Cheap Subwoofer Casing: PVC Pipe & Fiberglass Options

[exequor]

I'm looking at building a subwoofer from ground up, however i need something to put it in. currently I'm looking at using a pvc pipe fitting, like the pypbomb or fiberglassing something. The thing is 8" pvc fittings are expensive and are too strong since some are 80 scheduling (the pressure system for pipes). for the fiberglass a mold would be needed. Is there some cheap pvc product that can be used for this purpose?

 

[Michael_E]

exequor,
It depends on what you're needing and what tools you have to modify the casing to your needs. If all you need is cheap tube shape that's easy to work and will attenuate sound, then I would suggest getting one of those heavy tubes made from paper that are used as forms for making concrete columns. I think that Home Depot carries these and I know that most any concrete supplier would have them. You can cut this stuff with a hand saw, trim it with a utility knife and when you've got got it where you want it, you can saturate it with epoxy or polyester resin to stiffen it.

 

[Cliff_J]

I've built a sub enclosure from thinner PVC before, its expense and performance didn't match up very well. I ended up making some MDF reinforcement ribs to help stiffen it before I tired of it.

Fiberglass is going to offer a better value and is easy to brace for structural stiffness, as does wood products like MDF for the bulkheads.

If you are making a vented (ported) enclosure, this becomes even more important as the internal pressures are nearly twice that of a sealed enclosure as you approach the resonant frequency.

 

[exequor]

Michael_E, I like the idea of using those thick cardboard column formers, I know exactly what it is and it should work; there are some thick ones up to 1/4 of an inch. the funny thing is i can't seem to find it anywhere online.

Cliff_J, I was really into the idea of the pvc, and I even tried getting thinner ones, like for drainage or sewerage, but I still think that it is a bit costly for 8" and up. I even wanted to go with clear pvc until i learned that an 8" Tee costs $918.

 

[Cliff_J]

The thin stuff has fairly low damping characteristics, too much "ring" to it for my tastes.

Something like the Thiel CS7 with its concrete face to mount the speakers is a little extreme, but you want to hear the speaker and not the enclosure so extreme can be good. Most everyone else uses something like 3/4" MDF with some bracing and its a great compromise in terms of cost/weight/complexity.

Clear does cost more money, but sheets of acrylic aren't too expensive, the adhesives have become much better, you can heat it and bend it, and it can be worked with woodworking tools. So you could make a very nice looking macintosh computer looking enclosure for you subwoofer.

 

[exequor]

the thing is mdf is very popular and everything, but I also have to take into consideration such as tools for working with the mdf. i have finally found those paper tubes, which you can get in really large internal diameters and thicknesses up to 1.5". I have been able to source a 30" long piece for less than $20, so I have to look at ways to finish it off and probably reinforce it if necessary.

 

[Danger]

Paint it to look like a beer can.
I don't know anything about sound equipment, or the particular stresses involved in what you're building, but I've found that Varathane works pretty well for stiffening and weather-proofing cardboard.

 

[Michael_E]

exequor,
If you want to reinforce it I'd just get a smaller tube that you can "peel" to get a good internal fit and glue it in with epoxy. I used to use this stuff:
http://www.systemthree.com when I built a few boats and they have so many inexpensive epoxy products that it can really stretch your imagination. In particular their low viscosity epoxy would really saturate those paper forms , cure rapidly and give a good hard surface. This is their page with that stuff:
http://www.systemthree.com/p_rot_fix_2.asp. They also have phenolic microballoons that can be added to give a peanut butter like consistency for making filleted joints and surface filling. Adding the microballoons makes sanding much easier too. Make sure to wear a filter mask whatever you do !

 

[exequor]

thanks a lot, i think I'm going to work with the paper tube.

 

[vabbb]

Exeqor, where did you find the tubes at? Up to 1.5 inch thickness? wow!