Comparison of various subwoofers for 2 channel audio


I have a 2 channel audio system, and I appreciate how subwoofers have augmented the sound quality of my system (with electrostatic speakers).  I currently am using a pair of Martin Logan Balanced Force 212 subwoofers, but I’m thinking about adding more subwoofers for a total of four in order to help balance the low frequency sound waves.  I’m considering adding a pair of Rythmik, SVS, or perhaps Velodyne subwoofers to the system.  Does anyone have experience with many of those brands, and how well they integrate with electrostatic speakers in a 2 channel system, or perhaps should I just get a second pair custom built with certain specifications?  
Thanks.

drbond

I had a pair of SVS Micro 3000's which sounded excellent with the Dynaudio and  Graham Audio speakers I was using at the time. Now I have a single KEF KC92 sub paired with the Q Acoustics Concept 300 monitors, and I couldn't be happier. Great bass extension, definition, and the elusive texture people sometimes talk about when describing bass. I really didn't appreciate that until I experienced it first hand with the KEF. It allows one to hear the differences in bass instruments more clearly.

@vdotman 

What are your impressions about the KEF vs SVS dual opposed subwoofers?  (I realize that you also changed speakers, so a direct comparison may be difficult.)

Thanks.

@drbond Your speakers are 7 feet tall. How high is the ceiling? If it is over 7' 2" tall the behavior of your speakers drop to point source at about 130 Hz. If you are crossing below 130 Hz it is probably more accurate to stick with the two subs you have, cross at 100 Hz and turn up the volume on the subs. They should be about + 10 dB. What are you using for a crossover? 

I have succeeded in bi amping the Sound Labs. Roger helped with the conversion. There are no passive crossover parts in the system. It was not easy going, but the end result is pretty amazing. 

I would drop SVS from your list unless you desire one note boom bass

Instead add Rel to your list. As well as KEF, Golden Ear, B&W.

I would drop SVS from your list unless you desire one note boom bass

That’s a misleading and inaccurate statement.  I have an SB2000 sub, and while certainly not SOTA it is absolutely not “one note boom bass.”  Further, there’s a member here who had both the highly-regarded Rhythmik F12 and SVS SB3000 in his 2-channel system and found them to be very close in performance to the point of being almost indifferent between the two, which certainly would not be the case if the SVS sub was that bad.  Personally I’d take Rhythmik over SVS albeit at a higher price, but categorizing SVS subs as “one note boom bass” is an over-the-top and ridiculous statement.