What is the best subwoofer you have ever heard?

I've had a Paradigm servo 15, good sub. M&K MX-350 MK2 in really cherry wood. Good sub but just didn't have the low level extension. I now have a SVS PB13 Ultra and at 2 notches on the volume and -15 on my pre output level it is dynamicly robust .i do want to compare it to two SVS SB13 Ultras as I would like a smoother response and two will give tighter, faster bass.

I have owned B&W, Aereal, Rel & JL Audio. I like JL Audio f113 best. They are very fast so I can use them for 2 channel as well as home theater. I still have 1 of my Rel's but I use it as a rear sub. It is a Stadium III.

By far and away Servo-Drive Tech7's.

For powered in home use nothing comes close to the Velodyne 1812. I heard a pair supporting a pair of Avalon Sentinels. Sounds like sever overkill but the presentation was sedately stunning.

For HT you could save a great deal by using any formidable sub without EQ/room correction since the HT processor would be handling those duties.

I had a REL Studio III, JL Audio 113, and a Velodyne DD-18, in the house for a side by side comparison a few years ago. The JL and the Velodyne were clear standouts.

It depends also about your wishes and how you will use it? Is it for multi chanel or also for stereo use. Since today I did not hear a Rel or Velodyne demo were in stereo use the instruments still were very small and direct to point out. The EQ system of Velodyne solves the acoustic problems very well. But even at show's wenn I use my own music I never heard it 100% syngron with the speakers. These days I use the PLW-15 with my way of Audyssey pro measurment. It is the first time I have the stealth integration I was looking for.

Bo1972, I have always used my EARS to dial in my REL sub,it sounds very well integrated and does not muddy up my super fast main speakers (Dynaudio). The REL is very fast indeed and accurate.The REL allows my main speakers to be faster! And Its my EARS that tell me this Not some device. Not theres anything wrong with measurments but at the end of the day its YOU who has to like what your hearing. "If it sounds good, it is good". My quote of the day ..lol