Help me finish my polystyrene cab build

[neal sanger]

We build stuff out of foam all the time in the movie industry. When it's something that needs to be tough and be strong as heck, we have it sprayed in Line-X truck bed liner. Won't be cheap though.

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?

 

[agedhorse]

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.

 

[BassikBrad]

If you don't have any measuring equipment, you could use your ears.
Looking forward to the results.

 

[Five String]

Can't wait to see what's next

 

[Jim C]

Really original idea, and congrats.
Am I the only one that thinks if it's made purelu out of standard home insulation board that it's going to jump aorund on the floor like a Mexican jumping bean, and, the sides will vibrate like crazy?

 

[neal sanger]

Hey, if I goof this up, no one is going to fall out of the sky.

 

[neal sanger]

Really original idea, and congrats.
Am I the only one that thinks if it's made purelu out of standard home insulation board that it's going to jump aorund on the floor like a Mexican jumping bean, and, the sides will vibrate like crazy?

Jim, take a look at the bracing.

 

[Jim C]

About how much will this weigh without a driver?

 

[neal sanger]

12-18 lbs. IDK how much weight the glue gives up once it is cured. Driver is 11lbs (eminence beta). I don't have $ for a nice neo speaker, but meh.

 

[neal sanger]

Now that I think about it, a cab built from insulation foam, a magnet with a low curie temp magnet is probably a bad idea.

 

[agedhorse]

You will never get anywhere near the Curie temperature.

 

[neal sanger]

not even on a neo?

 

[Downunderwonder]

Now that I think about it, a cab built from insulation foam, a magnet with a low curie temp magnet is probably a bad idea.

I wouldn't think it can keep it a lot warmer than a 3/4 MDF cab with a 4" port.

 

[agedhorse]

not even on a neo?

Nope, not even close.

 

[alexclaber]

I was trying to think of materials that would make good laminates, but most of them were either flimsy (veneer)

If you can glue it properly across the entire inside and outside surfaces, then even a thin ply of very bendy veneer will add a huge amount of stiffness to the enclosure. Google "second moment of area" if you want to know why.

 

[Five String]

If you can glue it properly across the entire inside and outside surfaces, then even a thin ply of very bendy veneer will add a huge amount of stiffness to the enclosure. Google "second moment of area" if you want to know why.

You know you're on to something when the big guns start weighing in.

 

[zon6c-f]

So I saw someone on talk building a cab with fiber glass and insulation foam, and I am trying to do the same with just foam. I plan to use 10.125" of schedule 80 PVC pipe for a 31hz tuning port (the math just worked out nicely), and the checked it out with win isd and AJ vented designer MFC application and the cab resonances seem evenly distributed, but since it's polystyrene, I can't predict how it will behave, but that's not the issue. I'm planning to glue a piece of plywood with a cutout for a baffle in it to the last piece of foam board which will hold the speaker, but I can't think of a way to do this where I would be able to remove the speaker and swap it for another. anyway, if I mount the speaker directly to the foam core, I worry it will chew up the mounting points in short order due to vibration from the speaker. I have had poopy luck with T-nuts swapping drivers more than once, and once the last foam panel is glued, it will be nearly impossible to change anything without wrecking the cab. I'm a total noob and have never even built a cab before, but I just wanna finish this project because it's been sitting in my basement for a month and it's pissing off my family.View attachment 3277723 View attachment 3277727

Welcome to TalkBass!

 

[Downunderwonder]

If you can glue it properly across the entire inside and outside surfaces, then even a thin ply of very bendy veneer will add a huge amount of stiffness to the enclosure. Google "second moment of area" if you want to know why.

True, but that process should have been attempted before constructing the box I reckon. But then it would have stuffed his finger jointing maths. And made a lot more mess in his parents' basement.

I prefer the Boogieman's wood glue papier mache approach at this stage.

 

[RiffwRiter]

Would it be a good idea to counterbalance the weight of the speaker or anchor it to the floor? I keep imagining the cabinet doing a face plant with any bit of jostling.

 

[neal sanger]

If I decide to skin the box, I'm gonna try out the truck bed liner first.