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5. DD Box Design

In order to get the most performance from these non-optimum applications we have taken a different design approach. Vehicle interiors have limited space, so we started our research on making the most bass energy from a specific amount of space. The key is to extract maximum energy from a limited resource, cargo space.

We engineered a high efficiency type of ported box, then set about engineering a speaker to optimize the box energy. We keep the moving mass low, energy high and add a suspension with high restoring force to help control cone motion. This means that the subs will not have to rely on the box for their loading.

The vehicle itself will offer some loading to the system, and the transfer function will make the system play an octave lower than the tuning freq. So, if you could find some speakers that could stay in control below the box tuning, subs that are really tuned to the box loading plus the car loading, you could design a system to play low, loud and do it in a relatively small box. That is the DDbox.

Each Sub Series we make is designed to work in the DDbox system. Each size sub in the series is designed for the same airspace and same response. They all get the same motor, the same spiders, suspension throw and power handling. The 10 inch size will play just like the 15, but do it in a much smaller space.

Box Sizes for High Efficiency Subwoofer Systems.

^ft = cubic feet | sq" = square inch
All volumes listed are after vent, and subwoofer displacement; a.k.a. NET volume
This chart is for tuning boxes in the 35-40Hz range.

Get the DD Space Makes Bass Shirt.

Volume # & size of Drivers Port Area & Length
0.75^ft  (1) 8" 11.25 sq" vent x 22" long 
1.00^ft  (1) 8"  15.0 sq" vent x 23" long
1.25^ft  (1) 8" or (1) 10"  20.0 sq" vent x 23" long 
1.50^ft (2) 8" or (1) 10"   24.0 sq" vent x 22" long
1.75^ft (2) 8" or (1) 12" 28.0 sq" vent x 21.5" long
2.00^ft (2) 8" or (1) 12" 32.0 sq" vent x 21" long 
2.25^ft (2-3) 8" or (1) 12" 36.0 sq" vent x 21" long
2.50^ft  (3) 8" or (2) 10" or (1) 12" 40.0 sq" vent x 21" long 
2.75^ft  (3) 8" or (2) 10" or (1) 12" 44.0 sq" vent x 20.5" long
3.00^ft (3-4) 8" or (2) 10" or (1) 15" 48.0 sq" vent x 20" long
3.25^ft  (4) 8" or (2) 10" or (1) 15" 52.0 sq" vent x 20" long
3.50^ft (4) 8" or (2) 12" or (1) 15" 56.0 sq" vent x 20" long
3.75^ft (3) 10" or (2) 12" or (1) 15" 60.0 sq" vent x 19.5" long 
4.00^ft (3) 10" or (2) 12" or (1) 15" 64.0 sq" vent x 19" long
4.25^ft  (3) 10" or (2) 12" or (1) 15" 68.0 sq" vent x 19" long
4.50^ft (3) 10" or (2) 12" or (1) 15" 72.0 sq" vent x 19" long
4.75^ft  (3) 10" or (2) 12" or (1) 15" 76.0 sq" vent x 18.5" long
5.00^ft (3) 10" or (2) 12" or (1) 15" or 18" 80.0 sq" vent x 18" long 

  1. Any available space larger than above chart, simply use the chart to determine what multiples of subwoofers you can choose from.
  2. The above info and chart works with all DD Series woofers.
  3. We recommend to allow at least several weeks of playing time to break in DD Woofers, full break in may take many months. DO NOT play subwoofers at max amplifier power in the first couple of days, give the suspensions a chance to loosen up. As the suspension breaks in, the subs will play lower and louder.
  4. After you give the woofers a chance to break in (you'll know when this happens because the woofers will be playing lower and louder) you can start to look at port changes to alter the sound to your personal taste and your vehicles acoustic loading conditions.


The DDport was developed with the DDbox to increase the overall efficiency of the system and broaden the power response curve as discussed previously. In order to keep a 3-1 ratio of cone area to port area, use the following formula:

16 square inches of port area per cubic foot of box volume, make the port 18-20 inches deep. The port is tuned to the box volume, not the subs.

This generally tunes the box to the upper 30Hz area, with the vehicle transfer function extending the frequency another 10-12Hz or so. This is the most popular all purpose tuning.

If the system is primarily playing bass tracks and electronically massaged music, extend the port length in the 24-28 inch length. The box will lose a little upper frequency response while adding extending the low frequencies.

Once you determine how much space you have available, divide the sub(s) into that space. Don't cram the space, its better to error on the big side than the small side. A 10" sub will outperform a 12" sub if the space isn't big enough.

The proper combination of a vented enclosure coupled to a driver that is suited for this application can give a substantial increase in output for a given input power and yield outstanding SQ. A vented enclosure has increased output due to the fact that it has an increased effective radiating area.