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Old 01-01-2009, 05:17 PM
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Quote:
Originally Posted by krabapple View Post

Speaking of research papers, Sean (if I may call you that), what are your thoughts on this review of potential pitfalls of 'MUSHRA' and quality-evaluation-type blind tests, versus blind difference tests, by Zielinsky, Rumsey & Bech?

http://www.aes.org/e-lib/browse.cfm?elib=14393

Yes, I am familiar with this paper. It is a review of well-known biases related to any perceptual experiment. Poulton wrote a book in 1989 called "Biases in Quantifying Judgements" that covers this topic very well.
Most of these biases can be either eliminated, controlled or accounted for in the test design, and/or in the statistical analysis and interpretation of results. They talk about visual biases, which are easily controlled by doing the test double-blind (we wrote a paper on the effects of sighted vs blind loudspeakers tests, which as far as I know, is the only paper like it).

Where I part company from this paper, is what I feel is an overly paranoid, one-sided (dare I say biased), hasty view about preference (affective) tests. Zielinski, in particular, has gone on record eschewing preference tests because he feels preferences are too subjective, unreliable and give relative ratings--not absolute ones. In some cases that is true, but I've published research that shows listeners can give very reliable preference judgments of loudspeakers, particularly if you use trained listeners. He chooses to ignore that research perhaps because it doesn't suit his argument.

Humans are very subjective and affective beings. Consumers make purchase decisions largely based on affective judgments. If you avoid trying to measure them, then you are not getting to the bottom of the truth.

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Old 01-01-2009, 07:25 PM
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Quote:
Originally Posted by Tonmeister2008 View Post

Humans are very subjective and affective beings. Consumers make purchase decisions largely based on affective judgments. If you avoid trying to measure them, then you are not getting to the bottom of the truth.

I don't know much about the bottom of the truth, but I would wager that not heeding affective judgements could potentially lead a company to the bottom of its checking accounts though.

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Old 01-01-2009, 08:31 PM
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Originally Posted by QueueCumber View Post

I don't know much about the bottom of the truth, but I would wager that not heeding affective judgements could potentially lead a company to the bottom of its checking accounts though.

That's exactly what I meant. If you work for a consumer electronics company - preference is what matters.

To explain the underlying preferences, you also need to measure the salient perceptual attributes: timbre, spatial, distortion, and for these measurements trained listeners are generally needed. In my experience, the timbral or spectral differences among loudspeakers generally explain the largest proportion of variance in listeners' preference ratings. If you look at Klippel's 1990 paper, the lower directivity loudspeakers were preferred for their wider more enveloping auditory imagery. These experiments were done in stereo, so whether the same holds true for multichannel recordings remains to be seen.

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Old 01-02-2009, 05:46 PM
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i am sorry, but science has no place here. after all, we listen with our ears, not a scope!!!



sorry, could not resist.

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Old 01-02-2009, 07:41 PM
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Isn't that about the same reasoning as to why we don't need surround - because we only have 2 ears?

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Old 01-02-2009, 10:38 PM
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It's bad reasoning, the reason being that recording music and playing back music in two channels is spatially 'lossy' -- it's not rvery analogous to listening to the original 'live' event (assuming it was live, and not wholly a creation of multitracking). The losses occur at the recording stage, the mixing stage, and the playback stage. Surround setups (given proper recording and mixing for surround) get us closer to reproduction of the original '3D' event. See Floyd Toole's book for lots more detail on this.
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Old 01-03-2009, 08:21 AM
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Originally Posted by Alimentall View Post

Isn't that about the same reasoning as to why we don't need surround - because we only have 2 ears?

joke^

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Old 01-03-2009, 08:33 AM
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IME, wide dispersion speakers make for a more enveloping and seamless surround stage than narrow dispersion speakers. It's why we rebelled against THX dipole speakers early on and went for wide dispersion small speakers that could 'reach' out and fill the soundstage without forcing sound to bounce off the walls first. We did a 6-channel ultra-wide disperison Xd system in a 100 person auditorium for a surround demo and had the whole place filled with seamless sound an an encompassing sweetspot. Not a scientific study, just an anecdote, but playing the same material as DTS demoed at CES (though at lower bit rate) and with less expensive, wider dispersion speakers, the presentation was dramatically better and much more realistic/natural. At CES, I could tell exactly where the speakers were.

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Old 01-03-2009, 09:01 AM
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Doesn't a wide dispersion speaker imply sound bouncing off walls?

"I've found that when you want to know the truth about someone that someone is probably the last person you should ask." - Gregory House
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Old 01-03-2009, 09:25 AM
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A bit, sure, but it's not an attempt to force it. Plus you just get more even sound over a broader area and the room is 'lit up' more evenly.

