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May I ask why a wide dispersion speaker is preferred?

RayDunzl

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Am I right about this? The Magico M2 retails for about $56,000 (I presume that means a pair), and the OPTIONAL pair of M-pod stands retails for $7,600??? That's perhaps in yen not U.S. dollars? Do you think there is some softness in the price of the M-pod stands?

Magico inhabits the realm of expensive luxury goods.

---

edit: The M6 includes the stands, if that's holding you back...

Price: $172,000 per pair (includes MPod feet)
 
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MattHooper

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Check out Part 3 of this series (the first two are worth watching, too):



Thanks, some surprising (to me) info in there.

BTW, who is "Matt" in that video. Apparently he does some reviews? For what site, audioholics?
 

KaiserSoze

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Siegfried Linkwitz had something to say about this question in his explanation for his preference for dipole radiators. Here is a short excerpt:

"In a reverberant room, where the listener not only hears the direct sound but also the reflected sound, i.e. the off-axis radiated sound, the ear-brain perceptual apparatus must be allowed to withdraw attention from the room and speakers and focus attention upon the direct sound to create a convincing illusion of the reproduced acoustic event. For this to happen misleading perceptual cues must be eliminated. The speakers must be placed so that reflections are delayed relative to the direct sound. The speakers must be free from spurious resonant radiation and their off-axis radiation must follow their on-axis frequency response for the reverberant sound to be neutral."

Now it goes without saying that Linkwitz' ideas were off the well-beaten path. But you don't have to buy into all of his ideas to wonder if he may have been correct with this fundamental premise, that the reverberant sound should tonally match the on-axis response to the greatest extent possible.

As we all know, there isn't any way prevent the very lowest frequencies from being omni-directional. As such, it is manifest that when the dispersion of a speaker is made more narrow, that only higher frequencies are affected. Even if the response at every off-axis position is a perfectly straight line, it will still be downward-sloping line from low to high frequency. I.e., it will be bass-heavy.

I tend to notice mostly the things that are obvious to me and that don't require much thinking to understand, and that would not make good fodder for anyone's PhD thesis. I have never liked the fact that when you listen to a speaker off-axis the tonality changes, usually in a dramatic way. This annoys me, and this effect is exacerbated by the fact that the reverberant sound is even weaker in treble than the treble-weak sound you get when sixty degrees off-axis. To my individual point of view, this is an extremely simple and obvious thing, and it is why I prefer speakers with greater dispersion.
 

RayDunzl

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Headphone experiment, with "reflected" sound of the same frequencies as the source:

A "Rythym Track" in Audacity:

1599443833158.png

The sound is something like "Ding bong bong bong Ding bong bong bong"

Spectrum of the track:

1599445829774.png

Duplicate the track.

Delay the duplicate track by 5ms. a reasonable value for a sidewall reflection
  • Play - obvious "echo" heard
Attenuate the delayed track by 10dB
  • Play - audible echo
Attenuate by 15dB
  • Play - slightly audible, sort of a hollow sound, not identifiable as an echo
Attenuate by 20dB
  • Play, clicking mute on and off on the duplicate track - inaudible - can't tell at all when the second (echo) track is playing or not
---

Narrow (black) vs Wide (red) dispersion speaker ETC from measurement sweep in this room, which, I suppose, shows levels, but not frequencies, of reflection here.

1599444843221.png
 
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MakeMineVinyl

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And if the driver is narrow, like an exponential horn for example, aiming accurate sound at me like rifle vs the spray of a shotgun. Seems better, no?
I have big horns, and the last thing I prefer is to be staring directly down the barrel of a horn. Sounds too much like a PA system. Mine are situated pointing straight ahead, which gives a good balance of soundstage vs ambience. YMMV of course.
 

Duke

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One needs to take into the account at what time the side wall reflections arrive and the general acoustics of the room besides the polar response of the speaker. Without looking at this, conclusions of what's better or preferred ends up being quite meaningless.

Example: A side wall reflection which arrives 2-5 ms after the direct sound is audibly very different from a side wall reflection arrving after 10-12 ms or later. Very early reflections have much more negative impact on several areas compared to much later ones. There are no indications that very early reflections are beneficial in any way. [emphasis Duke's]

I totally agree with you that the arrival times matter.

Note that the single-speaker double-blind auditions conducted by Harman have the speaker laterally centered in a room that's a little over 21 feet wide. NO speaker is going to have "early" sidewall reflections under those conditions; all of the sidewall reflections will arrive late enough to be beneficial (in my opinion, and assuming they are spectrally correct or close). The long sidewall reflection path lengths also mean that the SPL of the reflected energy will have fallen off with distance, in addition to whatever effect the room's acoustic characteristics have (I think the room's walls may be broadband absorptive, but not excessively so.) Under such test conditions, imo it's not surprising that "wide dispersion" speakers are preferred.

