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From: karn@allegra.UUCP (Phil Karn)
Newsgroups: net.audio,net.flame
Subject: re: jj's Re: Thoughts on subjectivity and specifications
Message-ID: <2251@allegra.UUCP>
Date: Thu, 2-Feb-84 20:44:44 EST
Article-I.D.: allegra.2251
Posted: Thu Feb  2 20:44:44 1984
Date-Received: Wed, 8-Feb-84 01:47:34 EST
References: many, <779@drufl.UUCP>, <2387@rabbit.UUCP>, <782@drufl.UUCP> <2458@rabbit.UUCP>, <2248@allegra.UUCP> <821@drufl.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 30

Once again, the only fair way to evaluate ANY recording system is
to control ALL of the elements of the system EXCEPT for the presence of
the recording system under test in the path.  For example:

1. Pick an LP record and a turntable. Any record, your choice.
2. Play this record into a digital audio recorder (e.g., the
Sony PCM-F1 videotape adapter, since average people can't make CD
masters).
3. Requeue the record and digital player and play them in
synchronization with levels EXACTLY matched.  Getting a turntable
to play exactly in phase with the digital player over any length
of time will be very tricky.
4. Have a computer (or a confederate you cannot see) randomly switch
your speakers or headphones between the two sources (without telling
you which is which, or even if a change took place) and record your
guesses as to whether the source was switched, and if so, which is which.

Of course, if your point is to determine differences between CD players,
this is easier.  You can just start up two of them playing identical
disks, match the levels exactly, then start with #4 above.

If you can consistently tell which source you're listening to after many
such trials, THEN I'll believe you.  I suspect that you will find
it impossible to tell the difference unless a) you set the recorder
input level too high and clip the A/D converters, or b) the recorder
or media is defective.  Until you've been at least this thorough, you
cannot make your claims.  For all I know, you couldn't stand to listen
to the Sony because you blew out your tweeters on the previous player.

Phil Karn