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Old 01-03-2009, 09:46 AM
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Quote:
Originally Posted by Chu Gai View Post

Doesn't a wide dispersion speaker imply sound bouncing off walls?

Yes, the potential spatial benefits of wide dispersion speakers rely upon the listener receiving more early reflected sound from the side walls. Strong early reflections cause a greater apparent source width (ASW), and the later reflections (>80 msec) produce greater listener envelopment (LEV). Stereo reproduction in a typical room can't create much LEV because the first side-wall reflections (which are the most energetic ones) arrive much sooner (10-15 msec) than what is required. But you can easily create LEV with surround sound.

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Old 01-03-2009, 09:52 AM
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Originally Posted by Dizzman View Post

i am sorry, but science has no place here. after all, we listen with our ears, not a scope!!!



sorry, could not resist.

Science and listening are not mutually exclusive. The final arbiter of whether a product sounds good is always based on a listening test - not a scope. However, if you do a well-controlled listening test you can examine the relationship between listeners' judgments and objective measurements. From that, you can try to define which objective measurements best correlate with listeners' judgments.

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Old 01-03-2009, 10:01 AM
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Just how even do you want the dispersion to be from top to bottom, Sean?

"I've found that when you want to know the truth about someone that someone is probably the last person you should ask." - Gregory House
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Old 01-03-2009, 10:05 AM
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Quote:
Originally Posted by Chu Gai View Post

Just how even do you want the dispersion to be from top to bottom, Sean?

It depends on who is doing the dispersing?

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Old 01-03-2009, 12:30 PM
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Sorry Sean, i am a firm believer that listening without testing is as useless as the opposite.

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Old 01-03-2009, 12:39 PM
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I'm a firm believer that listening will get you 80% of the way and measuring will get you 80% of the way but you need both to get to the next level. Of course, it depends on your listening and measurement knowledge or you might not even make it close to the 80%, but i wouldn't call either useless on their own.

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Old 01-03-2009, 12:57 PM
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Quote:
Originally Posted by Chu Gai View Post

Doesn't a wide dispersion speaker imply sound bouncing off walls?

Sure, but some reflections can lead to a more enjoyable result. Wide dispersion speakers can make your front soundstage appear nice and wide, imaging outside your front L/R speaker locations. However, you have to be careful to get speakers with consistent sounding off-axis response. IF you are going to use reflections to expand the front soundstage, then you want those reflections to be tonally similar to the direct sound from the speakers. If the wide dispersion speakers sound very different off-axis, then I would absorb the reflections rather than use them. Since much of this is subjective, YMMV.

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Old 01-03-2009, 01:23 PM
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In your estimation Sean, and I guess without naming names, how well do the general crop of upper 5 figure and 6 figure speakers achieve the goals of even FR response coupled with broad, even dispersion?

"I've found that when you want to know the truth about someone that someone is probably the last person you should ask." - Gregory House
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Old 01-03-2009, 10:53 PM
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Originally Posted by Dizzman View Post

Sorry Sean, i am a firm believer that listening without testing is as useless as the opposite.

I didn't mean to imply that objective measurements are any less important than listening tests. We do both hand in hand. The listening test on a new prototype loudspeaker only begins when the objective measurements tell us that it is 90% in the ball-park. The listening test helps us get the remaining 10%.

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Old 01-03-2009, 11:10 PM
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Originally Posted by AndreYew View Post

Welcome Sean! Hope you stay a while.

One finding of Sean's that had me LOLing was the negative correlation of Consumer Reports speaker rankings with listener preferences!

--Andre

I finally posted the first article about Consumer Reports Loudspeaker Tests: Why Consumer Report's Loudspeaker Accuracy Ratings Are Not..

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Old 01-04-2009, 09:46 AM
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Old 01-04-2009, 09:59 AM
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I wouldn't count on it, they haven't listened (double meaning intended) for 20 years.

BTW, Sean, are they still using the same methodology from the early 90s? As I recall, it was something like 16 different averaged measurements, including above, below, behind the speaker and then, once they got the averaged measurement, they actually tilted it to make it closest to horizontal, then rated them by the deviation from this newly horizontal curve.

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Old 01-04-2009, 10:14 AM
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Thanks Sean. I remember seeing that graph in Floyd's book. I'm looking forward to the next part.

BTW, Siegfried Linkwitz has an interesting twist on the wide dispersion requirement. He makes the point that uniform dispersion across the audible frequency range is what's important, which is subtly different than wide dispersion.

Since almost all box speakers have omni bass, wide dispersion is the correct goal for box speakers, in order to better match the (very) wide dispersion in the bass in the rest of the frequency range. However, on a speaker with dipolar bass, the dispersion in the higher frequency ranges would not necessarily be as wide as on a box speaker. What do you think?

