Subwoofers for Magnepan 20.1s?


I used Granite Audio's Ultimate Low Bass CD and my 20.1s go to 25Hz at -10dB and my room is 16x26x10 (speakers approx 6ft from back wall and 3.5ft from side walls on ends). I can get -6dB in the 29-33dB range and then it is pretty flat with a slight drop in the 50-60Hz range. I am not a bass fanatic, but on some recordings, I wish I had some further lower bass extension without becoming unnatural sounding/boomy. I know HP likes Nola Thunderbolt subs with the 20.1s. Has anyone tried them or any others? Other system components: Pass X250.5 amp and Xono phonostage, Audio Research Ref 3 preamp and Ref 8 CD player, VPI superscoutmaster reference turntable/10.5 tonearm, Dynavector XV1S cart.
powerdoctor
Yes, I agree go sealed with low group delay and large woofer. It will be expensive as a good tight sub means less SPL output - so you need really big rather than a high output resonant sub
One word of caution re: subs w/extra large large drivers.

Just be sure they can be crossed HIGH enough in frequency to suit your needs. I know that people generally like to cross as low as possible, but if you eventually decide that you want to EQ problems in 50hz to 60hz region, you'll be crossing at 75, 80, or 90hz. I don't know the 31.5" driver in question, but I'd imagine that it's not designed for optimal performance that high up, since some manufacturers of 15" drivers caution potential buyers about this issue.

Just food for thought.

Marty
I heard a pair of 20.1s supplemented by a pair of JL Fathom f212 powered subs, each sitting right next to a 20.1 panel. This was at a high end shop's open house. I could not detect any discontinuity, discrepancy in speed, lumpy response, or any of the other pitfalls for blending subs. They extended the slam, extension, and room-filling abilities of the 20.1s about as much as you could hope for.

Since this was a balls-out demo with near unlimited funds, I'm sure you could get much of the same effect in a normal-sized domestic room from one or two of their Fathom f110.
Gladstone its the new Fostex fw800hs. My web masters cheap and I got what I paid for;) I asked for corection about a month ago should be changed soon. The older version is not designed for the cabinet I use more for inwall mounting.
Marty, The Fostex fw800hs 31.5in woofer can be used up to 250hz with no issues. Which drivers are you referring to that you have experience with that can not be used around 100hz? Large drivers have many benefits if designed proper, great transient response,very hi-efficiency, massive cone area. But costly -large.