The Isolation Boxes

For those who want to know why I made these isolation boxes, please refer to the previous post.

There were a few goals when building the isolation boxes. We wanted to hold all of the sound inside the box, we wanted to be able to hold a fairly large combo (I have a Fender Hot Rod Deville 4x10), and we want to make it cool. I guess I should mention that I didn't want to break the bank too.

Before I go any further, I have to say thanks to a few people. There was one person in particular who really helped me a lot. He let me use his shop (I don't own a table saw or some of the other tools that were needed), and he came up with a lot of the ideas and methods that we used. He even created the blueprints. Next, I want to say thanks to another guy who helped me. He was a second pair of hands when I needed them, and it was great to have. Lastly, thanks to my wife for letting me do all this without complaint, and watching me throw several hundred dollars down the drain.

As you can see, there were several pieces to the box. The frame consisted of 3/4" plywood as the outer frame, and then 3/4" MDF for the inner frame. In between the frame is plain-old fiberglass insulation (the same kind you put in your house). It is in 2 x 6 feet strips, and I think it is type R-19. I bought a huge bag from Home Depot.

On a side note, I got most of my supplies from Home Depot, and I find the people there to be much more helpful than those at Lowe's. I bought some of my hardware elsewhere (Harbor Freight), and it was very well priced. Home Depot & Lowe's have a gigantic markup on a lot of items. Harbor Freight is much better priced.

The outside frames are 36" tall, 36" wide, and 30" deep. I can't remember exactly what the dimensions are on the inside frames, but I think there is 2" of insulation in between the frames (I think there is about 6" of insulation smashed down to 2"). The layer on the bottom of the box has 2 layers of insulation. If my calculations are correct, that would make the inside frames 30.5" wide, 30.5" tall, and 24.5" deep.

The inner box was easy to make. We simply cut it up, made holes for the joint biscuits (2 biscuits per side, which means 24 biscuits for the inner box, 48 biscuits per whole box), and glued them together. We made sure that the top and bottom pieces of the box were the pieces where we glued the other sheets into the face of the box, and not the sides of the box. The sides were tacked on with finishing nails after the glue was applied. We used size #20 biscuits, and looking back, probably should've done 3 biscuits per side.

The outer box was more tricky, because we had to build it with the inner box and the insulation being applied. In the end, it was easiest to go ahead and build 3 adjoining sides (basically the top/bottom and 2 touching sides) first, and get them glued together. Then we added the insulation for those sides, laid the inner box in, and started applying insulation and outer boards one side at a time.

The lids were cut 12" from the top of the box. It was quite difficult to get them cut. In the end, we just laid the box on the table saw, extended the table saw blade as high as it would go, and pushed it across. Once we had cut a whole side, we just rotated the box, realigned it, and pushed it across again. It was important to cut it after the boxes were completely put together, so that the lids would fit perfectly. To keep the inner box attached to the outer box in the lid, we drilled holes in the inner box, and screwed nylon strips to the outer box and inner box. It works great. I then applied some rubber stripping to the inner box to help with the seal.

I then applied paint: 3 coats of primer, 2 coats of black, 2 coats of polyurethane. If I had this to do over, I would've painted the bottom part first, applied the casters, and then painted the rest. Because I waited until the end for the casters, the box would scratch and the corners would crack a little when I would turn it from side to side. That could've been avoided, and some repainting could'be been avoided if I had put the casters on first.

Once the paint was on, I put the casters on (2.5" casters). Then it was time for the hardware. First, we started with the nylon strips that held the lid up. Then came some 'L brackets', which I applied to the top corners of the larger half of the box.

After the rest of the typical hardware additions (handles, latches, corner pieces), we added the plugs and soldered them to the box. We have male XLR plug, a female 1/4" plug, and a recessed male power plug. The XLR plug was soldered to about 6 feet of balanced mic cable which terminated at a female XLR jack, and then a female 1/4" plug was soldered to 6 feet of instrument cable, with it terminating at a 1/4" jack. The XLR is obviously for the mic, and the 1/4" goes to the amp. The power plug didn't need to be soldered (had screws, like a light switch), and it was attached to a standard 6 plug power strip.

The end goal was to make sure that all we had to do was plug in once, and the only time the box needed to be opened was to turn on the amp. We wanted to provide enough cable so that everything could be reached within the box, and to have enough power plugs so that wall-warts could be added if needed. Wall warts come into play because we were going to add fans (using standard computer fans, powered by soldering them to wall-wart (AC/DC converters). The problem was that we should've added fans in the beginning. The use of fans would require a beveling system, so that sound didn't leave out of the holes for the fans. We would need 2 (one for in, and one for out), and ideally would want the "in fan" at the bottom of the box, with the "out fan" at the top on the opposite side.

We chose not to install the fans due to the fact that we would've had to have done a significant amount of cutting that would've been done, the risk of sound escaping, and the fact that I had exceeded my budget for this project. I ran the amps at church for about 3 hours one day, and while the boxes got a little hot at the top around the tubes, the heat was certainly within the boundaries of what is acceptable by an amp and its heat tolerances. I would prefer to have fans, but I just don't see it happening due to the amount of sound that would end up leaving the box.

After playing in the amp, we immediately noticed that bass notes were the worst. So we put the amp on some foam squares (actually, they were little foam seats for children to sit on), and it cut down on a lot of the vibrations. With my amp (60 Watt Fender DeVille 4x10) turned up to 7, you can still hear the sound outside of the amp, but it is definitely minimized, and is insanely quiet for the amount of noise inside the box.

As far as sound goes, it made my rig sound much better (going through a Digitech RP1000), but it made the other guitarists' rig sound worse (MesaBoogie 2x12 tube amp). The reason is that it deadened his sound. His amp was mic'ed in a huge room, and the sound was much more open and rich, almost like a natural reverb. Well, with the amp enclosed, that changed things big time, and it sounded very wooden. A reverb pedal is definitely in need.

Total, I think I spent about $350 a piece on each box. The wood was $300, and with all of the hardware, casters ($5 a-piece), wiring, insulation, and everything else, the price added up. The only upgrades that I wanted were some sort of assistance for opening the box, some locking casters, and some foam for the inside of the box (sound foam). If you have any questions, feel free to ask.