Expert: Cleggsan - 3/16/2009

Question
I'm a woodworker by trade and have been asked to build a box for a subwoofer.  After looking on a few internet sites I found that just building a quick box for a speaker takes quite a bit more info than I had realized. The subwoofer I was given is a Kicker C12d, Compvr 80 ohm. The guy wants a box built nice enough to place in his home and than eventually in a still undetermined car(trunk). The sites I have seen ask for a freq and other info that I don't know or have that I need to know in order to get a box volume. I am not sure how to get this info or if I even need it to build something that will be used in both a home and auto. I also am not sure about if it needs to be ported or sealed. Any help would be appreciated.

Answer
This page, on the last page

http://www.audiorama.com.br/kicker/kicker_compVR_d.pdf

gives some box dimensions.

Kicker has box design ideas at

http://kicker.com/Product_Manuals/96/355

but you must have more information from which to select from that menu or listing of yearly models.

Your customer should advise you on vented vs closed box design.  You cannot make that decision unless the customer gives you open book authority.

BUT:  Let me make it simple.  There are two approaches to subwoofer box design.  A) For home use the woofer acoustically loads into a big room so the box should be designed using acoustic principles in order to get optimum or selected performance based on the acoustic parameters.  These boxes are usually quite big; most often too big for mounting inside a vehicle (unless we are talking about the back end of a truck or van).  B) For car use or small vehicle, the acoustic space is the cabin of the vehicle and it reduces the acoustic equations to one of sound pressure.  So, the box parameters become less important and the box must be optimized for fit inside the vehicle space and contain the minimum cubic volume.

SO:  The box, once decided whether closed or vented (and I recommend a closed box design for car), you should make at least a 1 cubic foot inside volume.  Shape is not so important as long as it is somewhat cubic in geometry.  If you can squeeze greater volume that will help.  

AND: The box should be of 3/4 wood with good air tight seal at all corners, etc.  

FINAL:  It will work good in the car as these Kickers are designed to give good output with small boxes inside vehicle trunks.  It would not be optimum for big room use, but would work and may be surprisingly good anyway.

Hope this was not too confusing............  

C