HP & LP Filters and EQ

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MonoDuo
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Post 17 Oct 2021

So, I understand why you use LP and HP filters to carve out sonic niches for instruments, but what happens if I record a bass track and remove all frequencies below 60 Hz and then use an equalizer to boost the bass around 60 Hz. Does that negate the filtering I did? Does it technically make it more muddy? I know my ears can tell me this but I wanted some perspective and if I knew more I could explain this better. Thanks.

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guitfnky
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Post 18 Oct 2021

to some degree it does negate the other filter, but you’re essentially combining two filters to form a more complex curve that couldn’t be achieved with just one or the other.

if you’re high passing at 60 hz, that filter has a slope to it. boosting at or below this frequency is like adding a custom resonant bump at whatever frequency you set. if you like the sound of the high pass filter, but it’s cutting a little too much of a given frequency, you can use this to bring back a bit of that frequency. it’s only going to “add mud” if that’s what your ears are telling you it’s doing.

the short of it is, don’t be hesitant to stack different filter types in the same frequency range to achieve what you want. they don’t have to be the same EQ either. I regularly end up with 2, 3, sometimes even 4 EQs on the same track (sometimes one after another, other times in between other effects), and it’s very common to have them working in the same range.
I write bad music for good people

latest release—The Lake Door:
bit.ly/TheLakeDoor-Soundcloud
https://slowrobot.bandcamp.com/track/the-lake-door

MonoDuo
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Post 25 Oct 2021

Thanks Guitfnky, that response helped a lot. I went and listened to one of your songs first because if you had a cruddy song I would have had trouble with taking your advice, but your Lake Door song is great and may I say very dynamic (I'm not a fan of the Loudness Wars but I compress a lot) so anyway I'm going to EQ my bass in a very narrow band around 60 Hz by about 2 db unless that muddies it up. Thanks for your helpful advice.

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huggermugger
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Post 25 Oct 2021

A Pultec-style EQ (simultaneous boost & cut) can do some very nice things for your bass frequencies. It's not exactly what you're describing, but the concept is similar.
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jlgrimes
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Post 25 Oct 2021

MonoDuo wrote:
17 Oct 2021
So, I understand why you use LP and HP filters to carve out sonic niches for instruments, but what happens if I record a bass track and remove all frequencies below 60 Hz and then use an equalizer to boost the bass around 60 Hz. Does that negate the filtering I did? Does it technically make it more muddy? I know my ears can tell me this but I wanted some perspective and if I knew more I could explain this better. Thanks.
In theory filtering out the lows at 60 hz would remove everything below that point so a boost at 60 hz wouldn't do much.

In practicality though things like this are done though. As sometimes a highpass filtered bass followed by an eq boost or even just using a resonant hp filter can really emphasize the bass and is a popular low end trick. On whether it makes it muddy, that depends on how you are doing it and what tools you are using for the job (and how heavy you are using them).

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guitfnky
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Post 25 Oct 2021

jlgrimes wrote:
25 Oct 2021
MonoDuo wrote:
17 Oct 2021
So, I understand why you use LP and HP filters to carve out sonic niches for instruments, but what happens if I record a bass track and remove all frequencies below 60 Hz and then use an equalizer to boost the bass around 60 Hz. Does that negate the filtering I did? Does it technically make it more muddy? I know my ears can tell me this but I wanted some perspective and if I knew more I could explain this better. Thanks.
In theory filtering out the lows at 60 hz would remove everything below that point so a boost at 60 hz wouldn't do much.

