Been working on this for a while now. I've not been able to find a template for something like this, so made it up on my own. Thought it might be nice to post and maybe give ideas to others.
Wanted to replace my Rythmik E15 because, as nice of a sub as that is, it just couldn't fill my open space. These Dayton 18" Ultimax subs definitely fit the bill. I am surprised at how much tighter and deeper they play than the E15. I thought I was just missing volume, but not true! The overall quality of bass and impact is impressive. I especially notice the difference at low volumes where the bass before seemed to disappear. Now, my couch will shake with low tones even at volumes when the kids are asleep.
Fyi the other speakers are also custom builds using SB acoustics drivers in an MDF enclosure with a mottled makore veneer. Selah Audio designed the crossovers after I built the boxes. Took one of the grilles off for reference.
These are 2 18" each in their own (but connected) 4 cu ft boxes made of 3/4" MDF with 1.5" baffle.. I lined the boxes with some heavy duty foam (1/2" neoprene) to absorb vibration and made the shell out of 1/2" ply covered with rough-sawn pine. No hard connections to the sub box to help avoid transmission of vibration. The shell sits on the foam and uses L-brackets resting on foam pads on the back of the sub box to make sure it doesn't vibrate forward/backward. It floats off the floor...only the sub box touches the floor.
The openings for the subs are perforated sheet metal with a oiled bronze finish (difficult to see in the image). The top is 2cm albarene soapstone. The subs are powered by a Behringer nu6000 dsp.
The furniture matches the rest of the room and ths sound is killer. We are enjoying it! There were no resources for a project like this when I started so hopefully this can be one for anyone interested in building something in the future. I highly recommend these Ultimax subs!
Nick