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Since its inception ten years ago, the Harbeth User Group's ambition has been to create a lasting knowledge archive. Knowledge is based on facts and observations. Knowledge is timeless. Knowledge is human independent and replicatable. However, we live in new world where thanks to social media, 'facts' have become flexible and personal. HUG operates in that real world.

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Amplifier selection for your Harbeths (general, not specific Harbeth models)

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  • Re: Amplifier selection for your Harbeths (general, not specific Harbeth models)

    Hi All,

    try to check (if stated in technical specification) what is the maximum peak current of the amplifier. This is the key!
    (by keithwwk mentioned Electrocompaniet AW120 DMB has a peak current of 100 A )

    Comment


    • Re: Amplifier selection for your Harbeths (general, not specific Harbeth models)

      Thanks all for your replies.

      Ha ha - Alan my car is a Honda Jazz (Fit) so I fit in the puny end of spectrum! I just let everyone pass me on the motorway - besides here you are limited to 60mph (100km/hr) which is strictly enforced. As an analogy I am limited in my listening levels (everyday driving) to mid 80's tops (50mph) and usually (mostly) mid 70's (30 mph). 90% Classical. 10% everything else.

      Interestingly living in a busy city I suspect ambient noise also has a lot to do with it. The other evening it was softly raining which keep the noise right down (that is shut the fruit bats up) and the micro detail was so much clearer at low volume.

      Righto - it sounds like I might have to change the speaker to the SHL5 rather than change my amp. Or just stop whinging and enjoy what I have.

      As an aside I was listening to a album last night (Renegade Soundwaves) which I had not played in a while: I heard all sorts of things on it that prior to the Harbeth's I had not. It was a totally different presentation compared to my last 15 inch Coaxial monsters (as one would expect) - which were the perfect rock speaker as described by Alan. But pretty average at everything else.

      Cheers
      Andrew

      Comment


      • 100A amplifier output potential or how to set fire to your speakers!

        Originally posted by Vlado View Post
        ...maximum peak current of the amplifier ....has a peak current of 100 A )
        Whoa! Wait a moment! Stop now! This is crazy! Mayber or maybe not a certain amplifier has huge peak current capability. Do you know how much damage 100A can do? 100A is a seriously huge amount of destructive power. It could easily kill you and cause your organs to fry. It has no place in hi-fi. Or maybe it does have. Perhaps it's the extra thrill we're all seeking? I invite you to decide after carefully studying these facts ....

        First, let me show you what 100A can do .... take a look here at this arc welder used to weld steel together. See the welder's control dial is graduated up to 150A? 150A! That's what you need to weld steel. Now look at the destructive power of 100-150A and how you need a proper ventilation system. So remember folks - open the door before playing your hi-fi if you are driving 100 amps into your speakers! Essential - have the fire department on standby.

        Now look here look at what just a puny 1.8A can do. Frightening. This is exactly what I have been saying about needless amounts of power. You can't actually use it. The speaker just can't handle it. So why have it with all its destructive potential waiting to catch you unawares?

        OK - now the Christmas quiz. How many amperes does it take to utterly destroy a loudspeaker? Supplementary question - how many microseconds would the speaker last?

        Tip: before answering, check out this video. Answer maybe here .... count the seconds. Frying tonight? - probably only about 5-10 amps.

        Now, let's get back to the real world! Speakers can take hardly any power at all. The working heart of a speaker is the voice coil shown here upside down, the woofer cone/coil removed from its chassis. This shows what happens when too much power is applied. First the smoke, then the smouldering, then the fire?


        Alan A. Shaw
        Designer, owner
        Harbeth Audio UK

        Comment


        • Re: 100A amplifier output potential or how to set fire to your speakers!

