Partnering a subwoofer with a pair of Martin-Logan reQuests is a difficult venture. The reQuests already have significant low end response down to 30Hz. The problem becomes apparent upon using just the pair of speakers for 5.1 soundtracks or for audio sources that have music that can truly utilize the low end of the spectrum. For the 5.1 soundtracks, there's no easy way of getting the .1 output directly to the main pair without making a mess of the more essential qualities of the audio. The Depth i brings the response down to 20Hz without any difficulties. It can be wired simultaneously for both your digital .1 subwoofer output and for reproducing just the low end of the spectrum on 2 channel sources. To do that, you can run the patch cord for the digital .1 output directly to the appropriate input on the sub while also running a pair of cables for the RCA line level input. You may wish to ensure that your preamp can handle this easily or that you have the appropriate cables in advance.
The placement for the sub, which is a very nice looking and very heavy unit, is typically behind one of the front speakers. The sub's crossover frequency is easily adjusted as is its volume, so you can not only adjust it appropriately for your current speakers but can set it so that those in the family who don't appreciate bass are comfortable. This can be set up so that it makes your chair vibrate with the explosions or so that it adds a balanced extension of your system's overall frequency response down another few notches.
Setup was easy although you need two people to unpack and move the unit into position. You can leave the speaker switched on, in which case it goes into standby mode when no signal is being received, or can turn it on and off as desired. MartinLogan's customer service and online support has always been excellent. The manual is well written and straightforward.
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.
This is an amazing sub. I have it paired with my Acoustic Zen Adagio speakers and they complement each other perfect. The sub is fast, clean and handles down to 20 hz with ease. I use it mainly for music and the adjustment options on the sub are flexible enough that you should be able to blend it with just about any main speakers. It is a very musical sub, but also gives you that clean deep response needed for action movies. You truly will think you are part of the action. Just be considerate of your neighbors since it does pack a ferocious punch! I would not hesitate to recommend to anyone!