Martin Logan Grott i Sub for Two Channel?

Does anyone have any experience with this sub for two channel? I'm interested also in the quality of it's high pass filter. Will it degrade the sound any? Would be mating it with all tube McIntosh gear and Harbeth monitors. Thank you.
not familiar with that sub --but internal xovers usually will not be as good as an external xover--have used 2 diff subs with internal xovers and they were not as good as an active xover --rich
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Thanks for your replies. I've tried passive filters before and they really degraded the high frequencies. So active appears to be the way to go. Anyone out there with personal experience with this particular sub? Thanks.
I have the smaller Dynamo in my system and like it a lot. Its a very fast sub and very flexible in terms of features. Its small size makes for easy placement as well. For what its worth my local dealer pushed the less expensive Dynamo and Abyss over the Grotto which they did not care for as much. The Dynamo and Abyss are more flexible because they can be converted to either forward or downward firing. You could probably even do two Dynamos for the same price or less as the Grotto (as I recall). I also own the Depth(i) in my HT setup and although expensive, it is a true beast.