Benefits of a cardioid subwoofer?

Martykl, I believe that the rear-firing woofer's output is time-delayed in order to obtain the cardioid pattern.

Speaking from theory rather than experience here, I would think that the benefits of a cardioid pattern at bass frequencies are rather small in a home listening room. You see, the ear cannot detect the presence of bass from less than one wavelength, and it takes several cycles for the ear to discern pitch. Given the size of our home listening rooms in relation to a wavelength, by the time we hear bass tones the energy has been reflected multiple times. So the initial radiation pattern of that bass energy doesn't make a great deal of difference.

I'm not saying there would be no improvement... just probably not as much improvement in a home audio setting as implied by the superior radiation pattern control of a cardioid subwoofer.

Duke
dealer/manufacturer

Thanks RWW, Marty, and Duke. I have my suspicions about how well these subwoofers would work in a listening room. They are designed as professional audio subs, so the designers probably had a much larger room in mind than my poky little listening room. Maybe I will look at the larger JL's instead.

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

"...What am I missing?"

The time delay on the rear woofer corresponds to the time it takes for the output of the front woofer to wrap around the cabinet and reach the rear woofer. So the reversed-polarity rear woofer "fires" just as the output from the front woofer reaches it, and this way cancellation occurs behind the sub, rather than off to the sides, as with a dipole. The rear woofer's output might also be attenuated a bit relative to the front woofer, I dunno... never actually done it.

Duke

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