In practicality though things like this are done though. As sometimes a highpass filtered bass followed by an eq boost or even just using a resonant hp filter can really emphasize the bass and is a popular low end trick. On whether it makes it muddy, that depends on how you are doing it and what tools you are using for the job (and how heavy you are using them).
as I understand it (could be totally wrong—it’s been a while), the cutoff point for HP and LP filters are defined as the frequency point where there’s a 3 db drop in the frequency response. so a 60 hz cutoff means there’s still quite a bit of information at that frequency, even if you’re using a steep filter. a 12 db per octave slope filter is I think the norm, and at 60 hz, you’re running out of octaves anyway, so there’s likely to be plenty to work with still all the way down to the very bottom of the audible frequency range.
I write bad music for good people

latest release—The Lake Door:
bit.ly/TheLakeDoor-Soundcloud
https://slowrobot.bandcamp.com/track/the-lake-door

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guitfnky
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Post 25 Oct 2021

MonoDuo wrote:
25 Oct 2021
Thanks Guitfnky, that response helped a lot. I went and listened to one of your songs first because if you had a cruddy song I would have had trouble with taking your advice, but your Lake Door song is great and may I say very dynamic (I'm not a fan of the Loudness Wars but I compress a lot) so anyway I'm going to EQ my bass in a very narrow band around 60 Hz by about 2 db unless that muddies it up. Thanks for your helpful advice.
hey, appreciate the kind words, and I’m glad you found it helpful. I definitely value dynamics in my music, and I use quite a bit of compression too—it’s all in how you use it! 😊
I write bad music for good people

latest release—The Lake Door:
bit.ly/TheLakeDoor-Soundcloud
https://slowrobot.bandcamp.com/track/the-lake-door

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selig
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Post 25 Oct 2021

guitfnky wrote:
25 Oct 2021
jlgrimes wrote:
25 Oct 2021


In theory filtering out the lows at 60 hz would remove everything below that point so a boost at 60 hz wouldn't do much.

In practicality though things like this are done though. As sometimes a highpass filtered bass followed by an eq boost or even just using a resonant hp filter can really emphasize the bass and is a popular low end trick. On whether it makes it muddy, that depends on how you are doing it and what tools you are using for the job (and how heavy you are using them).
as I understand it (could be totally wrong—it’s been a while), the cutoff point for HP and LP filters are defined as the frequency point where there’s a 3 db drop in the frequency response. so a 60 hz cutoff means there’s still quite a bit of information at that frequency, even if you’re using a steep filter. a 12 db per octave slope filter is I think the norm, and at 60 hz, you’re running out of octaves anyway, so there’s likely to be plenty to work with still all the way down to the very bottom of the audible frequency range.
Came here to say this, but you beat me to it! thinking a filter removes "all the frequencies" above/below the cutoff is not at all accurate. Even 30 Hz is only 15 dB down, which an EQ can boost easily. But you didn't say anything about what type of EQ you were using or thinking about using, or WHY you want to do such a thing. Without knowing what you're going for, it's difficult to say exactly how it would affect your opinion of the sound. Or to put it another way, what were you HOPING would happen?
And out of curiosity, what EQ settings (and filter) DID you use that made it sound muddy to you?
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MonoDuo
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Post 26 Oct 2021

Wow, thanks for all of the replies. Huggermugger, that's an interesting program, I might check it out. Jlgrimes, I see what you mean, I should perhaps cut it around 58 Hz and boost a bit at 60 Hz for the equalizer, but I might just leave it alone after reading Selig's post...Selig, I don't know what I was trying to achieve other than making a bass line stay in a lower frequency range because "that's what you're supposed to do" and that's why I was asking. You made me realize that you can't have it both ways (cutting a low frequency bassline with a filter and then boosting the same frquency with EQ). What I was trying to acheive was to tame a bass line that had a lot of high frequncies and I achieved that with the filters alone. The mix sounds fine at this point, but I'm always looking for a way to tweak things so they sound better, hence my original question that you all have helped me get a better handle on. And Guitfnky, your idea about using multiple equalizers on one track is something I never thought of, a genius move. I'll be using that trick down the road on this song.

