internal volume calculation / damping / BR box


Lets say I need 100L internal volume for a BR box (bass driver only in this box).
This means I subtract:

1) the volume that the woofer itself occupies internally, 15in woofer in my case, for example by creating a 3d cone in order to simulate the magnet etc.
2) the bass reflex volume (the pipe for example).

3) ... this is where Im not so sure... how do I treat the damping material? Lets say I use a felt (8mm) all around, and some areas I use acoustilux (Cabinet-damping).
How do I calculate the volume I need to subtract for material that is not 'fully solid'? is there a factor/multiplier (less than 1.0)? Especially for acoustilux.

Any point to good reads regarding damping and calculations welcome!!


2013-11-24 8:13 pm
There are countless simulation software around which can account the damping material inside the box.
Rule of thumb is that, if you use some damping material, your virtual volume gets larger until you overdo the stuffing.
For BR, you don't want to fully stuff the box anyway, because you can easily block the port(s) that way and you get a closed box or aperiodic tuning, but these alignemnts can be advantegous too in some cases.


Paid Member
2008-10-18 11:31 am
Damping tends to make a box seem larger, when enough is used. Some suggest not overdoing it in a reflex box, but it still has a job to do. The rule of thumb is to ignore it. On the other hand there are box simulators that claim to deal with damping by specifying how much.
thank you both.

As Im designing my box in a parametric CAD software I was hoping to do the final net volume calculations there. (after I get the required tuning/volume parameters from a box software) I have a complex CNC'd structure so I need to also include the bracing etc in the net calculation.

I also didnt know that damping make the box "virtually" bigger!! thanks!
As you can see in Troels' link Im planning to follow his approach. not super stuffed.

Any links or pointer to good reads regarding damping?