Here I’m going to show you how I built this vocal reflection box for about 40 dollars (US). It can be made cheaper, and really 40 dollars should be the maximum anyone spends on this. You could probably achieve 90% the same results for as little as 10 dollars, depending on what materials you already have lying around. This can dramatically improve your sound, if you’re in an untreated room like I am. It’s easy to make, and the design and cost options are quite flexible.
If you’re anything like me, you’ve already done a bit a research on any possible cheap and easy DIY acoustic absorption options. The problem with that is that there are seriously so many horrible ideas out there from people who really don’t understand sound. And with so many baddies, it’s hard to find good information. I’m by no means claiming to be an expert, but I have done my homework and conducted my own somewhat scientific tests to find materials that actually work. I felt that calling this a “reflection box” was the fairest and most realistic name. You’re not “sound-proofing” or “isolating” yourself (as those would be more complicated and far more expensive), but you are cutting down on some of those nasty reflective frequencies in your room and therefore getting a cleaner recording.
Basically, this box is meant to minimize the amount of “room” you hear in your vocals, while affecting the tone of the vocal itself as little as possible.
The Materials and “Science”
Skip down if you want to see the actual build process. Here is where I’ll explain the materials that I chose and show the results of my tests.
Most of my testing consisted of positioning a microphone in front of a speaker, playing sine waves at different frequencies, and then repeating with various layers of absorptive materials between the mic and speaker. And if you’re thinking, “Hold on. That sounds way too scientific for me.” Then just know that I also basically recorded myself screaming into a box of towels. Science.
More specifically, I placed a microphone and a speaker about 12 inches apart on a table. I isolated these as much as possible from the room by surrounding them in acoustic dampening materials. Then I played sine waves through the speaker and recorded them into Cubase. After testing each measured frequency with each combination of absorptive layers, I measured the peak volumes of each clip and then put the values into an Excel document.
Acoustic treatments tested: 7cm pyramid foam, cotton bath towels (clean, maybe).
I found that just just two layers of towels had better sound absorption than the pyramid foam at nearly every frequency. The only exception would be for a few of the high end frequencies.
Four layers of towels did better than the foam at every frequency tested except for one (4khz). And it’s possible that this could be a result of my less than official testing methods. Where the four towel layers were similar or slightly better on the highest frequencies, they did much better than the foam on every lower frequency (sometimes by nearly double).
Combining four layers of towels with the one layer of foam provided the best results of all the tests I did. The low end results were almost the same as the four towels alone, but by adding the foam, we can see there is a large difference as we get closer to the high end. If you look at the frequencies above 630 hz, there is a noticeable difference. And as you get up to 1khz and higher, again the difference is between 1.5 and 2 times as much as the towels alone.
Here are the results as they were taken directly from the peak levels:
And here are the results measured only by how many decibels of reduction occurred:
The absorption will actually be a little different than how it happened in my tests, since the sound will have to bounce a little bit and maybe hit some treatment a second time at offset angles. I’ll include some sound clips here for you to check out. The speaking parts were slightly closer to the mic and do have a bit too much low end with the box here, but that could easily be fixed with eq or by backing off the mic. And you’ll notice that the boominess didn’t happen nearly as much for the “singing” and screaming parts (I don’t at all claim to be able to sing!). Actually for those parts, the vocal just seems more focused and has less ring from the walls in the room.
Note: There’s a bit of compression on the overall tracks in the video below. I know it’s not totally raw, but you’ll probably never have a vocal track for any purpose without compression anyways. So this makes the clips more helpful, in my opinion. No other EQ or post processing was applied.
Also, while there isn’t really any academic study properly measuring the sound absorption of towels (as far as I know), there are studies which measure absorption coefficients of other cotton materials such as carpets, curtains, and insulation. Many different sources for this can be easily found by Googling “sound absorption cotton.”
The Build Process
Okay, first things first, you need a box. The size and material of the box is totally up to you, although I would recommend getting one that is at least 13 inches on each side. Mine was 13 3/4 inches cubed, and you can already see that there isn’t much extra room in there (mostly height wise). Bigger can be a better thing here as long as you have enough material for the absorption on the inside. Ikea has a ton of options that would work great (and tons of design and color options for you box fashionistas). I’ve even seen people make similar builds from their 5 dollar box options. Here is the one I used: http://www.ikea.com/us/en/catalog/products/80334603/#/90334589
After finding your box, you’ll just need some basic cotton towels. The size doesn’t matter too much since you’re going to be folding and cutting them anyways. I got mine for about 2 or 3 dollars each at this little Asian outlet store near to where I live.