          Originally posted by A.S. View Post
          Whoa! Wait a moment! Stop now! This is crazy! Mayber or maybe not a certain amplifier has huge peak current capability. Do you know how much damage 100A can do? 100A is a seriously huge amount of destructive power. It could easily kill you and cause your organs to fry. It has no place in hi-fi. Or maybe it does have. Perhaps it's the extra thrill we're all seeking? I invite you to decide after carefully studying these facts ....
          Hi Alan,
          the 100 A peak of that amp is measured indeed in microseconds and in 0,5 Ohm ( the manufacturer guarantee the stability of that amp in 0,5 Ohm load). The high or very high peak current of an amplifier is important only at the moment where the impedance and phase curves are at their largest divergence. At that moment the amplifier should not limit the current consumption of the speaker. ie the speaker is drawing the current from the amp and not the amp is pushing the current into the speaker.

          BTW: the specification of that amp is 120 W/ 8 - 200W/ 4

          Comment


          • Re: 100A amplifier output potential or how to set fire to your speakers!

            Originally posted by Vlado View Post
            ...the 100 A peak of that amp is measured indeed in microseconds ...
            Even more weird! Music does not contain *any* frequencies that are as brief as microseconds. The real power and energy in music is built from frequencies that last about a thousand times longer than that i.e. milliseconds not microseconds. So, as I read it, the astonishing capabilities of the amplifier make it eminently suitable for generating a welding spark at radio frequencies (microseconds) and have no relevance whatever to the reproduction of music audio.

            Am I missing something?

            Now, here's an interesting thing. In this User Group we often say that Harbeths are designed and optimised for listening at a moderate listening level. We've recently put a number on that loudness of around (roughly) 85 or 86dB at the listening chair, say 2m from the speakers. Now, coincidentally, a typical Harbeth has a sensitivity of also about 86dB "for 1W at 1m" or something like that. So, if you are listening at our moderate level, 1m from the speaker, how much power would you need from your amplifier? Answer - 1 watt. Yes, that's right. Just one meagre puny little watt!

            Now, to be fair, most people don't listen at 1m from the speaker they listen at about 2m away. That extra distance from 1 to 2m reduces the loudness at the listening chair by 6dB (spl dB). So they need to turn up the amp to bring the level back to 85dB at listening spot. They will need to double the amplifier output and double it again (+3dB, +3dB power dB). So they start with 1W, they double it to 2W and then again to 4W. Let's add a bit for comfort and call it 10W. So what that means is that, with negligible power reserve and on low-dynamic music, it should be possible to produce the moderate sort of sound level we approve of with a small amplifier. Forget all about hundreds of watts. Completely disregard huge ampere specification. Ignore crazy peak output ratings. They are all totally unnecessary when driving a Harbeth at home. And never forget, regardless of how much power you pump into the speaker and how big the amp is, the speaker's power handling capacity is very small as I showed on the videos in my previous post. Too much power and it will burn out and/or catch fire.

            I'm pulling my (remaining) hair out wondering what I have to say or do to wean folk off the idea that you need brutal, monstrous killer amplifiers to make adequately loud music at home?!

            Look here: very good explanation.
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • Re: Amplifier selection for your Harbeths (general, not specific Harbeth models)

              Thanks Alan
              I have got the message and will happily stay with what I have got!
              60wpc is indeed ample.
              Cheers
              Andrew

              Comment


              • Re: Amplifier selection for your Harbeths (general, not specific Harbeth models)

                Good man! Could you hold a hot 60W light bulb in your hand? No. So don't expect the poor voice coil to be able to handle that power too!
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • IMPORTANT! Amplifier and speaker power and efficiency.

                  We've frequently touched upon the subject of amplifier power rating, speaker power rating and speaker efficiency.

                  For example here and here and here and here.

                  The misconceptions and myopic view of this particular subject really does worry me. It leaves the potential that you will damage your speakers (or amplifier) and waste time and money on spare parts. It's because consumers consider only one side twin sided problem. The user is looking only from his side, the consumption side, considering only how much power he wants to ram into the poor loudspeaker. But from my perspective as a designer, I'm acutely aware that what is far more important is the production side: what power the speaker can actually handle and what it can reliably deliver as clean sound, year after year.

