Kim Lajoie's blog

Are you making this common EQ mistake?

by Kim Lajoie on September 27, 2010

Often beginning mix engineers are told to use the ‘boost and sweep’ method to find and remove problem frequencies.

Essentially, this method consists of:

1) Making a sharp narrow boost with a band of parametric EQ

2) Sweeping the frequency of the band (this sounds a bit like a wah wah), listening for any spots that are particularly unpleasant

3) Changing the gain of the band from positive (boost) to negative (cut).

Theoretically, this is a way to improve the sound – especially when you can hear something ‘wrong’ with the sound, but can’t identify it with your ears alone. This technique on its own is not necessarily bad. I find it useful sometimes too. Of course, its becomes less necessary as you hone your listening skills. Even less so if you’re using well-recorded audio or samples.

The problem is when people make the assumption that since one band of ‘boost and sweep’ is good, more bands must be better. And so the fourth step is often added:

4) Repeat until you run out of EQ bands.

This is a really great way to butcher a sound! This approach will inevitably produce an EQ curve that looks like the sonic equivalent of Swiss Cheese – full of holes. This is because looking for ‘bad frequencies’ by boosting and sweeping will almost ensure you find something to cut. Strong boosts with a narrow bandwidth will make anything sound bad. There’s no point at which boosting and sweeping will stop finding ‘bad frequencies’.

The end result will sound very unnatural because the tonal shape of the sound is so warped. In addition, this kind of EQ curve can create resonances – dramatic tonal features that are constant and don’t change with pitch. These kinds of tonal features are also common in recordings made in small untreated rooms. It’s ugly! Don’t do it!

Boosting and sweeping is one of several techniques that a mix engineer can use to identify a trouble spot. But it won’t tell you if there is a trouble spot. For that, you have to use your ears and listen to the sound in context – in the mix. Sometimes the problem really is an ugly resonance that should be reducing using a notch EQ… but more often it’s something to do with the way several sounds are interacting together. And these problems are most often caused by inadequate monitoring or a lack of direction and focus.


9 thoughts on “Are you making this common EQ mistake?

  1. Mark says:

    Any tips on what to do as far as this article is concerned? I have used the boost and sweet technique for years and found that it does help. I will usually shape a sound in solo by finding the “bad” frequencies and then add them into the mix with other sound and then shape again from there as needed or to taste. Any other tips you can share would be greatly appreciated. Thanks for your great posts and info.

  2. Kim Lajoie says:

    Hi Mark,

    As I wrote in the post, boosting and sweeping to find a trouble spot isn’t necessarily bad – it can be used well. If you feel that it works for you, then keep doing it.

    The problem is when people boost and sweep when there’s nothing actually wrong with the sound. It’s because this method can very effectively find problems with the sound – even when there aren’t any.

    I recommend always using your ears *before* applying any EQ. Listen to the sound and try to determine *if* it needs tonal adjustment, and what kind. Only then should you start twiddling knobs. EQ is a powerful tool, and using it without knowing exactly what you’re trying to achieve with it will likely lead to worse results than when you started. It’s not a fishing rod – it’s a precision scalpel.


  3. Mark says:


    Thanks again for the reply and great info that you share with us, very useful and inspiring. I will add your advice into my bag of tricks and use it next time I am in the mix. I do live by the saying: “Crap in = Crap out” so I keep that in mind too. I have learned to capture the sound as you want it from the source and only if you cannot achieve the sound naturally is when you can get creative with EQ and FX.

    Looking forward to your future posts. Keep it up, I enjoy the reading!

  4. puddy says:

    I agree to a point . Allot depends on which eq you sweep with . Most average digital eq’s excell at making things sound crappy Sometimes even without the high Q factors and boost !!

    Of course any technique becomes a net-loss if you take it to far .
    Allot of low level room resonances don’t make themselves very apparent whilst you are tracking . Compressing can bring them to the forefront . There is a reason why most every quality console ever made has eq in each strip.

  5. Waza says:

    Hi Kim,

    Just like to say thanks for the tutorial like mark i’ve used this Technique for a few years now, but now will take another angle on it.



  6. Pingback: Using subtractive EQ | Kim Lajoie's blog

  7. Cat says:

    I’ve been a musician, audiophile and computer nerd separately for decades and only recently started recording. As life often happens, I got involved with a startup video company and have been cleaning up location sound and doing voice overs.

    I had never heard of boost & sweep until last night but its what I have been doing and I’m never happy with the results. Further to that; The results are not repeatable i.e. If I do a voiceover and the client wants changes, my voice sounds different 2 days later, the mic and room are a different temperature, the mains is different, Jupiter is in transit etc. and so its never the same sound. Even with saved presets it doesn’t work twice and the overdub stands out big time.

    What I have found is that using a proper compression setting and getting an EQ for the recording space is far more useful – I recorded my monitors producing pink noise in that room and very quickly was able to identify peeks and troughs. Correcting for this is one part but it can leave your vocal dry and dead so minor use of that EQ and sensible use of good classic valve / optical compressor emulation plugins really warm things up nicely.

    Sweep and Boost – reminds me ultimately of the phrase “You can’t polish a turd, but you can sure roll it in glitter.”


  8. Kim Lajoie says:

    Hi Cat,

    Sounds like you’ve found some good approaches that work for you. As you’ve noticed, consistency is very important! Thanks for your comment.


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