Now you just cut and/or fold your towels into shapes that fit in the inner walls of your box. I just used some scissors and a ruler for this. Using short nails (or staples if you have a strong enough staple gun), you can start putting these in place. If you’re not using a wood box, you can also use an all-purpose adhesive to put these in place, but it may be a pain in the ass if you’re using alot of layers and smaller scrap pieces.
|Nail positioning||Bottom (floor) layers|
I went for 4 layers on each of the sides and top, 2 layers on the bottom, and everything else I had leftover on the very back panel. I chose to keep only two layers on the bottom, so my mic would have a firmer ground to stand on. And I put roughly 8 layers in the back, because that’s where most of the sonic energy is going to be hitting during recording. You can really add as much as you want throughout the whole box, and more is typically better if you have space for it. It’s okay if you need to puzzle-piece some of your scraps together to completely cover the less visible parts. If you’re picky about how it looks, just make sure that the bottom layer and the front edges of the side layers are nice. You can do that on the sides by making the layer closest to the wood about an inch or so longer than the other layers, and then folding it over them and nailing it in all place. Then it can be easily hidden when we start adding the foam. Here’s a picture of how that would look:
Once you have all your towels good to go, you can add some foam. Here’s the link to the one I got:
This one cost me about 14 dollars for a 94 x 94 x 7 cm piece, which was way more than enough size for what I needed. So really you could get a much smaller piece if you can find it available where you live. Arguably, you may not even need the foam if you’re already happy with the level of reflection reduction provided by your cotton towels. This is just going to help out a little with some high end frequencies as well as cover up any uglier sections of your side walls. It’s really just the icing on the cake.
“Happy birthday, Johnny!”
Now you probably need to double check where your microphone and stand sit in your box before you start gluing foam everywhere. I found that I only had room on the 2 sides and on the back. I left the top and bottom foam-free so that the mic would have enough vertical space to stand properly without being obstructed. Measure how much you need, and cut the pieces out to size using your trusty scissors. Once you have them cut, you can begin gluing them in. The glue I used took about 10 minutes to dry, so I had to do one piece at a time. I set everything in place and then added a little weight on top to help it dry evenly. Gluing the back piece in is optional here. I found that there was enough other material in my box to hold the back piece of foam up without needing any glue. I chose to do it this way, so I can easily add more towels later if I feel like it still needs a couple of layers.
|The glue I used||Using weight to help glue set|
Once you have that done, that’s pretty much it! You should have something that looks a bit like this:
So there you have it! Cheap and easy room control at home. Although all the information you need is already here, I would like to leave you with some closing tips and suggestions that I myself may even consider for a future build. What I’ve done here will already be great for any home studio, but there may be some smaller ways to improve it even further that I’ve learned from this experience.
- Add more cotton towels. Remember those absorption charts I told you to Google? Well, you’ll see that the absorption really starts becoming more significant once you get your materials to about an inch thick. Just remember to check your budget though, because at a certain point, it may become more economical just to get actual insulation. (But please make sure you’re doing your research on health and safety if you’re getting anything other than cotton).
- Get a bigger box. This will help you fit a greater variety of microphones (or possibly even multiple mics at once, if you go big enough). It will also help for creating a little more space for vocal air, and for adding those extra towels I mentioned in the first point. I think if I do another build in the future, I’ll start looking for something closer to 17 inches cubed to start with.
- Look for other ways to compensate for the sound. If you’re finding the box is adding more low end, back away from your mic a little bit. Even just an inch or so can really help to counter any added low end. This is working off of your mic’s proximity effect (which adds more bass when you’re closer to your mic), and it’s also causing less energy to smash into your box (which leads to less reflections).
- Get creative, and don’t be afraid to bend my methods. The cool part about this is that you can really cater it to fit both your budget and musical needs. And depending on how you make it, you should be able to modify it later if you decide it needs more of something.