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.