Need more bass?
The Magneplanar Bass Panel (DWM) is a dipole, thin-film, planar/magnetic bass panel. It is two bass drivers in one panel. Two "voice coil" grids drive one bass diaphragm. The Bass Panel is essentially a small section out of the 20.7 bass drivers. But, please don't call it a "subwoofer". Subwoofers are a separate category from woofers. Subwoofers are intended for below 40 Hz and are known as "slow" and "muddy" when used above 40 Hz.
Subwoofers can be adjusted higher than 40 Hz, but you will achieve better sound by using the Bass Panel to optimize the bass of your Maggies. The DWM Bass Panel has no problem integrating with a full-range Maggie because it is "all Maggie."