We talk about getting great sound all the time, but what does that mean? I'd say there are a few key components to your monitoring situation:
Quality monitors (the actual speakers you're using + the amplifiers that drive them).
The interface you're using to send signal to those monitors (DAC)
Your own ears and the level of fatigue you currently have.
The room you are listening to them in.
Today, we're going to talk about the room you're listening in.
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Types of Problems
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I think the most important thing is to understand what the potential issues with quality are, as they pertain to your room. A horrible room is going to ruin the sound of the best monitors. And a lot of us aren't using the best monitors to begin with, so we really need all the help we can get.
But back to rooms:
Imagine if you were trying to mix on a desk next to a highway with cars driving by?
Or in a thin walled apartment right next door to loud angry neighbors with a baby and blasting music going all the time?
Or mixing on a desk in a sewage drain?
In these scenarios, it's pretty obvious that you're going to have a hard time mixing. The sewage drain is going to have long echoes that make it hard to hear anything clearly. And the other two examples are going to have other sounds bleeding into your mix, or the noise will mask what you are trying to hear.
Here is a breakdown of the problems you can have:
Certain frequencies are artificially amplified or diminished.
Reflections from each left and right side make your stereo image blurry and it's very hard to tell exactly where and instrument is in your mix.
The monitors sound uneven (one is louder than the other)
The monitors are out of phase
Comb filtering makes the audio sound "weird".
The room is too "dead" (makes things sound small and closed in are)
The room is too "live" (makes things sound bigger than they really are)
These are the things we need to think about and we're going to go through them all.
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Certain frequencies are artificially amplified or diminished.
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Audio is a predictable science. It's really just some very complicated math. I don't like math, but I really like audio and music. So I'm not going to make this math heavy. If you want to know more, you can buy a book on audio science. But we do need to understand a few things.
The main thing you need to know is that each frequency of audio has a wave cycle. The wave goes up, then back down and then back up to the center. This is represented visually in your DAW (Unless you have a DAW that doesn't represent the wave form). In real life, this is sound pressure expansion and compression. Sound is just a series of air pressure changes. No air, no sound. This is why there is no sound in outer space.
So why does this matter?
Both in the physical world and in your mix board / DAW, when a wave expands on top of another wave, they are combined together to make a bigger (louder wave). And likewise, when a wave compresses with another compressing wave, they diminish the sound together (lower volume).
If you layer a kick drum sample on top of another kick drum sample, it makes it louder, right? Well what happens if you layer a wave that is expanding (going up) with a wave that is compressing (going down) at the same exact time? This is called phase cancellation. And if the wave going up is a perfect inversion of the wave going down, they will 100% cancel each other out and you will hear NOTHING. Literal silence. This perfect cancellation to silence never actually happens in the physical world, because nothing is ever EXACTLY the same. The sound bouncing around us is too complex to line up just right for that. But what DOES happen is that certain frequencies are made louder and other frequencies are made quieter, depending on your situation.
Each frequency has it's own rate at which how many times in 1 second the wave goes all the way up, to down, and back to center (no positive or negative air pressure). This is represented in hertz. A 500hz wave will do this complete cycle 500 times per second. A 15khz wave will do this cycle 15,000 times in 1 second. Our hearing range is roughly 20 to 20,000 hz.
Why does this matter? Because frequencies bouncing around your room will have difference wave cycles, meaning that reflections in your room will make some frequencies extra loud and other frequencies extra quiet. These are called room modes.
Everything I just wrote may be interesting, but why does this matter to you? Here is the magic right here:
You mix based on what you hear. If your room is making your 100hz really loud, you're going to mix your 100hz too low, because it sounds better *in your room*. And if 12khz is extra quiet in your room, you're going to boost it in your DAW to make it sound good *in your room*. And even though it sounds good in your room, the second someone listens to it some where else, like their headphones, car, or their own house, it's going to sound like it has too much 100hz and too little 12khz.
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So now that you know about this problem, what are we going to do about it?
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The first step to solving every problem, is understanding what the problem is. You can't fix what you don't know. So step 1: Let's measure just how crappy your room is.
First things first, your monitors need to be setup correctly. There are other articles on that here, but the basic gist is that your monitors should be setup in a perfect triangle between each other and you the listener. So that means if your monitors are 5' from each other, they should also be 5' from you and angled in so the tweeter is pointed right at your forehead.
Back to the room.
We're going to do a series of tests to figure out which frequencies are amplified and which are diminished, at both your listening position AND various places in your room. In order to do this right, we need a decibel meter. You want to get a meter with "A" weighting in it. "C" weighting will work, but it's better do it in "A" weighting. If you cannot afford a decibel meter, you can probably use a phone app to calculate the sound dB. It won't be as accurate as a meter tool, but it's better than nothing.
