of the edge of the grille using the hook & just pull it out. As simple as that. Got to take my hat off to Jimmy for being able to come up with that. You need a fairly large paper clip though.

choykw
15-05-2008, 01:35 AM
Hi Choykw, basically its a paper clip bent to make it look like a hook on one end & a handle for you to get a grip on the other end. You insert the hook into the gap at any corner of the grille, get a hold of the edge of the grille using the hook & just pull it out. As simple as that. Got to take my hat off to Jimmy for being able to come up with that. You need a fairly large paper clip though.
Gan CK,
Thanks for the description on the simple tool. I will try it out and see if it works.
Best regards,
choykw

Soundbyte
15-05-2008, 05:05 AM
Hi Choykw, basically its a paper clip bent to make it look like a hook on one end & a handle for you to get a grip on the other end. You insert the hook into the gap at any corner of the grille, get a hold of the edge of the grille using the hook & just pull it out. As simple as that. Got to take my hat off to Jimmy for being able to come up with that. You need a fairly large paper clip though.

Agreed, Simple and effective tool invented by Jimmy! Here you go! Beware... it still can cause damage to the cloth grill.... so use at your own risk. I hope Jimmy wouldn't mind I share his invention!

http://i27.tinypic.com/jtb9yw.jpg


Cheers.

Gan CK
15-05-2008, 06:10 AM
Agreed, Simple and effective tool invented by Jimmy! Here you go! Beware... it still can cause damage to the cloth grill.... so use at your own risk. I hope Jimmy wouldn't mind I share his invention!

http://i27.tinypic.com/jtb9yw.jpg

Cheers.

Haha i thought of inserting the pic as well but couldn't find my paper clip. I guess a pic says everything & i am sure jimmy wouldn't mind sharing his invention with all Harbeth users here. :)

Soundbyte
15-05-2008, 06:14 AM
Haha i thought of inserting the pic as well but couldn't find my paper clip. I guess a pic says everything & i am sure jimmy wouldn't mind sharing his invention with all Harbeth users here. :)

Yeah... the funny is now I can't seem to get the picture into the forum!

choykw
16-05-2008, 04:55 AM
Agreed, Simple and effective tool invented by Jimmy! Here you go! Beware... it still can cause damage to the cloth grill.... so use at your own risk. I hope Jimmy wouldn't mind I share his invention!

http://i27.tinypic.com/jtb9yw.jpg


Cheers.
Soundbyte & Gan,
Thanks for the picture. It certainly helps - pictures says a thousand words!

Best regards,
choykw

denjo
27-05-2008, 07:50 AM
Hi Alan

There is a thread over at www.audiocircle (http://www.audiocircle) (Harbeth vs Salk) which might interest you and perhaps prompt you to reply there as well. The thread link is here http://www.audiocircle.com/circles/index.php?topic=54752.msg491391;topicseen#new

I thought the BBC hump only applied to Rogers LS3/5as?

Best Regards
Dennis

A.S.
27-05-2008, 08:58 AM
I read in your link "If I recall correctly, the BBC is famous for its "BBC hump" or the +3 to +5 dB spike in the midbass range, and the "BBC dip" in the upper mids and lower treble range. Many of these British speaker manufacturers voiced their speakers this way"

Ah, not really sure about this. Please refer to the attached frequency response plot of a selection of LS3/5a, dating back to serial number 005 - i.e. about 1974 vintage. All measured by me (and Derek) under controlled conditions in the anechoic chamber in June 2007 using CLIO test equipment and a calibrated B&K microphone.

Points ....

1. The response is basically flat. I've marked the average line across the whole frequency response. I wonder what he means by ' hump +3 - +5dB in the midbass'. If he means the situation around 100Hz then this is not supported by the measured data because that region is exactly in-line with the overall average.

2. Definitely no evidence of the 'BBC dip in the upper mids and lower treble'. This is self-evident by listening and again indicated in the measurements that the opposite may be true.

