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Path: utzoo!watmath!clyde!burl!ulysses!harpo!seismo!ut-sally!nbires!winograd
From: winograd@nbires.UUCP (Steve Winograd)
Newsgroups: net.audio
Subject: re: re: extra speakers: test methodology
Message-ID: <306@nbires.UUCP>
Date: Fri, 6-Apr-84 21:23:22 EST
Article-I.D.: nbires.306
Posted: Fri Apr  6 21:23:22 1984
Date-Received: Mon, 9-Apr-84 05:32:16 EST
Organization: NBI, Boulder
Lines: 47

The reply from nbires!rcd about my suggested "extra speaker test" methodology
gives me a welcome chance to try to avoid some potential disagreements which
would divert peoples' attention from the matter before us, namely whether
having extra speakers in the room affects the sound of a hi-fi system.

My suggested methodology is only a suggestion.  I do not claim that it is the
best or the only way to do the test.  Make your own variations!  Use tapes or
CD's or something other than records as the source if you think that multiple
consecutive plays of a record may be undesirable.  Be creative!

Now some quotes from nbires!rcd and my reactions:

 > The test ABSOLUTELY MUST be done with the help of another person to
 > remove and replace the extra speaker.  You (or whoever is doing the
 > critical listening) must not know whether the speaker is present or not.
 > Use a blindfold if you need to . . . but try to make the test unbiased.
 > If you know when the speaker is present and when it isn't, you may not 
 > be able to be objective.

I don't think that the test ABSOLUTELY MUST be done as he says, but I have
no objection to the idea.  I have often done tests on my system while I kept
my eyes closed and another person made changes.

 > One variation of the test . . .is to compare with the speaker always
 > present, but sometimes with the terminals shorted and sometimes not -
 > this SHOULD show a difference, though not as much as predicted for
 > removing the speaker entirely, if I understand the arguments right.

I don't know what rcd understands the arguments to be, but I don't claim to
know exactly why the extra speaker does what I have heard it do.  Shorting the
terminals may or may not do anything.  Some other net people, without ever
trying the test for themselves, have attempted to discredit the extra speaker
idea by first attributing any difference to sound absorption by the extra
speaker and then arguing that its absorption could not possibly have a
significant effect.  That is a totally invalid method of argument:
setting up a straw man and then demolishing it.

 > Use a pseudo-random sequence of changes. . .  That is, if 1=speaker
 > present and 0=speaker absent, don't use a sequence like 010101010101.
 > Instead, use something like 0101111000101011100.  In fact, runs of
 > "speaker present" or "speaker absent" are good for checking whether
 > the listener really hears a difference and is convinced of it.

Sounds like a good idea to me.

			Steve Winograd
			{ucbvax,hao,allegra}!nbires!winograd