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post #181 of 407 Old 03-26-2009, 09:34 PM
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Quote:
Originally Posted by Rutgar View Post

How do you measure: Spaciousness?

Interaural correlation in ERB's.
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Size of Soundstage?

Principle axis analysis
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Warmth?

Spectrum
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Bloated Sound?

Direct to reverberant ratio, spectrum.
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Muddiness?

Bass response
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Detail?

Amount of preemphasis.
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Openess?

Speaker radiation pattern, interaural correlation, interchannel time delay.
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Boxiness?

Frequency response.
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Accuracy is just a small part of the music equation.


Define "accuracy" for me, please.

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post #182 of 407 Old 03-26-2009, 09:36 PM
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Originally Posted by penngray View Post

Very true so why does 95% of the population pick from 100s of different brands?

People prefer different direct to reverberant patterns in the listening room.

That really is really the next issue beyond frequency response, I think.

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post #183 of 407 Old 03-26-2009, 10:13 PM
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Quote:
Originally Posted by jj_0001 View Post

Interaural correlation in ERB's.

Principle axis analysis

Spectrum

Direct to reverberant ratio, spectrum.

Bass response

Amount of preemphasis.

Speaker radiation pattern, interaural correlation, interchannel time delay.

Frequency response.



Define "accuracy" for me, please.

Good to see a professional in the audio field chime in. Your response is thought provoking, if a bit terse. Care to elaborate? What is ERB? And can a speaker "pre-emphasize" the signal it is being fed? Seems like that would require some sort of signal processing. And what is preemphasis? What do you look for in the "principle axis analysis" to predict the size of the soundstage? Why is the sky blue? Are we there yet?
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post #184 of 407 Old 03-27-2009, 05:07 AM
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Quote:
Originally Posted by hifisponge View Post

Your response is thought provoking, if a bit terse. Care to elaborate?

That quickly leads to a graduate-level seminar if not a whole course or series of them.

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What is ERB?

equivalent rectangular bandwidth

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And can a speaker "pre-emphasize" the signal it is being fed?

They all do that. ;-)

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Seems like that would require some sort of signal processing.

They all do that. ;-)

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And what is preemphasis?

Usually, some kind of non-flat frequency response.

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What do you look for in the "principle axis analysis" to predict the size of the soundstage?

"principle axis analysis" is a kind of statistical analysis that can be applied to sound field data to characterize its spatial nature.
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post #185 of 407 Old 03-27-2009, 05:52 AM - Thread Starter
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Quote:
Originally Posted by jj_0001 View Post

People prefer different direct to reverberant patterns in the listening room.

That really is really the next issue beyond frequency response, I think.

That one is way over my head

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post #186 of 407 Old 03-27-2009, 06:32 AM
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Originally Posted by JBLsound4645 View Post

Not sure about Tom Holman con this Auduesy or how ever its spelt I don't care not interested it sounds like a load of hot air.

Have you ever listened to a properly set up Audyssey based system? Do you have any clue as to what Room Correction is? Based upon your comment here I would have to suspect the answer to both of these questions is "No".

I have an Audyssey enabled Integra and the Pro kit and I can tell you first hand that it is anything but a con. I know from experience and an understanding of what it does that it is a very real benefit and far exceeds pretty much anything else you can do. In terms of value there is nothing else I can think of that provides as much value for the buck.

The irony here is on many levels. First, your comments in the rest of your posting amount to a crude attempt at doing what Audyssey does in a far more sophisticated manner.

Second, when using a system such as Audyssey, you reduce the impact of Speaker and Room induced distortions. While it will not produce absolutely perfect sound it does, in most if not all cases, make a massive improvement in the quality of the experience when done properly. If I turn the Audyssey system off the difference is like night and day and is audible to anyone that is not stone deaf. If you are going to quibble about the sonic differences in any component other than speakers then you have to try Audyssey as the impact on the sound exceeds pretty much anything else you can do.

