Bucket Sub

I started thinking fiberglass enclosure. Then I went to a flat MDF box (bought the driver at that point). Finally ended up with a 5 Gallon bucket & panel.



PLUS
-Light
-Cheap
-Easy to build
-Works great
-Tough cargo floor

MINUS
-Requires careful design
-Bucket could crack apart over time (not tough to replace tho)
-Won't stay up with just OEM tabs

So the materials are:
-Cabinet grade plywood
-5 Gallon "food-safe" bucket
-Dayton shallow mount 10" sub
-Screws, spray glue, threaded inserts, paint, rubber grommet
-Scrap stair tread (1" thick hardwood ply)
-Scrap 1/2" plywood
-PA Speaker handle

The driver is fine but I would get a conventional one if I had planned this from the start- thought my shallow MDF box would require it. The outer flange was just touch too large- clearance was tight with bucket.

Rejected fiberglass because I hate working with it. The MDF box was going to be silly heavy with proper bracing. Then it occurred to me that since I use the cargo area like a pickup (do a lot of DIY stuff), I could kill 2 birds with one project: Tough cargo floor AND a decent sub. Then I considered all manner of containers for the lower enclosure- most of which would vibrate like hell at even modest volume.

Cylindrical shapes are inherently strong under pressure (see air tanks), except for the ends, if flat (see air tanks with dome bottom). Food-safe type 5-gallon buckets are fairly strong and dirt cheap. If I could design a means to reinforce the ends, it should work well.



So the stock cargo panel is used as a cutting template for a high-grade 3/4" plywood (Home Depot) replacement. This panel is then the top cap of the enclosure, and quite strong. The ideal volume for a sealed enclosure for this driver, at the average diameter of the bucket (it tapers a bit of course) came damn close to exactly the bucket height needed to reach the floor pan. Building-up the height of the bucket with a spacer beneath, one that could be trimmed down to just the right thickness, would leave about half the weight of the unit carried through the bucket, and ¼ on each left/right hanging sill. This would put the bucket bottom, the surface most likely to become a resonator, in (hopefully) sufficient compression to keep it quiet. That was the plan, anyway.



After cutting-out the new panel, next step was to bore a series of holes to balance the open area for the sound to pass through with enough material for strength. I went with a gut estimate of about 1/2 bored. Drew a simple grid and used a forstner bit with backing scrap for clean holes. Easy peazy. Then installed the threaded inserts that will hold the driver from the top. Eased all the edges with a mini router.



More to come...

Next I made a thin bezel ring (1/2" plywood) to create offset so the excursion wouldn't strike the panel.



Then I made the larger mounting ring (1" stair tread) that holds the bucket in place. Horizontal screws (from inside) hold the bucket to the ring. Added some caulk as air sealant. A second set of threaded inserts bolts the bucket/ring unit vertically to the panel. Speaker gasket foam tape to seal the ring to the panel.






To add the needed bit of height and center the weight on the bucket bottom, I made a wood puck with a recession so it would have a large contact area with the bucket. Added a felt furniture slider to the bottom so the vibration won't wear a hole in the carpet and to reduce the chance of rattles.




I used acoustically transparent nylon taffeta over the hole array to reinforce under the carpet and as insurance against sand/dirt getting into the driver (would be a pain to remove). I cut off the panel's forward section to match the original pivot point, then contact cemented heavy nylon strap (old duffel shoulder strap) across the cut for the "hinge". Then I painted everything and covered the panel in speaker fabric.



A concert speaker cabinet handle was also installed to replace the pull- works perfectly.

Does it Work?

Yes, quite well- and I was concerned it might vibrate like hell. Interestingly, the plywood panel starts to resonate before the bucket, but that's at a level louder than I listen (even with Alter Bridge cranked!). Still, i think a little dampening material added to the underside of the panel is in order.

Sound quality is good, but honestly could be better/flatter with a better driver. The rest of the system ('15 GTI S Base Audio) is a JL XD400/4 and LOC under the passenger seat and Image Dynamics components in the doors/pillars. The crossovers are at the very nook of the passenger footwell (gotta love industrial Velcro) until the setup/tuning is done. Sounds quite good overall but I am picky- Mini DSP likely in my future.




One of the objectives was not only to carry heavy/bulky stuff and not damage the cargo panel (stock is foam of course), but also to be able to easily pull it all out for track days load, leaving no amps/wiring exposed, but keep the audio sans sub. The whole thing weighs just under 20 lbs. so not a problem. I have had several big loads back there since I got it installed- up to a 200lb air compressor for 60 miles. Not a problem.

The stock tabs that hold the panel in the raised position are not up to the task now (after a few seconds), so I may add a gas-charged hatch strut to support the panel if it gets annoying. But I don't go under it often.

I also DIY'd mounting rings for the door panels from PVC irrigation pipe and sheet steel- pics below.




I am thankful for good info I have found here so maybe someone finds this useful. Cheers!

JD

Can't see any of the pics