Maybe there is a difference between "good for music" and "good for HT"

Matthew J Poes

Matthew J Poes

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#41
I realize you went to some considerable length to then address the incongruity in the above statements (with your discussion of Logic 7); but I think that might breeze by my original point.

If you want a high level of room interaction (your 2-channel scenario); a wide dispersion speaker facilitates that.
If you want a low level of room interaction (your Multi-channel scenario); a low dispersion speaker facilitates that.

You speak of using processing to take a multi-channel, low-interactive room and play successful 2-channel music; but, while I think that's an important topic, it seems tangential. Your room-speaker interaction [and correct me if I'm mis-stating your position] should be different in a 2-speaker setup than in an 11-speaker setup. I assert that the room itself is only one part of that pairing.
Yeah I don’t agree that the speakers dispersion is as critical as you make it out to be, but otherwise agree with your point. The spatial cues of interest for recreating the virtual environment are mostly late reflections and both speaker types equally create those. The advantage of the more controlled dispersion speaker is that it has less early reflections which can smear the image. Early reflections simply cause virtual sources and when a virtual source is near the real source and of equal amplitude and near equal time, it’s not natural. A large acoustic venue never has that, so it’s one of the anomalies that would pull the brain back to reality. You recognize you are in a room again.

It’s also worth noting that the a controlled dispersion speaker like mine isn’t really that narrow. If you compare the radar graphs of an abbey to say a Revel, they won’t look as different as you might think.

I also think, as I mentioned, that very wide dispersion speakers like the MBL’s create a huge soundstage but I think they have too much reflected energy relative to direct. So I don’t happen to think that is desirable. I wouldn’t argue for that as a better 2-channel option. I think you want a specific ratio of direct to reflected energy.
 
AcuDefTechGuy

AcuDefTechGuy

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#42
I absolutely believe there are speakers that will sound great with EVERYTHING.

Yeah, you could theorize about speaker dispersion, among other opinions.

It's just a matter of finding those speakers. :D
 
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shadyJ

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#43
I'll agree that in a perfect world this should be true and may be the objective; however, the reality is instruments have directivity and to think that the directivity of the instrument is somehow captured and maintained all of the way to our ears without any regard to the directivity of the speaker or the playback environment seems a bit of a stretch.
The directivity of the instrument and its acoustic environment should be captured by the microphone, not the the playback system. Think about how the event was recorded in the first place.
 
JerryLove

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#44
The directivity of the instrument and its acoustic environment should be captured by the microphone, not the the playback system. Think about how the event was recorded in the first place.
In which case you want zero speaker-room interaction.

And I agree with you, BTW; but the effect can easily sound "dead" in a 2-channel setup.
 
Matthew J Poes

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#45
In which case you want zero speaker-room interaction.

And I agree with you, BTW; but the effect can easily sound "dead" in a 2-channel setup.
I agree with what you are saying here Jerry, but you lost me with the connection between the instrument directivity and the speakers directivity. In a musical venue the instruments are all point sources in a large acoustic space. In a 2-channel system, the instruments are virtual point sources. Even if the instrument were largely omnidirectional, I don’t think an omnidirectional speaker more accurately reproduces that unless you had a separate speaker for every instrument and a recording that captured it that way. I think that directivity impacts imaging but I don’t think it has any relationship to the recording.
 
KEW

KEW

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#46
The directivity of the instrument and its acoustic environment should be captured by the microphone, not the the playback system. Think about how the event was recorded in the first place.
So how do you prevent the playback system and environment from effecting the perceived directivity of the instrument?
 
Matthew J Poes

Matthew J Poes

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#47
So how do you prevent the playback system and environment from effecting the perceived directivity of the instrument?
Oh KEW, sorry I mixed your comments and @JerryLove up. Sorry Jerry. Ok you’ve lost me. See my comment to Jerry. I don’t see how an instruments directivity has anything to do with a speakers.
 
KEW

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#48
I agree with what you are saying here Jerry, but you lost me with the connection between the instrument directivity and the speakers directivity. In a musical venue the instruments are all point sources in a large acoustic space. In a 2-channel system, the instruments are virtual point sources. Even if the instrument were largely omnidirectional, I don’t think an omnidirectional speaker more accurately reproduces that unless you had a separate speaker for every instrument and a recording that captured it that way. I think that directivity impacts imaging but I don’t think it has any relationship to the recording.
Listen to solo trumpet and solo violin (the actual instruments) with your eyes closed and think about how precisely they image (or not). My contention is that the trumpet requires precise imaging that you would not get from an omnidirectional speaker and violin over speakers that image well will not sound right because the image will be too tight.
I may have adopted a red herring by associating it with directivity, but it has been my experience that speakers with horns or fairly pronounced wave guides image better than speakers with no wave guides and even more-so for speakers that are designed to be omni-directional.
Here is Cris Botti as I mentioned earlier:


The microphone is capturing the sound maybe 3" out at the center of the bell. We know this is a directional sound because it is coming out of a legitimate horn (not a sax or clarinet where much of the sound comes out of keyholes for most notes).
If you take the sound recorded by that microphone and play it over an omni-directional speaker, how could it ever sound like a real trumpet with that sound being broadcast into the back and side walls (so disproportionate to the real thing)?
 