I would hazard the claim that decent speakers in a room with Audyssey correction will sound better than fine speakers in the same room without Audyssey in most cases. The room distortion in most situations is so signficant that few other improvements can come close, and if the speaker does have some issues those can often be addressed as well.

I know this from experience and from my understanding of the technology. If you are going to make a statement like you made here I suggest you actually study the system and experience it before inserting your foot in your mouth.

I will close by pointing out that our company uses similar techniques to equalize the response of our audio systems which go into high end business jets. While not exactly the same methods, many of the same principles are used. Audyssey is a very real and effective technology.

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post #187 of 407 Old 03-27-2009, 06:52 AM
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Quote:
Originally Posted by xgecko View Post

Have you ever listened to a properly set up Audyssey based system? Do you have any clue as to what Room Correction is? Based upon your comment here I would have to suspect the answer to both of these questions is "No".

You should understand who you're replying to:

http://archive2.avsforum.com/avs-vb/...&&#post8979768

Sanjay
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post #188 of 407 Old 03-27-2009, 07:14 AM
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jj_0001 (James),

Your list is a reasonable first approximation, but of course the devil is in the details. Psychoacoustic qualities never seem to quite line up one-to-one with measured quantities. See for example, Lavandier et al., "Identification of some perceptual dimensions underlying loudspeaker dissimilarities," J. Acoust. Soc. Am. 123 (6), June 2008. This paper also contains a very nice literature review.

Add to this a healthy dose of linguistic ambiguity, which of course depends on specific language. I'm thinking of such studies as Ozawa et al., "Psychological factors involved in auditory presence," Acoust. Sci. & Tech. 24, 1 (2003). This research was specific to one particular Japanese sound word!

I believe that everything in sound perception is measurable with current instrumentation. But constructing accurate psychoacoustic correlates and models from this data is another matter, and one which will likely keep researchers busy for decades to come.

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post #189 of 407 Old 03-27-2009, 08:57 AM
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Originally Posted by sdurani View Post

You should understand who you're replying to:

http://archive2.avsforum.com/avs-vb/...&&#post8979768

Ah. I see. Yes, I forgot that there are folks like that out there. Thank you very much for pointing this out, I will not expect a rational response after seeing that...

I do appreciate your bringing this to my attention.

"But it's just a flesh wound!"
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post #190 of 407 Old 03-27-2009, 10:43 AM
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Originally Posted by arnyk View Post

That quickly leads to a graduate-level seminar if not a whole course or series of them.

Sounds like fun to me I wonder who would teach it. Maybe team taught.
What should the prerequisites be?

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post #191 of 407 Old 03-27-2009, 11:29 AM
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Quote:
Originally Posted by dknightd View Post

Sounds like fun to me I wonder who would teach it. Maybe team taught.
What should the prerequisites be?

MIT is not strong in psychoacoustics, but this might be a place to start (and the price is right!):
6.551J / HST.714J Acoustics of Speech and Hearing

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post #192 of 407 Old 03-27-2009, 11:53 AM
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Quote:
Originally Posted by Terry Montlick View Post

MIT is not strong in psychoacoustics, but this might be a place to start (and the price is right!):
6.551J / HST.714J Acoustics of Speech and Hearing

- Terry

Nice. Looks like there might some interesting reading material there It is a few years old, but still likely useful. Thanks for the pointer

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post #193 of 407 Old 03-27-2009, 03:30 PM
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Quote:
Originally Posted by Terry Montlick View Post

jj_0001 (James),

Your list is a reasonable first approximation, but of course the devil is in the details. Psychoacoustic qualities never seem to quite line up one-to-one with measured quantities. See for example, Lavandier et al., "Identification of some perceptual dimensions underlying loudspeaker dissimilarities," J. Acoust. Soc. Am. 123 (6), June 2008. This paper also contains a very nice literature review.

Add to this a healthy dose of linguistic ambiguity, which of course depends on specific language. I'm thinking of such studies as Ozawa et al., "Psychological factors involved in auditory presence," Acoust. Sci. & Tech. 24, 1 (2003). This research was specific to one particular Japanese sound word!

