Toe-in => What was the initial idea/view

[Hififan]

Dear All

After reading different explanation about this text on the web and as non of them was saying the same. (e.g. my dealer told me that the speaker should look the from wall, 0 angle) , I would like to know what was the original idea of Alan (best approach to start to reach C7 full potential). Text was :

"Although the reference listening axis is directly facing the front baffle , some users prefer both speakers toed-in towards the listening seat by 5-15°. Adjusting the toe-in alters the balance especially between the mid and high frequencies in your room according to your preference."

Reference listening axis in front of the baffle mean that we should see only the face of speakers from the listening position or should the speaker be parallel to the side/rear Wall (0 angle) as my dealer told me ?

I know that I should go to find MY preference but would like to start with sound for which the C7 was built to see the pros and cons of any changes.

Tks for the clarification

Phil

[Kumar Kane]

I am pretty sure there isn't a generic reply available to this question. The answers and the sound will vary according to speaker positioning (other than toe in) and room acoustics, so I suspect experimenting in your specific set up is the only solution to get the sound you like best.

[hifi_dave]

Room acoustics, layout of room and personal preference influence the sound obtained by angling the speakers.

Generally, angling in increases the apparent high frequencies and give sharper central images. Slight toe in, increases HF slightly and gives a wider sound stage. Certain, very bright speakers benefit from no toe in at all.

All you can do is experiment in your room with a range of recordings and settle on what suits you best but don't worry about getting it all exactly spot on, as the Harbeth speakers are very good for dispersion. Relax and enjoy.

[Hififan]

I am pretty sure there isn't a generic reply available to this question.

Dear Kumar, is dont see your point. My question is about "toe in" definition as defined by Harbeth.

1) Will speaker parallel to the side/rear Wall (like in the corner to be precise) , being identified as set with THE " reference listening axis" ... as my dealer told me. Then any change moving speaker baffle looking the listening position be identified as "toe in" ?

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X
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2) The opposit would be that the " reference listening axis" is when speakers baffle are looking directly the listening position, then "toe in" would means that the apex of speakers would be in front of the listening position and "toe out" behind listening position.

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X
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Hope my request is clear enought.

Objective is just to know if C7 where initialy designed to be place as define in 1.....or 2 ;-)

Phil

[STHLS5]

Hi Hififan,

My understanding is your No2 is the correct interpretation of the manual. The 5 to 15 degree toe-in refers to slight toeing of the speakers to be off axis depending on your preference and room acoustics. Please refer to the page 2 of the manual's illustration to see how the angle is calculated.

However, the numbers may differ if you setup your speakers and listening position at a different distance then what's shown in the illustrations. Don't be surprise if you find different angle suits better for different music.

ST

[hifi_dave]

See post no.3

[Hififan]

See post no.3

Tks Dave and STHLS5

I asked that because was surprised about the impact of Toe in my setup

- Not toe at all and the bass are full with smooth mid and high..not finger point , just a sound wave.

- Toe in (still able to see the inside part of the box) gave less bass but more impact one (strange) and a more detailed mid/high...more air but more directive too with less flesh on bones.

So some cd/vinyle were flat with Toe in (classic) and some really heavy in bass with no Toe (pop) ;-)

The bass impact is for me a surprise because though that bass was not sensible like it seams to be.

Phil

[A.S.]

To answer the question: if you look at any pictures I've posted of my measurement set-up (I'll look out another) you will see that the mic is (generally) face-on to the tweeter, that is, perpendicular to the baffle and at or about aligned with the tweeter dome. That's what I call 'the reference axis'. The speakers is designed, adjusted and auditioned in that way *with the grille on*.

It is a fact that off-axis all (conventional) sound sources, including woofers and tweeters, have a progressively diminishing audio output with increasing frequency. So what happens when you listen off axis - that is, the speakers facing forward along the room and you sitting some degrees one side or another? First, listening laterally off-axis,the top end of the woofer/midrange's operating range will have diminsihed in loudness. Second, the top end of the tweeter's operating range will have diminished in loudness. You may or may not prefer that sound, but measurably there will be a small energy dip somewhere around crossover frequency because a speaker can only be optimised for a (flat) response at one point in space - the reference axis. If you sit at that point, you will reproduce the design conditions. If you don't sit at the reference point, you are not replicating the design conditions, athough you may well prefer that sound. It is entirely a matter of taste and how your ear/room/music/personal preference guides you as to what is the 'right' bass/mid/top balance.

As to adjusting toe-in and the quality/quantity of bass seeming to alter: I doubt that this is a physical phenomena because over quite a wide positional arc the measurement microphone shows no difference in the bass response. Much more likely in my opinion is your perception of the bass is changing because as you are listening off-axis the altered intergration between the bass/mid unit and the tweeter is fooling your ears into thinking the bass has changes. It's not likely at all as the wavelengths of bass notes are about the same dimensions of your room. Hence swivelling the speakers a few degrees is unlikely to make any measurable difference.

Adjusting the proximity of the speakers to any nearby suface - floor, wall, ceiling - and/or the construction/damping of those surfaces will produce a likely sonic effect and one that can be easily measured.

[Hififan]

To answer the question: if you look at any pictures I've posted of my measurement set-up (I'll look out another) you will see that the mic is (generally) face-on to the tweeter, that is, perpendicular to the baffle and at or about aligned with the tweeter dome. That's what I call 'the reference axis'. The speakers is designed, adjusted and auditioned in that way *with the grille on*.

