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Destructive artifacts of an equalizer

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Destructive artifacts of an equalizer

Postby scoopsdardaris on Thu Nov 02, 2017 7:24 pm

Hey so I was just watching a video about how the samples for Toontracks Alt-Rock EZX were captured at Electrical Audio by Steve, and outside of the fact that it was a really interesting video, I was confused when Steve said "...without causing all the destructive artifacts of an equalizer on the original channel." What exactly is meant here? And are the destructive artifacts caused by just adding more circuitry to the signal path, or due to the nature of equalizers themselves? Is this something very obvious that everyone knows about and I just missed it at some point?

Any information would be great, thank you.

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Re: Destructive artifacts of an equalizer

Postby Anthony Flack on Thu Nov 02, 2017 7:46 pm

Equalisers mess with phase due to the nature of the equalisation process.
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Re: Destructive artifacts of an equalizer

Postby scoopsdardaris on Thu Nov 02, 2017 7:52 pm

Hey thank you so much! Can you go in depth a little more? Or is there a good resource you can point me to, to learn more about it?
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Re: Destructive artifacts of an equalizer

Postby regular username on Thu Nov 02, 2017 8:52 pm

scoopsdardaris wrote:Hey thank you so much! Can you go in depth a little more? Or is there a good resource you can point me to, to learn more about it?

http://ethanwiner.com/EQPhase.html
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Re: Destructive artifacts of an equalizer

Postby steve on Thu Nov 02, 2017 11:19 pm

Yeah I wasn't just talking about phase rotation, there are other problems. You can run out of headroom if the EQ is additive, and if you drive a channel or part of a circuit into distortion, the fact that it is a transient signal might make the clipping less noticeable while still degrading the sound. If you use HF eq to brighten the bass drum you'll exaggerate the dirty, trashy bleed of the cymbals and snare drum in the bass drum mic.

If you can solve a problem without using EQ, you avoid the unintended effects of the EQ. It's not a religious thing, like EQ is bad because it's fundamentally bad, it's just that when you use EQ on a mic, you're affecting everything that mic hears, not just the sound it is intended to pick up.
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Re: Destructive artifacts of an equalizer

Postby Redline on Fri Nov 03, 2017 8:01 am

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Re: Destructive artifacts of an equalizer

Postby Justin Foley on Fri Nov 03, 2017 1:49 pm

steve wrote:Yeah I wasn't just talking about phase rotation, there are other problems. You can run out of headroom if the EQ is additive, and if you drive a channel or part of a circuit into distortion, the fact that it is a transient signal might make the clipping less noticeable while still degrading the sound. If you use HF eq to brighten the bass drum you'll exaggerate the dirty, trashy bleed of the cymbals and snare drum in the bass drum mic.

If you can solve a problem without using EQ, you avoid the unintended effects of the EQ. It's not a religious thing, like EQ is bad because it's fundamentally bad, it's just that when you use EQ on a mic, you're affecting everything that mic hears, not just the sound it is intended to pick up.


How do you evaluate the relative impact of one equalizer vs another? I hear people say "this EQ is really phase-y" or "this one is really clean, has minimal phase shift" but I'd be lying if I could say I can reliably identify this by ear. Do you pay attention to something specific when you listen to a unit? Compare a particular spec?

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Re: Destructive artifacts of an equalizer

Postby Boombats on Fri Nov 03, 2017 2:01 pm

IANFMsteve, but I had a TL Audio tube EQ unit that had really obvious phasing at certain settings, especially when the parameters were set close together. Whereas my ART tube EQ that I use now has a lot smoother sound with less crossover weirdness. Dunno if that helps.
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Re: Destructive artifacts of an equalizer

Postby steve on Fri Nov 03, 2017 3:39 pm

Justin Foley wrote:How do you evaluate the relative impact of one equalizer vs another? I hear people say "this EQ is really phase-y" or "this one is really clean, has minimal phase shift" but I'd be lying if I could say I can reliably identify this by ear. Do you pay attention to something specific when you listen to a unit? Compare a particular spec?

= Justin

You can look at the flat and EQ'd signals on the oscilloscope but I usually just listen to the sound before and after and see if it sounds weird. There are some designs that are minimal phase or constant phase (the NTI equalizer for example) and the difference between them and device with greater phase shift is pretty apparent, though hard to describe.
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Re: Destructive artifacts of an equalizer

Postby bishopdante on Fri Nov 03, 2017 4:46 pm

scoopsdardaris wrote: are the destructive artifacts caused by just adding more circuitry to the signal path, or due to the nature of equalizers themselves?


In the analogue domain an EQ set to flat will do all sorts of stuff to a signal and potentially influence how the equipment connected to it performs, especially considering the majority of EQs are full of amplifiers and also have input/output impedances etc etc etc. They can add noise, they can clip, they can add distortion, and one has to bear in mind that no analogue component or process performs a totally clinical or exact mathematically simple function.

The nature of any particular equaliser is the extra circuitry in the signal path, which can be quite variable in design and quality.

steve wrote: when you use EQ on a mic, you're affecting everything that mic hears, not just the sound it is intended to pick up.


This is entirely true.

Also, listening to a signal on its own, alterations to phase won't be audible... but once you start summing those phase-altered signals with other signals... then it can make quite a bit of difference, so for an array of mics recording a complex source, frequency-specific changes to phase can be problematic.

One thing I can say for sure... SSL G series desk EQ run too hot does something profoundly horrible to the sound whether it's set flat or not. Many mixing desk EQ sections do something quite undesirable to the quality of a signal, some more than others, and none of them improve the quality set to flat.
Last edited by bishopdante on Wed Nov 08, 2017 6:24 am, edited 3 times in total.
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Re: Destructive artifacts of an equalizer

Postby Anthony Flack on Fri Nov 03, 2017 5:52 pm

Some internet dude runs test tones through a linear phase and regular eq and compares the results. He does it in software so the limitations are all in the maths.

The linear phase eq fixes the phase artifacts at the expense of introducing an overall delay to the signal.
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