Materials for guitar amp isolation box?

[MikeRocker]

Hello, I just stumbled across this forum, and it looks like a great resource! I did a search, but couldn't find answers to my specific questions...

I'm making plans to build an amp or speaker isolation box for recording, and I'm trying to figure out what materials to use. I (obviously) want to make it as soundproof as reasonably possible. To that end, I'm planning to use 3/4" MDF for the outside layer, and Quietrock for the inside layer (1/2" I guess), as well as some 2" acoustical foam on the inside walls. My questions:

-Are there better materials for maximum noise reduction and durability?

-Will it significantly help to quiet the sound of the box by installing a layer of Auralex Sheetblok of Dynamat between the MDF and the Quietrock? If it's not going to make much of a difference, I'd rather save the money and the hassle, but I'll do it if it'll help. Which of the two is better?

Also, a tech guy at a speaker company suggested that a baffle for one 12" speaker should be 3'4" thick, but it seems like a lot of people use 1/2". Is 1/2" strong enough to support a 12" speaker for the life of a speaker cabinet? Is there a recommended weight limit for a 1'/2" baffle (I know speaker weights vary greatly)?

Thank you very much for any help or advice!

[theunrulychef]

Hi, I made an isolation box out of 3/4" mdf, and 2 layers of sheet rock on the outside - glued on with regular ol' silicone & sheet rock screws. I used cheap stuff readily available at the hardware store, no audio specific stuff. It's very heavy & works very well. The baffle is 3/4" mdf. 2" foam all around the inside. I have a goose neck for the mic mounted inside & a small hole for the cables to make their way out - I never got around to making a patch box.

It's not completely silent, but I can crank an amp late night without waking up the family.


PS - Welcome to the forums!

[MikeRocker]

Thanks for the response! Is it pretty sound-proof with the amp cranked up fairly loud?

[theunrulychef]

Yeah, it's pretty good. You can hear it in the room of course, but it's more like having a muiffled stereo on. The loudest amp I've used it with is a souped up Princeton Reverb. Without the box it would rock the whole house. I've also had a couple speakers in there & the one I liked the best for the application was an old junky Fisher speaker from a Silvertone 1482. It's not the most efficient speaker to begin with, so it's better suited to keeping the volume down. Put a Celestion Blue in there or something & I have no idea how much more you'd hear on the outside.

One thing about how I constructed it is I staggered the layers so they cover the seem from the previous layer - kind of looks like steps when you look at the corner. I never got around to putting any latches on my lid. It's just really heavy & has a 4" lip that goes down around the sides. It fits nice & tight plus I've got weather insulation strip on the edge.

It's not pretty, but it gets the job done. I just realized I have a couple photos of it on this computer. Here they are.