On Wed, 17 Nov 2004 18:01:59 GMT, mick wrote:

On Wed, 17 Nov 2004 14:57:33 +0000, Don Pearce wrote:

snip

Thirdly, you can make it a half wave long at Fs and pad it lightly enough
that some energy emerges from the far end to prop up the bass response a
bit. It will be good for movies, but not so great for music.


Surely a 1/2 wave pipe will have a standing node at both ends so no (or
little) sound will come out of the other end at Fs will it? Shouldn't it
be 1/4 wave at Fs?

The damping ensures that there is no standing wave. And by making it
half a wave long, and adding the effective half wave shift caused by
using the back wave, the sound emerging from the end of the pipe is in
phase with the front radiation. This is pretty much analogous to what
happens at the port of a reflex speaker and the overall effect is also
pretty much the same.

d
Pearce Consulting
http://www.pearce.uk.com