It is a fact that off-axis all (conventional) sound sources, including woofers and tweeters, have a progressively diminishing audio output with increasing frequency. So what happens when you listen off axis - that is, the speakers facing forward along the room and you sitting some degrees one side or another? First, listening laterally off-axis,the top end of the woofer/midrange's operating range will have diminished in loudness. Second, the top end of the tweeter's operating range will have diminished in loudness. You may or may not prefer that sound, but measurably there will be a small energy dip somewhere around crossover frequency because a speaker can only be optimised for a (flat) response at one point in space - the reference axis. If you sit at that point, you will reproduce the design conditions. If you don't sit at the reference point, you are not replicating the design conditions, athough you may well prefer that sound. It is entirely a matter of taste and how your ear/room/music/personal preference guides you as to what is the 'right' bass/mid/top balance.

As to adjusting toe-in and the quality/quantity of bass seeming to alter: I doubt that this is a physical phenomena because over quite a wide positional arc the measurement microphone shows no difference in the bass response. Much more likely in my opinion is your perception of the bass is changing because as you are listening off-axis the altered intergration between the bass/mid unit and the tweeter is fooling your ears into thinking the bass has changes. It's not likely at all as the wavelengths of bass notes are about the same dimensions of your room. Hence swivelling the speakers a few degrees is unlikely to make any measurable difference.

Adjusting the proximity of the speakers to any nearby suface - floor, wall, ceiling - and/or the construction/damping of those surfaces will produce a likely sonic effect and one that can be easily measured.

Tks very much Alan for this very precise explanation, really appreciate it and the fact that you spend your precious time to do it.

Have a nice evening and i have to confess your speakers are......amazing ;-)

Phil

[hifi_dave]

You said it far better than I did.

[A.S.]

Here is a photo taken in 2008 in the nearby village hall (which they are only too glad to hire-out by the hour) of the prototype P3ESR. I've drawn a yellow line from the microphone to the tweeter.

When designing a loudspeaker system with multiple drive units, there can be only one point in space where, in the crossover region, the sound waves from those drive units reach the ear (or microphone) seamlessly integrated. That is, as a general idea, where the journey time from the woofer to the microphone and from the tweeter to the microphone are somehow related to each other. Not necessarily the same, but related in some determined way.

If one books the hall or anechoic chamber (they give the same result) there is a minimum booking time and fee - usually 3-4 hours. As it takes about an hour to set-up and about 40 minutes to knock-down, there is over two hours of time available to capture many acoustic measurements of the speaker. What I capture, as a minimum is .....

• Woofer on axis
• Woofer laterally at 30 degrees off axis
• Woofer 15 degrees above axis (+15 degs)
• Woofer 15 degrees below axis (-15 degs)
• Tweeter on axis
• Tweeter laterally 30 degrees off axis
• Tweeter 15 degrees above axis (+15 degs)
• Tweeter 15 degrees below axis (-15 degs)

That's eight acoustic measurements which can be said to reliably indicate how the two drive units - before the crossover is designed - will spray sound at the listener (on-axis), to a listener sitting somewhat laterally off-axis (who did not want to toe-in the speakers) and to a listener using very tall or very short stands. It's the minimum amount of data that yields the most usable information short of a theoretical '3D' acoustic plot with microphones at every point in space above, below and around the speakers. That would yield too much information.

That data is then fed into my simulator, and then I can start work on designing the crossover in the reliable knowledge that the simulation model of the 'raw' drivers acoustic response when laind onto the models predicted electrical response of the network will be so close to reality that it will be as if I had returned to the hall, set-up all over again and wired in a real physical crossover to the drive units and made another complete measurement run.

As with all computer systems though, 'garbage in, garbage out' which is why having confidence in the measuring set-up and process is 50% of the speaker designer's concern. And why I've spent months setting-up what I believe is a reliable measurement environment here in the Old Barn. It may look a little strange, but when dealing with acoustics the strangest environments and careful position of even humble wadding can achieve great results if you are willing to invest the time in minute adjustment.

* I am hopeful of being able to do an over-the-shoulder screen-cam on crossover design later this year when I'm less busy.

>

[JJack]

So, the reference axis has each tweeter pointing directly at the listener's ear that's closest to that tweeter?

Interesting, most setups I've seen have far less toe-in than that.

{Moderator's comment: every hi-fi box speaker we know of is measured and developed "on-axis". The lateral listening angle at home depends upon your sonic preference. Few listen on-axis either vertically or horizontally. }

[steveinaz]

These things are always very subjective due to personal preferences, room design/materials, etc; but I have found that I almost always get the best results with about a 1/2" of toe-in.

My speakers are generally 8ft apart (on-center), and my listening chair is about 11ft away.

[JJack]

So, the reference axis has each tweeter pointing directly at the listener's ear that's closest to that tweeter?

Interesting, most setups I've seen have far less toe-in than that.

{Moderator's comment: every hi-fi box speaker we know of is measured and developed "on-axis". The lateral listening angle at home depends upon your sonic preference. Few listen on-axis either vertically or horizontally. }

Re: the mod's comment: yep, I understand that.

Just for my own clarification I still have the following question:

Is the reference axis - the axis that AS refers to in his post in this thread - with the tweeters pointing directly at my ears?

{Moderator's comment: Alan must not anticipate any other point in space There has to be a reference. For all known speakers the tweeter is (+/- a inch or two) the reference axis. Think of that line as the design axis. Look at the curves for any non-concentric speaker e.g. Stereophile and you will see that is self evident.}

[JJack]

Re: the mod's comment: yep, I understand that.

Just for my own clarification I still have the following question:

Is the reference axis - the axis that AS refers to in his post in this thread - with the tweeters pointing directly at my ears?

{Moderator's comment: Alan must not anticipate any other point in space There has to be a reference. For all known speakers the tweeter is (+/- a inch or two) the reference axis. Think of that line as the design axis. Look at the curves for any non-concentric speaker e.g. Stereophile and you will see that is self evident.}

I'll take that as a "yes" to my question. I think.