In article , jakdedert wrote:
Ron(UK) wrote:
snipped for brevity

If you think about it, the bass drum head itself doesn't move much when
it`s hit by the beater, why should the speaker.

Actually, it does move quite a bit; but the operative dimension is not
the excursion, but the size of the head vs. the size of the speaker. To
move as much air as a 20-someodd inch bass drum head--moving x
distance--the 6 to 18 inch woofer cone has to move correspondingly
farther. I'm sure there's a mathematical relationship there that I
don't have the chops to calculate....


It gets a lot more complicated since a ported enclosure minimizes the woofer
movement. The port will be the dominate output device if the bass is near
the tuned frequency. The phase will vary around all this anyway so absolute phase
is a guess.

greg