"Mega MOFO" Dual 15" PR build

Well I'm finally re-building new subs. The compact "sealed with boost" setup I have now works very well, but I figure I should go bigger bass reflex just because I can. I jumped on CSS's APR15 sale last year ($60 ea shipped!), and got 4 of them. These are very simple to use with the included 900g washer kit and outer attachment point, one could adjust their tuning on the fly at any time.

http://www.creativesound.ca/details.php?model=APR15

I'm reusing my MOFO 152X woofers, and O Audio 500 watt amps

http://www.poweracoustik.com/pa2012/subs-MOFO-152X.html



My intended design is 6.5 ft3, with the dual PR's loaded with the full 900g mass for a 17hz tune. I'm going to down fire the active driver so I dont have to look at it (I considered repainting the blue areas), with the PR's side firing.


My actual box is probably going to be about 0.2 ft3 smaller, which shouldn't be an issue when those dimensions give 7 ft3.

WinISD model of the native alignment


And with the Oaudio's 20hz filter boost added


I'm predicting a rise below 30hz wont be a big deal due to sound perception, but I'm placing the amps out of the enclosures this time just in case I decide to change my amp setup.

Progress will likely be slow, as I'm not a very good wood worker, and am usually pretty busy. If you're a good wood worker, skip this part. I'm going to try and help other newbs out. Most of my clamps are 24" and this box is just large enough to make them useless, so I decided the glue/screw approach would work.

My method was to dry fit the panels, and adjust for squareness. I used clamps with light pressure to keep things aligned.


Once I was happy, I drilled pilot holes (3/32" bit) through the vertical pieces to prevent splitting, and to align everything. I marked to corners with letters so there would be no confusion.


I drove the screws thorugh the top/bottom panels just enough to grab the pilot holes.


Glue (PL Premium) was put on the bottom, a panel set on the screws, and then a few of the screws were drove into the piece to hold it. After both side panels were tacked, the top was set on and tacked, and all of the screws driven in tightly


This is the first set of braces, and where I'm at currently. I measured in equally from the sides and drilled holes, then screwed the braces in place. 2" x 3/4" strips of ply.

Bracing round 2 complete.



So far everything's gone smooth, I'm sure I'll figure out a way to mess up when it comes to the side panels/braces.

Yes, I'm still building these The side panels are only going to be 1/2" ply, so I'm adding stiffeners

I'm building two enclosures, each with a 15" active driver (mofo) and a pair of the CSS APR's.

I'll have to look at for those corner clamps Chop. Do you have a link to the exact one you're talking about?

Round two of side stiffener bracing complete.

Alright, I cross braced the stiffeners, and with that, I fill like there isnt any benefit to more bracing.



I'll have to glue up the sides one cabinet at a time as I dont have enough sand bags for both.

My high tech method for gluing the sides on



Humidity's really low right now, the PL still isnt cured after 24 hours

Here's a good shot of the bracing scheme. This is a pair of # braces tying the sides/top/bottom togethter, a + brace on the front/back walls, with a 4" cross brace connecting them. This entire scheme used a single 24"x28" piece of wood! Regular style window style braces would have used at least three 24" x 24" panels to equal this much bracing

I've got my exact cabinet dimensions now. 25.375" H x 23.75" W x 24.75" D with four of the panels being .704" thick, and two being .45" thick. After subtracting the bracing volume I'm left with 7.15 ft3! I'm figuring I'll lose another .25 -.3 ft3 for the woofer and PR's. The tuning point should be right about 16.6 hz after loading 900g on each.

Finally some progress updates

After flush trimming all of the edges, locating dead center on all of the panels was very simple, and the reason I assembled the cabinets in this manor. I stuck with the simple build techniques, a compass and ruler to trace the cutout diameter.


Jigsaw for a quick and easy job


The PR fits!


Not sure if I'll test fit the woofer for a while, but next up is some round overs, and then finishing.... ugh

Making a little more progress.

Normally I use bondo for all body work, but I want to try something simpler. I really like this plastic wood stuff. It isnt as good or strong as bondo, but it is easy to apply and sand, and it's a very good match for the wood if I wanted to use stain.


Also trying something else new. I rolled fiberglass resin on the cabinet, with the goals being a very smooth surface for paint, and a much more durable surface.

Well I haven't gotten further then the last pic shows, so I cant really say for certain. It rolled on very easy, and fairly smooth.

Just a regular old 3/8 nap roller. My trick to getting good results with a roller is to "de-frock" it. I'll have to take a pic when I do the second half of my cab. Basically you just take a roll of tape, pull a piece out and stick it to a table, then run the roller back and forth on the sticky side until material stops coming off the roller.