I believe that everything in sound perception is measurable with current instrumentation. But constructing accurate psychoacoustic correlates and models from this data is another matter, and one which will likely keep researchers busy for decades to come.

Regards,
Terry

I don't think it's quite that grim, but of course you've a very good set of points.

The problem comes from my last question, that being "what is accuracy". Given that when we record in an acoustic space, for instance, we capture about a bazillionth of the actual information in the sound field (most of which the ear could never resolve, btw), first we need to decide what we call "accuracy'.

Then we need to actually define terms like spatiality, etc, and then do a PEA to see how our terms fit to our measures using our definitions, and do another fit of the measures, and the definitions, to the common lexicon.

Yeah, I agree, it's not perfect, I certainly wouldn't argue that, but I think that the poster I replied to was arguing that science was helpless, and it certainly isn't.

James D. (jj) Johnston
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post #194 of 407 Old 03-27-2009, 03:32 PM
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Originally Posted by arnyk View Post

That quickly leads to a graduate-level seminar if not a whole course or series of them.

I'm afraid Arny is kinda right here. What one CAN measure, vs. what the industry usually measures, is a very long story. And it would be a series of courses, starting with "how the ear works".

A painfully condensed version can be found at www.aes.org/sections/pnw/ppt.htm but I admit that having the lecture to go along with it would help an awful lot.

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post #195 of 407 Old 03-27-2009, 03:34 PM
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Originally Posted by penngray View Post

That one is way over my head

Sorry, let me take it a bit slower.

Any loudspeaker has a radiation pattern that varies with angle, frequency, distance, etc.

This radiation pattern interacts with the acoustics of the room that the speaker is operating in.

The result is a particular direct to reverberant characteristic (both frequency and time) due to the combination.

Different people prefer different characteristics, and as such, different loudspeakers, different rooms, etc.

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post #196 of 407 Old 03-27-2009, 03:38 PM
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Originally Posted by dknightd View Post

Sounds like fun to me I wonder who would teach it. Maybe team taught.
What should the prerequisites be?

Well, a good understanding of frequency analysis, basic signal processing, and basic acoustics for starters.

You'll need the frequency analysis to understand time/frequency tradeoffs, the signal processing to be able to formalize how the ear works, what speakers do, how to measure signals, etc, and basic acoustics to build on how the ear interacts with the soundfield, how a room's impulse response looks, and how it came to be that way, etc.

I'd love to teach such a course, but it would have to be grad-level, or the prereq's would take a year or two.

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post #197 of 407 Old 03-27-2009, 07:36 PM
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Can't you encompass the room in binaural recordings?

Ultimately sound reproduction is an art and with that comes subjectivity. Evidenced by the extravagent prices people pay for their equipment. That is the differentiating factor between art and utility. People don't pay for a priceless nail but a Da Vinci can be priceless.

If people paid strictly for utility then there wouldn't be such a giant range of prices. The range is so large it is in magnitudes($100 to $100000). Conversely take the price of bread. We subjectively like the "taste" of bread but the range of prices for a loaf are between $2 and $8. Bread is not a form of art.

A significant factor of art is that we pay more for what we don't see. Compare market values of impressionist paintings to a literal Norman Rockwell to a very literal leibowitz photograph. The value we place on them is a combination of the actual thing you get, what you see, but mostly what you think the creating artist put into the work. that there is something deeper into the work that you just can't see.

Musical art is no different. My really favourite stuff can be revisited years later and I seem to hear different parts I didn't before. It was always there but I didn't notice it or wasn't sophisticated enough to appreciate it.

Since audio reproduction is subjective the science is only valuable if you have experience with your own tastes and can couple it with theoretcal understanding.
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post #198 of 407 Old 03-27-2009, 08:36 PM
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Originally Posted by GregLee View Post

But it's not exactly science they are arguing against. It is not a scientific fact or a scientific theory that one should buy a speaker with a flat FR, e.g. Science doesn't furnish "should"s. It may be a fact that a certain speaker has a flat response, but so what? How do such facts tell people what speakers are worth or which ones they should buy?