In a "normal" stereo setup, the only direct benefit I can think of to early sidewall reflections is, an increase in the Apparent Source Width (ASW), or image/soundstage broadening. This comes at the expense of image precision, image depth, and/or coloration.

However a possible indirect benefit of a wide radiation pattern (which would result in more early sidewall reflection energy) is this: We would correspondingly have more energy arriving as beneficial later reflections. So imo if we have wide-dispersion speakers, rather than absorbing that early sidewall energy, we might want to reflect it away from the primary listening area or diffuse it.
 
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Chromatischism

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Now it goes without saying that Linkwitz' ideas were off the well-beaten path. But you don't have to buy into all of his ideas to wonder if he may have been correct with this fundamental premise, that the reverberant sound should tonally match the on-axis response to the greatest extent possible.
Now we're very familiar with that idea here. What I'm interested in is his comment on minimizing early reflections and not the delayed reflections. What can we do in our rooms to achieve that (without DSP)? That's one reason why extreme toe in comes to mind.
I tend to notice mostly the things that are obvious to me and that don't require much thinking to understand, and that would not make good fodder for anyone's PhD thesis. I have never liked the fact that when you listen to a speaker off-axis the tonality changes, usually in a dramatic way. This annoys me, and this effect is exacerbated by the fact that the reverberant sound is even weaker in treble than the treble-weak sound you get when sixty degrees off-axis. To my individual point of view, this is an extremely simple and obvious thing, and it is why I prefer speakers with greater dispersion.
And what if you had speakers with off-axis sound that was the same, only quieter? That's the ultimate goal, and most speakers fail that test in one way or another.
 
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napilopez

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I totally agree with you that the arrival times matter.

Note that the single-speaker double-blind auditions conducted by Harman have the speaker laterally centered in a room that's a little over 21 feet wide. NO speaker is going to have "early" sidewall reflections under those conditions; all of the sidewall reflections will arrive late enough to be beneficial (in my opinion, and assuming they are spectrally correct or close). The long sidewall reflection path lengths also mean that the SPL of the reflected energy will have fallen off with distance, in addition to whatever effect the room's acoustic characteristics have (I think the room's walls may be broadband absorptive, but not excessively so.) Under such test conditions, imo it's not surprising that "wide dispersion" speakers are preferred.

In a "normal" stereo setup, the only direct benefit I can think of to early sidewall reflections is, an increase in the Apparent Source Width (ASW), or image/soundstage broadening. This comes at the expense of image precision, image depth, and/or coloration.

However a possible indirect benefit of a wide radiation pattern (which would result in more early sidewall reflection energy) is this: We would correspondingly have more energy arriving as beneficial later reflections. So imo if we have wide-dispersion speakers, rather than absorbing that early sidewall energy, we might want to reflect it away from the primary listening area or diffuse it.

My understanding is that the listening room, at least in its current form, allows you to adjust distance to the sidewalls and that it supports rapid switching of stereo and three channel setups as well:
Screenshot_20200907-004316.png


There's also a 1985 Toole paper that was conducted with the speakers placed at the corners, and this was a study of directivity specifically:
Screenshot_20200907-004041.png


So I don't really think the matter of the Toole/Harman apparent inclination towards wide-ish directivity has much to do with the listening setups.

While I get your and Bjorn's logic about very early reflections, personally it doesn't reflect my own experience. My current home has very narrow listening setup, with the speakers just 2 to 2.5 feet away from the sidewalls in a 12-foot wide room and my LP 10 feet away. Yet with a couple of dozen pairs of speakers tested over the past couple of years, I end up leaning towards the wider ones even in cases when they seemingly measure worse than the narrower.

Again, just my experience. You mention apparent source width and I think that's what it really comes down to. I don't tend to find it reduced imaging accuracy all that much so long as the speaker is well controlled in the first place. The sources seem bigger, so in that sense the sound is more diffuse, but I still feel like everything is in the right place laterally and depth-wise. The narrower speakers often just make me feel like instruments and voices are pinpricks floating the air. Which can be fun and impressive, but the former ends up feeling more natural to me. YMMV.

I'm moving to a new place where my speakers will be along the wide wall and somewhat asymmetrically positioned, so I'm curious to see if my impressions will change. Your point about having more energy in later reflections is interesting too and one I hadn't considered; perhaps wide directivity worked in my narrow room because it is a huge room otherwise.
 

