Pro Audio Files

Ask Weiss: Using Mid-Side Subtractive EQ in a Mix


Hey, folks. Matthew Weiss here —,, and

Welcome to the Ask Weiss series! Today’s question comes to us from Niko Maillet via The Pro Audio Files’ Facebook page, and Niko asks, “My question is regarding mid/side processing. I get the idea behind cutting out stuff from the sides, but an in depth look at a practical use of it would be great.”

Nico, I think that’s a great question. Thanks for asking. Mid/side falls into a very special category of processing that I think things like multi-band compression also falls into, and that’s stuff that’s generally over rated.

Now, this is not the same thing as saying it isn’t useful. It’s extremely useful, it’s just something that I think people tend to focus on as being the deal breaker between a good mix and not a good mix, when in fact it has very little to do with that at all.

The majority of your mix should usually involve simple balancing and EQ tonal adjustments, so basic shaping of sounds will get you through most of the mix, and the vast majority of the rest of the way is going to be your automation. How you move things around and change things for emotional impact.

Now there are situations that arise where you’re going to have to use some of the trickier stuff, like mid/side processing. So here, I’ve got a record pulled up where I will be doing just that. I haven’t even started working on this record yet, but you’ll quickly hear why it makes sense to have some mid/side going on.


I think I just scored the touchdown to win the game or something like that, and I don’t know, this is some pretty epic music. The arrangement gets very complicated and very dense. It becomes hard to figure out what’s going on and where, and a large part of that is because we have a ton of sound bouncing around the entire stereo field.

So let’s just solo this sound for a moment, for example.

[synth soloed]

So, it’s pretty obvious that there are some very present delays that are occurring that are bouncing around the sides when we solo that sound.

Now let’s listen to it in context.


Do we even hear those delays once everything is in? No, we don’t. So maybe we don’t need all of that delay in order to create a sound that’s more focused and is easier to digest.

Well, let’s see how we can do that. A little mid/side processing will go a long way. So what I’m going to do here is I’m going to filter the high frequencies out of the side signal, meaning those delays that have that sort of transient little pluck at the top – I’m getting rid of that pluck. So that’s going to make things easier on our ears right off the bat.

The other thing that I’m doing is I’m using the mid/side level adjustment here on the FabFilter Pro to take the side information down about five dB. So, what that’s going to do is it’s going to take all of those delays that are living on the side, and it’s going to turn them down without adjusting the center.

Then, in the center, in the mid channel, that core frequency that we’re hearing through the mix – that 700Hz that’s cutting – I’m going to boost that up a little bit.

So here’s before and after in solo.

[synth plays, before and after EQ]

Alright, and now let’s listen to the before and after in the entire mix.


Now, that difference might not be readily apparent. Mind you, this is only the first step in what would be a key in many steps. So, let’s listen again, and I’ll tell you what to focus on, and then I’ll show you another example where the same sort of thing starts to apply.

Alright, so what I want you to do – listen to that plucky arp synth and how it cuts through the center of the mix, and then also listen to the clarity of the strings that are living on the sides.


Cool. So I hope that made sense. If not, here I’ve got another example. We also have this pad that’s going throughout the entire record.


Now, with this pad, I don’t really need a lot of center information. I actually don’t have a ton of center information. It’s pretty spread already to begin with, but I’m just going to notch out some of the lower mid-range in the center. Let’s widen the Q a little bit. That’s going to open up the center channel just a touch.


Now, you might be saying at this point, “Matt, I’m not really noticing a lot of differences here. How does this really help me?”

Well, let’s bypass both of these and see if that makes a bigger difference.


Notice how that lead arp now starts to really poke out? Well, that’s what mid/side processing is about. It’s about manipulating the side information and the balancing, and the mid information and the balancing and finding something that makes sense, and I find that it’s most useful when you have particularly dense arrangements like what we have in front of us here.

Now, the other thing that’s cool about all of this is we can use our mid/side processing to adjust for the arrangement as it comes in. So we have a lot of delays on some of these elements, we have a lot of stereo information.

In the sparser parts of the song, I don’t think that I want to eliminate that stuff, I want to play that up. So I’m going to automate my mid/side controls to just alleviate either the mid or the side, depending on what the element is when the arrangement becomes more dense, and to make it all make more sense together.

Alright, thank you for watching. If you or anyone you know has a question, please feel free to leave it in the comments section below, or post it on The Pro Audio Files’ Facebook page. Don’t forget to like and subscribe.

Matthew Weiss

Matthew Weiss

Matthew Weiss is a Grammy nominated and Spellemann Award winning audio engineer from Philadelphia. Matthew has mixed songs for Snoop, Sonny Digital, Gorilla Zoe, Uri Caine, Dizzee Rascal, Arrested Development, 9th Wonder, !llmind & more. Get in touch:
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