Well, flat direct response? Flat power response? Flat both? What flat? At what distance, what angle?

There are many variables to loudspeakers.

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post #199 of 407 Old 03-27-2009, 08:43 PM
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Originally Posted by Ethan Winer View Post

Again, whenever you have THD you also have IMD. Like peas in a pod.

Well, IMD and THD are two aspects of nonlinearity, and you certainly must have one when you have the other.

The only real difference is that with THD you're looking at the results of one sinusoid, and with IMD at least two. But the mechanisms that give rise to one necessarily give rise to the other.

Of course, since everything has differently linearity at different frequencies, you may not see this as clearly in measurements as you might expect. I suspect a treatise on powers of (e^jw - e^-jw) (sinusoid) is not called for, let alone powers of a combination of several different 'w's.

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post #200 of 407 Old 03-28-2009, 05:15 AM
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Quote:
Originally Posted by Herc View Post

Ultimately sound reproduction is an art and with that comes subjectivity. ...
Since audio reproduction is subjective ...

I disagree with this idea. Audio equipment preference is subjective. Visual design, branding, price, fine Corinthian leather, etc. all figure into this. But equipment with perfect accuracy of reproduction should sound the same. Audible differences, as determined by double blind testing, must then be reduced to distortion. This begs the "what is accuracy?" question raised by jj_0001.

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post #201 of 407 Old 03-28-2009, 06:05 AM - Thread Starter
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Quote:
Originally Posted by Terry Montlick View Post

I disagree with this idea. Audio equipment preference is subjective. Visual design, branding, price, fine Corinthian leather, etc. all figure into this. But equipment with perfect accuracy of reproduction should sound the same. Audible differences, as determined by double blind testing, must then be reduced to distortion. This begs the "what is accuracy?" question raised by jj_0001.

Regards,
Terry

+1 I was wondering how to word the subjectivity...your "equipment preference is subjective" is perfect.

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post #202 of 407 Old 03-28-2009, 08:35 AM
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Quote:
Originally Posted by Terry Montlick View Post

I disagree with this idea. Audio equipment preference is subjective. Visual design, branding, price, fine Corinthian leather, etc. all figure into this. But equipment with perfect accuracy of reproduction should sound the same. Audible differences, as determined by double blind testing, must then be reduced to distortion. This begs the "what is accuracy?" question raised by jj_0001.

Regards,
Terry

Kinda off topic a bit but do you always want "accurate" sound? The pursuit of "good sound" and "accurate sound" are not the same. I would love an audio processor that would magically clean up Nina Simone records to something of FM radio broadcast quality. If it "distorted" the source, I wouldn't care so long as it sounded better. There is something lost in the voice of a Simone recording vs an Amy Winehouse recording. Can we measure the differences and add more to one and less to another? Not with todays technology but someday.
I don't believe our preferences will ever lead to a limit. Just a tight statistical deviation. I will always prefer a little less bass and I imagine I will always prefer less dynamic range (than those in this community). A basshead will always pound out the subs driving their riced up car. That is their preference of "good sound". It is no more wrong than what a measurement will dictate.

Science is an invaluable tool. I am not discounting it's worth. But the last mile..the part from the mp3 to my inner ear, that's all me and my preference. Science doesn't measure emotion or passion. They are critical to the pursuit of good sound.
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post #203 of 407 Old 03-28-2009, 09:52 AM
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Quote:
Originally Posted by jj_0001 View Post

Quote:
Originally Posted by GregLee View Post

But it's not exactly science they are arguing against. It is not a scientific fact or a scientific theory that one should buy a speaker with a flat FR, e.g. Science doesn't furnish "should"s. It may be a fact that a certain speaker has a flat response, but so what? How do such facts tell people what speakers are worth or which ones they should buy?

Well, flat direct response? Flat power response? Flat both? What flat? At what distance, what angle?

