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Dual 8" Audiophile Direct Servo Subwoofer

For audiophiles looking for uncompromising accuracy in both bass and the upper bass frequency range and for a higher crossover frequency up to 250hz, our F8 subwoofer is the ultimate choice.

arrow Patented Direct Servo technology
arrow 600 watt class D Hypex amplifier
arrow Adjustable damping and mini-XLR input

*Black Matte matches our 170/340/200 speakers

arrow Free continental US ground shipping
arrow 45-day satisfaction guarantee

Massive Dual 8" woofers

F8 Woofers
  • Low moving mass paper cone and foam surround to ensure exceptional transient response
  • Large magnet for high flux density in the gap to ensure low distortion
  • Flux modulation shorting rings to lower inductance and improve linearity
  • Extended upper bandwidth response allowing up to 200hz crossover point (-6db at 250hz and therefore can be used for Linkwitz Riley for crossover point up to 250hz).

For audiophiles and enthusiasts looking for uncompromising accuracy in an elegant compact package, the F8 subwoofer is the ultimate choice. It features two low mass 8" drivers with our Direct Servo technology to ensure accuracy and definition. This sub is designed to effortlessly play up to 250hz . While there are already many subwoofers on the market which can play deep bass, their sound quality and transient response degrade as the frequency goes up above 120hz. The F8 is a subwoofer that can cover more than a decade of frequency range of servo control from below 20hz to 250hz.

As a discerning listener you appreciate that bass is the foundation of a satisfying music or home theater experience. You also appreciate that there is more to a subwoofer than shaking the room, and that music and home theater can be far more satisfying with a subwoofer that can play deep and maintain its accuracy.

What makes this subwoofer unique? It's not that it can plumb the depths with authority. There are already many subwoofers on the market which can do that. The difference is that this subwoofer will reproduce bass with a level of realism that matches what our loudspeakers are known for...

We are most proud to represent these astonishing new subwoofers.

Direct Servo technology, US Patent #6,104,817: What is it?

Direct Servo Diagram

Conventional subwoofers have extremely high distortion. Well regarded conventional subwoofers typically have measured distortion levels exceeding 15% at 20 Hz at 100 dB. This includes many subwoofers costing more than US $3000. We think this is far too high. A well designed servo subwoofer will achieve distortion levels under 3% under the same conditions.

A servo is essential in a subwoofer that aims to be true to the original source material. The benefits are clear:

  • No voice coil thermal-induced compression or distortions.
  • Spider and surround distortion reduced by 6 - 9 dB
  • Flat frequency response that is less dependent on T/S parameters.
  • Audiophile bass sound at an affordable price: articulate, tight, transparent, and well-defined bass

These benefits are all unique to a servo controlled subwoofer, and can't be achieved in a practical and affordable way without a servo.

How it works

Direct Servo uses a very thin sensing coil which is wound adjacent to the voice coil. This coil induces a signal which is fed back into the summing points of the amplifier. This signal is used to correct sources of distortion, and this is achieved without placing any active devices such as transistors or operational amplifiers in the signal path. This simplicity eliminates any secondary or mechanical effects which plagues other technologies.

What are memory effects?

A subwoofer driver contains parts which have a memory effect. This means the driver will not respond perfectly to the signal. The spider and surround both contribute to memory effect in a driver. The voice coil which carries the signal that drives the cone also exhibits a memory effect. This is because the temperature of the voice coil changes with operation, and this changes the resistance. The result is a loss of dynamics. As the driver excursion and power input level increases, both effects get worse in conventional subwoofers. Detail and resolution is lost.

Direct Servo corrects both mechanical and thermal memory effects. The result is much lower distortion, and bass that is true to the original, preserving the subtle details, capturing dynamics and revealing a level of detail well beyond the reach of most conventional subwoofers.

How is Direct Servo different?

The primary philosophy is to make audio products as simple as they can be. Less is more. These subwoofers put as little into the signal path as possible. This approach applies to the amplifiers, Direct Servo technology and drivers. Most servo subwoofers use an accelerometer, which is another mechanical system with its own limitations. Also extensive protection circuits are required, and these further degrade the signal. As a result, accelerometer based servos are not as accurate as Direct Servo. The superiority of Direct Servo is derived from its simplicity.

Frequency Response:

In the chart below, with bass extension controls set to Low Music, the response is 3dB down at 20Hz. The response is flat and extended.

F8 Response Graph

F8 features bass extension switch allowing users to select among 3 different modes: Low Music (Q=0.5), Low HT (with a 18dB/oct rumble filter at 20hz), and High (with 18dB/oct bass extension at 28hz).

F8 Response Graph

Unique bass extension controls:

All of our subwoofers feature unique bass extension controls which are not normally found on consumer subwoofers. This enables the user to customize the output and extension to achieve the best compromise in any room. Most subwoofers neglect to provide bass extension control, and the result is that dynamic headroom is compromised.

F8 ControlsThe bass extension control enables the user to customize the frequency response of the low end for the best trade-off between output and extension. If set to low music, bass below 18 Hz will be filtered. The damping factor of this mode is 0.5 for the best time domain response. However, the disadvantage is slower attenuation of subsonic signals. For HT application, we recommend low-HT mode which incorporates a 3rd order highpass filter to filter out subsonic signals below 20hz. High extension setting is recommended for application where longer playback time and lower power consumption is required.

To suit different setups, we provide a 12dB and 24dB/octave crossover (as shown in the above photo) with adjustable range from 50hz to 200hz.

RCA input and mini-XLR input:

F8 Controls

120V-240 Switchable Voltage Selection:

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

F8 Controls


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...

Specifications F8:

F8 uses two Hypex Ucd class D modules in the power amplifier with each module independently driving an 8" driver. Hypex Ucd modules are considered as one of the best sound quality class D modules available. The standard amplifer is HX580 (300WRMS x 2 for a total of 600WRMS), It has one RCA and one mini-XLR input. The quickguide of the H580 amplifier can be found here. Three different finishes are available: piano black, black matte vinyl, and black oak vinyl.

Frequency Response (Anechoic) 18 - 250 Hz (-3 dB @ 20Hz)
Woofer dual 8" high excursion with custom sensing coil
Woofer Material Paper cone with lightweight foam surround, cast aluminium basket, copper flux modulation shorting rings
Amplifier 600WRMS class D (dual Hypex Ucd modules)
Dimensions W x H x D 11" x 20" x 15.5" (with grille)
Shipping Weight 68 lbs each
Crossover Slope Selectable 12 or 24 dB / octave
Crossover Range (Low Pass) Continuously variable 50 - 200 Hz
Rumble Filter (High Pass) 20 Hz 18dB / octave
Phase Response 120 degrees phase shift at 20 Hz
Phase Adjustment 0 - 180 degrees continuously variable
Bass Damping Factor Settings Low music (Q=0.5), low-HT(Q=0.9), high (Q=0.8)
Finish Piano Black, Black Matte, Black Oak
Standby Power 7W (standby, red light), 13W(ON,green light)
Warranty 5 years on woofer / 3 years on electronics
45-day satisfaction guarantee