3. Note how ragged the responses are. The LS3/5a sadly does not age well.

4. The grille was fitted for all measurements. If it had not been, the response would have been considerably more ragged in the treble region. Despite the anechoic response, the in-room response smooths out these wriggles and is flatter.

Setting aside the measurements, it is undoubtedly true that a listener can become accustomed to a particular sound balance and that becomes their 'norm' and frame of reference. I know nothing whatever of the other speakers mentioned so I can not comment but I would say that anyone who has become used to the lean, weightless, cool sound of a bipolar (panel) speaker would probably criticise box speakers for their perceived warmth. It depends upon what you are used to. But for our taste here, there is a strong empathy between warmth and emotional fidelity, and that is the hallmark of a good speaker.

>

Gan CK
27-05-2008, 05:01 PM
Hi Alan

There is a thread over at www.audiocircle (http://www.audiocircle) (Harbeth vs Salk) which might interest you and perhaps prompt you to reply there as well. The thread link is here http://www.audiocircle.com/circles/index.php?topic=54752.msg491391;topicseen#new

I thought the BBC hump only applied to Rogers LS3/5as?

Best Regards
Dennis

The Salk speaker in the thread uses Seas excel drivers with fanciful china made aurum cantus ribbon tweeters & reminds me of VMPS spks that uses the same tweeter. Looks like another "fashion" speaker to me.

A.S.
27-05-2008, 11:06 PM
There are several versions of the Excel tweeter including some new variants. In our opinion, whilst the newer derivatives may have some interesting features (to other manufacturers?) we are sticking with the original type which we believe is still the best overall solution for us.

codel
19-01-2009, 05:00 AM
I have heard from some audiophiles that the bare wire connection of the cables to the speakers, offers a bit more sound quality than the connections with spades or bananas.

I would like to have Alan's comment on this.

Costas.

A.S.
19-01-2009, 09:11 AM
Can any 'audiophile' imagine how an electric current flows through a metal? Can anyone explain why the last inch of an electric current journeying from the amplifier to the speaker along a metal-metal cable/connector should be so exceedingly critical to the reproduction of music? I can't so no comment.

giant step
24-05-2009, 02:59 PM
Dear Mr. Shaw,

I am a proud SHL5 owner, and I enjoy listening to it very much. During a heated debate over high end products I answered a member by showing the electrical load impedance and phase curve of the speaker ( the one appearing on your product page ). Some of the forum members, which are highly skilled in electronics, raised questions concerning these curves which appear to them as most unusual. As I know almost nothing about these matters I was hoping you might help with the answer. The members were concerned about the very high impedance peaks - especially the 2KHz peak. If I understand their claims, they say that with such high peaks the frequency response curve would probably be far from the claimed flat +-3dB. It has something to do with the tweeter's resonance frequency, which according to the curve should be about 1.8KHz and with its crossover frequency.

I was unable to find a response curve on the Internet, and my technical knowledge is insufficient to explain your crossover designs. I would very much like to read your opinion on the matter, and I apologize if my question is unfocused.

Thank you!

A.S.
24-05-2009, 06:24 PM
It's a perfectly reasonable question but I'm afraid utterly misguided. There is no absolute 100% correlation whatsoever between a speaker's impedance curve and the sound pressure level (spl or in common language, the frequency response) of the speaker or perhaps any speaker. In fact, as we'll see, the SHL5's impedance bump at the quoted "1.8kHz" has nothing whatever to do with the tweeter full stop.

I suggest that for 99% of all hi-fi speakers impedance variations do not effect frequency response and this truism has been an accepted and easily proven fact for at least fifty years.

