From: John Woodgate
Subject: Re: volume control at speaker location
Date: Thu, 26 Sep 2002 20:26:42 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Thu, 26 Sep 2002 22:22:27 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that N. Thornton
wrote (in ) about
'volume control at speaker location', on Thu, 26 Sep 2002:
>> I read in sci.electronics.design that Benoit Provost
>> about 'volume control at speaker location', on Tue, 24 Sep 2002:
>> > My sound system is in my living room, and I am installing speakers in the
>> >basement, wired to "Speakers B" on the amplifier. I would like to know if
>> >there is a simple (passive) way to adjust the volume at the speakers in the
>> >basement. The simplest way to do this is of course to put a potentiometer in
>Use a variable resistor in series. It is the easiest way to do it. You
>won't get a linear scale as you say, but I don't see how that is a
>problem to be honest. It still works perfectly.
That's what he did, AIUI, and he DIDN'T like it, which doesn't surprise
me. Adding series resistance changes the frequency response, because the
loudspeaker impedance varies with frequency, often by large amounts.
Consider an 8 ohm loudspeaker, which is really 8ohms (resistive) at say
400 Hz (typical), but is 32 ohms (resistive) at 100 Hz (also typical).
To reduce the sound level by 10 dB at 400 Hz, we need 16 ohms in series.
But at 100 Hz, the level goes down by only 3.5 dB.
You might argue that it's a desirable effect, because it provides
automatic 'loudness compensation' at low sound levels, and some people
might agree with you. But now consider the case of a 2-way system, where
the impedance is 32 ohms at 2 kHz as well. That is NOT going to sound
right to anyone!
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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