I owned a ML Depth for a few years, and I just loved it. I did not get it from Amazon (I worked at an electronics company and there was a promo contest). We'd do this sales trick where we'd put sub test discs (everything single frequency tones and sweeps from 20Hz to 100hz, to Durty South rap that kills lesser subs) into it, and it could play everything with grace... with a nickel balanced on the top. Seriously, no vibration at all. It knocked everything we could throw at it out of the park and it did so cleanly and clearly. It took serious effort to get it to even start bottoming out, but even then there was no distortion, just a little bit of knocking. The Depth and it's bigger brother (the Descent) are expensive, but to say it's an audio investment is an understatement.
This put a lot of oomph into my movies, music, and video games, but I had to sell it to buy an engagement ring.
If I ever have the spare cash for one of these again, I'd totally get another one (or hell, two) without hesitation or regret.
This is a clean, clear, and powerful full range subwoofer. It's unique design somehow cancels all vibration, err I should clarify cabinet vibration. It has the power to shake you out of your seat. The frequency response has to be measured to believe it. This sub handles 20Hz with ease.
The downside, true do any speaker or sub, is the response curve. I am able to balance my two MartinLogan Depth subs by offsetting Phase at 0 for one and 270 for the other. I find the 25Hz knob affects volume more than the 20-30Hz frequency range which is disappointing.
Still, this subwoofer is well built and designed. MartinLogan must have put everything in the cabinet, including the kitchen sink, because it is heavy. You better get some help moving this bad boy around.