Physics of downward firing woofers

inna - 

Usually done for omni or semi-omni directional designs, like Linkwitz LX Mini

http://www.linkwitzlab.com/LXmini/Introduction.htm

Floor bounce is the wrong word for bass, but interference is a real thing. Anytime you see a woofer far from the midrange and near the floor you are seeing designers think this is important.   Perhaps this is more related to having an even boundary re-inforcement? 

Best,

E

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

If I recall, it has more advantages than merely cosmetic.

The main advantage is you eliminate any sort of "floor bounce" effect, where the direct woofer sound is affected by the delayed floor response, causing interference, or a noticeable dip or rise in response.

What i don’t remember is whether there is improved acoustic impedance matching as well, adding to the woofer’s efficiency.

It does not eliminate the room response modes however.

Best,

E

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