There are many variables to loudspeakers.

My question was about "such facts", so it would be appropriate to consider any of the measures you mention, refined and elaborated in any way you think suitable, if you'd like to tackle the question I asked. I'm skeptical that there is any principled way to get from the science to the recommendations.

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post #204 of 407 Old 03-28-2009, 09:59 AM - Thread Starter
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Originally Posted by Herc View Post

Kinda off topic a bit but do you always want "accurate" sound? The pursuit of "good sound" and "accurate sound" are not the same. I would love an audio processor that would magically clean up Nina Simone records to something of FM radio broadcast quality. If it "distorted" the source, I wouldn't care so long as it sounded better. There is something lost in the voice of a Simone recording vs an Amy Winehouse recording. Can we measure the differences and add more to one and less to another? Not with todays technology but someday.
I don't believe our preferences will ever lead to a limit. Just a tight statistical deviation. I will always prefer a little less bass and I imagine I will always prefer less dynamic range (than those in this community). A basshead will always pound out the subs driving their riced up car. That is their preference of "good sound". It is no more wrong than what a measurement will dictate.

Science is an invaluable tool. I am not discounting it's worth. But the last mile..the part from the mp3 to my inner ear, that's all me and my preference. Science doesn't measure emotion or passion. They are critical to the pursuit of good sound.


You can separate the two.....measurement/science will give you a very good idea if a speaker is good or not. measurements should also give you an idea about how the speakers sound. This again is a hypothetical point because we all know many measurements are not accurate or they just are not done.

As for people wanting an accurate or inaccurate sound that should have little to do with speaker purchases...HONESTLY people shoulld buy speakers based on how well they are built, how well they measure, how much they cost (budget concerns) and how few flaws their sound has. Once the right purchase is made people should take that scientifically accurate/well built speaker into their room and EQ it to the sound they want!

Chasing a specific sounding speaker (inaccurate/distorted response) only to have it change in our rooms because of Audyssey, in room problems, System setup issues, etc makes me wonder daily how much people honestly do not care about the science and constantly convince themselves they are hearing something no matter what room the speakers are in.

More to the point, you do not find a speaker with more bass, you EQ your system to give you more bass...do you understand that? If you did choose well build/accurate speakers this is much easier to do....5 years down the road your preferences change, you do not buy new speakers you once again EQ to your current needs.

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post #205 of 407 Old 03-28-2009, 11:49 AM
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penngray,
I'm going to turn this around. You seem to like measurements. You've measured the speakers you've built. You like they way they sound.

What part of the measurements do you think is the most important?

Have you ever tried comparing your DIY speakers with something that can be purchased ready made? Have you done this blind? Do measurements tell you
which is better?

In a sighted test a DIY speaker will always be better - because you built it yourself.

If you compared two speakers based only on measurements, what would you look for in those measurements? If you had two speakers that seemed to measure the same do you think you could tell them apart - and more important, tell which was which without looking?

Everything I say here is my opinion. It is not my employers opinion, it is not my wife's opinion, it is not my neighbors opinion, it is My Opinion.
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post #206 of 407 Old 03-28-2009, 12:22 PM
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Quote:
Originally Posted by Terry Montlick View Post

But equipment with perfect accuracy of reproduction should sound the same.

Except that one of the important aspects of speakers in listening rooms is to attempt to replace or simulate, somehow, what was lost in the original recording by the simple fact that most of the information is necessarily lost in conversion to 2 channels of audio. Or 5, or 7. And different people may prefer different "replacements". So accuracy is reduced, I think, to something involving electrical inputs as they compare to speaker output. There are still many variables in radiation pattern, etc, to be dealt with.
Quote:



Audible differences, as determined by double blind testing, must then be reduced to distortion. This begs the "what is accuracy?" question raised by jj_0001.

Regards,
Terry

Not necessarily distortion. Distortion is generally used to describe nonlinear signal modifications. Things like frequency shaping, differences in direct vs. reverberant timbre in the playback room, etc, are not generally (leaving out buzzing, rattling lights, etc) nonlinear, but they surel cause differences.

