F25 Direct Servo subwoofer

Product features include:

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.

• 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

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.

All of our subwoofers feature unique bass extension controls which are not normally provided on 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.

The bass extension controls enable the user to customize the frequency response of the low end. The controls customize a high pass filter, which attenuates frequencies below a given frequency. If set to 14 Hz, bass below this point will be filtered. 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. The combination of 28hz and low damping is recommended for maximum SPL ouptut for all of our sealed subwoofers.

For customers with an AVR or pre-processor, we recommend LFE inputs which bypass the crossover control. In this case, the crossover should be controlled via AVR. If you are still using stereo receiver or conventional pre/power amp setup with no bass management, then we recommend LINE input and set the crossover/phase controls to where the front speakers start to roll-off. Please refer to quickguide of the model for recommendation. To understand more about how to correctly integrate your subwoofer, read our phase alignment article.

With many subwoofers, it is difficult to get a correct and seamless integration with the main speakers because the amplifier settings are often very different to the measured response. You may set the crossover point to 80 Hz, but the actual crossover point may be anywhere between 60 and 100 Hz!

With our subwoofers the upper and lower -3 dB points are a very close match to the settings selected. If you set bass extension to 14 Hz, that is exactly what you will get. All this is possible because Direct Servo ensures a stable and flat response.

Output, extension and user preferences

We use high quality high excursion drivers which make it possible to achieve high output in a relatively compact enclosure. Only with Direct Servo is it possible to achieve such deep bass extension, high output and very high damping simultaneously. The effective system Q is 0.3. A lower Q factor represents a higher level of damping, indicating control of the cone. A typical subwoofer has a Q of 0.707 and some achieve a Q as low as 0.5. The penalty is that the box is larger and the output is lower in order to achieve lower damping, but Direct Servo can achieve much lower damping without sacrificing output and making the box bigger.

When more output than one subwoofers can provide is desired, it may be tempting to look for a higher output option. Our subwoofers represent what we consider to be the output limit for an affordable and accurate subwoofer. It’s possible to get higher output with one subwoofer, but not without significant compromise and additional cost. We suggest multiple subwoofers as a much better option. A side benefit is that this can also improve the integration with the acoustics of each particular room.

The bass extension controls allow the user to customize the deep bass extension and the rumble filter to control cone excursion. For high SPL, one can set a higher cut off. For music one may prefer a lower cut off. Changing the settings can also result in a better integration with the acoustic gain of the room.