We all want to make mixes that sound cleaner, clearer, have more slam, more power, and more color. We all want interesting, professional sounding mixes, right? What can we do to close that gap between our mixes and the songs we hear from the pros?
I shared in a previous post on how to use reference checks to better help your mix sound pro and powerful. It's a tool I rely on with every mix I make. And I shared in a different post that mastering is more about fixing problems the mix contains than it is a defined process of its own. But is there a secret to making mixes that require less fixing in mastering? This is especially important for people mastering their own work.
There is. And the secret is to control the acoustics of your room.
Why Acoustics Matter
I know it's not fun for most of us to think about. Acoustic treatment sounds complicated and expensive, and it doesn't have the cool-factor that a shiny new piece of gear has, or the immediacy of downloading a hot new plugin. But the acoustics of your room shape your music far more than you realize.
Imagine a photographer has a big grease smear on his camera's lens. He'll still have a good idea what the subject of his picture is, but because his equipment is smeared with grease, he can't act with precision to capture exactly the shots he wants. Not to mention, there's a major flaw in each shot. And further, he probably can't even tell if each picture is in focus. Yikes!
It's the same with room acoustics. The average room accentuates frequencies that shouldn't be accentuated and minimizes other frequencies that shouldn't be minimized. Further, poor room acoustics cloud the details, preventing you from hearing with clarity. But when you fix some of these problems, you can begin to hear your mix with so much more detail and precision. Then you can hone in on the problems easily hearing what needs to be fixed, providing the direction you need to take a large step towards more professional sounding, better-translating mixes.
Why Does This Matter When My Fans Don't Have Acoustic Treatment?
It's true, most of your audience won't listen to your music in a treated environment. But consider that many of your listeners will be listening on headphones, where room acoustics have no bearing. They'll be listening to your music naked, not through a heavy parka. That's important to know.
But also, not all rooms with bad acoustics are the same. In fact, no two rooms are the same. All have slightly different problems. You need to be able to hear with clarity what needs to be done in your mixes so you can make good mix decisions, regardless of the environment your music will be heard in. You can't prepare for every stereo and every room that will play your music, but you can aim to make your music as clean and clear and balanced as possible, so it has the best chance of sounding good to every listener on every stereo.
And more to the point: you as the engineer strive to make perfect music, no matter who will listen back and what they will listen on. Good acoustics will help you zero in on what needs fixing.
Common Room Problems
What problems does your room likely have?
1) Masking of detail
- Sound travels directly from the speakers to your ears, of course. But sound also bounces off nearby hard surfaces and reflects back to your ears slightly later than the direct sound. This is a problem, particularly in small rooms. The result is that the sound emanating from your speakers sounds cloudy and indistinct, even a little phasey. High-frequency detail is significantly reduced, panning sounds less distinct, and this problem often adds a bright, ugly sheen to what you hear.
- To remedy this, place absorption at each of the first reflection points in your room. In other words, put something soft and spongy wherever the sound bounces from your speakers before reaching your ears. You can find the 'first reflection points' by using the 'mirror trick': sit in your mix position, and have a friend hold a mirror flat against the wall, moving it around. Wherever that mirror can be placed that allows you to see one of the speakers in the mirror, you should place absorption.
2) Uneven bass response
- The dimensions of all rooms cause problems: the walls reflect low-frequency sound waves back into the room. And the physical width and length of the room determine which wavelengths of bass get doubled up and which get canceled out, meaning that some frequencies are portrayed as artificially loud while other frequencies are artificially reduced in volume. This leads to very skewed mix decisions in the low-frequency realm, encouraging mixes that don't translate.
- The solution for this is to absorb as much of the bass as you can by using bass traps. Bass traps absorb bass energy, keeping it from bouncing around the room to further boost and null frequencies. The sooner in time your bass energy is absorbed, the less boosting and canceling occurs in your room. 'Trapping bass' sounds undesirable, since we all love the sound and feel of clean, deep bass. But that's exactly what we achieve when we absorb bass. Bass traps can't absorb bass before sound passes from the speakers to your ears, but only after bass has been bouncing around the room - and it's those extra bounces that lead to that messy, uneven bass sound. By soaking up the surplus bass energy reflecting around the room, we can hear more of the original sound from the speakers and subs, which gives us that strong, clean bass sound that we love to hear. Bass traps can be placed anywhere in the room, though they are most effective in the corners where bass energy builds up the most.
3) Tubby bass response
- Bass energy is very hard to absorb: it requires a lot of soft material to pass through before the sonic energy of bass can be transferred into kinetic or thermal energy. What happens when there isn't enough soft material in the room? The bass continues to bounce around and around, taking a long time to die. This sounds very ugly in music, in that the kick drum sounds more like a whoosh than the impact it's supposed to be. And it makes it difficult to discern the tone and even the pitch of synth bass and bass guitar notes. If you have a hard time hearing if your bassline is in tune, or if you're unsure if it's your drum samples or your room that makes your kick drum sound wooly and soft, you're going to have a hard time making music that sounds good on other speakers in other rooms too.
- Fortunately, the solution to this is the same as the solution to uneven bass response: absorb as much of the bass as you can as early as you can with bass traps. Bass traps are best built thick, a minimum of 4", but hopefully 6" or 8" thick, or even thicker in the corners. Absorbing the superfluous reflections of bass around your room will help clarify and tune up melodic bass content, and provide the slam that percussive bass deserves.
