Magnepan 20.7 and Subs

Most subs are themselves already rolling off at 30Hz. If you have the $, look into the Eminent Technology TRW-17 Rotary Woofer. It’s intended use is for the bottom octave (20Hz-40Hz) and below.

Stereo pair always sounds better.... but one in center works OK too.
Get one ... try.... either like it or buy another.... easy button.
Now go get a second job to pay for it... :)

My experience with 20.1’s may be of some value. Tried a pair of REL’s about 10 years ago, ended up working on the room acoustics to improve bass response. Now raggae music for example (Steel Pulse) kicks me in the gut (like it’s supposed to ;-)). Maggie’s strengths are a result of freedom from speaker enclosures, subs didn’t compliment them at all for me. I found dealing with the back wave using traps and diffusers made the bass very clean and deep. Good luck!

Duane

It's been over a month since I got my 20.7 as a new unit. It had too much bass and treble in the beginning, and I had to use attenuator for treble and adjust the bass with equalizer. It took over a month finally to stabilize the balance, I removed the attenuator and no tone adjustment.  

Magnepan never mentioned about breaking-in period but surely it needs to do so. I thought it was defect in the beginning. But I had to get more powerful amp and it helped for tonal balance.

I love 20.7s. Great speaker. They do bass better than most dipoles but still suffer a bit below 40 Hz. The cross overs are at about 450 and 3500 Hz and they are usually pretty slow. 12 db/oct. Putting subwoofers in will clean them up a bit and increase impact. You will need at least two subs and ideally 4. I would cross at 24 db/oct  100 Hz. I think the JL Audio f112s would be wonderful as a pair. But if you want the ultimate in powerful performances 4 all right up against the front wall with two in the corner and the other two equally spaced along the front wall. With the 20.7 driven by proper 200 watt or better mono amps you will be rocking for sure.