From: DPierce@TheWorld.com (Richard D Pierce)
Subject: Re: Cancel speaker resistance?
Sender: firstname.lastname@example.org (Mr Usenet Himself)
Date: Mon, 16 Sep 2002 00:17:52 GMT
Organization: Professional Audio Development
X-Newsreader: trn 4.0-test72 (19 April 1999)
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
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.
| Dick Pierce |
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