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shadyJ

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#49
So how do you prevent the playback system and environment from effecting the perceived directivity of the instrument?
I don't have time to post a big explanation, so I will try to keep this succinct. The recording has to capture the acoustic properties of the venue as well as the instrument. Let's say the instrument had an omnidirectional sound dispersion. Let's say you were playing this instrument in a concert hall, and the recording was made with a couple cardioid mics facing around the performer in a center area of the seating. The playback system has to recreate the experience of the mics at that position (assuming that is what the sound engineer intends). All of the directivity information is stored in the recording, i.e., the direct sound of the instrument and all of the reflected sounds from the concert hall surfaces. That environment has to be recreated by your system. You will hear all of the properties of the instrument as it was recorded. Your own acoustic environment can bring its own contribution, and that may be good, bad, or neutral depending on the room.
 
Matthew J Poes

Matthew J Poes

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#50
Listen to solo trumpet and solo violin (the actual instruments) with your eyes closed and think about how precisely they image (or not). My contention is that the trumpet requires precise imaging that you would not get from an omnidirectional speaker and violin over speakers that image well will not sound right because the image will be too tight.
I may have adopted a red herring by associating it with directivity, but it has been my experience that speakers with horns or fairly pronounced wave guides image better than speakers with no wave guides and even more-so for speakers that are designed to be omni-directional.
Here is Cris Botti as I mentioned earlier:


The microphone is capturing the sound maybe 3" out at the center of the bell. We know this is a directional sound because it is coming out of a legitimate horn (not a sax or clarinet where much of the sound comes out of keyholes for most notes).
If you take the sound recorded by that microphone and play it over an omni-directional speaker, how could it ever sound like a real trumpet with that sound being broadcast into the back and side walls?
I see where you may be going with this. Actually in general most instruments are somewhat directional. People have done studies on instrument directivity and short of like a harp, very few are Omni-directional.

In any case, I do think that specific issue is unrelated to the speakers directivity. It is true, I think, that as a speaker becomes more directional the imaging becomes more pinpoint. I also agree that certain musical venues and music types are better suited to a narrower dispersion speaker than a wider dispersion speaker. I don’t happen to like the sound but have noted that Omni-speakers have very diffused stages that I can see sounding more like a real symphony would. Those are huge, imaging is diffused, and the direct to reflected energy ratio is very low. Orchestras are full of highly directional sources but they are all Point sources in a field of point sources quite far from the listener.

I think the reason that speakers with narrower dispersion have more pinpoint imaging is due to less reflections off the walls and ceiling early on. Less very early reflections. I believe that Sean olive has made a similar point elsewhere but believes its best to achieve that via absorption. I believe the opposite, specifically because of his mentor Toole, who showed absorbs don’t absorb an incident wave evenly. As such I prefer to do so with the speaker since it can control the reflections in a more predictable way.
 
ski2xblack

ski2xblack

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#51
Yeah, you could theorize about speaker dispersion, among other opinions.
Is Toole's book merely opinion? How about others, such as PWK, Geddes, or any who focus on controlled directivity, are their ideas and research into acoustics merely opinions? There is quite a bit of information in this very thread that goes well past opinion. Hopefully others take it to heart and don't brush it off as merely opinions as you have.
 
Matthew J Poes

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#52
Is Toole's book merely opinion? How about others, such as PWK, Geddes, or any who focus on controlled directivity, are their ideas and research into acoustics merely opinions? There is quite a bit of information in this very thread that goes well past opinion. Hopefully others take it to heart and don't brush it off as merely opinions as you have.
Well a couple fine points here. Toole hasn’t advocated for constant directivity and controlled directivity is an undefined non-scientific term we took to using to avoid confusion with constant directivity, which is explicitly defined as conforming to a directivity fall-off that is flat and -6dB at 45 degrees to either side of center.

Toole advocates for a speaker whose response remains flat as you move off axis or mostly flat. He seems to be directivity agnostic in terms of the rate. I assume that he would not advocate for an omnidirectional speaker, but otherwise he has never been specific that I am aware about a specific DI preference. Geddes in the other hand explicitly advocates for a DI that’s is flat over at least 1khz to 15khz at an elevated level of 9-12dB or so. I believe specified for the frontal hemisphere rather than full power response.

