Room Acoustics Treatment Guide
We’ve all been there. You’d like to have a more acoustically neutral room, but that costs money, and you can’t really spend it on treatment right now. In this article, you will learn one of the most important aspects of a great home theater.
At home, we might be looking to deaden reverberations from untreated walls, soundproof the room to be more courteous to roommates, or address phase issues that standing waves in the room can cause.
Let’s take a step away from home theater for a minute and talk about something that more people have experience with - a kitchen remodel. While the design is fun, the function is at least equally important. What looks good and what works well aren’t always the same thing. This same concept also works for home theaters.
A theater that has addressed acoustical issues enables the movies to be far more involving. They draw you in, and you connect to them in an entirely different way. That, my friends, is what a great home theater experience is all about; escaping from the stress of our work lives and immersing yourself in another world for a few hours.
Getting great acoustics comes down to one simple concept: controlling reflections.
Understanding Sound Reflections
As you probably know, sound covers a pretty broad spectrum from the lowest low bass rumbles of an explosion to that sparkling high hat or tinkling of glass. As the low bass tone from your speakers or subwoofer(s) bounces around the listening room, depending on the room’s dimensions, those tones will build up in certain areas of the room and cause two problems.
Some low tones will be totally canceled out by the reflections and you’ll hear very little bass, yet other tones will get more pronounced and overwhelm other frequencies. Rooms with equal dimensions tend to have more problematic modes. Also, as a general rule of thumb, the smaller the room, the more issues you will have.
If you have ever noticed that in one listening position of your room, you can hear lots of low-frequency sounds and in another spot you can barely hear deep bass, you are experiencing how low-frequency energy can be an issue.
If you’re lucky enough to be building your home theater room from scratch or have some flexibility in the room dimensions, having a more rectangular-shaped room is best. The Golden Ratio (1:1.6:2.6) is actually a perfect way to go, with the first number being the height of the room and the other two being the length and width.
If your room is like many family rooms we see in modern homes, you may have many openings and it will be pretty far from a standard rectangle. While your initial reaction might be that this is a bad thing, depending on the shape and dimensions, it could actually work out in your favor, at least when it comes to lower frequencies.
Subwoofers and Room Correction
A few models of subwoofers come with a microphone kit for room correction. A typical room correction system involves placing the microphone in the primary or several of the seating positions. Having more than one subwoofer in a room will do wonders to minimize bass modes.
When you have the energy coming from different places in the room, the modes tend to smooth out. Two is better than one and four is even better than two. Doing something like this will give you and your guests an even bass response in most seating positions in your theater room.
And while room correction is great, starting out with your subwoofer or multiple subs in the best position will make a huge difference.
One other solution to bass modes is the use of acoustic treatments called “bass traps”. These are typically placed in the corners of your room. Bass traps have to be pretty large in size in order to trap the low bass note reflections. There are some mixed opinions in the audio community on their use.
As you can see, this part of the equation has many variables. At Audio Advice, our team of experts can look at your room plans and make suggestions based on our years of experience.
Treating High-Frequency Reflections
If you’ve ever been in an empty room with nothing but sheetrock walls, you know what upper-frequency reflections sound like -- it’s got almost an echo chamber effect. There are many choices for helping to reduce high-frequency reflections. Of course, in a home theater, this usually means acoustic treatments and acoustic panels.
While this article is specifically focused on acoustics for dedicated home theaters, we realize that many of you may have more of an open-concept media room. What we’re really trying to do is eliminate the chance of sound bouncing off of walls and windows and reflecting back at us, competing with other sounds. If we can tame the sound at the first reflection points we can keep most of it from continuing to echo around the room.
The best rule of thumb is to think soft! One easy way to find the reflection points is to sit in your main chair and have someone walk around the side walls holding a mirror against the wall.
A dedicated home theater room for movies, sports, and TV will have the most options for acoustic treatments. This can range from some basic absorptive wall panels spread out on your wall, to a full-blown acoustic treatment package hidden behind a custom stretched fabric system that covers all of the wall surfaces.
A full-blown acoustic design may include several different types of panels placed strategically on your walls. This is the ultimate way to go, but for the purposes of this article, we are focusing on the best value, which will be panels that absorb sound.
An important point to note is that some reflections are actually important. It’s really about finding balance and eliminating the modes more than deadening all sound. If you completely cover your room to the point that it can only absorb sound, you will wind up with a theater that lacks a sense of dynamics.
If you are digging around, you may see something called RT60. This is a measurement of how long it takes the initial burst of sound to drop by 60 dB after the sound stops coming out of your speakers. The number you are shooting for here will vary with the size of your room. We suggest you not get too wrapped up in this number unless you are going for an all-out design and first think about taming the reflections.
| Wall Surface | Recommended Acoustic Treatment |
|---|---|
| Side Walls | Acoustic Panels (absorptive) |
| Rear Walls | Acoustic Panels (absorptive) |
| Around Screen | Acoustic Panels (absorptive) |
| Corners | Bass Traps |
| Ceiling | Hanging Acoustic Panels |
| Floor | Rug or Carpet |
If you are trying to get the most bang for the buck, placing a few absorptive panels around the room is probably your best bet. A good rule of thumb for this method is to calculate the total surface area of your two side walls and get acoustic panels that will fill up about 35-40% of that area.
