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Old 19th November 2004, 02:28 PM   #21
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Sorry Wimms,

I read your post as saying the only way a flat response speaker could sound bad is if you used brute force to make it flat.


m0tion,

I don't think it's only distortion, although I'm sure it's a big factor. Different speakers sound different. Some I like and some I don't. Take 2 drivers that are both ruler flat in response over a specific range, but they don't sound identical. Is the sonic difference only distortion? Or is it something purely subjective?
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Old 19th November 2004, 02:34 PM   #22
SY is offline SY  United States
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Quote:
The measurements are done with slow sweep of pure sinewave.
Very rarely. The use of FFT/MLS is almost universal.

The point that's been brought up and then seemingly walked past is that the frequency response of a speaker is NOT a single measurement except in the special case of a true omnidirectional speaker. As soon as you say "flat frequency response," the question is "measured where?" If a speaker is flat at some point A, it won't be at another point B. Those tradeoffs are why speakers have to be designed.
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Old 19th November 2004, 02:39 PM   #23
jmikes is offline jmikes  Canada
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Default Another listen, this time to Patti

Hopefully, I'll get another listen in the near future. The owner isn't my friend, just an acquaintance. And if he reads this forum he certainly won't be either. But if I can, I want to take the best sounding CD I own and hear it on his system. That would be Patti Scialfa's "Rumble Doll."
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Old 19th November 2004, 03:08 PM   #24
Guss is offline Guss  Canada
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Quote:
Originally posted by SY
As soon as you say "flat frequency response," the question is "measured where?"
I'm satisfied with this thesis.


Quote:
why is everyone striving for flat freqquency responses, since that isn't how our hearing works?
Thats right, go buy a set of printing machines and have fun listening diferent apealing printing noises combinations.

Good Night
Goss
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Old 19th November 2004, 05:10 PM   #25
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I think a fair number of of 'in your face' mic'ed recordings would risk being strident played back on a really flat system. Who would stand immediately in front of a brass section when trying to hear a big band, anyway? And most speakers and amps will harsh up strong high frequency content material played back at live levels IAC even if it weren't already trashed out by lousy recording or CD mastering, making it much less pleasant. There's also the factor that the very nature of a stereo speaker setup will emphasize the highs of centered information by a few db due to differences in the incident angle to the ears and head diffraction compared to the live sound source directly in front of a listener that it is attempting to reproduce.

The power response flatness of the speaker and its interaction with the room will also affect the perception of brightness. A speaker with a beamy HF equalized for flat sine wave response at the listening position will tend to sound excessively bright on transients.
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Old 19th November 2004, 09:22 PM   #26
jcarr is offline jcarr  United States
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The subjective impression of a speaker's tonal balance is determined by the total amount of acoustic energy reaching the ear, and this includes both direct sound and sound that is reflected from the room surfaces (walls, ceiling and floor) and furnishings (coffee tables, TVs etc.). When a speaker designer tailors the tonal balance of a speaker, he needs to consider both on-axis response (direct sound) and off-axis response (reflected sound).

FWIW, it is possible to make a speaker which has damn-near flat response on-axis without having it sound bright. The key is to make the response fall smoothly off-axis, so there is less energy coming back at you from the wall.

One of our listening systems uses such a speaker and we listen very close (from a distance of 100~160cm). It is revealing in a similar manner as a pair of electrostatic headphones (it is supposed to, as we developed it as a monitor speaker), but it isn't bright. I've heard many brighter-sounding speakers that, when measured, actually have a more falling on-axis response in the treble range.

hth, jonathan carr
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Old 19th November 2004, 10:39 PM   #27
johnnyx is offline johnnyx  United Kingdom
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My latest speakers sound bright when adjusted to give a flat frequency response. It could be that I'm not used to listening to speakers with a flat response. I listen to the TV more often, and that is just one small speaker, no tweeter, so to hear a full range system is a surprise. The extended bass is a very welcome change, but the extended treble perhaps takes some getting used to.