Generally speaking, the higher the impedance at any frequency the less likely there is to be (a) any possibility of an obscure correlation between speaker impedance and speaker spl (loudness) and (b) less possibility of an obscure drive mismatch between the amplifier and speaker/crossover with some weird sonic issue. So, to give an extreme example, if the impedance peaked at a huge value of say, 1000000 ohms (one million ohms), this would most likely be a far better situation for the amplifier and loudness than if it peaked (or dipped) at 1 ohm. Think of the amplifier as a bicycle pump; put your finger over the hole and push the plunger - that represents the amplifier trying to drive an extremely low impedance: the amp is really working hard. Remove your finger and now the plunger can freely move - that represents the amp working into a high impedance.

A speaker designer concentrates on what actually matters when designing a crossover and what actually matters is not the kicks upwards in impedance, but the dips down. Every (and all) effort should be made to keep the dips from going below a safe amplifier-friendly minima (3 or 4 ohms) regardless of how high the peaks are. It's the dips in impedance where the amplifier is working hard. We'll see that on the graph as a purple dotted line.

MEASUREMENTS AND ANALYSIS (see attached)

I made a very quick, uncalibrated measurement of a complete, reference SHL5 I have to hand. The green curve is what your amplifier sees when it's driving the SHL5; a nice smooth curve, and the dashed purple line proves that the impedance never drops below about 5.5 ohms right across the audio band. This is an ideal impedance curve. It means the SHL5 is (of course) an easy load, as I designed it to be.

Then I went inside my SHL5 to get access to the crossover. The red line is what the amp would see if you cut the input to the tweeter's crossovers, just driving the bass unit via its crossover only. Again, a nice high curve.

The blue line is what your amp would see if you attack the crossover and snip out the feed going into the bass unit's crossover, driving the both tweeters via their crossovers only. As you can see, this is an excellently smooth curve demonstrating the progressive action of the tweeter crossover as it prevents low frequencies ever reaching the tweeters (i.e. the impedance rises at low frequencies to inhibit current flowing into and damaging the tweeters). Just to illustrate how completely misguided the comments about tweeter resonance are, can you see any evidence of the tweeter's (claimed 1.8kHz) resonant frequency influencing the impedance curve? Can you see in the blue curve a bump or anything unusual at 1.8kHz? No: perfectly smooth.

Now, the green impedance curve is what your amp sees when a perfectly normal, fully reassembled SHL5 is connected. Now we do have a little bump in the impedance curve at 1.8kHz or so. Is this something to do with the blue line, the tweeter? No. We've shown that the blue curve is smooth. How about the red line: the woofer. Anything odd there at about 1.8kHz? No - again smooth. So where has this innocuous little bump come from? Answer is it's entirely due to the the maths of connecting the tweeter and the bass unit and their crossovers together and connecting the combination to the amp: it doesn't represent anything mechanical in any of the drive units at all. And it has no effect at all on the frequency response. It is just a mathematical abberation.

Designing a speaker where rising impedance (or irresponsibly low impedance) has any effect on its frequency response would be an act of gross professional incompetence. It would be as ludicrous as a car designer designing a car that "doesn't do hills".

As I have said here many many times over the years, I am acutely - and I repeat that, acutely aware right through the entire design process that the impedance of a Harbeth must be benign. A Harbeth is designed to be amplifier friendly. It has to have an easy electrical load. It has to work with, as I've said before, 'any competently designed amplifier working to its manufacturers original specification'. That being so, our dealers and distributors can proceed to sell Harbeth to any customer and be confident that they will make a great sound at home with whatever the user already has for amplification.

Hope this helps.

>

giant step
25-05-2009, 08:43 PM
Thank you Alan!
I deeply appreciate the time and effort you took to write your reply. I must say was surprised how good the SHL5 sounded with my previous amplifier - a 10 year old LINN MAJIK integrated which supplies only 33w per 8 ohms when I first tested the speakers. What still bothers my friends is that a speaker implicates a reactive load with some capacitive effect on the amplifier, and does not represent a pure resistive load on the amplifier. Can you please elaborate your view on that aspect of speaker - amplifier interaction?

