I built Siegfried Linkwitz's Orion design, have run them in three different rooms so far, and have heard a handful of other Orion setups and other dipole bass/sub-bass setups in different places. They work great.
I've also heard Martin Logan's attempts to integrate monopole woofers with dipole main panels and that doesn't work well.
Ngjockey writes
>The reason you don't see much of this is because there's not many crazy enough to try. "Dipole subwoofer" is about as close to an audio oxymoron as an unbiased opinion.
As long as we're being relaxed about defining "sub woofer" like the original poster that's extending the headroom and extension of his electrostatic main panels or the consumer market definition which extends to 80Hz or beyond:
Compared to monopoles there are significant perceptual and measurable differences in how dipole bass couples to room modes (with adjustments possible through source rotation), has no gain below the space's fundamental resonance (why you can't put "big" conventional speakers in small rooms), has a different energy time curve, and has a more accurate modulation transfer function resulting from the speaker/room interface.
People don't do it because it's expensive. In a domestically friendly 14" deep enclosure you need four times the displacement of monopoles for the same SPL at 40Hz and 8X at 20Hz. For music the 40+ Hz output is the issue since even "bass heavy" music has last octave peaks 10-20dB down from the rest of the spectrum with the IEC musical power spectrum approximation specifying a second order high-pass at 40Hz. For mixed home theater use you also need a separate monopole sub-bass system for the lowest frequencies and probably LFE unless you take the Monte Kay approach using 24 15" drivers split into two 9' tall W-frame stacks with a total 1400 pound weight (That does yield 103dB @ 2.83V / 1 meter sensitivity at 18Hz with a 1% second harmonic and 1.5% third harmonic).
That's not very viable commercially in a world where designers lament that $8000 per pair MSRPs only allow for $80 midrange drivers and consumers would need to buy both dipole woofers and monopole sub-woofers for home theater.
I've also heard Martin Logan's attempts to integrate monopole woofers with dipole main panels and that doesn't work well.
Ngjockey writes
>The reason you don't see much of this is because there's not many crazy enough to try. "Dipole subwoofer" is about as close to an audio oxymoron as an unbiased opinion.
As long as we're being relaxed about defining "sub woofer" like the original poster that's extending the headroom and extension of his electrostatic main panels or the consumer market definition which extends to 80Hz or beyond:
Compared to monopoles there are significant perceptual and measurable differences in how dipole bass couples to room modes (with adjustments possible through source rotation), has no gain below the space's fundamental resonance (why you can't put "big" conventional speakers in small rooms), has a different energy time curve, and has a more accurate modulation transfer function resulting from the speaker/room interface.
People don't do it because it's expensive. In a domestically friendly 14" deep enclosure you need four times the displacement of monopoles for the same SPL at 40Hz and 8X at 20Hz. For music the 40+ Hz output is the issue since even "bass heavy" music has last octave peaks 10-20dB down from the rest of the spectrum with the IEC musical power spectrum approximation specifying a second order high-pass at 40Hz. For mixed home theater use you also need a separate monopole sub-bass system for the lowest frequencies and probably LFE unless you take the Monte Kay approach using 24 15" drivers split into two 9' tall W-frame stacks with a total 1400 pound weight (That does yield 103dB @ 2.83V / 1 meter sensitivity at 18Hz with a 1% second harmonic and 1.5% third harmonic).
That's not very viable commercially in a world where designers lament that $8000 per pair MSRPs only allow for $80 midrange drivers and consumers would need to buy both dipole woofers and monopole sub-woofers for home theater.