BTW. The ideal dimentions for the cabinet should have the ratios of 1:1.6:2.6
Aparently this Golden ratio gives the flattest frequency response curve. If you make the cabinets too narrow in their response, they will tend to give their own distinct accent to anything that is played on them. (very "Low Fi").
For the same reason, when you look inside decent speaker cabinets, you'll find that they are lined with anechoic material. It's the speakers that are supposed to supply the sound, not the box they're mounted in.
I know a lot of people like to have a really resonant base, and achieve it by mounting their speakers in large resonant cabinets. But if you really appreciate music, you should let the musicians (and to a lesser extent your amplifier settings) decide what it sounds like, not your speaker cabinets!
For the reasons I have just given, it should make very little difference what the resonant frequency of the cabinet material is. A decent speaker cabinet design should, as far as possible, minimise it's influence on the output. (rather than use it to super impose an artificial effect).
Just a personal opinion. If you like a droning base, make the cabinet ratios 1:1:1 (ie a perfect cube) and as large as possible, with a hard shiny surface inside, (such as laminate).
To calculate the resonant frequency of the case, take the largest dimention of the enclosure. Multiply this by 2. Divide this figure into 340.29 Metres (distance travelled by sound in a second). The resulting figure will be the resonance frequency (in Hz).
Hence, to give your cabinet a resonance of concert pitch A (440Hz) you would need to make your cabinet dimentions 38.67cm.