In Hi-Fi World's DIY projects, they balanced the frequency response of their speaker designs so that the treble response is gently rolled off. They said that a flat treble response sounds too bright.
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Old 19th November 2004, 11:47 PM   #28
Pan is offline Pan  Sweden
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Quote:
Originally posted by johnnyx
My latest speakers sound bright when adjusted to give a flat frequency response. It could be that I'm not used to listening to speakers with a flat response. I listen to the TV more often, and that is just one small speaker, no tweeter, so to hear a full range system is a surprise. The extended bass is a very welcome change, but the extended treble perhaps takes some getting used to.

In Hi-Fi World's DIY projects, they balanced the frequency response of their speaker designs so that the treble response is gently rolled off. They said that a flat treble response sounds too bright.
Most likely distortion and/or lack of baffle step correction. Strong early reflections from hard surfaces may contribute as well. Flat in itself does not make for bright or harsh by any means on most material.

/Peter
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Old 20th November 2004, 01:17 AM   #29
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In my experience it only takes a 2db raise in the treble/midrange to push the difference between 'bright' and 'normal'....

I'm guessing the original poster's problems are with either distortion or room modes though

fwiw : my speaks are pretty much flat from 15Hz to 25kHz...

Isn't there a recommended roll off at the top end for theater / cinema applications ? - maybe this would work for jmikes tastes.


Cheers,

Rob


btw johnnyx, if the speakers that hifi world made were rolling off early then the mid/tweets would be accentuated purely by the lack of bass to balance them. ie: no low bass, roll off the mid/tweet to stop them sounding 'bright'... if that makes sense..

my old b+w 602's sounded 'hard' but when I added a sub they 'warmed up' as the lower bass stuff balanced out the treble/mids.

Cheers,

Rob
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Old 20th November 2004, 02:42 AM   #30
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A summary of some research presented at the most recent AES convention might be interesting here (quoted from a summary by Earl Geddes' without permission):

Next was a very important paper by Sean Olive at JBL. He showed that in a statistically significant double blind test of a large number of listeners (not all JBL employees) that he could predict, from measurements, what the groups opinion of a loudspeaker would be 99% of the time (correlation was .995 but the difference for most people is not worth worrying about.) This is somewhat reminiscent of our recent arguments on this same subject where some contend that this is not possible.

Sean did a multiple regression of some 10 or 15 different measurements against the subjective impression and found that about three measures accounted for virtually all of the variability in the subjective impression. They were direct sound smoothness (about 50% of the variance), followed by smoothness of the power response (about 30%) and finally the spectral balance - overall flatness (about 15%). Of note is the fact that distortion did not enter into the ratings at all - it is irrelevant. I like to say that "loudspeaker distortion is not a problem, however overdriving a
loudspeaker is". Get speakers with enough output so that you don't have to overdrive them and distortion is not an issue. Hence largish high efficiency speakers.

I was personally very satisfied with these results since the rankings are exactly what I would describe as the most important criteria for
loudspeakers. One can spend endless hours worrying about things that are not in the top three, like phase response, time alignment, whatever, but if you don't get these three right, only you will like the sound of your speakers (which is always guaranteed). And, Oh, by the way, as I have said so often, simple piston sources cannot have flat power responses.

End quote.

Something else that Sean mentioned in his talk was that he found that the power response of a speaker should not be flat - it should roll off at high frequencies. IOW, narrowing of the polar response as frequency increases is fine, as long as the power response remains smooth. Further, I believe he said that all this research was stimulated by some of JBL's speakers being badly ranked by consumer reports. As part of the study, the consumer reports metric was included, and it was found to have a negative correlation with subjective opinion on a loudspeaker. I believe (didn't write it down) that consumer reports goes purely off power response - Sean pointed out that their method effectively said that the speaker should sound the same pointed into the corner as it would facing you which is obviously not true.

I would also say that I disagree with Earl's sweeping generalization that distortion is not important at all as long as you don't 'overdrive' them, as almost all loudspeakers have distortion as soon as they move from rest (ie, make any sound), and from other factors, but I would say that these are the sorts of things that us audiophile nut jobs should be persuing as the last 1% in our systems or whatever (because we should all already be able to design speakers with smooth, flat on-axis amplitude response and smooth power response).
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