--Andre
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Old 01-04-2009, 10:49 AM
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Quote:
Originally Posted by Alimentall View Post

I wouldn't count on it, they haven't listened (double meaning intended) for 20 years.

BTW, Sean, are they still using the same methodology from the early 90s? As I recall, it was something like 16 different averaged measurements, including above, below, behind the speaker and then, once they got the averaged measurement, they actually tilted it to make it closest to horizontal, then rated them by the deviation from this newly horizontal curve.

From what I've been told, they have a very good anechoic chamber, and collect a lot of raw data in the spatial domain. Frequency resolution is the real problem: they use 1/3-octave measurements, which can't accurately represent medium and high Q resonances. Secondly, in the calculation of the accuracy score, they only look at the total radiated sound power,which means they can't independently assess the quality of the direct, early and late reflect sounds produced by the loudspeaker. Thirdly, they make the false premise that the sound power should be flat, which means a well-designed speaker with a typical rising directivity will not score well in the CU test. In order to score well, you will need to boost the high frequency response and/or reduce the bass to achieve the flat sound power. That explains the negative correlation (r= -0.22) between the listener preference and CU accuracy ratings.

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Old 01-04-2009, 11:09 AM
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Quote:
Originally Posted by AndreYew View Post

Thanks Sean. I remember seeing that graph in Floyd's book. I'm looking forward to the next part.

BTW, Siegfried Linkwitz has an interesting twist on the wide dispersion requirement. He makes the point that uniform dispersion across the audible frequency range is what's important, which is subtly different than wide dispersion.

Since almost all box speakers have omni bass, wide dispersion is the correct goal for box speakers, in order to better match the (very) wide dispersion in the bass in the rest of the frequency range. However, on a speaker with dipolar bass, the dispersion in the higher frequency ranges would not necessarily be as wide as on a box speaker. What do you think?

--Andre

Having constant directivity seems to be a good idea whether the speaker is a dipole, omni, or line-array. With constant DI, it means that above the room transition frequency (200-300 Hz) no matter where you sit you are getting the same quality of direct and reflected sounds assuming you've treated the walls with broad-band absorbers and/or diffusers.

The argument is being made that so long as the direct and early reflected sounds arriving at the listener have similar spectra the precedence effect will take care of perceptually fusing the two events together, room adaptation takes over, and life is good. I'd like to see more research in this area before I accept it as fact.

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Old 01-04-2009, 11:18 AM
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Quote:
Originally Posted by Dizzman View Post

Sorry Sean, i am a firm believer that listening without testing is as useless as the opposite.

Listening is an integral part of the work Sean has published. One thing he showed is that listening without controlling for normal 'sighted' biases, can be substantially 'useless' as a guide to preference for actual *sound*.

That's one reason why, for consumers (who rarely if ever have the opportunity to 'blind compare' loudspeakers, good independent measurements can be a useful guide.
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Old 01-04-2009, 03:25 PM
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Re blind testing of speakers

http://www.moultonlabs.com/more/some_reminiscing/P0/

of course extremely hard to do for us mere mortals!

long story short, a set of speakers he had developed and was ready to take to market turned out to be extremely poor when tested blind, and against the competition.

Take TWBAS for example. I mean who would NOT be impressed upon seeing and hearing it, all the while completely aware of the components and their cost and reputation.

May only be me, but I wonder how it would stack up if done blind. Of course it would not be able to be done....the NRC only 'swap' speakers don't they (ie all would share a common front end) so even on that level it makes it harder to set up such a test.

Guess I am more interested in this than most as my speakers are DIY (hey, they're damned good!!- how else can I justify my thinking I have a right to post in this exalted section of the forum??heh heh).

Still, as good as I think they are, for all I know they might not stack up at all against the 'opposition' of done blind.

Would love to somehow do a test like that!
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Old 01-04-2009, 03:59 PM
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i seem to have been mischarachterized.

i firmly believe that listening without testing and testing without listening are of no good.

Testing tells us of accuracy and other important elements of a boxes technical merits.

hearing/listening tells us of its artistic merits.

A great speaker has both.

i am firmly in the camp of science tells us what is happening. our ears tell us if we like it.

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Old 01-04-2009, 04:14 PM
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Quote:
Originally Posted by Tonmeister2008 View Post

I finally posted the first article about Consumer Reports Loudspeaker Tests: Why Consumer Report's Loudspeaker Accuracy Ratings Are Not..

Thanks for the update.

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Old 01-04-2009, 05:17 PM
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Quote:
Originally Posted by Dizzman View Post


I am firmly in the camp of science tells us what is happening. our ears tell us if we like it.

You keep leaving out the part about how what your 'ears' tell you is being influenced by other stuff. Unless you're listening blind, it's never JUST your ears that are telling you if you like it, and there's also a good chance that, if you did use only your ears, your ears would tell you something different.
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