18sound 18” Dual Subwoofer build

Hi

Slight OT at first - Violin/cello makers map the resonances with rice grains. They put violin body pieces above a speaker cone, some 5cm away, and watch the grains making a pattern. I once made a 10-100 Hz 10" closed box and suitable analogue oscillator to a violin luthier as tuning tool. Of course the maximum spl is not the point here.

Back to the point;

I've done resonance mapping just like Ceharden says, on unbraced empty cabinet prototype but with rice grain or just feeling un-braced cabinet sides with my fingers and marking resonance nodes with a pencil. Almost every time node points form a pattern, just draw straight lines with ruler through these points and there are your required bracing lines visible. Therefore its handy to have one side of the prototype cabinet attached by screws and sealed with window weather stripping.

Usually I use 10-500Hz continuous sweep signal at first, naturally at sensible SPL level. Watch out the driver excursion! After bracing cabinet, apply recommended or calculated processing and repeat approaching nominal RMS power.

Do you mean the braces that are on either side of the baffle that aren’t touching the baffle? I extended them to touch the baffle after posting this, but I’m not sure if the drivers will fit to mount when done this way. Otherwise the back is joined with the baffle via the port divider, which is also sitting in a groove within the baffle.

Here's some photos I've snapped during the process.

Bracing structure cut on the CNC in three pieces and glued together with half-lap joints. And my cut list.

Milling the baffle. The CNC is 600 x 900 mm, so I couldn't mill the whole thing. 

So I decided to cut part of the second opening and make a jig that attaches to the mounting screws so that I can use a router with a flush trim bit (actually, I used a scroll saw to remove most of the material before using the router).

Voilá!

Dry-fitting everything before screws. The bracing sits in a 7mm deep groove all around, and the baffle sits in a 7mm deep groove on every side as well. 

A lot of screws, I know... But I want(ed) everything to sit as flush as possible, so I don't need to fill a lot of potential gaps. 

Here's how it looks now. Everything is screwed in place from outside to inside. Still need to route the holes for handles and Speakon. After that, I will take it apart, sand, and put everything except the top back together with glue and hide the screws with some woodfiller. Then I will use some silicone (or something else?) around the inside seams to make sure there is no leaks. 

Would you recommend to put silicone, glue, or something else in the screw holes with the screws?