[looneybomber]

I don't have WinISD with me, but from what I remember, the Mal-x 18 is better suited in a 16-20ft box tuned around 14hz...The next biggest hurdle is how big your port should be, but somewhere around 65-75in² should work great.

In order to get that big of a port to fit in a 10ft² box would mean either a real long port (low 1st port resonance) or a higher than optimal tune.

Here's another thing to look at. Model your sub with 1450w and make sure it doesn't go much past xmax within the pass band. If it does, you either need to shrink box size, raise tuning, or don't "crank it to 11".

 

[looneybomber]

RXP, using Mike P's models, the next thing to look at are excursion levels with 1450w. Do either cross xmax?

My thought on the whole box/power ratio, is get the driver close to it's limits (xmax or even a tad beyond) with the max power you will send it. For sealed enclosures that's super easy because all you do is change box size. For ported, you change box size and tuning points. If the box is too small you won't get as much output because you become amp limited. If the enclosure is too large, you become excursion limited and risk damaging the driver if you push it too hard.

Eventually you can balance everything out for your needs.

 

[looneybomber]

If you want to design different subs, one that will work awesome for movies and one that will work awesome for music, you really should spread the tuning points out on them. A purely for music sub would work well with a tuning of 25-30hz for the type of music I listen to. Most PA subs have an f3 of about 40hz so you could get away with even a 35hz tuning and an 18" pro style woofer. Then build a real large enclosure, tuned real deep for the Mal-x and cross them over with a DCX-2496.

Another thought (since you already have 3 M-x's) is just use multiple LLT's with the Mal-x; all of them being real big and tuned low. Sure, just one wont be as efficient or have as much output from 35-80hz like a higher tuned PA style, but you will have multiple subs covering the same area as opposed to one covering the deep bass and one covering the midbass.

Or, go with the in between design. 11ft tuned to the upper teens. You won't get crazy deep, but the 20-35hz output should be greater than the LLT.

Or, try...

Point is, there are a lot of options and I cannot give you a correct/best answer for your specific room and your needs.

If it were me, if I was putting them in a large room where size didn't matter and I'd not be moving them, I'd build really big boxes, tuned real low, and I'd have four of them. If I ever thought I'd have to move them around, I'd go sealed.