A.S.
25-05-2009, 10:44 PM
Glad I could help. It did take a couple of hours though. Show me a speaker that doesn't have a partially reactive load at some frequency or other and I'll swim to France.

This is a non-issue. And as I said in my last post - I am acutely aware during the design phase how a Harbeth must have an easy load. I didn't spell it out but by implication that means avoidance of low impedance and keeping the reactive element within about ?45 degrees. All competently designed amplifiers can cope with that with extreme ease. I stress: this is a non-issue; Harbeth speakers and all other moving coil speakers must, by definition, have a reactive load as that is a consequence of a voice coil being inside a magnetic field*. Theoretically, it is possible to cancel the reactance at (some) frequencies using huge components in the crossover network (the KEF conjugate load matching circuits come to mind from the 1980s) but what do you think the consequence is likely to be? Answer: needless increase in cost and complexity and a reduction in overall system impedance down to perhaps an amplifier-unfriendly ohm or two.

Electrostatic speakers, in comparison, are I believe horrendously reactive loads - but well designed amplifiers have no difficulty driving them.

Any amplifier designer worth his salt would make sure that the amp was "unconditionally stable into any load". Wasn't that an advertising slogan QUAD used some thirty years ago? Nothing's changed.

* Also, even in the simplest full-range speaker with no crossover at all, at and around the bass resonance frequency there will be a reactive element to the impedance. Does it cause any amplifier problems? No.

codel
29-05-2009, 05:37 AM
Alan can you please explain the difference between the construction of a Harbeth speaker and an Advanced Transmission Line speaker.
Thanks.

A.S.
29-05-2009, 09:29 AM
I would try but what is an "Advanced Transmission Line speaker"? Is that a marketing description? I'm not really up to date with what's on offer.

In my (limited) experience, the problem with loudspeaker design has always been of "one step forwards, two steps backwards" when considering alternative solutions to old familiar problems. When you say transmission line what I think you are referring to is a speaker box in which the rear of the woofer unit breathes into the room via pathway inside the box. That pathway or line is most conveniently made by an arrangement of shelves that force the rear sound to make a journey which finally exits in an orifice on the front or back of the cabinet. It's an alternative to the vented (ported) cabinet or the sealed cabinet but is a woodworking nightmare.

What are the claimed advantages? The claim is of deeper bass because the rear motion of the drive unit could (theoretically) create a sound wave that reinforces the sound from the front motion hence (perhaps?) 'bass energy for free'. That sounds plausible except there is never energy for free in nature. As you can imagine, there are only certain frequencies where the sound from the rear of the woofer is perfectly in-phase with that from the front of the woofer, and those frequencies are solely related to the length of the pipe. At all other frequencies, to one extent or another, the pipe's output fully or partially cancels the direct sound from the front side of the woofer because is is not exactly in-phase with it. This is a serious and unavoidable problem.

This design conundrum of pipe length, frequency and phase has been insoluble for centuries which is why church organs are still built with a series of pipes (http://musiclink.co.uk/pipeorgans.html) of varying length according to the note to be played. 'One pipe' length doesn't suit all bass frequencies: a pipe is only at it's best over a narrow range of frequencies. This becomes a problem when a loudspeaker woofer is mounted at one end of a fixed-length pipe.

The only way to avoid the unwanted cancellation due to the out-of-phase sound is to stuff-up the pipe to prevent the rear sound permeating down the pipe and exiting into the room to mix with the wanted front sound; but this would block the pipe at the wanted (in-phase) frequencies. This duality can't be achieved. The pipe cannot be selectively open or closed at specific notes nor can it vary it's length according to the music as a trombonist (http://en.wikipedia.org/wiki/Types_of_trombones) would slide (http://www.dailymotion.com/video/x2u2vo_ben-van-dijk-bass-trombone-plays-al_music) his trombone. The pipe geometry is totally fixed inside the speaker cabinet.

