Subwoofer enclosure build thread

Not too exciting or GRM, but I'm building boxes for some 10" subs. All of my fabricated enclosures in the past were uninspired Elmer's glue and MDF with a ton of screws. I decided to build some righteous boxes this time.

About a year ago I scored a 12' stick of 12" sched 40 PVC for $20. It is about 3/8" thick walled green pipe. So, I cut a couple of lengths to make some enclosures in the 0.9 cu ft range. Also, having worked at Home Depot, I snagged a whole bunch of 3/4" and 1-1/8" MDF. I had some leftover West Systems epoxy from my boat project, so all of the above means time for boom boom boxes.

Here was my initial sketch. I cut four discs out of 3/4" MDF and then carefully sanded them until I had a light press-fit inside the PVC. Then I used epoxy to laminate them to an outer square panel of 3/4" MDF. Then it was a matter of filling the edges with fibered epoxy (microfiber dust) and pressing them home using a finger to smooth out the squished extra epoxy.

Here is one of the pieces of PVC (with one end cap already installed) that I scuffed with a 100-grit disc on my angle grinder to give the epoxy some tooth. I did notice however that any of the epoxy that spilled onto even shiny PVC had to be ground off. I'm very happy with the tenacious grip.

Here is the first one fully glued and cured. Next step was to trim off the excess MDF and prepare for routing the edges flush. This next photo shows the flush routing done.

Then this photo shows where I trimmed the outside edges of the MDF with a roundoff bit.

And here it is with the driver sitting in it. At this point, this box is sanded and ready for coating. Not sure yet what I'll coat it with. Any suggestions? Something that will have some build thickness to it, is durable, and sticks to PVC?

curtis73 wrote: Not sure yet what I'll coat it with. Any suggestions? Something that will have some build thickness to it, is durable, and sticks to PVC?

Bedliner?

EvanB wrote:

curtis73 wrote: Not sure yet what I'll coat it with. Any suggestions? Something that will have some build thickness to it, is durable, and sticks to PVC?

Bedliner?

I tried a little DupliColor spray on bedliner a couple days ago on the PVC. It peeled off very easily. Worked nicely on the MDF but offered little protection for it. I might paint a coat of epoxy on the MDF for some additional surface durability before coating.

Bedliner the MDF and put some cheap grey indoor/outdoor carpet over the PVC.

Wrap the PVC in vinyl?

Rosco Tough Prime is one of the very few primers I know that will stick to PVC.

Yeah, but how does it sound compared to all your other enclosures?

Nice project. Are you planning on putting wiring terminals on the non-speaker end? Using any fill? And most important, how does it sound?

Once I get them coated and dry I will hook them up to something. I don't have anything with a low-pass crossover hooked up right now. I'm planning on putting them in the El Camino if they fit, but likely in the trunk of the Impala is where they'll end up.

re: wiring terminals. Yes. I was in WalMart today and didn't expect to find them (and didn't) but they did have a relatively nice selection of car audio accessories. I went to Radio Shack to get some. THEY DON'T HAVE THEM. Seriously? I looked them up on my phone so the nerd knew what I was looking for but they don't sell them. I'm making a Crutchfield order anyway so I'll just have to wait for them.

I retried the bedliner on the PVC. I scuffed it with 80 grit, cleaned it with Acetone, and I think it might have decent adhesion. I might give it a shot but I'll be pissed if it scrapes off when I put it in the car. I also had the idea of thinning some of the epoxy and coating the whole thing with epoxy first. I know that the epoxy sticks to the PVC, so maybe the bedliner will stick to the epoxy.

I thought about the carpet, but I mildly shot myself in the foot on that. I used the router to cut the MDF flush with the OD of the tube. If I had thought ahead, I would have left a 1/8" lip on it so the carpet had an edge to hide behind. I might be able to trim the ends of the carpet with something, but there will be a funky transition where the PVC continues to curve and the MDF doesn't.

I have about 50 oz. of polyfil to fill the boxes. Do you think I should line the ID with something? I think it will be fine with the polyfil, but will the smooth interior surface cause any issues? I did some more accurate measurements. I get 0.9052 cuft empty, minus the 95 cu in volume of the speaker gives me 0.8498 cuft. Minimum sealed recommended is 0.8 for these drivers so I should be spot on. I like it tight. Who doesn't?

