Subs that keep pace w/ribbons & electrostatics?

Gradient makes subs that are supposed to work well with Quads.
One very well known & respected Vandersteen dealer told me that he thinks the Vandersteen sub is an even better match. Haven't heard it, though.

A lot of people are using REL subwoofers with Martin Logans

Martin Logan Depth or larger Descent subwoofer.

Adire Rava subs ...one of the best values in subs for audiophiles.http://www.adireaudio.com/home_audio/loudspeakers/exact_series/rava.htm

I know of some folks that were running Entec's with panel's. Sean
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I have the (10" woofer) Sunfire Architectural. They also have the Architectural(12") Signature. Carver created these for two channel listening. Very fast, tight with deep extension. My monitors are lightning fast, but certainly not the speed of electrostats. I've heard, many, who use the Sunfire Architecturals with Maggies and are VERY content. I had AB's these babies with many, and I preferred these, hands down. You'll probably hear from those audiophools, but if not, just some FWIW. peace, warren

The Vandy mates well, I have custom subs on Maggies, and it's a very nice match but I use a 24 db electronic X/O.

loon

REL's and Vandy's are very good suggestions. However, I would like to add the importance of connections to these subs. P/C's and I/C's will have much to do with how transparent, detailed and how controlled the sound is.

I would suggeest looking into Velodyne's new DD series. Very tight control of the bass and fast response. Add the benefit of equalizing the room modes and nulls with teh built in equalizer and provided video output/remote/microphone and I don't think you can get any better at that price.

I have a DD12 in a very small room and love it. Flat response from 125hz to 15hz.

Probably the hardest panels to integrate a sub with are the Martin Logan CLS's. They are just so fast! When I bought mine 15 years ago, the only thing I could find that would match their speed was a pair of Wilson Puppies (which Wilson says aren't "true" subs, but ya could'a fooled me!) I sold them when another CLS friend convinced me we should buy the last two pairs of Kinergetic SW800's (supposedly made for the CLS's) MAJOR DISSAPOINTMENT! Finally got rid of them and got just one Depth. It's even faster than the Puppies. It's also faster than the Descent because it has smaller, faster woofers. Plus it has a very powerful amp and with servo feedback, and some really useful contouring controls. It doesn't have XLR inputs like the Decent, but that's not too important for a sub. Moral: Buy two Depths instead of one Descent!