In accordance with what you would expect from (acoustically) short pipes in real-world (small) speakers, regardless of whatever is claimed to be gained at say, 40-50Hz, pipe speakers I've measured feature a significant dip in overall energy in the lower midrange due to the pipe's output being anti-phase to the main output. Stuff foam into the pipe's mouth and the midrange level recovers. How does this depression sound? It seems to diminish weight and warmth - and makes male voice sound like female voice. I find the sound thin, unnatural and uninvolving. I just cannot imagine how short pipes can be made to work - but I know that many designers have tried every conceivable variation on the theme.

If you compare a domestically sized pipe system (they've been around for at least fifty years so there are various examples) with a sealed box or ported system it's apparent that whatever the claimed benefits, the BBC and other commentators concluded that there was no pressing advantage, and some significant disadvantages. If I remember correctly the phrase used was "the transmission line speaker offer no advantages over other well executed designs including vented (ported) cabinets". I guess that if there were worthwhile advantages at a reasonable cost we'd all be using them!

If you are curious about the tremendous difficulties of TL design, here (http://www.t-linespeakers.org/design/MJK-for-dummies/index.html) is a good overview. Fig 3 and 6 demonstrate the problems of the inevitable series of resonances that exists in all pipes and the suckout I've mentioned in the midrange.

++++++++++++++++++++++++++++++++++++++++++++++

P.S. I made a very quick search for some more information in my paper archives because what I read in the reference (marked here above) reminded me of an analysis published many years ago.

I said above "the transmission line speaker offer no advantages over other well executed designs including vented (ported) cabinets" I think that a less contentious statement (until I can find that exact quote) is 'the transmission line speaker offer no advantages over a sealed cabinet'. [Reference: D.A. Barlow, H.J.Leak & Co., Letters to the Editor re: A.R. Bailey's 'A Non-resonant Loudspeaker Enclosure design' Wireless World 1973/4]

codel
31-05-2009, 10:44 AM
Alan, thank you very much for your reply and your time spent. A friend of mine is now convinced about the lack of advantages of an Advance Transmission Line speaker and the advantages of a Harbeth speaker technology, as he was wavering between a Harbeth speaker and an A.T.L one (a P-- speaker specifically).

Karim
01-08-2009, 07:03 AM
Dear Alan

First, you must excuse me if my English isn't quite up to the standards here as it isn't my first language.

I've been recently introduced to your speakers and I am fascinated by Harbeth's history, or rather legacy, in speaker design but there is one issue regarding the design process which is not yet completely clear to me and after participating in couple of different discussion forums I noticed that there also seems to be great confusion regarding this subject.

As far as I've understood voicing is mainly frequency response adjustments when designing a speaker but I am sure there's more to it. How do you voice the speakers and how important are adjustments in frequency response in this regard? As I've understood even the chosen materials for the driver affect the tone (obviously not preferable yet inevitable) of the reproduced sound but do you take that in to consider when voicing a speaker? In other words, where do you draw the line when it comes to conscious decisions regarding the overall tonality of the speaker in your design processes?


Many thanks, K.A.

hifi_dave
01-08-2009, 10:02 AM
While we await Alan's definitive statement can I just say that Alan must spend an awful lot of time just listening and tweaking to get the best balance between measurements and natural sound.

I don't think you can make great speakers without actually listening to them. Far too many speakers (especially from larger companies) are designed by computer and commitee. The computer does the work and the commitee tick the boxes at the end of the design process. The result is an awful lot of stylish but boring and bland speakers. Style over substance.

Apologies Alan for jumping in.

A.S.
02-08-2009, 11:13 AM
Thanks for the question. Your English is completely perfect and you have raised an important question. Actually perhaps it is the question which every loudspeaker buyer should carefully consider. Where can I start to answer you?

The first point to make is that I really don't know how other speaker designers think or work. I'm perfectly content to work alone - actually I prefer to do so - but I have worked in a large foreign corporation so I have first hand experience of the commercial, emotional and psychological pressures that are brought to bear on designers generally by me and my staff in the commercial departments.

