Why do planars have poor bass extension?

You need to hear some Apogees driven well. No bass problems there...

You can have low bass with proper room placement, no piles of equipment and racks, behind, and between the speakers.

Also an adequate sized, but not large room, with not a lot of furniture, and sit in the right spot.

Read "Get Better Sound" by Jim Smith for great info.

My Magnepan 3.6's go down to about 30Hz in the several different rooms I have had them in!

It takes time and careful listening, if you take the effort.

Dipole panels have the same problem with bass as open baffle cone speakers. The technology is less relevant than basic acoutics. As an experiment, try 1' deep plywood "U-frames" on panel speakers.

Due to the energy lost into the acoustic short circuit between front and back surfaces in a domestically friendly 14.5" wide planer speaker or deep W/H frame you need 4X the displacement compared to a monopole and 12dB more raw output compared to the same speaker at 160Hz (so total excursion is 64X what it is at 160Hz).

It's better to roll-off the response than have the speaker encountering its mechanical limits.

If you want dipole bass (it couples differently to room modes, and sounds subjectively better with Siegfried Linkwitz hypothesizing it's due to preserving the bass signal's envelope better) with low extension and the ability to handle music at less than scale model levels in a spouse friendly package the only practical solution is W or H frame woofers with electronic boost at low frequencies.

The Orion designed by Siegfried Linkwitz (http://www.linkwitzlab.com) and sold by Wood Artistry (Starting at $14,750 - http://www.theorionspeakers.com/speakers-and-cabinets/release-orion-4.html) does this. Gradient sells the SW-63 sub-woofer for the classic Quad ESL 63. Martin Logan has a few speakers with physically opposed cone woofers that start out as dipoles and transition to monopoles as excursion becomes a problem and you're getting below the room's fundamental resonance where it's not buying you anything.

Thanks all! I'm particularly interested in the canceling effects inherent in the dipolar radiation pattern – could anyone point me to some more in-depth literature along the lines of Drew_eckhardt's response -

"Due to the energy lost into the acoustic short circuit between front and back surfaces in a domestically friendly 14.5" wide planer speaker or deep W/H frame you need 4X the displacement compared to a monopole and 12dB more raw output compared to the same speaker at 160Hz (so total excursion is 64X what it is at 160Hz)."

References are greatly appreciated!