Those who are arguing the issue ought to read Floyd's book, I think. It gets into many of the issues, and while I don't entirely agree with it, it's a good start for speakers that don't deliberately have dipole/bipole radiation patterns.

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post #207 of 407 Old 03-28-2009, 12:25 PM
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I'm skeptical that there is any principled way to get from the science to the recommendations.

"recommendations" require some knowlege of the listener's preferences in distortions, frequency shaping, and direct to reverberant ratio for listening at the very least.

You are leaving out the need to evalute the listener for the listener's preferences, and you can't do that. Preferences vary widely, perhaps even wildly. Some 30% or so prefer very diffuse sound, and go for a particular kind of speaker. Some others prefer almost all direct. Most us not in those two groups want different direct/diffuse combinations for different music.

So, first, know your preferences. It is likely you can relate them to actual measurements to start with, if given the right information on setups that you listen to. THAT information is just about always 100.00% absent.

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post #208 of 407 Old 03-28-2009, 12:33 PM
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Originally Posted by jj_0001 View Post

Well, flat direct response? Flat power response? Flat both? What flat? At what distance, what angle?

There are many variables to loudspeakers.

Thank you.

The problem is not measuring speakers (see NWAA Labs & ETC Inc). The problem lies in the complexity of assembling the data which can be gathered into a single representation of what we will hear.

The notion of a fully comprehensive set of measurements which wouldn't miss issues makes my head spin if you want to get really detailed. In most cases the most telling measurements are reasonable in number, but come from investigative work based on observations of other measurements. The talk of distortion and IMD is a good example, as it is easy to move weaknesses away from the test ranges until you get into full transfer function measurements, which then have the problem of being very hard to interpret visually and are generally 3-4D problems.

I do see some strong potential in convolution with proper binaural auralization. Tools for this and further convolution with a carefully modeled acoustic environment already exist. The biggest limitation here is that you cannot capture any dynamic changes in behavior of a loudspeaker, although a complex enough model with detailed measurements and auralization options could at least let you hear the character of a loudspeaker, potentially approximated in your own room.

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post #209 of 407 Old 03-28-2009, 01:11 PM
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Except that one of the important aspects of speakers in listening rooms is to attempt to replace or simulate, somehow, what was lost in the original recording by the simple fact that most of the information is necessarily lost in conversion to 2 channels of audio. Or 5, or 7. And different people may prefer different "replacements". So accuracy is reduced, I think, to something involving electrical inputs as they compare to speaker output.

Yes, that was my meaning. The same electronic signal, however it was recorded, as reproduced by different speakers in the same acoustical environment.
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There are still many variables in radiation pattern, etc, to be dealt with.

Yes, as there is no standardized reproduction environment for 2-channel audio, as there is for motion picture multi-channel sound. But I think it can be generally agreed* that flat frequency response, both on and off axis, are minimally necessary for accurate reproduction. That is straightforward to measure and plot, and relatively easy to interpret visually.
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Not necessarily distortion. Distortion is generally used to describe nonlinear signal modifications.

Not for the most general meaning of the term. It can include many linear phenomena, such as frequency and phase distortion.

*And confirmed by Sean Olive in his excellent paper "Differences in Performance and Preference of Trained versus Untrained Listeners in Loudspeaker Tests: A Case Study," J. Audio Eng. Soc., Vol. 51, No. 9, 2003 September.

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post #210 of 407 Old 03-28-2009, 01:24 PM
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Things like frequency shaping, differences in direct vs. reverberant timbre in the playback room, etc, are not generally (leaving out buzzing, rattling lights, etc) nonlinear, but they surel cause differences.

Sorry, I missed reading this initially. Yes, however such things as direct vs. reverberant timbre can and should be dealt with by the instroduction of standardized listening conditions and the publishing by manufacturers of (already standardized) polar speaker response measurements.

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