Building a Cab-Depth Formula

I was told that the depth of the speaker cab, makes a difference in the sound, as does open or closed back. Is there a certain mathematical formula to follow to determine the proper depth. And should I go with open or closed back.

I will be using Eminence Legend 125 speakers, in a 2 X 12 configuration.

I have never heard of depth having anything to do with that. Coming from a professional car-stereo-enclosure-for-killer-bass point of view, I do know that you should have at least 2 inches from the magnet and the back of the cabinet in order to not overheat the voice coil. (yet that little vent on the back of the speaker really does something).

I know that in a bass enclosure, the size of the enclosure matters for tuning reasons, but I don't believe it is very critical in a full range speaker.

I'm building the cabs for my guitar rig, not for a stereo.

Reading this thread may give you some ideas. Using the search icon at the top of any forum page can dredge up all sorts of stuff from previous threads.

If you're brave, (and wealthy), you can get into some interesting experiments that may, or may not, expand the collective knowlege in the field of speaker enclosures.

To reply to your original question: The depth of the cabinet is just one dimension, along with the height and width, that determines the volume of the cab. The volume is a major factor in determining the resonance of the cabinet, which in turn affects how it reacts to the speaker.

If your existing speakers came with a tech sheet in the box, usually you will have an ideal number to go by airspace wise.... BTW cabinet design is universal... all the principals are the same. The only difference is the way a speaker will react. That is why they give you all those nifty numbers they call "theil-small parameters"

Anyways if they give you an idea box size like 1.25 cu.ft. per driver, you can use the formula LxWxH/1728 to get cu.ft. Be sure to use INNER dimensions to get your airspace and not OUTER. an inch and a half all the way around can make a large difference in how the driver reacts.