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From: sjc@angband.UUCP (Steve Correll)
Newsgroups: net.audio
Subject: Re: How to choose speakers
Message-ID: <47@angband.UUCP>
Date: Tue, 26-Feb-85 16:30:40 EST
Article-I.D.: angband.47
Posted: Tue Feb 26 16:30:40 1985
Date-Received: Sun, 3-Mar-85 04:30:40 EST
Distribution: net
Organization: S-1 Project, LLNL
Lines: 29

>  Um, I may be off base here, but my understanding of A/B comparisons was that
>  the extra impedance that had to be switched in to equalize the loudness of
>  two speakers penalized more efficient speakers. A local high end audio dealer
>  here (Gala Sound) demonstrated this to me once -- he took a reasonable (but
>  not great) set of accoustic suspension speakers, and A/B'd them with a pair
>  of highly efficient (and expensive) ones. The expensive, efficient speakers
>  sounded terrible by comparison. Yet, removing the extra impedance from the
>  circuit and driving it on the same source material, it was readily
>  ascertained the expensive drivers were doing a better job reproducing the
>  sound.

If my dealer equalized loudness by putting impedances between the amp
and the speakers, I'd find a new dealer. Such impedances would impair
the ability of the amp to control the reactive load which the speaker
presents to it, and they would be expensive and inherently hard to
adjust accurately because they would have to be wirewound potentiometers
to handle the power.

Fortunately, it's cheap and effective to adjust the loudness by
switching among ordinary potentiometers located between the preamp and
power amp; these have no more deleterious effect on the sound than do
the volume control and selector switch within the preamp itself.  If
you're skeptical that loudness affects your perception of sound, you
might find a dealer with such a setup and try comparing two very
similar speakers at various degrees of loudness mismatch. I find I can
confuse myself thoroughly with such an experiment.
-- 
                                                           --Steve Correll
sjc@s1-c.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc