Hey guys, Eric Tarr here. I’ll be demonstrating how to use signal processing techniques if you’re mastering in a home recording studio. I’ll focus on spectral shaping techniques to prepare a final mix for other processing I do during mastering. Here’s the session. It’s a pop/rock song with multitrack drums, bass guitar, electric and acoustic guitar, organ, and vocals. I’ve got my final mix. I’ve got the levels how I like them and individual processing on each instrument.

Then I sum all these signals together on my master fader. I’ve got the iZotope Ozone 5 plugin with all modules bypassed. There’s no processing taking place inside the plugin. I’ll play you the mix so you can hear it before I do processing in Ozone.

[song for mastering]

I want to use this EQ module as the first processor when my final mix hits the master buss. To change the order or figure out what order these modules are inside of Ozone, click the graph tab. That’ll show you the order of processors. So here’s my EQ.

First step is getting rid of really low frequencies and high frequencies that can show up in a mix. These frequencies can barely be perceived by a human ear. These really low and high frequencies can even screw up your finished product. Low frequencies can cause your dynamics processors to over-react. Your compressors and limiters. And high frequencies can cause aliasing if harmonics are created above the nyquist frequency.

When music was originally created and printed onto analog tape or vinyl, these mediums basically had built in hi-pass and low-pass filters because they couldn’t record all frequencies equally. People got used to this. If you’ve been working in a digital recording system or tracking, mixing and mastering, you might wanna think about rolling off some low and high frequencies. If you’re worried about your mix sounding too digital, this is one difference between digital and analog recordings.

Let me show you how I use low pass filters and high pass filters to remove problem frequencies in a mix. I’ll start out with low frequencies and high pass filters.

What I do is use linear phase filters inside of the Ozone plugin. This is a special filter that makes sure I’m not screwing up any other aspect of my mix when I’ve got all these different frequencies summed on my master fader. I don’t want to cause phase distortion. So I use linear phase so the only thing I’m changing is the relative amplitude of frequencies.

Next I go back and use this first filter. Switch to high pass and start with a brick wall filter. This has a steep slope at the cutoff filter so all these low frequencies below 25 Hz get cut off quickly. These high frequencies in the pass band above 25 Hz aren’t affected. You can also experiment with flat type filter and change the Q to something very high like 48. If you have 12 it’s a shallower slope, but if you get up to 48 it gets steep. I’m gonna use a brick wall filter. Sometimes I add a second high pass filter. I’ll use a resonant one. I’m gonna change the Q and cutoff frequency. This brickwall high pass filter has a sharp skirt. I’ll use this high pass filter with a very flat skirt so it’s gradually rolling off low frequencies before they hit this very steep filter. Change the Q. I don’t want to roll off too many low frequencies but I want to have a nice slope gradual roll off.

There’s the high pass filter, brick wall and the gradual one. The combo has a sharp skirt down and then a gradual one. Anything you’re doing in mastering shouldn’t be very dramatic. You should hardly hear it. I’m cleaning up the signal, preparing it for dynamics processing.

[song + iZotope Ozone 5 EQ]

Now the same thing mirrored for high frequencies. I’ll turn on this filter. Select a brickwall low pass filter. I’ll select this to be about 19 kHz. Humans can’t really hear above 20K and most humans, especially if you’re a musician, probably can’t hear above 18, 19.
Next I’ll add another with a gradual slow. Low pass filter, a resonant one. Bring the frequency up. Change the Q. Sometimes I change the Q so I’m adding high frequencies before I cut them off for some extra top end sparkle, but I don’t have to worry about adding too much top end because I’m rolling off the very high ones. Then play around with the Q and frequency cutoff.

[song + Ozone 5 equalizer]

Subtle, gradual processing. I’m cleaning up the signal for other processing during mastering — dynamics or harmonic exciters.