All commercial loudspeaker products are brought to market with (presumably) some differentiation from other existing loudspeakers. That differentiation may be cosmetic (cabinetwork), commercial (price) or technical. The marketing process takes control of the cosmetics and commercial details, but is at arms length from the technical process - there is usually some friction between these two functions. This division of responsibility between the pure engineering and creation of the product and bringing it to the consumer is a dangerous gap. The marketing people believe (and have to believe) that they can sell anything and the engineering people obviously don't want to create perhaps insurmountable technical hurdles for themselves - they too have a life outside work. So, with these two functions somewhat pulling against each other, the result tends to be products with attractive ergonomics (styling) and mediocre technical performance. And that's the rut that the speaker industry has been in for many years.

Consider for a moment that a mass produced woofer, the engine, the working heart of a loudspeaker, the part you're really paying for, costs less than a family meal at a burger bar and it's obvious that at that price level technical excellence has been compromised right through the part. How can a loudspeaker system designer, selecting such a unit from a trade catalogue, expect technical excellence? Of course, he can't. Everything in the drive unit design will have been cut-down to the bare minimum to minimise the supplier's costs, maximise profit and enhance speed of assembly. Many of these woofer parts are made in huge factories by the millions every month, and whilst the QC is generally good, they display no technical excellence whatever. They make a noise, they have adequate technical parameters of frequency response etc. but they are not exceptional.

As noted, the division of responsibility between sales/marketing and design means that there is a reticence for the one function to probe or interfere too much with the other. When marketing visit the design dept., engineers hide papers, bury prototypes in cupboards and make the their commercial visitors unwelcome and uncomfortable. They certainly don't expose intricate technical concerns that they have - perhaps about latent coloration issues in those cheap drive units they've selected - because marketing people by definition need to believe in the design process.

Yes, the "voicing" process is significantly one of manipulation of the energy levels in various frequency bands, plus very careful consideration of how the speaker fires into the room - its dispersion characteristics. But that's only part of the story. What if the designers we mentioned above discover, right at the end of the design process and now with the cabinets designed and prototyped, the launch photography done, price lists calculated, pet-customers teased for orders .... that "something doesn't sound quite right"? What would they do? What could they do? What should they do? What would you do? Would you be the one volunteered to crawl into the Engineering Director's office and tell him that the design was a failure? What does happen is that the product is launched and comes to market. The marketing boys either know that it's not a good as it could be but have to sell it anyway, or couldn't care. They know that all consumer products no matter how ill designed or poorly conceived or manufactured will sell at a price with sufficient promotion - example the goods sold in an "everything is a dollar" type of clearance store.

And the solution? As I hold a remit for marketing, design and finance it seems logical to me that to maximise our financial return Harbeth should create products that are at a technical level excellent and market themselves (happy users are our best advert) without needless promotional expenditure dressing mutton up as lamb. As those speakers last for 20+ years you too benefit.

kckwong723
27-12-2009, 04:39 AM
Hi Alan,

I have viewed the long video showing how you fine-tuned your speakers during the design stage and it well impressed how your work was so hard, exhausting and time-consuming.

I wonder what amplifier(s) and speaker cable(s) you were using during the design stage for M40 or other models? Any change when designing M40, M40.1 or other models?

I learned in this website that humble 79 strand speaker cable was recommended as a long-term reference when choosing speaker cables. So are 79 strand speaker cable your reference speaker cable in your lab?

Cheers,

Ken Wong

garmtz
27-12-2009, 09:43 AM
AS will not give away what equipment is used. Many have tried... ;) I have a very strong hunch to what the equipment (amplifiers) might be, but I will leave it at that, as it is simply not important to the user. Use whatever floats YOUR boat!

