Benefits of a cardioid subwoofer?

Honestly, I'm not sure that the idea is even workable. Low frequencies (long wavelengths) wrap around the baffle and become omnidirectional regardless of the launch pattern. Below 100hz, I'd think front baffle mounted, cardioid (bi/di-polar), and omni drivers all behave very similarly. Just an observation.

Marty

Duke,

Thanks for clarifying, but that raises another question:

Both waves will still be omnidirection. So, the wave from the forward woofer goes outward (not forward), there is a computed delay, and then the back wave goes outward (not forward). This does not look much like the behavior of a di-pole at higher frequencies, and doesn't compute to a cardiod pattern, either.

What am I missing?

Marty

Duke,

So the null is behind, rather than beside the cabinet (normal dipole) - I'm not sure how that plays out. If the sub is in free space, there will be less/no subsequent reflection off the wall behind the woofer which should reduce random destructive interference from that reflection - yes? But can't you drive that cancellation frequency up in pitch and down in amplitude by placing the woofer flush to the rear wall, anyway?

Is the idea basically to allow placement away from the rear wall, or is there another benefit here?

This is kind of a brain teaser for me - I can't visualize the impact that the designer is attempting to generate.
Sorry if I'm a bit slow on the uptake here, but any explanation is - as always - appreciated.

Marty

Drew,

Thanks, the dipole effect on gross output level didn't occur to me in considering this question.

Kirkus,

Your point re: unpredictable distance to various boundaries certainly did occur to me and, intuitively, it seems to suggest that the benefits of controlling directivity at very low frequencies in a typical domestic listening environment would be difficult to determine with any consistency.

Overall, there's more to think about here than I'd have figured, although - after reading all that's been posted here - I'm not sure what net benefit you're likely to get with this approach.

My thanks to Drew, Duke and Kirkus - I feel (a little, at least) more educated already.

Marty