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Author Topic: "Subractive EQ" vs. "Additive EQ"?  (Read 6701 times)

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Offline Sloan Simpson

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"Subractive EQ" vs. "Additive EQ"?
« on: April 02, 2008, 02:14:17 PM »
So I've seen mentioned several times that one should only cut frequencies in EQ, and not boost.  Could someone expand on why that's so?  I've been curious about this lately, and don't recall ever seeing an explanation.

If I've come up with an EQ curve for a recording that sounds good to the ear, but boosts some frequencies, should I then reduce everything in the curve by an equal amount?  I.E. so that the shape of the curve is retained, but everything is subtractive rather than additive?

Offline bluegrass_brad

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #1 on: April 02, 2008, 02:42:35 PM »
Boosting frequencies tend to sound harsher and more artificial than reducing frequencies in post. It's just the way the human ear perceives it. So, for instance, if you were boosting the mids, it may sound better (depending on the amount of boost you are giving it)  to actually reduce the other frequencies around the frequency you want to boost.  Which is pretty much what you described.
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Offline Sloan Simpson

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #2 on: April 02, 2008, 02:46:59 PM »
Boosting frequencies tend to sound harsher and more artificial than reducing frequencies in post. It's just the way the human ear perceives it. So, for instance, if you were boosting the mids, it may sound better (depending on the amount of boost you are giving it)  to actually reduce the other frequencies around the frequency you want to boost.  Which is pretty much what you described.
Thanks, that makes sense.  I'll play around with making a snapshot of the additive curve I liked, and adjusting it all downward and see if I can match it right.

I've had a few tracks used for release that were mastered by a guy in town (not a famous name, but the big guy in town for mastering) and he mentioned boosting highs, etc. when I asked what he'd had to do to my recording.  He may have just been dumbing it down for me and giving me the quick answer to end the conversation  ;D

Offline bluegrass_brad

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #3 on: April 02, 2008, 02:55:11 PM »
You may not have to reduce the frequencies as much as you had to boost. If you know what I mean.
"That was back in a time when society was not quite ready for this music. Anyone remember those days? That's when punk rock was dangerous, right?  You couldn't walk into a mall and get your little pussy pierced, and your little Doc Martin boots and your crazy color for your hair.  You walk down the street with blue hair you was gonna get in a fight with about 5 angry construction workers, or the local college football team, rednecks or cops. Sometimes they kicked our ass, but you know what?  Sometimes we beat the fuck out of em"  - Mike Ness, Social Distortion

Offline Sloan Simpson

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #4 on: April 02, 2008, 03:07:45 PM »
You may not have to reduce the frequencies as much as you had to boost. If you know what I mean.
Gotcha.  I was hoping it would be a direct correlation, like -6db across every band.  Life isn't easy  :P

Thanks for the help

Offline bluegrass_brad

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #5 on: April 02, 2008, 03:12:41 PM »
It will mostly depend on the frequencies you are working with. Good luck!
"That was back in a time when society was not quite ready for this music. Anyone remember those days? That's when punk rock was dangerous, right?  You couldn't walk into a mall and get your little pussy pierced, and your little Doc Martin boots and your crazy color for your hair.  You walk down the street with blue hair you was gonna get in a fight with about 5 angry construction workers, or the local college football team, rednecks or cops. Sometimes they kicked our ass, but you know what?  Sometimes we beat the fuck out of em"  - Mike Ness, Social Distortion

Offline alpine85

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #6 on: April 02, 2008, 03:19:32 PM »
if you boost frequencies, there's always the risk of clipping too, especially if your levels are already high
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Offline Church-Audio

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #7 on: April 02, 2008, 03:44:59 PM »
The way I eq is pretty simple. Take the bumps out and leave the rest alone.. So if you have a recording that is hot around 150hz you use a parametric eq and adjust the Q or bandwidth so your just wide enough to take that bump down and only that bump and with the spectrum analyser and your ear :) You can reduce the gain on that band until you have it pretty flat.. I find that having 5 bands per side of a stereo mix is more then enough to do any type of eqing that might be needed. Anything more then that and you have a real problem with your source. And you need to rethink your approach.

