|
General Asylum General audio topics that don't fit into specific categories. |
|
|
|
General Asylum General audio topics that don't fit into specific categories. |
|
In Reply to: A funny story about square wave test on speakers posted by beppe61 on December 13, 2014 at 23:34:18:
The fact that we don't listen to square waves is largely irrelevant - the square wave test is just that. A test. It verifies the existence of a transient accurate system. The big deal is that a transient accurate (TA) speaker does has constant group delay, aka the rate of change of phase wrt to frequency is linear. When you have a nonlinear relationship, you get group delay. This results in more delay in lower frequencies than higher ones. Unfortunately, since this delay is nonlinear, it takes more than some simple time-alignment to "fix" things. In fact, without DSP and forward-reverse processing (and a requisite time delay) you CANNOT fix phase distortion once it's imparted on a signal.So, if a speaker system passes the square wave test, that's a big deal in that no phase distortion has been imparted on the signal. How big of a deal is this?
Opinions range from "gotta have it" to "can live without it". I'm more in the latter camp where other factors are more important considerations. This is after chasing the transient accurate "panacea" for years and doing years of research, testing, measuring and learning.
Some claim that absolute polarity experiments are meaningless if they are not done on a transient accurate system. Some claim that absolute polarity experiments are ALWAYS meaningless! ;) Lol.
If you believe that transient accurate performance is important, then a positive result for square wave reproduction is important, because that is what that particular test proves.
If one does NOT believe non-constant group delay (phase distortion) is a big deal (i.e., 2nd order Linkwitz-Riley, 3rd order Butterworth, 4th order Linwitz-Riley, etc.) then it's not a big deal. But this does not eliminate the validity of the square wave test for a transient accurate speaker.
Note: 4th order Linkwitz-Riley has all drivers connected in the same polarity and is phase for all frequencies but does not have constant group delay. (360 phase shift puts things in phase but results in longer delays for lower frequencies resulting in phase distortion.)
I've experimented with this stuff quite a bit. My favorite experiment is with WMTMW speakers with are 4th order (acoustic) where I can essentially switch in and out active/real-time phase correction. I can not only get "theoretical" transient accurate response by recording and summing the output of the crossovers, but I get measured transient accurate performance on the design axis as well. I must say, literally "erasing" the phase distortion from a 4th order acoustic impulse response was quite exciting.
The differences in before/after performance, however, were quite a bit more subtle and in no way the panacea that some offer it to be. (In my humble opinion anyways).
Of a transient accurate versus non-transient accurate speaker, I would still simply go with the one that sounds better to me and not have "square wave performance" as a deal-breaker by itself.
Cheers,
Presto
Edits: 12/14/14
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: A funny story about square wave test on speakers - Presto 16:57:27 12/14/14 (1)
- RE: A funny story about square wave test on speakers - beppe61 22:20:20 12/14/14 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