                  There are constant anxiety about 'how much power is needed to drive speaker ABC'' and there are those who believe that huge, macho amplifiers are essential to hi-fi reproduction at home. Conversely, there are others who claim that only small amplifiers have detail and resolution. I'll leave you to mull over all those sonic arguments for and against big/little amplifiers. I'm going to show you the reality of the the situation from the perspective of the poor little loudspeaker. It's clear to me that huge macho amplifiers are not only unnecessary but a hazard in waiting. So, to start at the beginning - attached is a photo of a steam train and a conventional 8" woofer. As you can see, the train is puffing its heart out pulling the coaches up a long incline.

                  Question: What have the steam train and woofer in common?

                  Answer: They are both power converters. The steam engine converts the energy locked within the coal into heat, and then into steam and finally through pistons into motion. The woofer takes a current from the amplifier which cause the voice coil to move, and as the coil is attached to a cone, causes motion of the cone which produces a variation in local atmospheric pressure which we call sound.


                  Question:
                  Can the efficiency of the steam engine and woofer be measured? I mean, can we calculate how much of the energy going into the them (from the coal, from the amplifier) arrives at the wheels as motion, or as sound pressure from the woofer?

                  Answer: Yes we can. We can measure the number of watts of energy in and out. For example, we know that a kg of coal has a certain calorific value (we can convert calories to watts) and our domestic electricity meter measures the wattage being drawn by the amplifier from the national grid.


                  Question: What happens to the energy that doesn't reach the wheels as motion or as sound pressure generated by the woofer?

                  Answer:
                  It's wasted as heat. Heat is useless. It doesn't move the train any further or faster. Heat doesn't make the woofer any louder. Once energy is wasted as heat, it's lost forever. Although we've paid good money for that energy we've thrown it away. We've nothing to show for it apart from a rise in temperature. That's a really lousy bargain.

                  Question: Have a guess at the % efficiency of a typical steam engine or woofer. In other words, guess how much of the power input is wasted as useless heat.


                  Ready for a nasty surprise........ ?

                  >
                  Attached Files
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • Re: 100A amplifier output potential or how to set fire to your speakers!

                    10 watts, Alan? So my 12 watts are fine? Right? At 2 metres...

                    David

                    PS I love steam trains, but their efficiency is appaling. About 8%? Don't know how loudspeakers match up...

                    Comment


                    • Re: Amplifier selection for your Harbeths (general, not specific Harbeth models)

                      Ok...I just dug out my 2-3 wpc SEP:
                      http://i153.photobucket.com/albums/s...22/Spud_16.jpg

                      hooked it up, mucked around with my Dac/Pre output and let me say at normal listening levels on simple music it is sounding pretty darn good.

                      So if I only have 2wpc going and it's working well I guess that means all I need.

                      Comment


                      • Re: Amplifier selection process and service backup ...

                        Originally posted by Teuton View Post
                        True, I have not heard of people pairing the two. Though I doubt it would prove to be a bad match.
                        Hello everybody,

                        Belated response to this post, just came across it. My first post!

                        Just for the record, I tried a Bryston 4B ST with a pair of P3 and P3ES back around 1996 (I think with Quicksilver and Gryphon preamps) for a month or so. The sound in my 20x12 ft living room (speakers on the long wall, open to the rest of the house at one end) was very well balanced and all of a piece; good to very good overall, with no apparent faults. The combination sounded, well, bomb-proof, such was the integrity of the reproduced sound.

                        I still have the same pair of P3ES, and would run the 250 watt Bryston but for owning an Audio Note Kit 1, 8-9 watts, single-ended triode, in a smaller room, approx 15x10ft.

                        Won't bore you with a description of the sound, suffice to say it works too. How about that for the P3's versatility.

                        jason

                        Comment


                        • Re: IMPORTANT! Amplifier and speaker power and efficiency.

                          Originally posted by A.S. View Post
                          Question: Have a guess at the % efficiency of a typical steam engine or woofer. In other words, guess how much of the power input is wasted as useless heat.
                          D.S. has commented (different thread) that "PS I love steam trains, but their efficiency is appaling. About 8%? Don't know how loudspeakers match up... "

                          Sadly, you're way off target. The answer to my question above is that 99% of the energy input to the steam train (from the coal) and the drive unit (from the amplifier) is wasted as useless heat. Only 1% of the coal's energy reaches the wheels as useful motion and less than 1% of the amplifiers energy to the loudspeaker is converted to sound. Typically, a boxed loudspeaker has an efficiency of about 0.5%. Truly shocking isn't it.