None of these folks have ever studied or really mused much about the value of various directivity levels and imaging. I believe someone started such a conversation over at AVS and Olive and Toole have weighed in. Olive made a comment that speakers with wider dispersion may contribute to a more natural stage, but his definition of wide was based on how the Revels did against the M2. So we are talking about speakers which both have somewhat controlled directivity, one is simply more controlled and somewhat narrower. I wouldn’t call the M2 narrow though. To me that is more like 60 degrees or less. He also noted that narrower dispersion may contribute to more laser sharp imaging but felt that wasn’t desirable. If I recall, he mused this may have explained why the Revel had a higher score than the M2 in listening tests.

I agree with his view on how directivity impacts imaging but disagree on what is desirable. To me the pinpoint laser sharp imaging is more natural and desirable. This of course is just our opinions as there is NO research to prove either right or wrong. I also believe that it makes more sense to control those reflections (which is what contributed to the sharper imaging) through the speaker instead of acoustic panels. I believe panels are imperfect absorbers at incident angles. While Toole shows this to be true, I too have measured this by capturing the reflection off a panel and showing that the reflection response does not match the speakers response. But the reflection off the wall mostly does.

I talked to Welti about an idea I have to actually do sound quality tests for this. It’s very tricky, but basically using special software I can create a binaural impulse response of a room of a particular acoustic type. I can also create a binaural impulse of a speaker of a given type and directivity. I can then create test tracks that are encoded with the combined binaural modification. The technology is actually used to allow someone to hear a room before its built, but it works here too. It is essentially what Crutchfield did to make it possible to hear their speakers over headphones (I bet you didn’t realize it was so sophisticated). This works, but is imperfect. Without mapping a persons HRTF or tracking head movement it isn’t totally believable. A related experiment that was recently at University of Michigan found the effect not believable enough to totally fool a person into thinking they are hearing a real speaker in a real room. In any case, it’s a far more reliable way to experiment with what directivity sounds like. Using MUSHRA software you could then test in a reliable manner how directivity impacts a persons perception of imaging. I’d love to work out the kinks and make this happen, but I’m not an acoustic researcher and this turned out to be a lot more work than I originally anticipated. Oh well, maybe someday!
 
ski2xblack

ski2xblack

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#53
Yeah, interesting Toole tidbit. In the first edition of his book, sec. 18.2.3, he discusses blind testing of horn loaded speakers, in particular the JBL K2S-9500, which just happened to sit at the top of double blind speaker ratings against all other loudspeakers tested. That bit is conspicuously absent from the third edition. He also brushes off the distortion reducing benefits of horn loading, as though all consumers exclusively use direct radiators.

Oh, and sorry Andrew, I think I was unnecessarily channeling some grumpiness your way. What I should have kept it to is this: I think a basic grasp of the speaker/room/listener interaction will tremendously help those looking for that 'perfect' speaker that does everything well.
 
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shadyJ

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#54
He also brushes off the distortion reducing benefits of horn loading, as though all consumers exclusively use direct radiators.
To be honest, most consumers don't push their speakers into distortion much, so I mostly agree with him that it isn't a big deal Your standard three-way tower has more than enough dynamic range for most people.
 
AcuDefTechGuy

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#55
Is Toole's book merely opinion?
Is it a proven mathematical equation?

Is it black and white and carved in stone and agreed by 100% of all people?

If not, then it’s his opinion.

It’s 100% not rocket science or neurosurgery or medicine.
 
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ski2xblack

ski2xblack

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#56
I would say the opinions come into it when preferences do, for example, in the context of this discussion, a listener who likes more early reflections as Matthew put it, or less.

Acoustics and psychoacoustics are branches of science, and speaker engineering is applied science. The whole hobby, as Toole put it, is science in service of art. An understanding of the speaker/room taken as a whole can help inform that person as to which speaker will be the right tool for the job at hand. Note that the OP started this thread with excellent examples of each approach, with his Phils and Klipsch Kl-650THX. He was fortunate to have both at his disposal, to put some of what Matthew described into practice.
 
Matthew J Poes

Matthew J Poes

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#57
Is it a proven mathematical equation?

Is it black and white and carved in stone and agreed by 100% of all people?

If not, then it’s his opinion.

It’s 100% not rocket science or neurosurgery or medicine.
This is not an accurate statement at all. I think you should take a little time to learn about this science and the ones you compare it against. I am a scientist, I study human behavior, and my work straddles medicine, psychology, and human perception. My expertise in designing studies encompasses all of these. Then there is audio, more a hobby, but one I've taken very seriously and have real academic credentials for. Audio is physics.

It is a mistake to suggest that human preference studies are mere opinion as they misunderstand what is being studied. Further, it is a mistake to assume that these other sciences are as concrete as you suggest.

Is pain management studies merely opinion since they cannot directly equate taking a pill with a direct measure of pain (such as nerve receptors leading to the firing of electrical impulses caused by pain)? No it is not opinion, because the methods used are highly objective and rigorous.

