From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Cancel speaker resistance?
Date: Mon, 16 Sep 2002 05:23:52 GMT
NNTP-Posting-Date: Sun, 15 Sep 2002 22:23:52 PDT
Kevin McMurtrie wrote:
> In article ,
> DPierce@TheWorld.com (Richard D Pierce) wrote:
> >In article ,
> >Kevin McMurtrie wrote:
> >>Is there any advantage in using current to voltage positive feedback to
> >>cancel the coil resistance of a single speaker driver? Would
> >>eliminating the 5-something Ohms improve the sound or is it
> >>insignificant compared to other factors?
> >One can easily construct an amplifier that has a net negative
> >output impedance, thus resulting in a net reduction in the
> >total loop resistance of the amplifier/speaker circuit.
> >Would it IMPROVE the sound? Yes, it would, if the electrical Q
> >of the driver was too high, resulting in a total Q that was too
> >high. If the electrical and total Q are what they are supposed
> >to be, reducing the total loop resistance would result ina
> >driver that is too OVERdamped and the resulting system would be
> >less than optimum.
> >More generally, if a speaker is competently designed to begin
> >with, eliminating the DC resistance of the voice coil would NOT
> >be a good thing. As a corellary, if you ARE going to go through
> >the effort of reduing the effective resistance with something
> >like a negative output impedance amplifier, it would most likely
> >be for a specific design, i.e., a specific driver used with a
> >specific amplifier.
> >Why would one want to do that? Well, getting the Q low enough in
> >a driver can be expensive, because it means, generally, a bigger
> >magnet, and the magnet is the most expensive component in a
> >driver, for the most part. Now, if you were designing an
> >integrated speaker/amplifier, and were constrained by budget or
> >size, then such a scheme might make sense.
> It now sounds like something I won't rush to try. The component count
> to implement it is low so I was curious what it would do. I've heard of
> it being done before but I couldn't find any links because it gets fancy
> marketing names.
> I got thinking about it because I'm trying to build an inexpensive sound
> system for a small room that will play music from a computer jukebox.
> It doesn't need to be loud but a broad and smooth frequency response is
> important. I've looked at computer speakers but they've all had shrill
> satellites with buzzy subs. It looks like a component amp plus
> competent floor speakers will cost $300+ dollars.
> My current idea is to build a little 40 WRMS Class AB amp and a speaker
> set for it. I have spare time and tools so putting it all together is
> not an problem.
In that case, pretty conventional design is fine. Get low resonance
woofers of about 8 inches or a bit bigger, good mid range speakers and
tweeters. You then need to work out the crossover networks.
Living in an apartment as I do these days, I have concluded that the
speaker system manufactures could eliminate the mid range and tweeters
without much notice being taken by the people that buy the garbage.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org