A.S.
27-12-2009, 10:43 AM
Thank you. As you say it is completely unimportant what cables, amps, CD player, stands or beer I drink during design! I am listening through the electronics to the speakers. The absolute and most vital thing for me is that the electronics are stable from month to month, decade to decade. This rules out tube electronics which slowly but inevitably degrade from the moment they are first switched on. So even though I like the romance of tubes, I dare not use them. It also rules out brands that do not have a proven long-term commitment to after care, newer brands, brands of unknown origin etc. etc.

Cables: I bought a reel of 79 strand or similar some years ago and it works for me.

Note: I am most definitely not saying that my choices are the best. I guarantee that with time, care and money you can do better. But they are a stable base line for me, within my budget and use common industrial parts so available for many years. I have many amps of the same brand/model as backups and all can still be serviced to original spec.. That's good enough for me! I hesitate to name names simply because I am not kidding myself or you that what I use is in any sense an audiophile system. It isn't. It's a ordinary bloke's average+ system and no more.

A.S.
27-12-2009, 10:59 AM
... have viewed the long video showing how you fine-tuned your speakers during the design stage ...so hard, exhausting and time-consumingLong the TechTalk (http://www.harbeth.co.uk/uk/index.php?section=products&page=designersnotebook) video may be (sorry) but what you are seeing is just a few minutes on one day, one of many days spread across months or years. Looking back from twenty or fifty years, nobody will believe that such a painfully slow process was the correct way to design speakers. Surely no designer would voluntarily invest so much mental effort into a design unless there really was no alternative method. And that is the point we are stuck at; we have all the fancy test equipment, it's reliable and fast but it doesn't tell you how the speaker sounds, in a room. It tells you how it measures and that's a completely different thing - or may not be. I just wish there was a better way.

I dread to think what it must be like to work as part of a design team. Can you imagine dancing around changing this or that component, asking the panel of listeners what they prefer .... better/worse? yes/no? keep/reject? What would come out of that collaborative effort would be a product reflecting the wishes of the dominant personality of the listening panel. That's human nature.

We have recorded about 800GB of raw video footage in the past few years covering many aspects of the design and manufacture including videos of measurement sessions at the BBC chamber, village hall and outside in the garden. I think Trevor has mentioned that now we've figured out how to put videos on the website we will start to roll out more next year. We are now very much aware that what we record here may well have a long term curiosity value for future generations and we're trying to use the best current technology to archive as we go. Video recordings we've made since April 09 (such as at the X-Ffactor studios) have been filmed in widescreen 16:9 HD direct to hard disk in the camera. Before that it was 4:3 SD.

I'm aware that as internet speeds increase as we eventually go to an all-fibre network we can re-master from the original source files so we aim for the best possible source quality.

george_k
10-02-2010, 04:47 AM
...We have recorded about 800GB of raw video footage in the past few years covering many aspects of the design and manufacture including videos of measurement sessions at the BBC chamber, village hall and outside in the garden. I think Trevor has mentioned that now we've figured out how to put videos on the website we will start to roll out more next year. We are now very much aware that what we record here may well have a long term curiosity value for future generations and we're trying to use the best current technology to archive as we go. Video recordings we've made since April 09 (such as at the X-Ffactor studios) have been filmed in widescreen 16:9 HD direct to hard disk in the camera. Before that it was 4:3 SD.

I'm aware that as internet speeds increase as we eventually go to an all-fibre network we can re-master from the original source files so we aim for the best possible source quality.

Sign me up as customer #1 for the DVD/Blu-Ray documentary ;-)

Kumar Kane
02-05-2011, 05:33 PM
With the amp on one side of the room, is it ok for the speaker cable runs to the two speakers to be of unequal lengths? I thought not, but my recent professional cable installation was done with 3 metres of cable for one speaker and 15 for the other. Decent quality 4mm square section copper cable. Are the unequal lengths a factor?

tto123
18-06-2011, 06:38 PM
Should the woofer and tweeter screws be tightened to specific torques? Are there any torque specifications available somewhere?