The DD Box

The DDbox was developed over a period of about 10 years, through countless speaker designs, box designs, car types, music sources and power levels.  The goal was to come up with the best all purpose design, that worked well in most vehicles, while providing the standard from which users could fine tune the sound to their personal tastes.

The resulting in-vehicle response from a DD woofer and DDbox provides wide bandwidth and excellent power response, meaning you get low bass, clean bass and a lot of it.  There are many factors and design elements that must work together to bring about this output curve, many more than a single speaker spec, box tuning number from a computer model or power rating.  Getting the most from the system required all variations to be tried and design paths followed to achieve higher performance.

The DDbox and DDwoofers are designed to maximize efficiency from the in-vehicle response at 35-45Hz.  The unique suspensions of the DDwoofers allow them to stay loaded below box tuning and provide wide bandwidth response from 30Hz to low pass cutoff.  The DDbox system uses acoustic loading from the vehicle, the box/port and built in loading from the woofer suspension to generate its broad output curve.

The DDbox system also takes into account the wide power curve needed for our enthusiasts demands.  The DDbox sounds good at low volume and stays clean at extremely high power inputs also.  The low speaker cone area to port area ratio is a key to keeping velocities low and clean output high.  This places harsh demands on the woofer motor, suspension and coil which is why there is more to a DDwoofer than meets the eye.  The DDbox will model different in every box program someone has written, we aren't really interested in what number a model spits out.  We invested our time in literally 1000s of real world applications, using real music, real power and real people deciding what really bumps and what doesn't.

The DDbox system is meant to be your starting point to your final system design.  We suggest using the DDbox/DD woofer combo for a few weeks or months to let the suspension break in.  We build the woofers for long term sound quality and this requires our unique suspension method.  The DDbox/woofer will play lower and louder as the woofer loosens up and stabilizes.  Then you can make port adjustments to fine tune the sound you like, add port length to tune lower, subtract to tune a little higher.   The actual tuning freq you end up with doesn't matter but what sounds good to you should be the goal.  Remember, you aren't listening to a number, your listening to what moves you.

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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.

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. Sure that you have noticed these stats are all vented, we have the chart this way for a reason. (Refer to "Why go ported?
  3. Yes, above, you read right. The DDW6.5 can double as a potent subwoofers in situations where you can't get performance out of a larger subwoofer.
  4. Here is the basic breakdown for each size sub, in cubic feet: 6.5"(.4-.6), 8"(.7-1.0), 10"(1.2-1.5), 12"(1.7-2.5), 15"(3.0-4.5), 17"(4.5-6.0). The port formula is 15-16 sq. in. of port area for each cubic foot of box volume. A port length of 18-20 will generally give you an open air tuning around 40Hz. The average in-vehicle sweet spot will be 7-10Hz lower. Remember, the port is tuned to the box volume, not the sub(s).
  5. The above info and chart works with all DD Series woofers.
  6. 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.
  7. 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.