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EQ: Cutting frequencies below certain dB?
Old 22nd September 2012
  #1
EQ: Cutting frequencies below certain dB?

In an effort to demystify EQing and mixing I've started looking at the frequency spectra of various instruments.

Let's take a simple synthesized hihat (808 sample). I've noticed a bulk of the the intensity is between 4kHz and 10kHz roughly speaking. At the level I have it set, the signal's highest peak is -48dB which occurs at around 7kHz.

Below 4kHz the signal doesn't go up past -72dB.

If I put a low-pass shaped EQ with fc=4kHz most of the hihat sound is gone. If I put a high-pass shaped EQ at the same fc then most of the sound is still in tact, in fact it sounds close to the sound without the EQ. This is all as expected given the frequency analysis.

Now, my question. Is there a given threshold range of volume (dB) relative to the signal's peak at which a signal can safely be filtered out? And if so, is it good practice to do this, or is there no real benefit?

What I mean is that if the bulk of the signal energy is above a certain dB, is it safe to filter out the signal below a certain dB delta?

More concretely:
Let's say most of the meaningful signal is above -20dB for example (let's refer to this as Y).
Is there a delta dB amount (call it X) which when subtracted from the level Y can safely be ignored as "pointless"?
So let's say X=20dB, then Y-X = -40dB, so all frequencies where the signal doesn't go past -40dB can be filtered out without noticeable effect. The numbers here are just examples.

I hope that made sense.

I'm not sure if a low dB signal can positively or negatively impact the mix when it starts to interact with other signals in the same frequency range from other tracks for example.

If someone can shed some light on this I'd be grateful. Perhaps I'm thinking of it too mathematically/surgically. But so far I've been using my ears only to mix+eq and haven't been happy with the results. So I either have to train my ears better or do things scientifically lol. Or I probably just need to finally acoustically treat my room

I've attached a screenshot of the 808 hihat frequency spectrum I'm talking about here.

Thanks!
Attached Images
File Type: jpg 808_hihat.jpg (26.8 KB, 929 views)
Old 22nd September 2012
  #2
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If you filter every sound, the mix will end up sounding fake. Its less "punk." EQing is safe for rebalancing or re-focusing sounds. I don't like to take away too much sonic energy. The end result will go through compression for me, so I only filter audible problems. (having a cymbal go to 100hz may not hurt anything) Just an opinion.
Old 22nd September 2012
  #3
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Praxisaxis's Avatar
 
🎧 10 years
Quote:
Originally Posted by bloodsample ➡️

If someone can shed some light on this I'd be grateful. Perhaps I'm thinking of it too mathematically/surgically. But so far I've been using my ears only to mix+eq and haven't been happy with the results. So I either have to train my ears better or do things scientifically lol. Or I probably just need to finally acoustically treat my room

Thanks!

In my personal opinion, yes you're beginning to think of it too mathematically... the science only matters inasmuch as when it provides you a result that your ears are pleased with, which, in most cases, is a result you can achieve just by using your ears.

High passing may or may not provide a noticable effect (obviously).
High passing a high hat at around 1kHz which has most of its content above (using your example) of 4kHz, will make little or no noticeable difference (as you mention).

The reason I believe it's good to habitually high pass tracks like that in a mix is simply because bass is "energy expensive" and the more you free up the better; not really because you're creating a sonic effect on one track but more the cumulative effect of practicing that over the whole mix. It makes little difference in the end and it possibly doesn't really matter.

On the other hand, with some instruments - e.g. synths, pianos, guitars, etc - a good amount of their timbre or sonic character depends on their low end. In these cases, high passing certainly has a noticable effect, and therefore in these cases it is not a "habitual" exercise, but a conscious choice to cut away and free up room in the lower end, with the understanding this will noticeably alter the sound of that instrument, hopefully for the benefit of the mix.

So with the latter, high passing is important and noticable; with the former I don't think it hurts, and it might make a small difference, but not such a big deal.

Edit: I do agree with the previous poster that high passing can zap out energy unintentionally. If you've had a session where you've been aggressive with the high pass, it's worth coming back later with fresh ears and reassessing to make sure you got it right. It's easy to unintentionally overdo it.
Old 22nd September 2012
  #4
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Amun Ra's Avatar
 
🎧 10 years
Why would you filter out something thats 72dB below peak? Is there something there that you can actually hear?

Skip the analyzer, it will just mess with your mind if you´re an analytical, right brain, visually oriented person (like me).

Try to EQ with a PURPOSE. Unfortunately there are no rules, no tricks and no patent soulutions. Close your eyes, listen, and do as little damage as possible. Switch the EQ in and out and decide if you like what you're hearing. Repeat.
Old 22nd September 2012
  #5
Gear Addict
 
🎧 10 years
yeah you really should just be going by ear. There's tons of sample packs out there you shouldn't have to settle for samples that need to be drastically eqed/filtered in the first place. Mind you as you place more sounds in the mix you may find it useful to high pass it a bit further to make room for other sounds such as a lead synth or pad.

