Proper marine box building

I've been building boxes and doing installs in my own boats and cars for the last 15 years but there's always much more we can learn about doing things the proper way! I want to focus this conversation on marine environments considering we're on a boat forum.There's always a right way, a wrong way and somewhere in the middle (probably my installs). Hopefully some of the pros like David and the chucktronics guys (I know there's others too) will give us guys some help!

One of the biggest things I see is material choice in box building and amp racks. What I've done in the past is use 3/4" MDF and coat inside and out with resin for waterproofing. I use basic plastic speaker terminals and off the shelf wire connections. I usually have used wood screws but covered after resin layer. Is this correct or not?

I know most poor installs I see are improper subwoofer volume and port sizing and materials used for the application but what are some others people are seeing and what is the correct way? What are some tips of building amp racks correctly and stable (besides the obvious things).

My last box was built by the box guy Dave. I love it and it made a huge difference. It's made with birch coated inside and out. I like birch cause one it's a lot more water resistant than mdf and ton lighter.

Many moons ago, I built the box for my boat out of MDF. Just a simple, 1cu.ft. sealed box. I hoped it would last at least one season without any type of waterproofing. It was glued and screwed together and all the seams were caulked from the inside. That's it. No paint, no carpet, nothing. This was back in '06. It's still in there and as tight as ever. One thing I did though was get it up off the floor as far as I could by building a shelf for it. In the bulkhead under the helm, I only cut a hole for the sub itself. There are no exposed parts of the box at all. I think those are the reasons it's still even in existence. I would never recommend not waterproofing a box but, with a few little design elements, it can be done.

I'd love to see some good simple sealed box designs. I keep threatening myself with redoing my sub set up.

I use Azek. It's a little pricey but it's totally impervious to the elements, it holds screws like mad, and you can screw right up to the edge without it splitting. I've also started to use it when having new upholstery pieces made.

I wouldnt use MDF, even if you coat it. My last box in my old boat started rotting after I summer and it was coated in resin. Since then, I use birch for sub box and amp rack. I've always had some sort of port noise on my slot port enclosures, but since I did a precision port kit this time, it blew me away and sounds great IMO. I also normally drill a hole thru the back of the box, just big enough for a small bolt to go thru, and run the negative and positive to a bolt and stick it thru the box, and hook the wires from the amp to the appropriate bolt with a ring crimper, and lock washer instead of trying to caulk a hole big enough for the wires to go thru.

All the boats we do at my shop including my own boat is built out of 3/4" mdf and then I take them and get them linex'd. Never had a problem

I haven't heard of azek for box building, how is the structural integrity of it? Anybody else have experience with this?

Birch wood comes in many different forms, I assume your speaking of plywood (3/4" or equivalent). Plywood birch also comes in a variety of quality/layers. Can anyone comment on the specifics? Using basic birch low grade plywood I would assume it wou not be adequate for this purpose?

Azek is close to indestructible. I've had a 6 inch plank of it supporting a 1000 pound fat sac over my bow walkway for 5 years and it's still exactly like the day I bought it. And it's wet up there 90 percent of the time. It's outdoor decking material sold at Home Depot. Lowes sells Trex, which is similar. The only downsides are the cost (a 12 inch by 8 foot piece runs about 70 bucks here in Philly) and the limited sizing - 12 inches wide is the widest I've found in stores.

I think the 12" width is too limiting to be a choice for most box designs. Possibly an option for smaller tho.

Mine was built with 13-ply baltic birch

Yeah the last one I did I had 2 have a seam which I backed up with Silicon and 1/4 inch pvc on the back and another piece of Azek on the front. Kind of a pain but it's worth it to me bc my boat's in a slip and doesn't get totally dry very often.

Azek, Sintra, etc. are brand names for expanded PVC. I use different thicknesses in my business and it is available in 4' x 8' sheets. I think a 3/4" 4' x'8' sheet runs around $175. Not cheap, but a box built out of would last forever.

Wow that's a really small box eric!

People using birch...are you coating it with resin or something else to seal?

Yeah, that's a .8 cubic footer for a wetsounds ss10b. Sounds nice. It's crazy tight under my dash, and I didn't want to give up any legroom.

Although I haven't built boxes for marine use, I have built a few out of Apple Ply. and it's available up to 1 1/2" thick.

http://www.appleply.com/

This stuff is super solid with pretty much no voids and glues and screws well. The edges look good enough all you have to do is sand them down and clear coat them. I would think if you made a box out of this stuff and biscuit-ed, glued and screwed it together with a couple of coats of varnish it would last quite awhile.