I got them both done tonight (ready for coating). I can't wait to get them pounding, but I will have to wait for my Crutchfield order. I've decided to coat the whole thing with bedliner. If it scratches off the PVC, I will put some small trim on the lip of the PVC to make a reveal for carpet. Hopefully more pics tomorrow.

Painted them with two coats of Rustoleum Bedliner this morning. They look great. The bedliner did a nice job of covering imperfections. Here's hoping it sticks well.

Crutchfield speaker connectors due in tomorrow, then polyfil, then finding a low-pass 800w signal to test them. Guess I'm hooking up the amp to the tractor battery for a test

I also sprayed the inside of the tubes and the rear baffle with undercoating. I figured that might deflect waves and take the porosity out of the MDF. If I snap my fingers inside the enclosure it still sounds like a hard plastic tube, but maybe the polyfil will be enough.

So I finished them up this morning and found an interesting snafu... They seal too well. Normally I wouldn't think that was a problem, but here is what happened. I installed the speaker connectors, filled them half way with polyfil, hooked them up and they sounded awesome. Later in the afternoon, mom and dad came home and I demonstrated them... they sounded awful. They were over extending and I couldn't get it right. The amp was shutting down because of its overload circuit.

Then I realized, the speakers were partially extended at rest. When I installed them it was 50 degrees. Where they sat all day was in the sun. They are actually sealed boxes. I had to drill a 1/16" hole in the speaker connector plates to engineer a leak.

Long story short, they are very stable and tight. The Yellawolf CD I used to test them probably only gets down to about 40hz, but they handled it nicely, but I could tell there was a pretty good dB drop below 50-60hz. The is totally expected with 10" subs in a small box. I'm more interested in Jazz and classic rock, so small-volume tight reproduction is exactly what I hoped for. But its nice to know these can still hummmm when I want them to.

RMS handling on these subs is 300w each and I'm giving them about 450w RMS, but the boxes are so tight that I couldn't make them over-extend. In fact, the amp was drawing more amperage through the 4-ga jumper cables than it could take. I was going into amp shutdown before I could over extend the subs.

I am so friggin happy. I will link to a video when it gets done uploading.

http://vid162.photobucket.com/albums/t264/curtis73/Mobile%20Uploads/20140924_164730_zps3mthqae9.mp4

This whole thing has snowballed. I'm now nearly completing a 1500-watt install with SiriumXM, bluetooth microphones, and I have raised and leveled the trunk with new carpet.... Its a major project.

It started with building these:

Then I wanted to raise the floor of the trunk to make a flat floor.

And deaden some sound. People often warn me about fiberglass and condensation, but it has never haunted me. This is some fiberglass I found leftover from a project in 1978.

Then the basic 3/4" MDF floor. I also cut a piece to cover the rise over the axle but its not shown here.

Then I cut a piece of MDF for a baffle to hold the amps behind the back seat. I placed the amps and pre-drilled for all the wiring. I backed it with some of the old trunk carpet to prevent rattles between the MDF and metal. The front is coated with leftover bedliner and then a couple coats of gloss black.

Then here are a few shots with the new floor carpet cut and the subs in place. There is also a picture of the amplifier board (missing the last amp that should come tomorrow.) I really took some extra time and routed wires so that they were neat, tidy, identifiable, and serviceable without encroaching on ANY cargo space. I really haven't taken up much space at all. Just basically the 2 cu ft of the enclosures. Notice how I tucked all the wires back through the baffle. Even the rear deck speakers I routed completely up against the deck.

My hope was to minimize cargo space reduction and make a bulletproof installation that doesn't have exposed wires to be abraded, tugged, stressed, or taxed. Everything is tucked away, secured, and safe. I can toss a small block in that trunk and let it roll around without worrying about my components.

Oh... and controlled by this head unit: http://www.crutchfield.com/p_113KDCX798/Kenwood-Excelon-KDC-X798.html?tp=5684

really clean install...nice!

Damn Curtis, that is an awesome set up. The tubes looked way bigger before they when in the trunk of the SS.

I got the last shipment of stuff today; one last amp, an ANL fuse holder, and the DIN dash adapter... but they forgot to put the ANL fuses in with the shipment. Grrr. Otherwise it would have been done today. Tomorrow I get the fuses (100 amp... sheesh) and then I'll set gain and levels on the amps.

Then I think I need a road trip

... aaaand now something is wrong. High levels of distortion from all four smaller speakers. They sound blown, but I doubt all four would have blown at the same time. Grrr.