Physics of downward firing woofers

The sound waves do indeed, at least to some extent bounce back from the floor, go through the driver cone and back into the enclosure and, while that's not necessarily the greatest strategy sound-wise, it will not really mess things up all that noticeably if there is sufficient airflow at volume. Were all the walls of the enclosure to extend down to the floor cutting off the woofer to the outside air then at volume such a sub would sound absolutely terrible and probably blow itself up. But sound waves at low frequencies tend to be more omni-directional, so having them pointed directly at the ear is not thought of as critical when crossed over low enough in frequency. 

While not treating the woofers like higher range drivers and pointing them at the listener is not as critical, doing so, for a number of reasons technically, is still a good idea and all else being equal the direct setup will sound better in terms of things like phase response, frequency response...even dynamics.

This was likely a design trend that was originally employed to offer better integration into a decor by giving it a more "furniture" look, sometimes in conjunction with a reduced size enclosure for a smaller footprint. Otherwise in general there is nothing particularly good performance-wise about that kind of approach, but they are not really egregiously bad sounding or anything.

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

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