You can’t mix music with your eyes, but we often see people trying to do just that. Matching the frequency spectrum of your track with a reference track might seem like a good idea, and there are even some plugins with an EQ matching function so you don’t even have to listen to the music. The results however, can be unpredictable at best and are often less than pleasing to the ear, so if you are thinking of using a spectrum analyser in that way, the question you should probably ask yourself is this:
"What if, after matching the EQ plot, I am still not happy with what I hear?"
The answer of course is that you will still have to use your ears to make the final decisions, no matter how funky that graphic display is, so using 2D spectrographs and 3D spectrograms is always going to be a bit of a gamble. I have spent a lot of time staring and listening as the displays move with the music, and I am often amazed by how misleading they can be.
That’s not to say they are completely useless though. I have an Alesis DEQ230D stuck on the end of my metering chain purely for its hardware spectrum analyzer. Its always on, silently tracking the level of every bit of audio coming out of the monitors, in discrete 3rd-octave bands from 20hz to 20khz. Its probably fair to say its one of the hardest working bits of kit I own, even though I never use it to actually EQ anything!
A rough guide: the Alesis DEQ 230D has a handy spectrum display mode
So what do I use it for? In fact, what do I use any of the various metering tools in the studio for? Why not just use my ears 100% of the time, and master with my eyes closed? The simple answer is that listening to audio all day is tiring. Not just the physical exertion the sound waves place on your ears, but also the mental exertion of processing that audio in your brain and making decisions about it. A spectrum analyser can take some of the load off your brain, allowing you to work for longer, and more efficiently. Of course there are limits to what it can tell you, but I would never be without one, so that’s what this top tip is all about: when to use a spectrum analyser, and when to use your ears.
The mantra I always tell myself to avoid spectrum analyzer abuse is this: only look to the frequency analyser when you want a clearly defined answer. “Does this mix sound OK?”, for example, is obviously not something you should be asking. So what sort of question should you be asking? When can a visual tool help to make decisions about sound?
Measuring the Response
There are plenty of prosaic uses for a spectrum analyser of course. EQing a room for example, and we even use one to tune the vinyl cutting lathes in the studio (we feed white noise through the system and try to get it looking as flat as possible on the way out) but that’s not the reason most software EQs these days are kitted out with a bewildering array of visual tools.
Of course, one of the most useful capabilities of a spectrum analyzer is the identification of a certain problem frequency. Some people are great at spotting what pitch a note is at and translating that into hertz, and there are techniques for indentifying a sound using exagerated boosting around a narrow band, but by far the quickest way to locate the frequency is watching the display. Once you have done that, you can quickly dial in the EQ, and confirm it by listening.
The thresholds of human hearing
Even if you are lucky enough to have excellent hearing, there can still be large amplitude signals lurking just out of earshot. Most analysers only go down to 20hz, but some (including the excellent Dualism from DMG Audio) go down to below 10hz, allowing you to see whether the audio needs a high pass filter. Big 10hz waves could be sucking valuable dynamic range from your track, so it often pays to take a peek down there. Likewise with very high frequencies, we often get pre-masters in the studio that have alarmingly high amounts of treble in the 15-20khz range, and although these sounds are audible to most people, they can sometimes be hard to make subjective judgements about. Excessive top end can be very fatiguing on the ear, and can also cause havoc on vinyl. A good spectrum analyser can alert you to these potential problems quickly and easily, before your ears get habituated to the airiness of the sound.
Under the radar: the DMG analyzers can zoom in on frequencies you can't even hear
Pinpointing sonic elements in a stereo field can sometimes be tricky, especially at low frequencies, and its hard to keep track of several parts at once. A spectrum analyzer with M/S display lets you easily spot which parts are wide or narrow and so you can set the tonal balance of the side signal really easily.
Mid = White, Side = Blue.
Discrete Parts: taking off the mask
The masking effect can be a very powerful thing, hiding some elements of a piece of music so they become hard to discern. Some modern 3D spectrograms allow you to see how each part of a piece of music is made up - the attack and decay of a drum, the harmonics of a synth, or the spectrum of a pad. If you wanted to brighten up the metal on a snare for example, you can see exactly where to place the boost. Or if a pad sounds too muddy, you know exactly where to cut. But perhaps most crucially, you can also see what other elements you might be affecting, without having to rewind over the same passage so often.
DMG Dualism: a powerful 3D analysis of frequency / amplitude / time.
These are just some of the uses we have found for spectrum analyzers, and we could list plenty more, but the bottom line is, they are great for identifying problems areas (even the ones you can't hear), but when it comes to treating the sound, your ears get the final word.