Physics of downward firing woofers

One example is the Alison Model 9.

Roy Alison’s later models tried very hard to eliminate boundaries as reflection points, and this was an example of his ideas. While the woofer was down firing, the entire speaker was meant to be placed along a wall, increasing efficiency and eliminating early reflections of rear walls. I’m sure that I do not do Roy’s designs and brilliance justice, but you can find more online.

The woofer was meant to excite the wall and floor at the same time, again, taking advantage of increased efficiency and eliminating the possibility of a late arrival screwing with the perceived response.



Best,

Erik

Thanks for this short discussion 

Just did a little more reading, and there are indeed reasons NOT to do a downward firing woofer, one of which is simply gravity. Gravity will pull a cone downwards, moving the resting point away from the neutral position, and straining the suspension over time.

This may mean linear excursion is better in one direction than another, but I think this is something that could be compensated for with custom drivers.

Best,

E

Jim - thanks for bringing it up

ivan and Erik - thanks for food for thought 

Bass waves are many feet long so the floor a few inches away doesn't have any bounce effect really.  The sound typically radiates out Omni-directionally and this decreases bass resonance in the room.  ATC makes down-firing subs and it's not cosmetic at all.  Even the pro versions that don't take cosmetics into account fire down.  I've had both down and front-firing subs and I think down-firing is a fine decision.  You probably can't get the perfect integration that you could theoretically get by having the sub lined up with the speakers so the whole system is time aligned and all frequencies arrive at the same time but the problems with deep bass in most rooms mean you don't typically have the sub lined up that way anyway.  It's usually placed to be out of sight or placed to minimize bass peaks and valleys caused by the room's resonant frequencies.