You’ve probably heard about ‘phase’ in some musical context or other. Whether it’s using a phaser effect on your pad sounds to give them a bit of movement, or that strange and mythical beast called a ‘linear phase EQ’, phase can be complicated area that can really cause problems. So how can you avoid them?
First, we need to know what ‘phase’ is: it’s basically the relationship between two signals. It’s easiest to imagine sine waves, and you probably know the basics – when two identical waves are fully in phase, then they’ll create one loud wave. Turn them fully out of phase (there will be a plugin for this in your DAW) so that when one is at a peak, the other is at a trough – and the result will be phase cancellation. Silence.
It’s pretty rare that this kind of example turns up in the real world, however. Which is just as well, because it would be difficult if your bassline kept disappearing. But we can still have problems. Try loading a full track into your DAW, and putting it on two channels. Now if you delay one channel by a couple of miliseconds, you’ll hear it sound very odd indeed. A bit like a phaser plugin, but not moving. This is due to ‘comb filtering’- where lots of different frequencies are being cancelled in various amounts.
That sound is something you should be looking for in your mixdowns, as it can happen in lots of ways. The main way, and fortunately it’s not one that will concern the majority of dance music producers, is when you’re recording an instrument with more than one microphone (or if the microphone is close to the floor or the wall where it could pick up reflections). That’s complex to solve, and so we won’t go there today.
So where does it happen? First, look to the low end. Sub-bass is a problem area; if you have two notes playing at the same time, for instance, there can be cancellations which affect the volume of the sub. It may be clashing with your kick drum; try soloing one and then the other. If it feels like either one is losing impact when they both play, it could be a phase issue. Simple ways to get around this could be changing the pitch of one of them, or using EQ so that their frequencies don’t overlap so much. Or, and this is always the most effective way – re-program them so that they don’t play at the same time. The same can apply with any other low-end components – kicks, deep pads and basses, and so on.
The next big issue is when you’ve done some external processing with some of your sounds. If you record a drum track out through a guitar amp, or an old mixer or something for a bit of grit and distortion, then when you try to layer it back into your track next to the original you may find an issue with phasing like we described earlier. In that case, you should use a ‘sample delay’ plugin, which moves the audio earlier or later by one sample at a time – fractions of a milisecond. Solo the two channels, and just tweak this setting until the phase sounds right. Trial and error is your friend here! Putting a sharp transient at the start of the audio will help you line them up – an 808 hi-hat for instance, which you can remove later.
But what about that Linear Phase EQ? What’s that all about? Well, that’s for using when you want to send a signal to a buss channel, you need to EQ it, and you’ll be mixing the buss signal back in with the original. For instance, if you’re doing parallel compression or somesuch and want to tweak the EQ on the return.
Most other plugins should be ok: although in theory running a signal through a compressor would introduce a time delay, if you do everything in the box, your DAW will compensate for that and match the phases up (but check, just to make sure, since some third party plugins can be faulty!). The thing with EQ is that it actually works by altering the phase of a signal. So if you just had a compressor on your buss, it would be fine; if you just had an EQ, you may get phase problems. Linear Phase EQ, however, works in a different way, so that it doesn’t alter the phase. If you need to EQ a signal that’s going to be mixed in with an original, this is the one to use. But don’t think that this means you should use it all the time. First, it’s much more CPU heavy so it could sap your computer’s capabilities. But more than that, it can affect the transients of your signal. Not too much, but using one on every channel will add up. Use a normal EQ where you can!
This is a basic grounding in how phase might affect you – and as mentioned, if you start recording drum kits you’d be advised to read up a lot more – but for dance music artists, this should be enough to get you moving without too many troubles. So get that DAW going, fire up some tunes and don’t let phase bother you any more!