Toole's work is not his opinion because he used a scientific method of inquiry that minimized sources of bias. He and his colleagues have openly published their work in 3rd party peer-reviewed journals. It is a requirement of published research that you openly share everything you did such that any other knowledgable scientist could recreate what you did.

You asked if there is a formula that underlies what he says. The answer is yes. You seem to think no, but I suspect you never read his published articles. They absolutely created a mathematical formula used to indicate if a person will like a speaker or not based on its anechoic measured performance. They compared numerous algorithms to find out which combination of measured performance led to the highest prediction of preference. For example, they found that response smoothness and bass extension were the most important indicators in the formula, but not the only indicators. Sean Olive pointed out to me in a recent email exchange that the smoothness of the response off-axis is a more important indicator of sound quality than is the rate at which it falls. In other words, having a flat DI is more important than having an elevated DI.

What I think you don't like about this work is the notion that we can mathematically predict, from a probabilistic standpoint, what sounds good. I believe, from past comments, that you believe that sound quality is a personal thing. You are correct in that what matters most is what sounds good for you. The problem is that is not science and the assumption that everyone's perception of good sound is unique for them is flawed. Humans are far more similar than different and our tastes are no different. This isn't marketing, nobody is designing speakers with a particular sound and then using marketing to influence what people like. That would be a silly thing to do, as there is no benefit to treating a speakers frequency response like a fashion trend.

What Toole and colleagues did was use a rigorous understanding of human physiology and research (much of it done by other people, not themselves) around psychoacoustics to then understand how that plays into what we like in the sound of a speaker. This was tested in double-blind manners to ensure they were not biased. A lot of that work started and was done at the NRC, not Harman, and the NRC had absolutely nothing to gain from their research. Harman allowed (and still allows) it's research team to operate separate from the marketing and development of products. They don't have scientists invent a new product, and then ask the research team to prove its best. It goes the other way. They use their research to discover what leads to the best technical performance. They use the products that come out of that to then test their hypothesis. When its confirmed, the products remain in production and they share the results. When it doesn't, it becomes an aspect of published research, but obviously not something that remains in production or is touted as a great innovation by marketing.

One thing to remember is that Toole, Olive, and Welti are all very careful about sharing opinion or speculation. When they make a bold claim, it is almost always backed up by rigorous scientific evidence and supported by a sound understanding of human psychoacoustics.

It's also important to know that most of the best and most innovative research in medicine and physics today is also probabilistic. I know because I do some of this work. One of the hottest new medical trial designs for evaluating the effectiveness of a treatment is known as a Bayesian Adaptive Trial. I modified that approach for use in evaluating the effectiveness of social support policy programs. These use both Bayesian statistics as well as the general concept of Bayesian inference to allocate individuals to different treatment arms based on the probability that they will have a successful outcome. An algorithm is used to make predictions at the point of randomization (they are randomized with a probability bias toward the most effective option) and once that algo basically makes near perfect predictions, we can stop the trial and know how to make a diagnosis and treatment that works. This approach has led to major breakthroughs in cancer treatment. I fully expect it will also lead to major breakthroughs in how we educate our children, what services we make available to families in need, and how we address public health crisis.

Lot's of speaker manufacturers develop products based on nothing more than strongly held opinions. Companies like Harman, Kef, and RBH are not examples of that, they rely on rigerous human perception studies.
 
J

JengaHit

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#58
Not being an engineer, I can only speak to my subjective experience with omnidirectional speakers (Mirage OMD-15) and constant-directivity speakers (Hsu CCB-8) in my multi-purpose listening/living room, and how they compare to my longtime classical concert-going experiences. Short answer, after having lived with the CCB-8's for about 2.5 months: I prefer the Hsu's to my old Mirage's. When placed using time-intensity trading and extreme toe-in, the Hsu's can do large soundstages with excellent ambience retrieval/decay while still imaging holographically and accurately. It's a convincing balance, and to me, musical soundscape. This does conjure what I've experienced in real concert halls. And the sweetspot is wide. This is excellent for rendering largescale symphonic/opera recordings as well as rock-concert blu rays like "Stop Making Sense" or "Queen: Rock Montreal". The Hsu's imaging prowess also gives me an excellent movie phantom center and crisp dialogue intelligibility. By contrast, the Mirage's soundstage impressively, image decently, but slightly more diffusely, and provide a huge sweetspot (bigger than the Hsu's). Good for classical and acoustic recordings. But this comes at the expense of dialogue intelligibility with movies in my 2.1 system, though the Mirage's phantom center usually locks onto screen images, eerily. Images with the Mirage's can also seem slightly larger than life, depending on the recording. So, as many in this thread have pointed out, the applications or types of recordings have played a big role in determining what works best in my set-up.
 
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