[dgilme]

I think what you have looks great. I'd offer one alternative.

Since you are putting the box in the garage, is an Infinite Baffle setup an option? You could have 2 18s or 4 15s in manifold with the opening in your wall being basically the same size as the shiva box you have planned. That would help with the "musical" ability of the sub if you are of the camp that says ported subs don't sound as good as sealed for music.

 

[dgilme]

I was thinking something like this sounded like it would work great for you.

Put 4 of Kevin's DPL-15s in, 2 in each manifold. Trust me I've modeled the out of it and drooled over the results. Sadly the wife is still not sold on the idea of a big hole in the ceiling and is scared of the back waves making the rest of the house "boomy" since I have to use an attic not a garage.

On the topic of your box though, the second bend in your port may not be a good idea. Is the box tall enough to run it straight up and have enough clearance? I've been under the impression that keeping the opening of your port as far away from the driver is the best way (but not 100% necessary).

 

[dgilme]

Here is the spl from 1 ported shiva in the box you describe (with a high pass filter) vs 4 dpl-15s in an IB setup, dpl in yellow: