Lexan / Plastic Subwoofer Boxes
 

Hey guys,

Was looking for some opinions, suggestions or options. A couple years ago I built a subwoofer box for a 10 inch subwoofer out of wood and covered it in fiberglass resin. It lasted about 4 years before it started to get saturated with water and fall apart. It is located on the floor of the boat, under the back seat, in a cutout where a cooler originally was. It doesn't have an easy life as the boat stays in the water all summer on a mooring, and sits in the side yard of our cottage in the spring and fall. I can't really complain as the previous box lasted 4 years under these conditions. Was thinking this time around building one out of lexan or plastic so that I do not have to worry about rot. Has anyone done this? Is there a website I could order a custom one from or am I going to have to make it myself? I was thinking a 3/4 or 1 inch thick sheet of lexan and just building it like a regular subwoofer box?


All ideas welcome!

Thanks!

Coosa board and bed liner or glass it

it will be HEAVY. Maybe some foam/coosa stuff, glass it before you cut it and tab it together.

If you build a new box make it 1.5 cubic foot and put a vent in it with 25 square inch surface area and 16 inch long. I would not use lexan/plex it will not sound right. I would use 3/4 " MDF and then resin it like you did last time, but resin all of it not just the outside.

Why would MDF have a different sound then acrylic? Never heard this before and I'm just wondering. I would think that an acrylic box sealed properly with some weld-on 4 or 16 would work fine?

MDF is made up of several materials that have different resonant frequency's, so it will not add its own resonating sound to the music. You could use acrylic but it would have to be really thick not to add a hum to the music.

I wouldn't go with plexi. Super heavy,probably not best sound quality. I would not use MDF either, stuff absorbs water like a sponge and after you glass it inside and out I would think you would lose a lot of the sound quality benefits it offers. I would look at Starboard, correct me if I am wrong but I think it is very similar to Coosa board. I would not use MDF anywhere on a boat.

I just pulled a MDF box out of my boat that was covered with resin and about 4 years old, It sucked up water and turned into sh!t. I built the new one out of marine grade plywood, but if I was in your shoes I would go with 3/4" starboard, ebay is going to be your best bet for a deal.

coosa would make a nice box and it is available in several different densities from 15 to 26 p/cf.

BYC how do you think a composite board would perform over MDF? Do you think like densities of Coosa and MDF would yield like performance? Would it be best to go with the highest or lowest density?

Dave, I am willing to volunteer my boats services as a coosa speaker box test mule....

My sub box for two 10w7s is built out of marine plywood and fiberglassed. It's heavy, but it sounds great; and it's lasted for years.

MDF in a marine environment is a bad idea. I know the properties are great for building driver enclosures but I would gladly take the trade off of a water resistant material. Just resin is not enough to seal MDF. It will crack and break down over time.

I know MDF is not good to use in a marine environment and I would not use it for anything besides a sub box. But I look at a sub box as something removable that may need replaced every once in awhile. I'm a sound guy so I would rather have the better sound. Most people would not know the difference in sound between a mdf and coosa or some other composite boards. So I'm sure coosa would work fine, and use the higher density stuff. I would still not use lexan/plexi. If weight is an issue then just find somewhere that you can cut a hole in a panel that will reasonably separate the front wave of the sub and the back wave and mount it with no box. It will player lower and almost as loud.

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I built this box out of MDF then premiered and painted. It stays outside in the weather all year long and has taken a lot of abuse. It was several years old in the pics with the girls dancing on it.

Forget MDF go to Lowes and buy a sheet of Advantek It's way more dense and near water proof. I've had a sheet in the bed of my 1 Ton since 2009 still 3/4" thick and solid as the day I put it there.

I give up on MDF a few years ago they don't make it the same as 10 or more years ago seems like pressed paper anymore

I was talking with a composite materials distributor and he mentioned expanded PVC sheets. We It was my intention to use it for transom core at the time but it may work excellent for a box. It was explained to me that it was high density. Maybe glassdave can confirm this.

Lexan works just fine for sub boxes. It used to be the thing back in the day. It was just very expensive. I would look for HDF and resin the heck out of it myself, or use marine ply and resin it good.

If you look at my build in the cig section you will see 2" think foam board glassed into the gunnel that's the speaker boxes. The foam is the same stuff used in ice boxes on shrimp boats. No rot and very dense. It's also light. All you have to do is resin it. Will try and get more pics
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looks like its normally used as subflooring

Ok guys, so we looked into the options, and we found in our situation it would still be best for us to use MDF. I looked for the Advantek and coosa, but neither was very readily available, and truthfully, I do not mind replacing it every few years. So, I now have the next question. What type of resin to use. West systems epoxy or west marine polyester resin. Is hardener necessary? Also, would it be beneficial to put a layer of fiberglass on it, or would that just be a waste?

Thanks for all the input.

Have had excellent results skim coating the mdf with fiberglass reinforced body filler. You must follow up with a coating after. Makes a nice smooth surface for painting too if you're not planning on using upholstery.

I just get the regular resin you can get at any hardware store. If you need it to be pretty sand the box and fill with bondo it needed. Then 2 or three coats of resin with a light sanding between coats. Then paint. I think my cabinet/bench seat is 4 or 5 years old and no problems from water.

you can use any cheep resin to coat the box. I would put a layer of fiberglass so when the wood starts to swell at the seams it will not cause cracks that could let in moisture. (Kind of like tape on drywall seams to keep from cracking)

If you coat and glass everything (including the cutouts), and seal all the screws, it should hold up well. I would use AdvanTech also, but it's hard to find.