"Don Pearce" wrote in message
On 27 Apr 2007 11:23:18 -0400, (Scott
Dorsey) wrote:
Mark wrote:
You can't fix a time issue with a frequency fix. It's
like pushing down a ping pong ball into a bucket of
water with your thumb, it just keeps rolling around
it. Someday the minds of dsp will realize this.
Time response and frequency/phase response are just two
orthogonal views of the same thing. For every
frequency/phase response, there is one and only one
time response that is associated with it.
No. This is only true in a minimum phase system. Rooms
and speakers are not minimum phase. Electronics usually
are, though. --scott
Speakers are generally minimum phase.
While its not said specifically, it would appear that the intention is to
talk about speaker drivers, as opposed to speaker systems.
I believe that waveguide (horn) speakers and dome tweeters and midranges are
examples of speaker drivers that tend to not be minimum phase.
Any speaker driver whose cone is not breaking up will probably be minimum
phase, at least on-axis. As soon as the cone starts breaking up, all bets
are off.
Each resonance is a
mass and a compliance (equivalent to an L and a C in
electronic terms) and can be individually corrected with
electronic components or DSP.
Speaker drivers tend to be minimum phase, but that's not a universal rule.
Speaker systems tend not to be minimum phase.
The usual fly in the minimum phase ointement for speaker drivers are time
delays, usually due to vibrations passing through some part of the speaker
driver itself. The problems with speaker systems are more often due to
delays caused by sound passing through variable amounts of air.
Rooms are generally not resonant, apart from a single
Helmholz frequency related to room volume and a doorway.
Cars with all the doors shut are examples of rooms that are resonant, but
that lack doorways as such. They still manage to resonate.