Chris
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Offline Church-Audio

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #8 on: April 02, 2008, 05:06:57 PM »
if you boost frequencies, there's always the risk of clipping too, especially if your levels are already high

You can also increase signal amplitude with subtractive EQ!  So you must always leave adequate headroom at all stages until the very last process.

Don't you mean If your taking away frequency level you are reducing the overall level?.. your are Not adding to the level. If you boost you are adding but if you take away your not increasing level at all just the opposite. Now once you have taken out all the "bumps" you can normalize and get more over all level, now because you have reduced peeks.. in the spectrum, but again taking away or reducing a bump will not increase level one bit by it self. Only boosting a frequency or group of frequencies will add level thus clipping or headroom when your cutting is a non issue. Unless after cutting you boost the overall level.. But that's not part of the eq process.


Chris
« Last Edit: April 02, 2008, 05:10:26 PM by Church-Audio »
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Offline ghellquist

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #9 on: April 02, 2008, 05:14:09 PM »
In my humble opinion: Cutting is a very good starting practice as it is less prone to create disasters when compared to boosting. In order to really hear what is happening when boosting I find that it takes really good listening equipment. A bit of experience is a good thing as well then. But the only thing that counts of course is what it sounds in the end.

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Offline Church-Audio

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #10 on: April 02, 2008, 05:27:52 PM »
In my humble opinion: Cutting is a very good starting practice as it is less prone to create disasters when compared to boosting. In order to really hear what is happening when boosting I find that it takes really good listening equipment. A bit of experience is a good thing as well then. But the only thing that counts of course is what it sounds in the end.

Gunnar

The main issue I have always felt about boosting.. Unless its say bottom end.. Is if it ain't there you can twist the knob all you want.. All your going to add at the end of the day is Noise.. I agree with you. Very few mastering engineers guys who are trained to fix things.. Don't boost very often.. if ever.....

The major problem with boosting is your reducing dynamic range every time you boost your bringing your self closer and closer to 0.. And because music is dynamic its very hard to apply a boost on a piece of music that will sound musical..

On a bass drum for example I will always cut 150-250hz or so and boost 60 or so hz and then boost 4-7k on the top end I might even cut around 800hz as well..and in some rare cases I dont even have to do anything :) But this type of eq I would never apply to a song. Just a kick drum.. That type of eq adjustment is really for shaping the tone of the drum for the PA. Alot of people try to apply the same type of approach to doing final eq on a song and it never works. IMO..
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easy jim

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #11 on: April 02, 2008, 05:57:23 PM »
The way I eq is pretty simple. Take the bumps out and leave the rest alone.. So if you have a recording that is hot around 150hz you use a parametric eq and adjust the Q or bandwidth so your just wide enough to take that bump down and only that bump and with the spectrum analyser and your ear :) You can reduce the gain on that band until you have it pretty flat.. I find that having 5 bands per side of a stereo mix is more then enough to do any type of eqing that might be needed. Anything more then that and you have a real problem with your source. And you need to rethink your approach.

Chris


The major problem with boosting is your reducing dynamic range every time you boost your bringing your self closer and closer to 0.. And because music is dynamic its very hard to apply a boost on a piece of music that will sound musical..

On a bass drum for example I will always cut 150-250hz or so and boost 60 or so hz and then boost 4-7k on the top end I might even cut around 800hz as well..and in some rare cases I dont even have to do anything :) But this type of eq I would never apply to a song. Just a kick drum.. That type of eq adjustment is really for shaping the tone of the drum for the PA. Alot of people try to apply the same type of approach to doing final eq on a song and it never works. IMO..

