Mid/Side EQ Masterclass

Mid/Side EQ can feel confusing, but it's a powerful tool for tightening your low-end, creating focused definition and separation between your tracks, and width in your mix.

We have talked about general EQ techniques a lot on the blog, but mid/side EQ is a little more advanced.

Here are some suggestions on how you can use this advanced EQ technique to improve your mixes.

What is Mid/Side Processing?

With the stereo field, we divide the spectrum into a left and right field between the two speakers.

With mid/side processing, we have a "middle" field and a "sides" field.

These images will help you visualize how the stereo spectrum changes when you change from L/R to M/S:

The mid/side process allows for creative equalizing that adds depth and width across the stereo spectrum. M/S EQ  gives you some advanced techniques that the L/R EQ doesn't support, like tightening up your low-end, separating your tracks to create clarity in the center, and adding width to the sides.

Common Mid/Side EQ Applications

• Tightening the low-end - Filtering out the bass frequencies in the sides and forcing the bass into the center of the field makes your low-end tighter.
• Separating your tracks differently - Instead of creating separation across the stereo spectrum, you can separate instrument in the center only, like a vocal and guitar, while leaving those frequencies alone in the sides. You can also boost a panned instrument in the sides, which will add clarity at the edges of the mix without masking the center.
• Focusing your center field - You can get more surgical by adding clarity and focus in the center of the spectrum without adding it across the stereo field. A boost in the high-mids can often bring the center forward, making the essential elements jump out of the mix.
• Adding width to the sides - Just like you can focus the center by bringing it out, you can add width in the sides by boosting the highs.

Mid/Side EQ Quickstart for Your Mix Workflow

Let's say you have many synth and keyboard tracks in your mix, and they're clashing with the vocals. Usually, I would recommend an 800  Hz- 3 kHz cut on the instrument buss to make room for the vocal. However, you can do it in mid/side mode instead, which will keep those synths wide in the center while giving the vocal room in the middle.

You can even add an extra step and add a high-frequency boost in the sides to get the synths to cut through in the high-end. That way, you not only end up with a clearer vocal track that cuts through the mix and jumps out of the speakers, but you also have a wide instrument track with presence and air.

Of course, this trick isn't only applicable to synth tracks but any instrument group in which you want these results.

Mid/Side EQ in Your Mastering Workflow

For mastering M/S EQ, I tend to do two things: Tighten the lows and widen the highs.

On my mix/master bus, I have an EQ preset that has an L/R high-pass filter set to 30 Hz to that elimina any unnecessary low-end rumble. Then I have a second high-pass filter in M/S mode at 75 Hz that cleans up the rest of the bass frequencies in the sides. You can experiment with the frequency cut-off but I've found 75 Hz to be a good starting point. This way you'll get a focused low-end in the middle of your mix, tightening up any stray bass frequencies that might skew the stereo spectrum in the low-end.

Then I'll add an air-shelf in the Sides above 10 -12 kHz or so. It'll be a subtle boost but the mix will feel wider and clearer. With an M/S EQ you're adding an additional dimension to your smiley face curve. The LOUD button on your stereo increases the bass and the treble, creating a smiley curve that our ears like. That's why we like mixes that have a thick low-end impact and rich high-end sparkle.

However, with M/S EQ you're adding an additional dimension across the stereo spectrum. That way you're not just adding a smiley-face EQ curve from low to high, but also from left to right so your mix feels more three-dimensional.