Building a Subwoofer

Here's how this all came about. There's a room on campus that is a performance space. The P.A. system that is flown is basically a pair of Yamaha club speakers. Nothing fancy, durable and decent for vocals when a band shows up.

Keyword; Band. However the DJ's have been feeling a little light in the low end, when the bass drops.. these poor Yamahas can't handle it. They weren't intended too. We need some bottom, we need a subwoofer.

Ok we could go the easy route and JUST BUY ONE. But where's the fun in that?! More fun to build one! So here we go!

Our basic dimensions were for two 10" subs mounted in the box, 3" of gap on each side, a box depth of 10" and the whole thing would be 32" long. 

Parts:
2 10" Subwoofers from Parts Express. Rated 600watts each 4 ohm.
2 Speakon connectors
1 Speakon plate
1 DBX EQ to act as a crossover filter
1 Crown XLS 1000 amp
1 Sheet of 3/4" MDF
1 small roll of hardware cloth
Speaker wire
Glue
Screws
Sandpaper
Primer 
Paint

Tools:
Table saw
Jig Saw
Drill/screwgun
Tape Measure
Miter saw
Compass
pencil
Straight edge ruler

Ok, I'll be honest, most things I build are SQUARE! adding angles made things a little harder.

SO our first mistake was to create the face plate first. Wrong-O. What that did was waste material as a slight deviation in degree when cutting makes for a larger gap.  So learn from my error.

Here's what we did right. Set the table saw up to 22 degrees and made a gauge. THEN cut the sides and back and glued those together.

WITH MDF PRE-DRILL PILOT HOLES!! Seriously, ask me how I know. The screws are only to hold things together till the glue dries, but you don't need them splitting and making a mess of the MDF.

We were going to use a pneumatic nail gun, but found that the MDF was unpredictable when firing a finish nail into it. After two weird mis-fires, we opted for screws. (we missed our thumb! yay!)

From there we cut some of the MDF into 2" by 10" strips and cut them at the same 22 degree angle. These would be secured inside to firm up the walls and give me something to screw the face too.

The angled box and baffles should confuse any standing wave that wants to hang out inside. The ports will help too.

As I mentioned, we started with a face that we cut out. When we went to put it onto the side-back piece we built, it wasn't wide enough, by almost a half inch.

waaaaaa! (insert sniffle sfx here)

So fine, we set the table saw back up to 22 degrees and cut a new face, sneaking up on the final measurement one hair at time till it fit just right.

THEN we cut holes for the speaker and ports. We also fashioned end pieces, basically by tracing the side-back onto a sheet of MDF and cutting with a circular saw. We cut to allow for some overlap.
 

Using 60 grit on an orbital sander, we knocked off the sharp edges and smoothed things out. Looks nice so far!

From there we primed the MDF with some spray primer and let it dry. We have one more hole to cut, on the back for the plate that will hold the two Speakon connectors.

From there we painted with some Hammerite spray paint. Giving it a dimpled and tough surface. The plan was for a grill to protect the drivers, so we added an additional bit of framing around the speakers to support the grill.

We ended up not using it as it vibrated too much at low frequencies.

I did not come up with the name. The name is all Connell's suggestion. Mother Hucker.

Printed out the name with Coder font, cut it out, made a stencil and sprayed it up. The overspray is intentional. 

You'll also notice the eyebolts on the ends so we can fly this from the rafters. of the performing arts space.

Being a fan of District 9, I chose the colors for the name...

Ok, we get to install stuff!

I soldered the speaker cable to the SpeakOn connectors +1 and -1, negative for ground. These particular speakers have a dual voice coil, so I wired them in series to get a 4ohm load on each speaker.

Everything gets screwed in tight, low frequencies have some serious vibration!!

Initially we had some port tubes installed. The idea was to tune the ports much like a pipe organ once we got it fired up.

We ended up removing them as the airflow through the port was too noisy. There was thoughts of having a sealed cabinet but the bass didn't sound as open. Removing the port tubes stopped the wind noise. (sounded like heating vents!)

What's Next?

You'll notice that there's no crossover in this design. It's just a big speaker cabinet loaded with some chubby drivers. The Subwoofy will be powered by a Crown XLS1000 amp, which has a built in low pass filter, but for added tuning we're adding a DBX 215s equalizer to the mix to fine tune the cabinet. 

So far it gets REAL loud at 80db, so we'll smooth that out.

I know, I know, "Only a 1000 watts?!?" Yep. with the two drivers at 500 watts each, this thing THUMPS. The space it's going into isn't that big, and this Mother Hucker will handle the low end just fine. So much better than the two Yamaha club speakers up in the air.

Total cost for everything was $747.24 plus some scrap MDF and screws and other salvaged bits. SHOOT  we should have called it 747!

Once these are chained to the rafters, we'll retune the room so that the subs handle everything below 180hz. Boom ya.