                          So my point is this .... it's madness to believe that you can force lots of power into a speaker because 99% of the power you apply just cooks the voice coil. And because so little of the power input becomes sound, the user turns up the volume (more power input to the speaker) which speeds-up the cooking process. In addition, under heavy-drive conditions as the copper wire of the voice coil heats up, its resistance increases, so it draws less power from the amp, so there is less sound generated. So the user turns the volume up even more and the coil further heats-up. This is typical of what happens at a party, when the parents are out and the kids are home alone with the hi-fi. This cycle continues until the coil is destroyed by overheating. And remember - the heat is an unwanted by-product due to the appallingly low efficiency.

                          Also have a look at what happens to the voice coil when this process runs-away .... a destroyed woofer returned from the BBC due to an amplifier fault. This speaker was connected to a very powerful amplifier which failed when the engineer was away from the studio on his tea break. When he returned, it was too late to save the speaker. Had he been using a smaller amplifier with less power (less damage potential) of a more appropriate power match to the speaker he may have had enough time to disconnect the amp (or switch it off) and could have saved the speaker. Or the smaller amp with a smaller fuse may have tripped. The bigger amp, with obviously a bigger fuse didn't trip for several minutes.

                          Huge, powerful amplifiers are no more reliable than small ones. But when they fail, their destructive potential is far greater. So, beware of using a power amp that is needlessly larger than the power you actually need for everyday hi-fi listening at home. Forget hundreds of watts and huge current potential - all that does is puts you into the meltdown danger zone which is not covered by Warranty.

                          >
                          Attached Files
                          Alan A. Shaw
                          Designer, owner
                          Harbeth Audio UK

                          Comment


                          • Plinius amplifier specification ...

                            Dear Alan,

                            How much about my Plinius SA102, is it huge and powerful amp?

                            Comment


                            • Huge amplifiers, huge car engines = danger

                              I don't know. What does the Instruction book say?

                              I'm sorry to bang on about this subject, but I've been stating my opinions about amplifiers, power, vice coil practical limitations for some years. Clearly during that time lots and lots of hugely powerful amplifiers have been sold to presumably happy users so my influnce over consumption behaviour, even as a speaker designer, is obviously zero. The last person to take any advice from is of course the chap who does the job, day in, day out. Now, as you may by now be aware, the tell-tale signs of amplifier overload of the speaker drive unit are obvious. As is the burning smell. We can video the dissection of any defective drive units (according to our IS09001 procedures) and we cannot provide any Warranty support for overloaded drivers - they need to be replaced outside Warranty.

                              New drive units are expensive but they are not profitable business for us because they divert time from production of complete systems. So we do not want you, our users, to damage your speakers because unlike many other brands, we do not position or want our spare parts business to be a profit earner (profit centre). This is a very important business strategy point.

                              Huge amplifiers increase the damage potential as huge car engines perhaps increase the chance of a crash and a very expensive repair.

                              Don't be nervous. Again, as I've said here before in explicit detail, it is you, the user that has to power to command the amplifier. You switch it on. You set the volume level. You have to be responsible for your actions. As I said, using a big amp is like driving a big fast powerful sports car. The reason insurance companies penalise young drivers is because they know from their records, that power in the hands of a young enthusiastic driver is a fatal combination. But the same engine power controlled by a middle aged man is quite safe - unless the brakes fail. It's the same with amplifier.
                              Alan A. Shaw
                              Designer, owner
                              Harbeth Audio UK

                              Comment


                              • Power and class A or AB?

                                This, Alan, is what my Plinius SA102 instruction book say:

                                Power:
                                125 watts continuous per channel into 8 Ohms
                                2 channel stereo mode
                                400 watts continuous into 8 Ohms
                                Balanced mono mode

                                Does that mean my SA102 has 125 W at both A or A/B mode? Thanks!

                                Comment

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