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Budget Friendly 15" Servo Subwoofer!

FVX15, a lower power version of our highly regarded FV15HP, is our answer to the need for a "bang for buck" home theater solution that retains the dynamic and accurate bass that we have become known for.

Correctly integrated, our vented subwoofers can achieve the tight bass normally associated with a sealed enclosure, yet with greater low frequency output. We recommend this subwoofer for systems in which home theatre has a high priority. FVX15 also features multi-tune capability. Customers can select either one-port or two-port operation.


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Direct Servo Technology

All our subwoofers use our patented Direct Servo technology, providing high end performance at an affordable price. It allows us to use lighter and more efficient drivers and still achieve deep bass without using excessive amounts of power. The servo reduces memory effects, counteracts thermal compression and various forms of driver non linearities.

HX405 Amplifier and DS1502 Driver

FVX15 uses our new Hypex UCD HX405 servo amplifier and DS15102 driver. DS1502 features anodized aluminum cone, a 3" voice coil, and 200 oz magnet. Its linear excursion range has increased to +/- 20mm (from +/-15mm of DS1500). The quickguide of the amplifier can be found here



Features & Options

Product features include:

  • Patented Direct Servo technology
  • Hypex Ucd module-based amplifier with toroidal power transformer and two large 12000uF/80V capacitors
  • 15" black anodized aluminum high excursion driver
  • Solid and very inert enclosure with multi-tune feature
  • Bass extension control allowing adjustment of bass extension and excursion control
  • Selectable 12/24 db/octave crossover filter slope

Direct Servo technology

All our subwoofers feature our Direct Servo technology, which is our secret to achieving tight and accurate bass. The benefits are far more than simply achieving low distortion.

Direct Servo closed loop technology

Learn more in our technology articles >

Hypex Ucd module-based amplifier

Hypex Ucd modules are known among audiophiles to be one of the best sound class-D modules. While class-D can reduce the footprint of amplifiers, other companies have further incorporated switching power supplier to save cost and space. However, the disadvantages of switching power supplier are complexity of circuit leads to higher failure rate, higher compression at high transient current demand, and inflexibility of 120/240V switchable operation. The amplifier in FVX15 uses conventional toroidal transformer to address these issues. In addition, two large US-made (CDE) 12000uF/80V power filter capacitors are used to ensure stability of power supply even during the most demanding HT special effect.

15" black anodized aluminum high excursion driver

Driver features include:

  • Rigid silver anodized aluminum cone ensuring control at high SPL
  • Low moving mass to ensure an exceptional transient response
  • High flux density in the gap to ensure low distortion
  • Flux de-modulation shorting rings to lower inductance and improve linearity
  • Extended upper bandwidth response allowing a higher crossover point than most

While designed primarily for their sound quality, these custom designed drivers are also stylish in appearance with a anodized aluminum cone and rubber surround. Unfortunately, it's not possible to judge the accuracy of a driver by observing its appearance. There are other drivers on the market which in fact look quite similar, and it's tempting to think that they are comparable. Many of them are inferior in performance due to a heavy moving mass, the absence of shorting rings, wider gaps around the voice coil and high inductance which limits the useable high frequency cut off point. Many aren't suitable for a crossover point higher than 50 Hz. This is very limiting when one considers the large number of home theatre speakers which perform better when relieved of bass duties.

Read more >

Quality enclosure

Our enclosures are very solid and well braced to minimize any cabinet resonances or coloration. The baffle into which the driver is mounted is double thickness.

We also provide a range of finishes. Our range of attractive and excellent value vinyl finishes including:

  • black matte
  • black oak

Bass extension controls

A370 controls The bass extension control in FVX15 enables the user to customize the frequency response of the low end. It combines multi-tune specific frequency contouring and damping control in one switch. The damping control determines the slope of roll-off and the amount of time domain ringing. High damping provides the least amount of time domain ringing and the most gradual roll-off curve. Low damping provides the steepest roll-off at the low end at the expense of added time domain ringing. There are two positions for 1 port operation which extends to 12hz. 1P-music uses high damping while 1P-HT uses low damping. High SPL playback should use 2 port setting. The damping in this position is low.

Crossover options

To suit different setups, we provide a 12 db and 24 db/octave crossover. If you are still using stereo receiver or conventional pre/power amp setup, then we recommend the 24 db switch setting. To understand more about how to correctly integrate your subwoofer, read our phase alignment article.

120V-240 Switchable Voltage Selection

Correct voltage must be selected before use. Voltage switch is shown below.

voltage selection


FVX15 uses our new Hypex module based HX405 amplifier. We also develop a new DS1502 driver featuring two stacked 25mm magnets to improve excursion limit. Its physical dimension is exactly same as FV15HP. As a result, one can expect the full benefit of FV15HP design but with 2.5db less output.

Driver DS1502 15" high excursion with custom sensing coil
Driver materials Black anodized aluminum with rubber surround
  Cast aluminum basket
  Aluminum flux de-modulation shorting rings
Amplifier 400RMS Hypex Ucd module based patented servo controlled
Dimensions 18-1/4"(W) x 24-1/2" (H )x 24-1/4"(D) - (26-1/2" D with grille and control knobs)
Shipping Weight 120 lbs (net weight 100lbs)
Frequency Response 12 - 200 Hz (-2 dB @ 17 Hz, -6db@12hz) with LFE input
  12 - 90 Hz (-2 dB @ 17 Hz, -6db@12hz) with LINE IN input
Multi-tune 18hz (2 ports) and 12hz (1 port)
Crossover slope Selectable 12 or 24 dB / octave
Crossover range (Low pass) 30 - 120 Hz (Line level frequency response tops out at 100hz)
Rumble Filter (High pass ) 18 Hz 18 dB / octave for two port tuning
Phase adjustment 0 - 180 degrees continuously variable
Bass damping factor settings Q=0.5 (1P-music) and Q=1.1 (1P-HT and 2P)and low (Q=1.1)
Finishes Available in black matte vinyl and black oak vinyl
Warranty 5 years warranty on driver and 3 years on electronics
  45 day satisfaction guarantee


FVX15 has two port openings. With one port open, the max extension is 12hz and the bass extension toggle switch should be set to either 1P-music or 1P-HT. The latter is recommended for HT playback. The bass extension toggle switch needs to match the number of ports used.

In the following is the frequency response when bass extension is set to 1P-HT with one port open.

sealed response

Fig 1.0 - FVX15 Frequency response chart with LFE input 1P-HT and one port open

To achieve lower group delay in one port operation (such as for music playback), users can set the bass extension switch to 1P-Music. It has a more gradual roll-off compared to that of 1P-HT. In the following is the requency response comparison between these two modes.

sealed response

Fig 1.1 - FVX15 Frequency response comparison of 1P-music and 1P-HT with LFE input

For highest SPL HT playback output, users should select 2P mode with both ports opened. While the extension is only limited to 18hz, the power of the amplifier is better utilized for audible frequency band instead of less audible sub-sonic band. In the following is the requency response of 2P mode.

sealed response

Fig 1.3 - FVX15 2p mode response with LFE input and two ports open


One important aspect of getting a correct integration is phase alignment. We have written a guide on how to achieve a phase aligned subwoofer. More >



These are some of the finest subwoofers ever manufactured and the difference in sound quality between these subwoofers and the typical big-box ported subwoofer is surprising. You will hear the difference the very first time you listen and as so many have said, you will never go back to a non-servo subwoofer.

Rythmik FVX15 15" Ported Subwoofer

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