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Help me finish my polystyrene cab build

#82
:rollno::rollno::rollno::rollno::rollno::rollno:
agedhorse said:
Coloring outside the lines is fine as long as you understand and define where those lines are. Otherwise it can lead to unpredictable and generally terrible results.

Those that appear to color outside the lines and are successful generally understand the topic they are dealing with very, very well. The danger of coloring outside the lines is where a parameter is incorrectly or variably defined, or the lines are moving and you don't know how far they may move.

You will also find that the air frame power and avionics industries never color outside the lines, they very carefully expand the lines based on tremendous research, knowledge and experience.
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You fly guys always have gliding, unless you're rotary wing.

Screw up underwater, you ain't getting to the top and the final trip down will eventually be somewhat cramped.
 
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#84
There was a company many years ago, I think it was called Audio Composite Engineering (or something like that) which got purchased by QSC maybe 15 years ago. Their specialty was composite cabinets, they were quite good but contained significant engineering and were very expensive.

Close, here's the scoop: December 2001 QSC formed a strategic alliance with Audio Composite Engineering, Inc. (ACE) to produce loudspeakers using ACE's patented Composilite material. The new speakers would incorporate QSC amplifier, signal processing, and transport technologies.
 
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#88
zac2944 said:
I built cabs from foam and fiberglass many years ago and posted about them here: DIY Lightweight Composite Cab Build

I still use these cabs today. Probably a few hundred gig and still going strong.
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I'm using a loctite foamboard adhesive, and while it's pretty low VOC, it takes FOREVER to dry because I'm not laying down 1/4" beads like the package says. It's been a bandaid for my otherwise mediocre cab building skills, and the many gaps I left necessitated the use of about 15 tubes so far. I have one last panel to glue. Everyone on this thread helped me puzzle out the way I plan to mount the baffle and get the plans in my head, but it's gonna be about 2 weeks till it's ready to play at all. Any thoughts on the just foam construction as opposed to fiberglass reinforcement? Thank you for commenting and linking that, other people have mentioned your thread in passing, but I hadn't read it yet.
 
#92
neal sanger said:
That's a terrific idea. I found some off brand bed liner for like $16 a can, i might give that a try, but I am taking into account that the un-laminated foam might have desirable acoustic properties. Any ideas on how to test that assumption?
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Totally different type of material. Line-x is a 2 part polyurethane that is damn near bullet proof. No, really, they line rooms in the Pentagon with this stuff. It does go on hot though, so no telling how the type of foam you used will react. I spray standard bead foam with it all the time and it holds up just fine.

If I was doing something like this, I would probably use something like a 3/4" or 1" rigid foam with maybe some lightweight balsa for the interior bracing. Then have the entire cab shot in Line-X including the inside. And yes, the cab won't be as stiff as wood and it's certainly going against standard practices, but isn't that what makes it fun? I've played through numerous technically "bad" cabinets in my day that I thought sounded pretty damn good with my instrument. Don't be afraid of making mistakes. Do something crazy and see what happens.
 
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#94
It's not cheap for sure. It's a 2 part product that has to be applied professionally at their location. The DIY stuff in cans is little more than a tough paint like coating. It won't give you the stiffness of a Line-X type material.
 
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#95
+1 on the skin. It will be much stronger. And you can insert wood on edges and around the speaker hole.

For the covering. Search around for chopped fiberglass fiber. It's on amazon. It's used to strengthen things like concrete and plaster. A bag is cheap. You could try an experiment to mix it with some paint for the undercover, then cover that with a final coat of something else so fibers don't poke out.

For gluing sometimes I just don't have the time to wait for the real holding glue to cure, and I don't like leaving things clamped for days. I do a common cabinet maker trick of using some dots of CA glue on parts to the glue up. It adheres instantly and works as a good clamp for non-expanding main strength glues to cure.

All IMHO, YMMV, have fun and you just might be on to something.
 
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#100
It's difficult to attach any sense of 'permanence' to foam. I'm not against foam, but's not an easy material for lasting use. The adhesives are tricky. I have used several specific "foam adhesives" that worked well for a while but failed after a few months. These would be the usual suspects at the Home Depot. For a quality foam adhesive. your best bet will be at a sign supply store. (They use a LOT of foam in that business) They also handle foams in different densities - most denser and stiffer than Home Depot insulation foam. Certainly more expensive than insulation foam, but it's far more structurally stable. I like the idea of a foam enclosure though. The next time we use 'sign foam' at work, I'll try to grab enough scraps to make a small cab.
 
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