Subwoofer for electrostats


I'm a new here and have a question... :)

Few months ago I bought Martin Logan Scenario speakers...
...everythings okay. but I decided to build a subwoofer for
them (no bass below 40 hz).
But it turned out that most ported sub's will destroy bass
quality (ML uses sealed encl. for bass)... so there's the
question .. :

What driver(s) should I consider, for sealed box with an alignment
about 0.5-0.6 to obtain bass that would go down to 20 hz without
sacrificing the speed...? I think about a kind of box with two
drivers you put in the corner (like Audio Physic Terra)...I'm I right
with that..?


Considering your MLs and trying to match the speed if, 25 Hz is low enough get a pair of Eminence Kappa 18" and build a pair of down firing passive subs. Paper cones and the size should keep up with anything. Those cones will only need to move a fraction to get the same results as a smaller driver. I am sure you have your MLs away from the wall a bit so I would build something that will go in the corners and will make nice pedestals for sculpture to go on. The reason for passive is that I have found that using a good amp made for HiFi sounds great and you control it from the same location as your other gear so it is easier to fine tune to your speakers. I am at the moment using a Fisher tube reciever that has a center channel output so getting the signal out to the garage sale find Marantz that drives the sub is easy and I seldom have to adjust the Marantz since the center channel is controlled with the volume pot of the Fisher.
Thanks for help! Well, Eminence may be a great idea, but what
about filtering when used as passive..? I don't want to spoil
things like midrange clarity and mid to bass perspective...what
xrover freq would be qood (my Scenario go down to 50 hz)..?

btw. I've came across Focal drivers, especially their 10 inch drivers
are worth considering, not to mention Audiom series, but i find
these too expensive...?
What about using a Scan Speak 25W8565 (I can get them for
reasonable price)..?