Four ways to use mid/side EQ

Several EQs now have a mid/side mode. This opens up a lot of possibilities, but can be difficult to use effectively. Instead of simply tweaking the sound or the range of the controls, mid/side mode completely changes how the EQ behaves and sets new rules for how it can be useful and effective.

It helps to stop thinking about mid/side EQ as an equaliser – but instead to think of it as a surgical frequency-focussed stereo width adjuster. It works best on complex stereo material, such as groups or the mix bus.

  1. Mono bass. Not just bass, but lower mids too. It’s easy – use a highpass filter or low shelf (with negative gain) on the side channel. If you’ve mixed well, this won’t actually reduce the level or impact of your low frequencies (especially the ever-critical kick and bass). Instead, it will add focus and tightness in a way that doesn’t detract from the overall perceived stereo width of the mix. Experiment with the frequency – you’ll find you can probably go a lot higher than you might have expected. Unlike simply collapsing the kick and bass channels, using a mid/side EQ (particularly with a higher filter frequency) will also catch the lower mids in other instruments. And instead of making space in the mix by reducing their level, the mid/side EQ maintains their energy by simply collapsing them to mono.
  2. Top end dimension. This is achieved by utilising a high-end boost on the side channel. Usually only a small amount is required – less than 6dB. Doing this to a mix can add dimension and air without the harshness of other tools (such as harmonic exciters or other saturation). It can also help open up a ‘small’ mix without losing the focus in the lows and mids.  Some mixes will benefit from a more balanced approach – instead of adding 6dB to the top of the side channel, try adding only 3dB to the top of the side channel as well as reducing 3dB from the top of the mid channel. Not all mixes will benefit from this – it will sound more like a regular EQ boost if the top of the mix is already quite wide.
  3. Focussed vocals. This can be done by reducing the width of the midrange. As with the above two tips, the most transparent way of doing this is by adjusting the side signal (by applying a dip using a parametric band) while keeping the mid signal untouched. Doing this can reduce a lot of clutter surrounding the vocals, helping them to become clearer and more focussed. If you’ve got access to the mix, however, it’s obviously better to do it the old-fashioned way. Consider using a mid/side EQ for this job as a ‘magic trick’ that you might resort to when your other options have run out.
  4. Giant lower mids. This one’s great for special effects – try boosting the lower mids in the side channel. It’s an easy way to make something sound huge, without the associated headroom problems or (as much) mix mud. Of course, this technique is often as delicious as it is inappropriate, so have fun with it but remember to go easy in the final mix. A little bit goes a long way.

You’ll notice that all these tips focus on making changes (either boosts or dips) in the side channel while leaving the mid channel (mostly) untouched. This is deliberate – it allows the width to be changed in a way that doesn’t destroy the overall balance of the mix.

With these tips and a bit of practice, you’ll be soon finding your own uses for mid/side EQ.


    • Piotr
    • April 30th, 2010

    “Top end dimension. This is achieved by utilising a high-end boost on the mid channel” Could you explain why to boost a mid, not a side? Because you also wrote that
    “You’ll notice that all these tips focus on making changes (either boosts or dips) in the side channel while leaving the mid channel (mostly) untouched”
    Greetings from Warsaw, by the way your blog is really amazing I always look forward to reading your new posts


    • Jason
    • April 30th, 2010

    Thanks, Kim! Very timely for me since I’ve recently been dabbling in more m/s processing, mostly on more dramatic effects, but the usefulness of the application of EQ in m/s hadn’t occurred to me. I’m definitely looking forward to giving these little tips a whirl.

  1. @Piotr

    My mistake – that should have been ‘a high end boost on the side channel’. Good catch. It’s updated now.



    • hector
    • May 17th, 2010

    Bravo Kim.

    • Waza
    • October 20th, 2010

    Just wondering what Eq’s have these mode.

  2. @Waza
    I personally use the T-RackS linear phase EQ (but not in LP mode). I think Blue Cat and Brainworx also make EQ plugins that do M/S mode. You’ll probably get even more suggestions if you ask around on forums. ;-)


    • Waza
    • October 20th, 2010

    Thanks for this Kim. Really enjoying reading your blogs.


    • van
    • October 29th, 2010


    m/s processing is an interesting subject; thumbs up for providing your views with simplicity, people should be encouraged to try things out instead of being intimidated
    by tech speak

    try FabFilter’s Pro-Q you won’t regret it

  3. @van
    Thanks Van. There are some concepts in audio engineering that are quite difficult to explain. But just because they’re difficult to explain doesn’t mean they *shouldn’t* be explained. We have access to amazing tools these days – what’s often missing is the knowledge to make it all work.


    • 3ee
    • January 6th, 2011

    Undesirable side effects to mid/side processing?
    Been reading somewhare something about mid/side and mono compatibility and there seem to be some side effects involved but as I didn’t experiment with mid/side eq before I didn’t fully understand it.

  4. @3ee
    You’re right – it’s easy to mess up mono compatibility if you go overboard with mid/side processing. Basically, there are two ways a track can become mono – either by summing the two sides or by taking one side only (eg sharing iPod earbuds)

    When a track is summed to mono, basically the entire side signal is lost. When one side is take, the mid and side signals are summed (with the side inverted, depending on which side you take).

    Generally, if a mix is well-balanced, either method of making a track mono should not significantly affect the balance of the mix.

    I often use mid/side EQ to *improve* mono compatibility by deliberately shaping the side signal.


    • Tzvika
    • November 3rd, 2011

    Hi, Kim.

    Could you give an example for how would i use mid\side eq with large saw trance pads? I’ve been exparimenting with eq-ing them using the mid\side technique but i can never get it to sound reasonable and not mask the bass frequencies.

    Thanks in advance! (to Kim, or anyone who would answer my question)

    Tzvika :)

    PS – i use ableton live 8

  1. January 6th, 2011
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