Acoustics - Hearing your room

Think your room is that great sounding huh? Well try this:

I've attached a test tone file in 24bit AIFF and WAV format that takes a sine wave and sweeps it from 20Hz through to 400Hz over 45 seconds. It's at -6dbFS so be careful it's quite loud! The AIFF format is great because if you use QuickTime player you will get labels for each frequency band visible on the player (and selectable from a menu). These files were made with Make A Test Tone from Audio Ease which I highly recommend for very high-quality test tone generation!

Play this file over your system and have a listen from the mix position. This can tell you tons of stuff about your ability to hear what you're doing, and how it may be compromised.

First off, when playing 20Hz you probably won't be able to hear it. But if you can hear a tone (one above 20Hz), it may be harmonic distortion somewhere in your monitoring chain. That's a bad thing and you probably want to address it by pulling crap that doesn't belong in it out or gain staging things better.

As the sweep goes up, take a look at where you can begin to hear things (or maybe just "feel" them). That's as low as your monitoring will go. If it's above 40Hz or so, you will probably benefit greatly from adding a subwoofer.

Now as the tone goes up, do you hear anything rattling in your room? If you do, that's extra percussion being added to all of your mixes...perhaps it's simulating someone playing tambourine in sync with the kick drum. Obviously, you will undermix "click" for that kick if you have rattles going on. Hunt for those rattles (a steady sine wave tuned to the resonant frequency will help) and tamp them down!

As you ascend in frequency, if the sound gets louder or softer, or starts moving left to right or dipping oddly or something, you are in need of improving your monitoring and/or room. You should first start by taking any EQ off your monitoring...obviously it wasn't working. If you do add EQ, it should be done last, and only as a last resort. Make sure your speakers are wired in proper phase. Then focus on your position in the room (38% of the length of a rectangular room, with 62% of it behind you, is considered ideal by some) and the position of the monitors (their position relative to the walls and corners is important, plus their stereo image and mid-side balance). And then you will probably need bass trapping of some sort to even out the imbalances that remain due to room modes.

Lastly, while sitting in silence at the mix position, clap your hands in front of you to generate a nice little impulse. Do you hear a nice dead clap or is there a flutter echo or metallic resonance? If the sound isn't fairly dead or at least nice in its decay you will need treatments of your reflection points (if the walls were mirrors, where you could see yourself and your speakers) with absorption and/or diffusion measures.

The acoustics forum here on gearslutz is a great place to ask further questions. Remember, you are only going to generate work of the quality that you can hear the flaws of...any flaws you can't hear may well be heard by others when it's too late for you to do anything about them.

But also keep in mind that it costs hundreds of thousands of dollars to design, build and treat a room that won't have problems revealed by this test, so don't worry yourself stiff if you can't fix everything. You will need to learn your room and your monitors even if their frequency response is relatively even. You just want to make sure there aren't gaping holes in the frequency response that will leave your mixes with massive kicks or missing bass notes etc.

Have fun making music peoples!