You'll need something to write down data with. We're going to make a chart. Pen and paper, or you can do it on your computer. Doesn't matter.
The last thing we'll need is a way to play back sine waves from your DAW. When I did this originally way back when, I downloaded a pack of wav files to play back. Now there are plugins to do this. I have Waves eMo Generator, but there are other options. I haven't used this one, but it looks like it should get the job done: https://socalabs.com/developer-tools/tonegenerator/
What we're going to do, is set a sine wave frequency and then measure how loud the meter says it is. We're going to do this for a bunch of frequencies. So each time, write down the frequency (hz) and how loud the meter says it is. You can do as many different frequencies as you like.
Before we get started, we need to set our monitor level and then don't touch the volume until we're done. This is important to get accurate readings.
Generate a 1khz sine wave and then set your monitor level where it is loud, but not loud enough to hurt your ears. write down what your starting 1k dB is. It'll probably be something like 80dB.
The exact frequencies you do don't really matter, but here's a starting point:
20, 25, 32, 40, 50, 64, 80, 100, 125, 160, 200, 250, 315, 400, 500, 600, 800, 1000, 1250, 1600, 2000, 2500, 3000, 4000, 5000, 6300, 8000, 1000, 12500, 16000, 20000
At your listening position (your desk chair) write down what the dB reading is for each of these different frequencies.
**bonus: Also, for each frequency (especially everything under 1khz), slowly walk around your room and listen to how the sound changes depending on where you stand in your room.
Once you have completed this test, you now know what frequencies are artificially boosted and which are cut. So now you know how you might have to change your mix, based on what you hear.
You're probably going to be really discouraged at first. You're going to think your room sucks. And you're right! Your room does suck. But the good news is that we can do something about that. Knowledge is power. Keep reading!
Side note: There are tools to make this process easier, like SonarWorks Reference 4. They are AMAZING tools. I still recommend doing this manual test at least once in your life. It really opened my eyes up.
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Why is my room so bad?
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After doing this test, this is probably the question you're asking yourself. I gave some clues in the very first part of this article. Let's continue to go through them.
The first thing you should know, is that every perfectly rectangle room sucks for audio. Ever noticed how every major studio you go into has weird walls and crazy angles? Those are on purpose. 90 degree angles in your walls will cause the worst reflections. Since most of us can't afford to hire a professional studio designer and build our own custom studio, we'll have to figure out other ways to make what we have, better. This is room tuning!
Here are the core fundamentals on how to address each major problem with your room. This is super simplified. Again, you can read entire books on this topic and they're extremely math heavy. The goal here is to give you an idea about what you can do to start you on your journey.
Absorbers are used in a lot of these cases. I have learned from this group, that not everyone has access to the same materials or budgets. Things you need to know about sound absorption:
Different materials absorb different frequencies at different rates.
NRC values show how much sound absorption a material has. More here: https://www.soundacousticsolutions.com/.../what-is-nrc/....
Beyond NRC, each material has sound coefficients at different frequencies. Notice here that some material is better than others at absorbing specific frequencies. It's a good thing we just charted out our room to know what our problem areas are. If we're trying to fix 60hz, there is no point in using a material that stops working well below 500hz. See this as an example of coefficients: https://www.bobgolds.com/AbsorptionCoefficients.htm
Audio foam does very little to control anything but the highest of frequencies (top part of flutter echoes). They mostly just look cool
Things you can do:
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Monitors
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Put your monitors on isolation pads. These are typically foam. They will help vibrations to NOT pass through to other objects like your desk. When things vibrate, they make noise.
Also if you have the room, don't put your monitors right up against the wall. Having some space between the wall and the speaker will help with early reflections from your front wall / corners.
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Front wall absorbers
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Behind the monitors, it's good to place some good absorbers to get rid of those first order reflections right next to your monitors. These are highly likely to cause phase issues. So in additional to placing your monitors not right against the wall, it's good to absorb what does hit the wall.
In my case, I have a big subwoofer as well. My entire front wall is covered in 4" panels to help control (tame) bass reflections. If you're going to have a sub, you have to be extra careful with the lows.
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Side reflection absorbers
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Stereo images is SUPER important. Lack of clarity between the left and right channels will definitely hinder your mix, as a big part of your job as a mixer is to create a lush space for your sound. The specific problem you can have is that what comes out of your left monitor does this:
Directly hits your face, on the left side mostly (good! this is what we want to happen!)
Hits your left wall and bounces and then hits the left side of your face, but is slightly delayed, because reflections take a little longer of a path to get to your face, than the direct sound.
Hits your right wall and bounces and hits your right ear.
And then the same thing happens for the right monitor.
So how do we fix this? Absorbers! You're going to see a theme here. You want to put big fat absorbers on your left and right walls so it stops these reflections from happening. Instant stereo image fix. This was probably the biggest thing I did to make my mixes better. Immediate results.
