This thread will detail the build of the two subs that are going behind my screen wall. This will be more of a discussion type thread than a how-to. I'm not going to show how to connect two panels together...it's not a tutorial.
Driver is the Dayton Ultimax-18 aka UM-18. Material is 3/4" MDF with a double front baffle, so a 1.5" front baffle.
Airspace is 18cf net, 21.7cf gross before driver, port and bracing displacement. These are not small boxes. External measurements are 47.5"w x 35.5"h x 25.5" d.
The port is 4" x 12" x 40" internal, giving the cab a 12Hz tune.
miniDSP for DSP, pro amps for power (QSC RMX2450a, one channel per sub @ 4 ohms = 800watts)
I don't know if these qualify as LLTs, but I can tell you they are large for sure and 12Hz is a lower tune than any other cab I've had.
Here's the WinISD SPL/FR graph. This is with 600 watts of power, 11Hz, 4th order Butterworth high pass and 80Hz 4th order Butterworth lowpass. No EQ applied to this graph. 108.5db at 12Hz. That's one cab.
I can't remember how many iterations of cab size/port size/tune I went through before arriving at this design. I had lots of great advice from
@More is Better
and others. A big THANK YOU to all of you.
I know I'm going to be happy with these. There will be two other subs in the rear of the room, same tune, but radically different in cab design. They'll be ported and tuned identically, but very different in appearance. I'll do a separate thread for those.
The mandatory "stack of cut panels" pic. This isn't all the panels for both cabs, just some of them.
These suckers are flippin' HUGE. Carrying them about 75 feet including a flight of stairs is gonna be FUN.
Internal width shot.
Here's the parts list and cut sheet from Cutlist. Best free program ever. Don't know why it's showing "1.38 x 97" for material. I'm using 3/4" MDF which is actually not 4'x8' but an inch larger all around at 49"x97". I used 5 full sheets of material for these two subs. Getting those sheets of MDF onto the table saw and cutting them accurately by myself was a heck of a workout.
*edit* If you want to duplicate these cabs, add TWO MORE Piece #15
(they are the same dimensions). You need FOUR TOTAL pieces at 40" x 4" for the port. The additional two pieces can easily be cut out of Supply Piece #4.
My first "Oh crap moment"...that didn't take long, did it? You may be wondering why there is a "port top and port bottom" but only one side. The port will use the rear panel and side panel as parts of the port. I want to roundover both the port and the outer edges of the cab itself. Trying to fit two 3/4" roundovers on a 3/4" panel won't work, so I need to double-up any port surface that also touches a cab surface. So, I screwed this part up. Darn! I'm missing another side piece for the port. Better to be missing a piece than to cut a piece incorrectly! No biggie as I have plenty of scraps and extra MDF too. So, add another Panel 15 & 16 to the parts list. Thankfully, I haven't cut the port opening out of the side panels yet. Didn't do any "panel machining" today, just cut them all to size.
This port will take up approx 1.7cf. Driver displacement is .250cf. That leaves 19.75cf, or, 1.75cf for bracing. Plenty.
Not sure how I'm going to do bracing, but it's most probably going to be simple stick bracing, using lots of the cutoffs from today....I save everything. With a cab this large, I'd feel better if I used 1" MDF, but way back when I bought this material, the lumber yard was out of 1" MDF...after they told me on the phone they "had plenty." They gave me a nice discount on the sheets I bought, so it all worked out. I'll just have to brace the snot out of it.
Next up will be gluing up the double front baffle and cutting the driver hole. As these cabs will be behind a screen wall, they will get a slathering of flat black paint and the driver won't be recessed. The other two cabs going in the rear of the room will be Duratexed and the driver recessed with an additional piece of 1/2" MDF laminated to the double front baffle.
More to follow. Thanks for reading.