4) Ugly reverb
- Quite simply, this is caused by having too many bare, hard surfaces in your room. You can hear it from clapping your hands, and even just speaking in a lot of rooms. I know I could when I first moved into my current studio space, an extra bedroom in my apartment. When the high frequencies are allowed to bounce around endlessly from bare wall to bare wall, from hard floor to bare ceiling, the room takes on an artificially bright sheen that isn't pleasant sounding at all. And when your room has its own reverb going on, you'll tend to mix without enough reverb, which will sound funny on headphones or in other rooms, or you won't hear your music with the clarity you need to make the right mixing decisions as the reverb in your music conflicts with the reverb in your room.
- The trick to squash this, yet again, is more absorption. But this time, you need to aim for more coverage instead of extra thick absorption, since high frequencies don't require a lot of thickness of mass to absorb. Place absorption on your walls wherever there is room.
- Flutter echo is the high-frequency zinginess that many rooms inherently have. Virtually all bedrooms and small rooms suffer from flutter echo. It's caused by having hard parallel surfaces, like walls, that are left bare. You can often notice something is off just from spoken voice, but it's very easy to identify by clapping your hands once and listening for little rapid zings back and forth. This problem sounds less like reverb and more like weird delay.
- Like all the other problems I've mentioned today, the solution is absorption. It doesn't need to be thick to combat high frequencies, but it does need to cover as much surface area as possible, particularly in asymmetrical patterns. After all, you only need to treat one side of two opposing walls to kill flutter echo.
First, I should mention that every solution I'm offering today is accomplished with absorption. Diffusion is also a powerful tool for acoustic treatment. In short, diffusion disperses sound waves minutely in a myriad of directions instead of strongly in one direct reflection, accomplished without absorbing the sound. Used in quantity, it maintains or even lengthens the decay of sound in a room.
However, good diffusion is difficult and expensive to implement. Also, it is only suitable for large to very-large rooms, while many commercial studios and the vast majority of project studios exist in small rooms. And most importantly, the five common room problems I mentioned above are the five you're most likely to have in your room, and the five that are most important to treat. And it so happens that all of them are most easily and effectively treated with absorption, not diffusion.
Second, though I mentioned that detail masking and ugly reverb and flutter echo all can be absorbed by thin acoustic treatment, it's vitally important not to only use thin absorption. If you only use thin absorption, like 1" pyramid foam, for example, you'll suck all the high-frequency reflections out of the room while doing nothing to combat the bass problems and almost nothing to combat the mid-range problems in your room. To avoid this pitfall, it's important to treat with a mix of depths of absorption with a minimum of 2" thick for any absorber. It's more important to cover 30% of your walls with absorbers twice as thick than it is to cover 60% of your walls with absorbers half as thick.
Milo, I Want To Do This Right
Good, so do I. You can buy absorption from companies like RealTraps, GIK Acoustics, Ready Acoustics, and more. Or you can build your own, like I did, to save money. If you're building your own, use rigid fiberglass (I used Owens Corning 703) backed by a wooden frame and wrapped in breathable fabric. Cheaper alternatives like mineral wool are also an option, though they may not maintain shape their shape as neatly. My favorite construction video is by Nenne Effe on YouTube: she makes it look easy, but her clever design avoids many of the pitfalls of other absorption recipes, and she does it all on as tight a budget as possible.
A good starting point is to place panels 4" thick at the first reflection points: the side walls, behind the listening position, and ideally in front of the listening position and on the ceiling as well. Add thicker 6" traps, or even better, 'super chunk bass traps' in the corners of the room. And add miscellaneous 2" traps in any areas left over to soak up as much ugly room reverb and flutter echo as you can.
Milo, I Can't Afford To Do This Right
No worries, neither could I for many years. You can check your mixes often on headphones, since acoustics have no bearing on the sound you hear with headphones. And you can sit very near to your speakers or monitors: the closer you are to your monitors, the quieter the room's acoustics will sound to your ears by comparison.
Egg cartons are a virtually useless acoustic solution and a fire hazard, so don't start lining your walls with them just because the shape looks similar to pictures you've seen of "studio foam". And those pyramid-shaped studio foam products are a bad choice anyway: the material is too thin and porous to reflect and diffuse high frequencies, much less low frequencies, so by adding pyramid shapes to the foam, you're digging into the thickness the product would otherwise have, which just reduces its low- and even mid-frequency absorption.
You can hang blankets on your walls. The thicker the better. Even the thickest blankets won't do much for your bass problems, but it can help tighten up the highs and high-mids, giving you a bit more instrument clarity and a bit more precision with panning and location.
Things get trickier if you're recording instruments or voice with microphones, because acoustics are paramount for recording too, not just the mixing environment. If you have a large, irregularly shaped room to record in, do your recording there. If you can afford the Portable Vocal Booth made my RealTraps, that can go a long way toward helping you achieve a clean and dry vocal sound. If you can't afford one, see if you can assemble a temporary version out of couch cushions or anything else that is plush. And if you're recording something other than vocals, bring as many cushions and pillows and comforters as you can into the room you're recording in, to help soak up some of the room's ugly reverb.
That's about it for the basics. Write in the comments below if you'd like me to explain an area more clearly or go further in depth. If you want to dig deeper, I shared about my own journey with acoustic treatment in another post. Also, if you haven't put thought into speaker placement, that can have a huge impact on what you hear as well. I wrote more about that here.
Also, feel free to let me know if there are any aspects you feel I missed, or if you'd like to share your experiences with acoustics or room treatment with me: I'd love to hear them.