Iso-Cab Layout and Materials

[kevster]

Hey All!!!

This Sunday I planning on cutting the materials for building an iso-cab for use at my church. I planned on using 3/4" MDF for the cab itself, but I'm still looking for effective soundproofing options that won't cost a fortune.

The basic layout is generally going to be a "Home Plate" shape. The sides of the "point" will be angled about 40 degrees (not 45), and the "point" will actually be a 6"+/- "flat" (back wall parallel) section for mounting the gooseneck. I'm planning on doing a hinged top, so this will be a top loader with the size built to accommodate a Fender Twin (2 x 12") cab. Any comments, yea or nay?

For the acoustic dampening, I've looked at a couple different things. Corning 703 insulation and different sources for reticulated foam, etc. I'm also evaluating the whole "box in a box" layout as a possiblity, but I wouldn't prefer that. I'm planning for an eventual side mount fan and an eventual grill on the top rear for heat, but it won't be necessary to start with as I won't use a combo with it.

So, anybody got experience with what works and is cheap? I'm looking to do at least -30 db. The more the better, because I want to turn my ODS 50 clone (single EVM-12L) UP!!!! Any suggestions for material and sources with good $$$?

The completed cab will live on a four-wheeled flat dolley so it is portable.

Thanks for any comments, suggestions, ideas, or links!!!!

[overtone]

One thing I was told was that foam alone does not really dampen the sound. It was suggested to me to make a sandwich of dense foam / thick bitumen roofing felt / dense foam. Maybe high quality dense-rockwool may perform better than the foam. You have to be clear that you are going for sound reduction, rather than treatment - which is what most of the internet chatter is about.

A cheap version that I heard of was to just bury the cab under a mountain of still wrapped square bales of mineral wool.

Another thing: I would recommend it just being a dedicated speaker rather than trying to lift your twin in there.

Randall is now offering one with a labyrinth air-vent to try to get around the dead sound.

I got as far as ordering all the material for two iso-cabs, then realized that I had spent nearly the equivalent of a Palmer speaker simulator. So I stopped and ordered the Palmer. I can actually lift the Palmer with one hand.

Best, tony

[xtian]

Blocking 80% of the sound is easy--just make a tight enclosure. And that might be enough for a live setting. Easy experiment: put your closed-back cab face down on a carpeted floor!

Blocking the last 20% is tougher--guitar cabs can thump out 20-60Hz waves when you whomp the strings with your palm, and those waves need thick, heavy insulation. The last bit of low frequency energy needs to be soaked up with four-inch insulation and a loose-hanging rubber sheet. But again, you can be satisfied with a little rumble escaping the iso box as a trade off for 6-10 inches all around for extra sound proofing!

That said, I had great success in my studio with four-inch rockwool from the local insulation installer--much cheaper than Owens Corning, and very similar in absorption properties.

[vibratoking]

+1 on the Palmer. I actually have an extra one that I am willing to sell...PM if interested.

[kevster]

Thanks for the replies. The good news is that I just have to get the ambient volume down to probably 65db... We run the house at 90db peak, with subs, so I just need to take it below the threshhold where it can't be heard over the house.

I WON'T be putting an amp in it, though I don't want to limit it down the road. I'm just going to put a speaker cab in it. Right now, just my EVM-12L in an old Crate 1x12" combo cab (temporary speaker cab).

I'd love to get a PSS, but I have some other things too high on the list. A GCX switcher, a couple of X-Blenders, and a 4-6 space rack case for starters.

I had heard about the sandwiching technique for soud dampening. I was considering 2" foam and the Corning 703 together. I'll check into the rockwool though. The "sandwich of dense foam / thick bitumen roofing felt / dense foam" makes sense too. I'll see what kind of foam I can find locally. Once I find the thickness of the foam, I can nail down the dimensions... If I can do it with 3" per side, great...

I'm thinking that this will be a $150-$180 project. My time is worth plenty, but it is also the experience... I need some sort of project therapy, and this'll probably go pretty quick.

Thanks again... Anything else?

[DonMoose]

Maybe high quality dense-rockwool may perform better than the foam.

Maybe I'm just old (50+), but I hear rockwool as asbestos .., which isn't good.

/ hope I'm just old.

[overtone]

Maybe high quality dense-rockwool may perform better than the foam.

Maybe I'm just old (50+), but I hear rockwool as asbestos .., which isn't good.

/ hope I'm just old.

Kind of, not always - it depends on the type.
My bad, I use rockwool as a generic term.
Data sheets will help, or here:
http://www.gearslutz.com/board/bass-tra ... eview.html

On building contracts we get it tested and often in older buildings it means seal the area and have it removed by a qualified contractor.

[Structo]

Yeah rock wool is nasty stuff to breath.