When you mix in headphones, you actually kind of have the opposite problem. NONE of your left channel is going to your right ear. So it creates an unnatural sound. This is why I like the Boz Pan Knob so much. It pans your instruments, but still makes them sound more natural in headphones.
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Cloud ceiling absorbers
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The ceiling can be a bad source of reflections as well. Above the listening position, a lot of studio rooms will have a "cloud". This is just hanging absorbers or an absorption wall. The cloud is typically angled a little so not only is it absorbing, but also reflects sound from the monitors to send it towards the back wall. The back wall is a little special. We don't typically do tons of absorption on the back wall. Instead….
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Rear Diffusion
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I have absorbers on my lower back wall, because my room needs to contain bass frequencies. I also put a drummer towards the back wall and the more absorption I have, the less drums blow up the entire room!
But traditionally (and I do this as well), the back wall is primarily for diffusors. Instead of absorbing sound, diffusors scatter the sound all over the room. The effect that you are left with is that your room will sound more "live", but typically in a pleasant way. But you can go too far with diffusion. I was on another mastering page where someone created tons of diffusion and it actually made the room too "wide" and scattered. The sound bounced off the diffusors and then back to the listener creating phase issues and a blurry image. You probably won't have this problem, but it's something to be aware of.
I have some basic diffusors on my back wall. I'd like to get some nice quadratic diffusors eventually. To scatter the sound and to also look cool. Because they look great and part of having a studio is making it "feel" exciting as well as sound good. But again, don't go too far. Too much of a good thing, makes it bad.
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Corner Bass Traps
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Remember how I said that rectangular rooms and 90 degree angles are bad? Well, they're specifically bad for bass frequencies. These types of symmetrical walls do horrible things to your bass. There are many many many strategies to controlling bass frequencies. Too many to really go into super deep and frankly, I'm not an expert on this stuff. My strategy is to add things to my room and then re-test using the db meter to see if it's better or worse. If I knew the math, this would probably be a lot easier on me, but I don't. And as I mentioned, I hate math .
So in general, we want to make our room "less rectangular" and at the same time absorb as much bass that hits these corners. I personally use corner traps from gik acoustics. They're not cheap, but they do a pretty decent job at controlling bass.
But you'll notice that they start to lose effectiveness around 100hz. They do help with 50hz and below, but notice that the lower the bass frequency, the harder it is to absorb. This is just the nature of bass.
There are other techniques to controlling bass too, like Helmholtz resonators and things like that, but frankly, I'm not qualified to talk about those. And I have zero experience with them. I'm just doing the best I can with what I've got and learn a lot along the way.
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Floor reflections
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I have a highly reflective floor (wood), which I like for recording on. It creates a "live" feel. but for mixing, this is the devil. So as such, I put down some thick rugs under my desk and chair area. It helps control some of the reflections. I also put down rugs in other parts of the room.
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Controlling live room reflections
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I have a standard height ceiling in my studio. Which means, I don't have vaulted ceilings, which is why I don't typically record drums in my studio. but I still record them and play them. Above my drums set, I have a cloud that are 1/2 circles that both absorb and diffuse. This helps the sound to be more controlled and pleasant in both general listening and in recording. In fact, this is my favorite area to record vocals (I don't have a dedicated vocal booth). Don't underestimate just how many reflections come off the ceiling.
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Random reflections
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And you can also put panels up anywhere to help control reflections. You don't want absorbers EVERYWHERE. but you can put up lots of them. A lot of studios have absorbers scattered about. So on one wall it may have a 4" absorber for 2 feet and then a few feet of sheetrock and then another absorber. This makes it so the room still has a "live" feel, but the reflections are better controlled.
Furniture can also do the trick! In a lot of studios, on the back wall are diffusors and then below them is a big couch for the clients. The couch is for sitting….. but it also acts as an absorber itself! The more things you have in your room, the more the room geometry changes from being a "rectangle" to being something else. But as with all things, some furniture may solve some problems, other will create new ones. And the only way to tell is to re-measure your sine tests after making big changes!
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The final polish
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Once you've tuned your room the best you can, there is one final thing to do that will make it the best it can be. Using a digital room correction plugin. The standard that most people seem to use is Sonarworks Reference 4. It comes with a microphone and software and it does the equivalent of those sine tests we manually did. And then it adjusts what is sent out your monitors to compensate for issues in your room.
I want to be clear that this is really intended to be the LAST thing you do. You want to physically control your sound as much as possible, so you're allowing sonarworks to finish the job. If you have bad phase issues and a blurry stereo image, sonarworks will still make it better, but it's still not going to be great. It cannot perform miracles.
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I really hope this helps in understanding some things about room tuning. It's a very complicated topic, but most of these things are relatively straight forward to understand. And like everything, it's a work in progress. Best of luck audio legends!