Cabinet isolating.

[DracWell]

Hi..

Does anyone know how to build a soundproof box to put a 4x12 and a mic into it so I can turn up the volume without being thrown out to the street by the landlord? ;)

Thanx in advance.
-Mattias

NP Dead Man Rising - From Deep Within

[EricV]

Hi there... I did use that kinda system on tour in the States once. I just got myself a road-case ( you know, the ones you can get custom-made... they´re used for transports on the road )
I had a 2X12" in a closed case, and there were two holes which were adjustable in size. Through those, I put in the wires from the poweramp and to the mic.
Sounded great, not only keeping the volume down but also giving it a nice sound.
If you don´t wanna shell out that kinda money ( after all, custom-cases are expensive, although you sure can try to get a used one with the right size... many big PA-providing companies often sell those for not much money ), you should use thick wood ( I once heard of a wood that was kinda dipped in oil, soaked with it, those are really tight, heavy and should be good for keeping the volume down ) and some fitting stuff ( from case-building ) to assemble it.
I recommend to apply that foam-stuff that is used for studio- and rehearsal room-isolation to isolate it. YOu can get that stuff in bigger musc-stores
Hope this helps
Eric

[DracWell]

Thanx!

I'm just designing a vocal booth that can be taken apart so it's easy to move when you move around the country =)

That one SHOULD be able to isolate the sound from a 4x12 too.. Oh well... It's ok right now aslong as I record during daytime

[steve grimm]

The only things that stop a sound wave are: Rubber, cement, and sand.

[Gandalv]

Erm..doesn't just about anything stop sound, as long as you have enough of it?

[LarryJ]

Theres an excellent series of articles on www.guitar.com about this. Its like a 28 part series with an award winning sound engineer. He talks about baffling and some other stuff you might be interested in.

[metalprep6969]

How would you fit the mic into the road case? From what I've seen, there wouldn't be room for the mic or the soundkilling foam padding inside a case cuz they are built without much extra space inside of them. Are you talking about a case that's custom-sized? If so, what would the dimensions be roughly?

\m/

[metaljustice83]

would using a hot plate, have the same effect just easier?

[Rented]

DracWell, this question is right up my alley :cool: I have a degree in acoustics an specifically in Noise & Vibration Control. This post will be a bit technical, the purpose being for me not to tell you exactly what to do, but for you to understand what needs to be done in general.

steve grimm is, of course, wrong. Any material will help stop sound waves. Its a matter of how effective they are. Actually, "stop" is the wrong word. You either absorb (some of) it, or you dampen it. You absorb air borne sound waves, you dampen sound waves in solid materials (usually termed vibrations).

If your objective is to make it quieter inside the box/room, you want to absorb the sound waves (assuming the walls are thick enough not to act as membranes). If your objective is only to make it quiet outside the box/room then you may get by with only dampening the box's/room's walls. In your case, I think you should concentrate on dampening the walls, and maybe add a bit of absorption to lower the reverbaration inside the box.

There are basically two ways to make a wall dampen vibrations in order to reduce the transmission factor (that's the tech term for how much of the sound hitting the inner wall actually makes it through the wall and out the other side :) ). You can use weight, or you can use some sort of dampening material in the wall. A combination of both is best, as there really is no substitute for weight when it come to sound transmission. Actually, it gets a bit more complicated than that, because pure weight is not enough. The material should be as soft and flexible as possible and as heavy as possible. A reaaly dense (heavy) and soft rubber matt is excellent for these purposes. A really dense conctrete wall is (relatively) useless.

Because weight is such a burden and costly to ship or carry around, modern technology has come up with some interesting materials that come close to (and sometimes improve upon) the soft heavy materials. These are so called viscoelastic materials. Viscoelastic is a state between viscous (e.g. running water) and elastic (rubber band). A viscous material never returns to its original state, and elastic material does so immediately. A viscoelastic material will do so, but with some lag. Put a rubber band in the freezer for a while and then take it out and stretch it out. You will notice that it returns to its original state, but sloooowly.

Why does this work so well? That lag is the secret; it absorbs more energy than merely being stiff, or being elastic. Try the following experiment with a friend. Grab hold of each other's hand and ask your friend to relax and follow your hand. Then move your hand/arm forewards and backwards. Easy right? Now ask him not to budge. You will excert some energy trying to move your arm, but nothing will happen. Now, ask him to loosen up a bit, and give in to your pulling and pushing, with a little resistance, but ONLY after a little delay! Keep that delay all the time, not just in the beginning. You will notice how much energy you are using to move your hand back and forth.

For reasons I will not be explaining, the best place to put this material is right in the middle of the wall, where the wall moves the most. This creates a so called sandwich construction. So, you should make your walls out of two sheets of MDF (medium density fiberboard [spånplatta]) or HDF with a viscoelastic material between them. Since you live in Sweden, call these guys and order their DG-A2 dampening glue: http://www.swedac-acoustic.se/pages/vibra.damp.htm#DG%20A2. Easy to use, just glue together the two sheets of MDF with this. The thicker the MDF sheets, the better. Call these guys and ask for detials on application though.

One last thing. Openings are the enemy! You will obviously need to thread cables, etc. into the box, have a door, etc. Sound loves to escape through those holes. Try to get hold of some foam to keep those holes sealed up.

[steve grimm]

Dead air space