The main thing to remember is that filtering very low level noise will probably yield little to no headroom gain and could even cause higher peak levels due to phase shifting.
Old 22nd September 2012 | Show parent
  #6
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🎧 10 years
Quote:
Originally Posted by Augsy ➡️
The main thing to remember is that filtering very low level noise will probably yield little to no headroom gain and could even cause higher peak levels due to phase shifting.
Yeah that's an important point, although can be mitigated by filtering with a not-too-steep slope.
Old 22nd September 2012 | Show parent
  #7
Quote:
Originally Posted by Praxisaxis ➡️
The reason I believe it's good to habitually high pass tracks like that in a mix is simply because bass is "energy expensive" and the more you free up the better; not really because you're creating a sonic effect on one track but more the cumulative effect of practicing that over the whole mix. It makes little difference in the end and it possibly doesn't really matter.
Good info, thanks. This is exactly what I'm starting to think more about, namely how various stacked sounds/tracks interact together, this is the part of EQing that isn't intuitive for me yet. I mean it's one thing to tweak a lone sound, but it's the combination of that sound with other sounds which starts to get tricky.

Quote:
Originally Posted by Amun Ra ➡️
Why would you filter out something thats 72dB below peak? Is there something there that you can actually hear?
As it stands, the stuff below -72db don't bother me. I was just thinking of maybe keeping every track as "clutter-free" as possible so that when I start adding many more tracks the combined effect of the clutter would be minimal. My thinking was that one track with a little noise is ok, but dozens of tracks with their own little noise might end up combining into something noticeable. This is why I'm wondering whether there's a ratio of signal to noise at which point it's safe to remove. By safe I mean that it won't impact the overall sound in a negative way.

Quote:
Originally Posted by Amun Ra ➡️
Try to EQ with a PURPOSE.
This is the ultimate goal indeed. But for now that "purpose" isn't very obvious to me. My intuition is often not to EQ much, if at all, and focus on arrangement. But I've noticed some of my tracks are a bit muddy which leads me to believe I need to brush up on my EQing a little.

Quote:
Originally Posted by Augsy ➡️
yeah you really should just be going by ear. There's tons of sample packs out there you shouldn't have to settle for samples that need to be drastically eqed/filtered in the first place. Mind you as you place more sounds in the mix you may find it useful to high pass it a bit further to make room for other sounds such as a lead synth or pad.
There's nothing wrong with the sample I'm using, it sounds really nice. I just used it as an example here. I guess I'm thinking ahead a little bit and trying to avoid as much mud as possible down the line by being a little bit more careful with each sound I use from the get go. Perhaps it's not the best approach.



Thanks for all the tips so far.
Old 22nd September 2012
  #8
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Praxisaxis's Avatar
 
🎧 10 years
Quote:
I mean it's one thing to tweak a lone sound, but it's the combination of that sound with other sounds which starts to get tricky.
That's the secret to EQ. It's really important to craft the overall sound... try to mess with the EQ while playing back the whole mix, and only solo for technical purposes. Do this in combination with monitoring at a fairly low volume, and you begin to teach your ears - you pull the mix apart mentally, but listen as a whole. Take frequent breaks so you can "re-calibrate" your brain.
Old 22nd September 2012
  #9
Gear Head
 
🎧 5 years
I strongly disagree with the premise that you should filter out what you are not hearing anyway.

A good excercis to do is this -

get up a quick mix with no plugs at all. Now place the same eq across all the tracks.


Now start hipassing elements. when you high pass the guitars what happens to the snare. Whne you low pass the guitar, what happens to the vocal...when you hi pass everything except th ebass and Kik (a popular myth) what happens to the mix?????


You will be very surprised as to what happens to elements that you didn't think would be affected.

EVRYTHING AFFECTS EVERYTHING.
Old 22nd September 2012
  #10
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John The Cut's Avatar
 
🎧 15 years
what?
Old 22nd September 2012
  #11
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Praxisaxis's Avatar
 
🎧 10 years
Quote:
when you hi pass everything except th ebass and Kik (a popular myth) what happens to the mix?????
What happens to the mix? It changes, which is to be expected.

I do agree that in mixing you should never just do something because you're "supposed to" without a thought for what it sounds like.

However, I often find that high passing some of the main tracks besides bass and kick can be very useful, but of course you need an ear out for what's going on. On some instruments like mid range synths and guitars the change will be dramatic, so you have to take care with the slope of the filter and the frequency at which the roll off is beginning. It depends on the character of your tune too - thoughtlessly removing mid-low content will certainly zap the power out a tune. But all this goes without saying really.
Old 22nd September 2012 | Show parent
  #12
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Amun Ra's Avatar
 
🎧 10 years
Quote:
Originally Posted by Praxisaxis ➡️
That's the secret to EQ. It's really important to craft the overall sound... try to mess with the EQ while playing back the whole mix, and only solo for technical purposes. Do this in combination with monitoring at a fairly low volume, and you begin to teach your ears - you pull the mix apart mentally, but listen as a whole. Take frequent breaks so you can "re-calibrate" your brain.
+1. Forgot that one. Essential.
Old 22nd September 2012
  #13
Gear Addict
 
🎧 10 years
I think to sum this up, you should be high passing to keep things out of the low frequency range that may interfere with you bass/kick/synths, not just because you think those frequency's aren't needed.

For me effect's, and background sort of stuff that I use *generally* get high passed pretty extremely (sometimes close to 500hz) if I already have lots of things going on in the low-mid's. I try to keep everything balanced though as I find having too many sounds high passed too much and the mix will start to sound a bit lifeless.
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