Acoustic Treatment: Where To Start?

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Acoustic Treatment

photo via auralex.com

Acoustic treatment is a widely discussed and argued topic on almost every audio blog, forum, or website. It’s super easy to get confused in all that noise which often times leaves you, and me, frustrated.

Over the years the one thing I learned from recording and mixing in my own studio, watching other well respected internet audio dudes videos, and reading numerous articles, is to keep it simple.

I’ve tried reading all the super technical articles around the science behind acoustic treatment and how it all works, and I just find myself with information overload.

The truth is we are all most likely inside a bedroom, a garage, a basement, or whatever space inside your house or shed you could find to set up a DIY studio.

These spaces were NOT meant for recording and mixing. They were made for every day living and storage, and typically have parallel walls with highly reflective surfaces. These are not ideal recording and mixing environments.

So the solution to converting these unfit spaces into a room we can actually get some good results from, is adding a little acoustic treatment.

Now before I go any further, Some people have very valid arguments that you can get great recording and mixing results with very little, if any acoustic treatment.

The truth? Yes you can, but I personally think its beneficial to the individuals who are just starting out to add at least some acoustic treatment to their rooms. Not always, but usually the people cranking out good mixes with no acoustic treatment are pretty seasoned.

Meaning they know how to “learn” a room and get passed all it’s audio imperfections. Their ears are more experienced and trained to know how to compensate for any issues that are present. These people are more familiar with using reference tracks to determine
the moves they need to make inside their rooms.

More power to them, BUT I will admit i’m pretty seasoned, but I’m also intimidated a little by trying this method. I prefer adding some treatment on the walls and ceiling to give me a little piece of mind when I’m starting a new project.

Before I get into what kind of treatment you need, and where to put it, I want to get into the why.

Why Acoustic Treatment?

Like I said before, I don’t want to get too sciencey on you ( that’s a new word), but I do want you to understand a little bit of the reasoning behind it.

Basically, when you are in a room with 4 parallel walls and highly reflective surfaces you are going to have sound waves bouncing
all over the place and colliding with each other.

All this bouncing and colliding can cause some serious harmful and deceiving to the ear audio problems.

The main one is called Comb Filtering.

The wikipedia definition of a comb filter is:

“a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced notches, giving the appearance of a comb.”

photo via wikipedia

Acoustic Treatment

Basically what this means, is sound will bounce off the reflective surfaces, (walls, ceilings) and collide with each other at different times and spaces.

So if you’re are mixing in front of your speakers, you will get the direct signal from you speakers, but also the same signal that has left your speaker, hit a wall, and bounced back to your ears. These two signals could potentially arrive at your ears at different times.

If the two audio waves (think waves in water) don’t exactly line up, meaning the peaks and valleys of the waves are opposite, they can actually cancel out each other.

For example, If you’re mixing a snare drum that was recorded with a fat tone, the two waves hitting your ear at slightly different times can make the snare sound like its thin and powerless.

Then you would start adding all kinds of plugins trying to add beef, and tone back into that snare. In reality you were just lied to by your room. The snare is still fat, but your room is messing with you!

Also, in smaller rooms like most home studios, bass, or low end is a big problem area.

Low end frequencies need more room, or length of time to dissipate. It’s hard to do that in small rooms.

Low end frequencies tend to build up in the corners of your rooms and can wreck havoc on the perception you will have on how much, or how little bass content your recordings and mixes have.

So we need to treat this issue as well by placing what they call bass traps in the corners. They’re just really thick absorbers.

I can go further and get more complicated, but lets stop there and get into the what and where?

What Kind?

You have 2 kinds of acoustic treatment. absorption and diffusion.

Absorption… well… absorbs sound and traps it. It keeps its from bouncing around the room.

Diffusion lets the sound bounce around the room, but breaks it up. It prevents the same sound from hitting one wall,
bouncing off another wall, and then colliding with the direct sound which can cancel earth other out.

They basically solve the same problem just in different ways.

I first started out with only absorption, and now I have a little of both in my studio.

Where to put it?

The main areas you need to put acoustic treatment are at the early reflection points near you listening position.

So directly to the left, right, top, back, and front of your ears.

Right now as I’m typing this, I’m in my mixing position. If I look to my left, right, and above my head, I will see some absorption panels I’ve built. If I look behind me on the back wall directly behind my head, I will have some diffusion panels I’ve built.

At the moment I do not have any in front of me behind my computer. I have a glass window looking into my small live room from my control room. I am in a one car garage converted into two rooms.

The key is not to be perfect, we are not in perfect rooms, but to try and address some of the issues we’ve talked about.

I have some more absorption panels (2’ x 4’) I’ve built spaced out on the walls. So there is a good mixture of bare wall, and absorption/diffusion panels.

You don’t want to completely cover your walls and kill all the acoustics. I don’t know if there is a ratio of bare wall to treatment, but I’m probably at 60:40 ratio, 60 being the treatment, 40 bare wall. Maybe 50:50?

Again my room is still not perfect. I have dramatically improved it though and thats the important part.

You can go to websites like www.auralex.com, or www.sweetwater.com and buy some acoustic treatment packages, but they can get a little pricey.

If you are like me and like to do everything DIY, you can find some material at hardware stores or home improvement stores.

For my absorbers, I built 2’ X 4’ wooden frames out of 1” x 3” cuts of wood, stuffed them with safe n sound roxul 3” thick insulation batts from lowes, and covered them with burlap. Then I just hung them on the walls. I stuffed some burlap sacks with no frames with the same stuff and hung a few on my ceilings.

For my diffusers, I cut up a bunch of 1” x 1” boards at all different lengths, 1”, 2”, 3” and 4”, and glued them on a piece of thin board. So it’s a bunch of wood sticking out at all different lengths to break up the sound. It looks pretty sweet also! I stole the idea from Blackbird Studios in Nashville, TN.

I think I was supposed to follow some sort of exact mathematical blueprint on what lengths to place where, but ain’t nobody got time for that. It does the trick.

Another hack to help out with some audio issues, is positioning your desk and speakers in the middle of a wall instead of pressed all the way into a corner.
This will get you in a symmetrical spot in your room where less of these issues can occur.

I’ve shot a video of my studio below showing you my panels and where I have them placed inside my studio. I hope this gives you a better understanding of where, what, and why you need acoustic treatment.

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