KaiserSoze

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Now we're very familiar with that idea here. What I'm interested in is his comment on minimizing early reflections and not the delayed reflections. What can we do in our rooms to achieve that (without DSP)? That's one reason why extreme toe in comes to mind. I'm not liking the strong early reflections in my current placement so I'm going to experiment with that.

Strong toe-in should help and I do it for much that reason. And other than that, with most rooms in most homes you're just kind of out of luck. But after I get myself re-situation, I plan to set up a room just for stereo listening and I do plan to place a fair amount of the most effective absorptive material I can find on the side walls close to each speaker. It won't fully eliminate those early reflections of course but should help a lot. As I've thought more about Linkwitz' approach, it seems to me that it does make a lot of sense, since there is a null to the sides of the speakers. Cancellation of bass is stronger than cancellation of high frequency, because of the greater dispersion of bass. It's kind of like using the greater dispersion of bass against itself, so that the lateral response will be much less bass-heavy. I'm not quite convinced that it is desirable to have that much acoustic power radiated from the rear of the speaker and reflecting off the wall behind the speaker, and I don't like the fact that the bass practically kills itself such that you need massive bass capability to get useful bass to the front and to the rear. These concerns are the reasons I'm not fully in that camp. Every possible solution comes with specific drawbacks.

And what if you had speakers with off-axis sound that was the same, only quieter? That's the ultimate goal, and most speakers fail that test in one way or another.

The Definitive Tech speakers with the extra midrange and tweeter facing the rear have a separate level control for the rear-facing drivers. I suspect that for this to live up to its potential you need a very large room such that the speaker are a good distance from the wall behind them. In most homes it probably does not work at all well, which is probably why those speakers weren't loved by a lot of people. I suspect that most people who bought them gradually turned down the rear drivers over a period of time until they were eventually silent. But I don't know.
 

Chromatischism

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All I know is that there is a careful balance. I hate being in hard, reflective rooms – they make me uncomfortable, and they sound bad. I also don't think I would like a heavily damped room that sounded like I'm wearing headphones. Finding that balance is where I'm at currently.
 

Duke

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My understanding is that the listening room, at least in its current form, allows you to adjust distance to the sidewalls and that it supports rapid switching of stereo and three channel setups as well:

My understanding is that Sean Olive's study, published in 2004, used the 21.6 foot wide room exclusively. Nor am I aware of any subsequent single-speaker studies where they used a narrower room. In that 2004 paper, Sean lists four limitations of the study. The first one is this:

"Up to this point, the model has been tested in one listening room."

There's also a 1985 Toole paper that was conducted with the speakers placed at the corners, and this was a study of directivity specifically:
View attachment 81782

So I don't really think the matter of the Toole/Harman apparent inclination towards wide-ish directivity has much to do with the listening setups.

I agree that in Toole's 1985 paper the sidewalls are close enough that early sidewall interactions are included. I was talking about the tests done by Harman in their 21.6 foot wide speaker-shuffler room, hence my wording.

I think the caption for the diagram of Toole's 1985 test includes incorrect information: To the best of my knowledge the Quad 63 WAS NOT "equipped with absorbing pads on the rear half of the enclosure to attenuate the output above 500 Hz." It was the original Quad, the "57", which was. I have owned both. Otherwise the description matches the ESL 63.

In my opinion the Quads were handicapped by having the high frequencies in their backwave energy absorbed by the drapes. One of the things the 63's get right is that the backwave energy's reflections are spectrally correct, and the drapes prevent that.

The Definitive Tech speakers with the extra midrange and tweeter facing the rear have a separate level control for the rear-facing drivers. I suspect that for this to live up to its potential you need a very large room such that the speaker are a good distance from the wall behind them. In most homes it probably does not work at all well, which is probably why those speakers weren't loved by a lot of people. I suspect that most people who bought them gradually turned down the rear drivers over a period of time until they were eventually silent.

I have manufactured controlled-pattern bipolar speakers in several variations, and as you suspect the distance from the wall matters... or more precisely, the amount of time delay before the arrival of the "backwave" matters. I recommend enough distance to get at least 10 milliseconds time gap between the direct sound and the arrival of the backwave energy, which normally translates into about 5 feet from the wall. My more recent models aim the rear-firing drivers upwards somewhat which decreases the distance from the wall needed because the reflection path now also includes a ceiling bounce.

