SW-12-04 Servo Sub Woofer


The SW-12-04 sub was specifically for the discerning audiophile looking for the ultimate in accuracy and sound quality.

Mechanical Drawings: Here



The SW-12-04 sub was specifically for the discerning audiophile looking for the ultimate in accuracy and sound quality. It is meant to be used with the Direct Servo plate amps. Direct Servo is a patented technology that is far more effective than any other servo control systems of the past. No other sub-woofer system on the market offers this level performance. With this sub-woofer system you will hear articulation and resolution in the low bass region far beyond standard passive systems regardless of how well the woofer is made. Distortion levels are also extremely low and well below other sub-woofer designs.  The SW-12-04 gives new meaning to the terms fast bass. Fast bass has been a debatable term but really refers to a drivers ability to return back to a resting position. Any other sub must rely on the suspension alone to allow it to return back to a resting position. Any sub capable of playing down to the 20Hz range will also need a very heavy cone and a really low Fs. The heavy cone and its stored energy from the inertia of its movement make it difficult to quickly return to the resting position. The Direct Servo controlled sub can make use of a much lighter weight cone as the servo system will virtualize the parameters and add output as needed to maintain a flat response to below 20Hz even with a light weight cone that has a higher Fs. Not only does the light weight moving mass minimize the inertia but the Direct Servo control system effectively slams on the brakes electrically to much more quickly bring the woofer back to its resting position. Due to the electrical control of the Direct Servo system a larger than typical optimal box can be used to allow lower levels to be reached with less amplified gain. We recommend a sealed enclosure in the 1.5 cubic feet range (per woofer). Ported enclosures can also be used with the Direct Servo system for additional output levels.

SW-12-04 parameters:

Mechanical Parameters:

  • Fs = 21.3 hertz
  • Qms = 4.308
  • Vas = 4.849 cu.ft or 137.3 liters
  • Cms = 0.071 in/Ib
  • Mms = 4.903 oz or 139 grams
  • Rms = 9.495 Ibs/sec
  • Xmax = 18 mm
  • Sd = 76 sq.in or Dia = 9.83 in or 250 mm

Electrical Parameters:

  • Qes = 0.298
  • Re = 3 ohms
  • Z = 4.0 ohms
  • BL = 13.7
  • Pe = 200.0 watts (conservative rating)

Combination Parameters:

  • Qts = 0.279
  • Sens = 88.4 dB (2.83 V)

Additional information

Weight 22 lbs
Dimensions 17 × 17 × 11 in

Cabinet Plans

Standard single woofer cabinet plans are available here: singleservo

Cabinet plans for the “Sand Box” (sand filled box) click here: sandbox

Here is an Audio Circle thread on the “Sand Box” with pics.


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