Maker Pro

One more subwoofer (this time in the garage)

An in wall subwoofer to add bass in 2 rooms

Project Log

When I set up the subwoofer in the basement shop I started thinking about adding one in the garage. Our garage is basically square with a wall down the middle (between the overhead doors) and 8' ceilings (with a storage attic above). Looking at it from the driveway the left side (AKA the big space) is where my wife parks her car in the winter but when the weather warms up she parks outside and it becomes shop space for woodworking, motorcycle repairs or anything else that needs a lot of room. The right side is divided again with the end near the overhead door for parking the sidecar outfit I am currently using (I have one for winter and one for summer) and the inside end is the shop, with a workbench, tool storage and a computer that is mostly used for playing music while I work.
I have an amplifier and a small set of ceiling mounted wedge speakers in the shop and another amp in the big space with Poly Planar flat styrofoam speakers in minimal enclosures. The bass wasn't great in either room (especially with the 4" "woofers" in those wedges) so this time it would be mounted in the wall between the shop and the big space so that it would add bass to both rooms. So I ordered an amp and started checking the thrift shops for an odd speaker I could harvest a suitable woofer from.

My daughter found this one for me. It had an Acoustic Authority logo and an input/output panel (there was an amp inside but the plug in control box was missing) and it has no model number or other useful information. I wasn't sure if the grille was part of the woofer or could be removed separately so I started by cutting the bottom out of the cabinet.With the bottom open I could see that the speaker was screwed on from the front so I pried the grille off and removed the woofer.
I couldn't find any information about this design but it it looks like the port was tuned so low it needed to be bent to gain length. And the driver looks like exactly what I wanted.
03 - Acoustic Authority sub.jpg


For those who don't already know, the purpose of a speaker cabinet is to prevent the sound waves produced by the back of the cone from meeting the waves from the front and cancelling. In theory if you were to mount a speaker in the middle of a flat board of infinite dimensions the front & rear waves would never meet (since a sealed box would also do this a sealed speaker cabinet is sometimes called an "infinite baffle") but in the real world the board only needs to be big enough that the waves from the back would be weak enough by the time they met the waves from the front that they wouldn't make an appreciable difference. A wall should do nicely.
And since sound is produced from both front & back of the speaker a subwoofer mounted in the wall will add bass to speakers in both rooms.

I might have gotten away with cutting a hole in the drywall and bolting the woofer to that but with that 40 oz magnet I wanted more support so a wooden panel would be needed. And I also wanted to give the back of the speaker a bit of protection from debris, bugs &c (it is a shop area) so I'd need to build a box with a more or less open back and some kind of grille into the wall. I had a couple of aluminum 10" woofer trim rings and matching grilles in my speaker parts, just right for protecting both sides of the speaker.

Next step: Pick a place where I could open a hole between 2 of the wall studs, find a piece of 2x6 to form the bottom of the box. You can see the Poly Planar speakers in the big space and the back of one of the little speakers in the shop through the hole
04 - Hole in the wall.jpg


After that I found some suitable pieces of wood (particle board actually), 11/16" for the front and 1/2" back. I could have cut the plain hole for the back with a jigsaw but if I wanted to use the trim ring the woofer needed to be recessed into the front and that required a bit more precision. So I looked up how to cut round holes with a router, made myself a router trammel and got to work.
The back had woodgrain vinyl in decent shape so I just painted the edges black. The front was pretty rough so I sanded it a bit and used up some left over spray paint on it
05 -  Baffles.jpg


Woofer mounted
06 - Woofer installed.jpg


Rear panel added. Inset: close up view of the perforated plastic grille (they are formed to fit inside the rings and have a slight dome shape for strength).
07 - Rear baffle installed.jpg


And from the other side. BTW, the little blue box hanging under the shelf is the old amplifier (the bit beige box next to it is an ancient Spacemaker kitchen radio tuned to the FM transmitter that's hooked up to the living room stereo for when I want to listen to what's on the TV).
08 - From shop.jpg


And finally, this is what the XY-E30H subwoofer amp looks like. I didn't like the idea of it being in the clutter on the computer shelf (not to mention that it would be easy for something conductive to end up poking in through the open sides or wires breaking or being pulled out) so after I took the pics I made a bracket
for it that hangs below the top shelf.
09 - XY-E30H amp.jpg


I spent this afternoon in the garage shop and I have to say that the subwoofer has transformed the sound of those tiny wedge speakers.

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Sidecar Bob
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