From: email@example.com (N. Thornton)
Subject: Re: volume control at speaker location
Date: 27 Sep 2002 03:37:52 -0700
NNTP-Posting-Date: 27 Sep 2002 10:37:52 GMT
John Woodgate wrote in message news:
> I read in sci.electronics.design that N. Thornton
> 'volume control at speaker location', on Thu, 26 Sep 2002:
> >> I read in sci.electronics.design that Benoit Provost
> >> > 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!
Yeah, I half agree, things _can_ go off course, I guess I just haven't
found it to be a problem in pratice myself, with moving coils. Other
types of speaker are another matter of course. So I accept L pads
would avoid the chance of a problem. Maybe I'm overzealous on energy
To Benoit: I wonder what exactly was the problem with the series pot
in your case. I presumed, perhaps wrongly, that it was nothing more
than non-linearity of the volume setting.