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In Reply to: RE: Validity of the measurements is very much the topic posted by E-Stat on June 25, 2015 at 15:10:23
JA did not say the measurements are clearly wrong, he said "The usual assumption, that the measuring microphone is very much farther away than the largest dimension of the speaker being measured, is clearly wrong." To that he was referring to the far field assumption, which is an incorrect assumption for most multi-driver dynamic speakers. The assumption is especially wrong for big speakers with 3 or more drivers, line arrays, and panel speakers. Nevertheless, it does not invalidate the measurements, because at typical real world listening distances, you are still in the near field of such speakers. It's not like the measurement is near field but listening is far field. They are both near field.
Follow Ups:
Have you ever heard a Quad with a 10 db rise at 40 hz? I sure haven't.
Quad 2805 measurements
When listening to panels and other open baffle speakers in the near field, the bass balance is a variable of distance. With big panels, it's less so, because the smaller the panel, the greater the affected frequency range. I did hear Quad 988s once in a more nearfield setup at ~7 ft listening distance and there was a noticeable rise through the bass, probably not 10 dB but enough to make some tracks sound over-ripe in the bass.
All of Stereophile's loudspeaker measurements indicate bass output greater than what you will get in room, due to the near field measurement technique. JA explains this over and over again. Panels are more affected than other designs. As long as you are aware of what to expect from a given measurement technique, you can glean useful information from it.
Just from looking at the Quad 2805 measurements, you can guess that they should sound very neutral in the midrange and coherent, and have pinpoint imaging, but rolled off on top. And that correlates reasonably well with my other listening impressions. I recall a very clear and neutral midrange, tiny pinpoint images, and less sparkle, shimmer, and air on the top end than I'm used to.
As long as you are aware of what to expect from a given measurement technique, you can glean useful information from it.
I aver most folks are not and unless they read all the qualifications, would not understand. I don't know of anyone who would listen to large panels at a 4' distance which is how they are measured.
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