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In this installment of the Foundations of Audio series, author Brian Lee White shows producers and audio engineers how to properly apply equalization (EQ) and improve the sound of their mixes. The course covers the use of parametric and graphic EQs—and filters such as the high/low pass filters and shelf filters—in a variety of musical settings. These principles can be applied to any digital audio workstation platform, including Logic and Pro Tools, as well as analog workflows.
Have you ever done what you thought was a killer mix only to take your mix elsewhere and be utterly disappointed: what was the perfect amount of bass is now way too much in the car, or the chunky tone of your guitars ends up being hollow and thin on friend's speakers? Mix portability, or how a mix translates from room to room and speaker to speaker, has been toiled over by mixers of all skill levels for years. EQ is all about altering the frequency balance of a signal, adding or subtracting energy from a waveform's amplitude.
Rather than relying on a list of frequencies and recipes to cut or boost, seasoned engineers use their ears to apply EQ. What if your speakers and room are coloring the frequency response of your mix? In other words, what if the EQ adjustments you think are making your mix better are actually just a response to how your room's acoustics are shaping the sound coming from your speakers? Let's try an experiment. I'm going to play back a 100 hertz tone, and I want you to turn up your speakers and walk around your room as the tone plays back.
As you walk around, note any changes in the perceived level of the tone. If you're using headphones, this won't work, so come back to this example when you can listen on speakers. (Tone) Unless you're lucky enough to be in a perfectly tuned room, you probably noticed that the tone increased and decreased in level as you moved around the space, most likely building up in the corners of the room.
What you're experiencing is additive and subtractive phase cancellation of the 100 hertz sound wave bouncing off the walls and ceiling and recombining with the direct signal. These standing waves create pockets of build up where the waves combined constructively, a push added to a push, or destructively, a push added to a pull to create pockets of reduced level or near silence. The creation of these standing waves are based on a room's modes.
Room modes are a collection of resonances that are based on a room's dimensions, with small rooms exhibiting more aggressive modal resonance because physically larger lower frequencies have nowhere to go except to bounce around and overlap on themselves. Sitting at your mix position using your speakers, take a listen to this bass playing the chromatic scale. Note that each note is played at the same exact amplitude. (music playing) Did you notice any notes that seemed to stick out as if they were louder? If yes, then you're experiencing the effects of your room's modal response.
Try going back and playing the same example listening with headphones, and see if you notice a difference in the balance of the notes. Remember, each note is being played back at the same exact amplitude, so if you have a fairly balanced pair of headphones, you shouldn't notice much difference in the amplitude of each note. Now, imagine you're trying to find the perfect level and EQ for your bass guitar and the root node of the bass line sits at one of those frequencies that is either getting boosted or cut due to your room's modal response and standing waves.
You may be inclined to make an EQ or balance decision that has nothing to do with the actual signal itself, but only how that single is reacting to your speakers and room. It's like trying to paint accurate colors with sunglasses on. An exhausted review of acoustic principles, properties, and treatments is beyond the scope of this course, but all I want to do here is make you aware of the fact that your room is probably lying to you, and that the principles shown here bring to light one of the main reasons your EQ decisions might not translate from space to space.
So what can you do? Well, short of hiring an acoustician and building a new studio, you can start by learning more about acoustics and acoustic treatments. Take the time to learn your room and its shortcomings by listening to a lot of reference material. Learn and use a pair of favorite headphones as an additional reference, and listen your mixes in different environments to see how your EQ decisions transport from space to space. In all circumstances, use reference mixes that you know sound good out in the world and compare their frequency balance side by side to your mix.
Does your favorite mix sound like it has too much bass in your room, then you will likely have to make your mixes sound like they have too much bass in order to translate well to other playback systems. Bad rooms can screw up the best engineers and turn them upside down when trying to make EQ decisions. Know that even with treatment, it's almost impossible to completely fix a room, and even multimillion dollar studios have similar problems. In fact, I'd rather do a mix in a bad room that I'm intimately familiar with than in a tuned room with unfamiliar sonics.
After learning what your space sounds like, you'll be able to craft consistently strong mixes despite any shortcomings.
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