Excellent advice Chris!  This matches nearly verbatim how I was 'trained' by a couple engineer friends when I asked for pointers and help a couple years ago in 'mastering' my 4 track stuff.  +T  I was also told/shown that it is generally better to compress before EQing vs. the other way around, since compression (not multi-band) will also affect the frequency spectrum.
« Last Edit: April 02, 2008, 06:01:18 PM by easyjim »

Offline Church-Audio

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #12 on: April 02, 2008, 09:42:57 PM »
Don't you mean If your taking away frequency level you are reducing the overall level?.. your are Not adding to the level. If you boost you are adding but if you take away your not increasing level at all just the opposite. Now once you have taken out all the "bumps" you can normalize and get more over all level, now because you have reduced peeks.. in the spectrum, but again taking away or reducing a bump will not increase level one bit by it self. Only boosting a frequency or group of frequencies will add level thus clipping or headroom when your cutting is a non issue. Unless after cutting you boost the overall level.. But that's not part of the eq process.

No, that is absolutely not true.  It is possible to increase peak (and RMS) level with an EQ cut.  It doesn't always happen, but it does happen enough that it's important to always leave headroom during processing.

I repeat:  if you have a signal that is peaking at 0dBFS, and you apply an EQ cut, it is possible that the resulting signal will peak over 0dBFS, without applying any makeup gain whatsoever.

Consider the example of a square wave, then apply a low pass just above the fundamental.  The overtones will be reduced or eliminated, causing the resulting wave to be a reconstruction, so to speak, of the sine wave of the fundamental, which will peak above the original square wave.

That's not just an unrealistic made-up scenario; I see it all the time in mastering peoples' mixes.  Often when I clear up presence peaks with subtractive EQ, the signal peaks at a higher level, up to maybe +1dB.  And often that missing low-midrange suddenly appears . . .

Don't get me wrong, I'm a fan of subtractive EQ.  I am a bigger fan of headroom.  It is much easier to clip a signal by boosting, but cutting isn't a free lunch.  One still can't be sloppy.

Also, don't be afraid to boost; when it works, it works.  Just depends on what the track needs . . .

In 20 years of mixing I have never cut a frequency and had the overall level go up.. Ever. That's all I know lets think about this your taking away a frequency how can that increase level?? You might notice the Midrange more because now its not clouded by a bump in the low end. But thats not an increase in level that a perceived increase in level.. And not the same thing as an increase in level.. Now if you had a compressor on the mix and you reduced a frequency say 150hz because it was a peak.. You could end up bringing up the over all level because you are not hitting the compressor as hard as before when you had the peak in your signal.. But when I apply a cut I am reducing gain because the Q of the filter will also effect frequencies around it and yes harmonics but guess what if the harmonics are also reduced so is the level. When you use a graphic analog eq it is possible that you will have band interaction that can boost frequencies around the center frequency as a trade off of a bad filter design.. But when we are talking digital that does not happen.. Unless your using some cheap ass plugins..

Anyway you have your way I have mine.. Its worked for me so far. I don't usually disagree with your advice but this time, I do. I would love for you to send me a sample file that will increase in level if I apply a cut.. That would be very interesting. When your talking about a pure tone.. anything can happen.. But thank God music is not just a square wave. It would be very hard to listen to. 


EDIT... It just occurred to me talking to a fellow recording studio engineer that some plugin's and some mastering software have gain compensation.. Meaning that when you cut a frequency and reduce level it will automatically bring the track or what ever the plugin is being used on back up to unity gain.. That might be what is going on with your experience of level change when reducing a frequency. Just a thought  ;)


Chris

 
« Last Edit: April 02, 2008, 11:06:31 PM by Church-Audio »
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Offline Javier Cinakowski

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #13 on: April 02, 2008, 10:18:20 PM »
Yinz guys are dorks!

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Offline dactylus

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Re: "Subractive EQ" vs. "Additive EQ"?
« Reply #14 on: April 03, 2008, 07:07:17 AM »


Can someone provide a link to a chart that lists the octaves of the musical scale and their corresponding frequency ranges?



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