Rythmik Audio FV15HP servo ported subwoofer Articulate bass for HT and music application

The unit is brand new. This new revision now has 4-1/4" port opening (vs 3-1/2" opening before).  This allows air velocity from port to decrease by at least 20% and hence less port noise.

This subwoofer uses a patented servo feedback technology called direct-servo, meaning the sensor is just a sensing coil directly detects the cone velocity signal and then the servo signal goes back to the feedback network without any active device to ensure most prestine servo signal received by the power amplifier. This is contrasted with approaches from Velodyne and others which use piezo sensor. Piezo does not react to velocity directly. Instead it reacts to pressure. So there is a mechanical conversion process from velocity to pressure that can add coloration. And yet the signal coming out from piezo sensor is so weak that it needs opamps to amplify the signal before it can be used. The patented directservo technology addresses all these problems and the result is a very musical sound with articulation and clarity not heard at this price range.

With its direct servo feedback, the subwoofer amplifier adjusts the cone movement speed in real time by comparing the servo sensor feedback to  the supposed speed. If the cone moves too fast, the amplifier immediately applies electrical brake to slow down the cone speed. If the cone moves too slow, the amplifier immediately applies (up to its full power) to the cone  to speed up. So what can make cone speed deviate from the supposed speed?  Standing waves inside enclosure is one major source. Sounds come off the driver cone on both sides of the driver. We hear the sound from the side of driver facing us, but where does the sound from the other side go? They don't just magically disappear. Some say the sound absorbing material got some of them. But Dacron and other premium sound absorbing material is only effective above 80hz.  So for the subwoofer operation range, we need to use a different method to absorb that energy. Another problem is you can make the enclosure absolutely rigid with the so-called knuckle test. Try that knuckle test on your driver (figuratively) make you realize the cone itself is the Achilles's heel of sealing the unwanted nasty standing waves inside your enclosure.  DSP cannot address boxy sound problem because the standing waves are too complex to model.  Now that is where the servo control of this subwoofer comes into play.  It is essentially an electrical braking and acceleration enhancing system with improvemen of 3x (or 10db) reduction in boxy sound compared to conventional non-servo subwoofers.  The outcome is a bass: 1) absent of boxy sound coloration, 2) with details and articulation, 3) wide sweet spot (you can now hear articulate bass even at lower playback volume) and 4) easily blend with your front speakers instead of constantly drawing your attention that you have a out-of-place (or chatty) subwoofer.

The amplifier is a class H amplifier with linear power supply (not SMPS) and the driver cone is made of one piece dish aluminum. Subwoofer with similar cone sells at least twice as much. This subwoofer represents the best combination for HT subwoofer: servo technology on a ported sub. The amplifier also has a damping factor control to control the amount of ringing to each person's liking. Low damping gives more ringing and hence more full body bass sound and high damping gives the least amount of ringing and thence more agile and articulate bass sound. With one port plugged, the extension can go down to 12hz. The size of the subs is bit on the large size 18" wide, 24" deep and 24" tall. But large size enclosure improves efficiency tremendously. Sealed subs with 15% smaller in each dimension will need 4x the power to achieve the same output.

The subwoofer has been selling for over 3 years and receiving consistently positive feedback. One can google "Rythmik FV15HP" and find out. We also have customer feedback at

The subwoofer for sale has a black oak vinyl finish for $1368. Piano finish version (SE version) is also available at $1649. The amplifier and driver are identical for all finish. This subwoofer has received consistently good review in a recent northeast GTG event. One attendeee who has a pair of 18" subwoofers himself has said he is impressed by FV15HP and this subwoofer is his favorate choice under $1350. 

Feel free to ask questions. Shipping within continental states is included. Shipping to Canada, AK, HI, PR is extra.