So for a wall 9’ tall by 18’ long, four panels 36” wide and 6’ high will do the trick. You can greatly improve a room that is just painted sheetrock by doing this for the two side walls, rear walls, and either side of the screen with a few panels. Should you wish to get into using different types of acoustic panels and take it to another level, please reach out to our team.
Center Channel Speaker Considerations
The center channel speaker is perhaps the most important speaker in a surround sound system. This is where the majority of the dialogue comes from. Of course, in the real world, this is rarely what happens. Oftentimes we come into existing home theater only to find the critically important center channel relegated to a cabinet to hide it.
While the designers or cabinet makers may have the best intentions, a lack of experience or attention to detail in this area means that most center channels in cabinets just don’t sound very good. The issue comes down to the resonance produced by the wooden cabinet.
We’re purists here at Audio Advice, so we will usually recommend having the center channel unencumbered. At the same time, we realize that for many of you, it just has to be in a cabinet. Luckily, in our many decades of installing home theaters, we’ve picked up a few tricks along the way -- and we just happen to have one to address this very problem.
First, find some of those little stick-on rubber feet at your local hardware store. Put those on the bottom of the center channel to help isolate it from the wooden shelf. From there, find the crossover setting for the center channel in your home theater receiver menu. It is probably set for 80hz. Put on a movie with some people who have deep voices and listen to a couple of minutes of dialog. Now try raising the crossover to 90, 100, or even 120hz.
As you do this, you should notice less resonance as you are removing deeper bass from your center channel thus preventing the wooden bookcase or cabinet from resonating.
Acoustic Treatment on a Budget
First of all, it won’t cost you anything to arrange your space in such a way that minimizes reflections. So, start by moving your speakers away from the walls. You’ll want your desk to be centered on one dimension in your room, and at least a foot away from the walls on any side.
You want to hear as much of the signal coming directly from your speakers as possible, and as little of the reflections as possible. So, point your speakers such that the two speakers and your head form an equilateral triangle when sitting at your mix position.
The next step will be to find any soft fabric materials you’re not currently using, and arrange them in your studio space. Then, arrange or hang them on any flat, hard, reflective surfaces (like bare walls or windows) that are in your studio.
If you want to effectively do some home studio acoustic treatment for under $500, I recommend making your own acoustic panels and / or diffuser. DIY panels can be just as effective as store-bought ones, and they offer a more customizable look as well as better value for money. What better way to spend a weekend than making your own acoustic treatment?
It’ll be fun, and your studio will sound so much better once you’ve hung them up. If you’re a young person reading this, and you plan to try to make your own treatment, good for you! You’ve got it together way better than I did at your age.
If you don’t have the funds to buy a full set of panels, but you still need accurate monitoring capabilities for mixing or mastering, I love to recommend Sonarworks’ software. Although this won’t directly help in terms of treating your room, it’ll provide a trusted reference point.
In other words, it brings your setup closer to a truly flat frequency output. This makes SoundID a great option for those who have a bit of money to spend, but not enough to invest in a full set of panels. I use SoundID whenever I’m mixing with headphones, and I suggest switching between your headphones and speakers as you mix.
Mid-Range Budget Acoustic Treatment
Now we’re cooking with gas. If you can afford to spend up to $1,000 on the acoustic treatment for your home studio, you’ll likely be able to achieve a really solid sound without having to DIY that much. At this budget, it’s time to consider the floor and ceiling.
These are reflective surfaces just like your walls, and treating them can make a huge difference, especially if you’ve got hardwood floors in your home. Laying down a rug will isolate vibrations from your desk and absorb additional stray reflections. If you’re really feeling it, try hanging a panel from your ceiling.
The ceiling is another reflective surface, and adding a hanging panel (a.k.a. For my personal home studio, I chose Output’s new Eco Acoustic Panels. They look attractive and perform admirably in my space (Output didn’t sponsor this post, but in case anyone from Output is reading this-call me).
Output’s Bass Traps are very similar in form, but they’re designed to fit in the corners of your room. I’ll give an honorable mention to GIK Acoustics’ panels as well. I considered these, but decided that the Output panels fit better with my room’s decor.
They’re similar in price to the Output panels, if not a little cheaper, and I know several colleagues who’ve use them and experienced great results.
While understanding the basics of acoustics and these tips are important, the fact of the matter is that getting acoustics perfect is really a science. If you have or are planning to make a serious investment in the home theater gear in your room, we highly recommend a full acoustic plan. At Audio Advice, we can be a big help with choosing design and products.