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From: gregr@tekig1.UUCP (Greg Rogers)
Newsgroups: net.audio
Subject: Re: Unmeasurable differences?
Message-ID: <1512@tekig1.UUCP>
Date: Sun, 15-Jan-84 19:06:19 EST
Article-I.D.: tekig1.1512
Posted: Sun Jan 15 19:06:19 1984
Date-Received: Sat, 21-Jan-84 01:30:52 EST
References: <2389@rabbit.UUCP>, <6590@unc.UUCP>
Organization: Tektronix, Beaverton OR
Lines: 34

Well controlled double-blind testing should prevent the problem that you site.
Very simply, the frequency equalization device is only applied to one of the
units under test at a time.  That is one component is equalized to the other, 
not both components to some arbitrary flatness.  There are two distinct cases.

If the objective of the test is to disprove a particular component superior to 
another, the equalization device is applied only to the presumed inferior 
device which can only result in making it even more inferior except with 
regard to frequency response of course.  If the test then shows no detectable 
difference between components, the equalization device certainly cannot be 
blamed for degrading the "superior" component.  The assumed superior
component is hence proved equivalent except for frequency response variations
which can be simply corrected as in the test. 

If the purpose of the test is to prove no differences exist between components 
(neither being claimed as superior) then the test should be run twice with the 
equalization device first applied to one component and then the other.  If 
both tests show no differences between components, then it is proved that no 
differences exist other than frequency response which again can be simply 
corrected as in the test. 

It is of course more complicated if the results of the test indicate that
differences do exist.  It is then necessary to isolate the cause as either
the equalizer or components.  There are numerous ways of doing this but it 
would then be up to the OPPONENTS of component differences to prove the
equalizer at fault.  In other words, the use of an equalizer could incorrectly
influence the result in favor of those that claim differences in components,
but CANNOT favor those that claim no differences when done in the correct 
manner that I've outlined.  I hope this helps you understand how really
objective these objective tests are when designed within the rules of 
scientific method.
				Greg Rogers