i am gonna build a box sealed and i have just purchased a used 15" mag off a guy for a good price. i want the volume to be 2.5 cubes and have figured out the size i want to accomidate it in my chrysler 300 trunk. the measuremants will be L 24" H 18" and W 10" which comes to exactly 2.5 cubes and i want to know is the width of 10" enough since it requires a mounting depth of 8 1/8"?

Actually, you will have less space than that.

Assuming those are your external measurements and you're using 3/4" material, you only have 1.82 cubic feet of internal airspace. I know for a fact that you will not be happy in this application. You need to find some more volume or get a different driver.

Now, if those are the internal measurements, you are fine for both volume and pole vent clearance.

As a general rule of thumb, you should allow at least and inch of clearance from the pole vent to any object.

as long as you can get about 2.25-2.5 cuft after driver displacement you will have great performance out of it.

Mine is in a 2.45 sealed (using the same box for my new one as my old one) and I love it. As I am sure you know you get more spl out of a ported enclosure but to really let the Mag shine on sq go sealed.