We have conducted in-house blind listening tests and find that there is a "sweet spot" regarding how loud the backwave energy should be. If it's too loud, clarity starts to be degraded. But at levels just below the clarity-degradation threshold, envelopment and timbre are enhanced with no audible detriment. IF the clarity-degradation threshold is exceeded, then there are tradeoffs involved. In my opinion rear-firing drivers have the potential to improve both the spatial and timbral qualities, when done right... but "done right" implies designing with their contribution in mind from the outset, rather than tacking them on as an afterthought.
 
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napilopez

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My understanding is that Sean Olive's study, published in 2004, used the 21.6 foot wide room exclusively. Nor am I aware of any subsequent single-speaker studies where they used a narrower room. In that 2004 paper, Sean lists four limitations of the study. The first one is this:

"Up to this point, the model has been tested in one listening room."



I agree that in Toole's 1985 paper the sidewalls are close enough that early sidewall interactions are included. I was talking about the tests done by Harman in their 21.6 foot wide speaker-shuffler room, hence my wording.

Oh yes, you're right about the Olive 2004 blind studies using the wide room with a centered mono speaker. I was just confused because you said wide directivity speakers were preferred in that study. As far as I know, the Olive preference studies don't reach any conclusion on how wide or narrow directivity should be -- only that it should be smooth.

In fact, the second 2004 paper says pretty much just that in the limitations section:

"In this study, loudspeaker directivity by itself had little predictive power of listener preference. It is unclear what the ideal directivity of the loudspeaker should be, except that it should be smooth."
 

Duke

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Oh yes, you're right about the Olive 2004 blind studies using the wide room with a centered mono speaker. I was just confused because you said wide directivity speakers were preferred in that study. As far as I know, the Olive preference studies don't reach any conclusion on how wide or narrow directivity should be -- only that it should be smooth.

In fact, the second 2004 paper says pretty much just that in the limitations section:

"In this study, loudspeaker directivity by itself had little predictive power of listener preference. It is unclear what the ideal directivity of the loudspeaker should be, except that it should be smooth."

I had overlooked that Olive said "loudspeaker directivity by itself had little predictive power of listener preference." My mistake - thank you for pointing that out.
 

Kvalsvoll

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I totally agree with you that the arrival times matter.

Note that the single-speaker double-blind auditions conducted by Harman have the speaker laterally centered in a room that's a little over 21 feet wide. NO speaker is going to have "early" sidewall reflections under those conditions; all of the sidewall reflections will arrive late enough to be beneficial (in my opinion, and assuming they are spectrally correct or close). The long sidewall reflection path lengths also mean that the SPL of the reflected energy will have fallen off with distance, in addition to whatever effect the room's acoustic characteristics have (I think the room's walls may be broadband absorptive, but not excessively so.) Under such test conditions, imo it's not surprising that "wide dispersion" speakers are preferred.

In a "normal" stereo setup, the only direct benefit I can think of to early sidewall reflections is, an increase in the Apparent Source Width (ASW), or image/soundstage broadening. This comes at the expense of image precision, image depth, and/or coloration.

However a possible indirect benefit of a wide radiation pattern (which would result in more early sidewall reflection energy) is this: We would correspondingly have more energy arriving as beneficial later reflections. So imo if we have wide-dispersion speakers, rather than absorbing that early sidewall energy, we might want to reflect it away from the primary listening area or diffuse it.

This is a very important observation. The typical listening room I see around is quite small, and speakers will always be located quite close to side walls.
 

BradleyPNW

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Dr Earl Geddes is a relevant subject matter expert.

"The idea of an “ideal” directivity will be examined and it will be shown that CD alone is not enough, in a small room one needs a narrow
directivity that is also CD." - Geddes

I buy into the light bulb, flood light, spot light analogy. I accept what Geddes says but I also think you can choose a different sound field to accomplish different goals. If I choose a different approach I need to accept I'm making compromises.

http://www.gedlee.com/Papers/directivity.pdf
 

Duke

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Dr Earl Geddes is a relevant subject matter expert.

"The idea of an “ideal” directivity will be examined and it will be shown that CD alone is not enough, in a small room one needs a narrow
directivity that is also CD." - Geddes

Agreed.

Earl uses directional speakers and further minimizes the amount of energy in the early sidewall reflections by using a lot of toe-in, such that the first significant sidewall reflection for the left-hand speaker is the across-the-room bounce off the right-hand wall, and vice versa. But his room is acoustically lively, so he preserves the level and spectral content of the later-arriving reflections as much as is reasonably possible.

These are pretty much the concepts I embrace, i.e. minimizing early reflections, but cultivating spectrally-correct later ones.
 
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