I will express a somewhat different experience based on my experience. I had Martin-Logan CLSs paired with a pair of Entec LF-20 subs. These subs each had two 10 inch woofers that were servo controlled and I had new surrounds put on by the original manufacturer. Each was probably about 75 lbs and the pair would have been about $6,000 in the late 80's to early 90's. A very high-quality pair of subwoofers.
When I moved up to a pair of Martin-Logan CLXs, I wanted to take advantage of the custom crossovers provided by Martin-Logan for these speakers as mains, so I sold the Entecs and bought one Martin-Logan Balanced Force 210 sub. It sounded great with the custom crossover filter. It also had more than enough output for my 25x20x11 listening room. It is currently placed in between the mains.
What is the game changer for this subwoofer though it the ability to use the Perfect Bass Kit (PBK) to create an inverse correction filter for room nodes. To be honest, I was skeptical at first, and put off doing the set-up for weeks, to my deficit. The difference in bass quality and musical enjoyment between corrected and uncorrected is stunning. You know how in some songs some of the bass notes are more prominent than others? That ends. Runs up and down the neck of an electric bass are now essentially equal in volume. Same with double bass and lower cello, etc. I agree with many above that multiple subs provide a smoother response across the whole room, which is a great reason for multiple, but in my single listening position, I can get a much flatter bass response curve than most uncorrected multiple sub systems.
@puppyt, if you have not done the PBK, it is essential before trying other things. If you are still dissatisfied, I am a potential buyer of your 210. I want another one, not for output, but I do think there is stereo bass information to be recovered in some recordings, principally in live concert recordings.
When I moved up to a pair of Martin-Logan CLXs, I wanted to take advantage of the custom crossovers provided by Martin-Logan for these speakers as mains, so I sold the Entecs and bought one Martin-Logan Balanced Force 210 sub. It sounded great with the custom crossover filter. It also had more than enough output for my 25x20x11 listening room. It is currently placed in between the mains.
What is the game changer for this subwoofer though it the ability to use the Perfect Bass Kit (PBK) to create an inverse correction filter for room nodes. To be honest, I was skeptical at first, and put off doing the set-up for weeks, to my deficit. The difference in bass quality and musical enjoyment between corrected and uncorrected is stunning. You know how in some songs some of the bass notes are more prominent than others? That ends. Runs up and down the neck of an electric bass are now essentially equal in volume. Same with double bass and lower cello, etc. I agree with many above that multiple subs provide a smoother response across the whole room, which is a great reason for multiple, but in my single listening position, I can get a much flatter bass response curve than most uncorrected multiple sub systems.
@puppyt, if you have not done the PBK, it is essential before trying other things. If you are still dissatisfied, I am a potential buyer of your 210. I want another one, not for output, but I do think there is stereo bass information to be recovered in some recordings, principally in live concert recordings.