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huggermugger
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Post 27 Oct 2021

MonoDuo wrote:
26 Oct 2021
Wow, thanks for all of the replies. Huggermugger, that's an interesting program, I might check it out.
The one I showed costs money. Here's a free version of the same thing, an EQ with simultaneous boost and cut in the lows.

https://sonimus.com/products/soneq
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selig
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Post 27 Oct 2021

MonoDuo wrote:
26 Oct 2021
Wow, thanks for all of the replies. Huggermugger, that's an interesting program, I might check it out. Jlgrimes, I see what you mean, I should perhaps cut it around 58 Hz and boost a bit at 60 Hz for the equalizer, but I might just leave it alone after reading Selig's post...Selig, I don't know what I was trying to achieve other than making a bass line stay in a lower frequency range because "that's what you're supposed to do" and that's why I was asking. You made me realize that you can't have it both ways (cutting a low frequency bassline with a filter and then boosting the same frquency with EQ). What I was trying to acheive was to tame a bass line that had a lot of high frequncies and I achieved that with the filters alone. The mix sounds fine at this point, but I'm always looking for a way to tweak things so they sound better, hence my original question that you all have helped me get a better handle on. And Guitfnky, your idea about using multiple equalizers on one track is something I never thought of, a genius move. I'll be using that trick down the road on this song.
I didn't mean to imply you COULDN'T do what you suggested, just that it would have a very specific response which would be different with different EQ/Filter types/slopes etc. So there really isn't "one" answer as to exactly what would happen with what you suggested, but for each combination of EQ/Filter both tuned to the same frequency, there very well could be some useful settings. BUT, how useful it was would 100% depend on what exactly you were trying to achieve!
Basically, it's difficult to work back from a solution without first asking about the problem! ;)

Looking back on past mixes, I've definitely done similar things. Sometimes it's a progression, adding low shelf first and later noticing some sub-sonic garbage that needs to come out. Or the other way around more likely, but I would probably not say "I think this track needs a cut and a boost at the same frequency. Sure, I might end up there, but I'd have made intentional choices along the way that just happened to both have the number 60 in them.
For reference, here's a quick comparison of filter + EQ at same frequency (60 Hz) with two different boost amounts on the EQ to show the potential variations.
Image
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moofi
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Post 30 Oct 2021

The colourcoding along with the descriptions I find confusing. ;-)
selig wrote:
27 Oct 2021
[...]
Image

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selig
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Post 05 Nov 2021

moofi wrote:
30 Oct 2021
The colourcoding along with the descriptions I find confusing. ;-)
selig wrote:
27 Oct 2021
[...]
Image
The green line is just the EQ.
The orange line is just the HP filter.
The red line is high pass and EQ, as per the OPs question.
Make sense?
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moofi
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Post 11 Nov 2021

Yes, I got that far, thank you. :-)
The confusing part is there are 4 differently coloured labels while there are 6 graphs with 5 different colours.
What are the purple and the second blue one?
selig wrote:
05 Nov 2021
moofi wrote:
30 Oct 2021
The colourcoding along with the descriptions I find confusing. ;-)

The green line is just the EQ.
The orange line is just the HP filter.
The red line is high pass and EQ, as per the OPs question.
Make sense?

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selig
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Post 11 Nov 2021

moofi wrote:
11 Nov 2021
Yes, I got that far, thank you. :-)
The confusing part is there are 4 differently coloured labels while there are 6 graphs with 5 different colours.
What are the purple and the second blue one?
selig wrote:
05 Nov 2021


The green line is just the EQ.
The orange line is just the HP filter.
The red line is high pass and EQ, as per the OPs question.
Make sense?
Oh sorry, just a different amount of boost on the EQ showing how boost affects the curve - was in a hurry, could have left those off…
The bottom line is this is not an odd or even uncommon thing to do.
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moofi
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Post 11 Nov 2021

Ah, ty :-)
selig wrote:
11 Nov 2021
moofi wrote:
11 Nov 2021
Yes, I got that far, thank you. :-)
The confusing part is there are 4 differently coloured labels while there are 6 graphs with 5 different colours.
What are the purple and the second blue one?

Oh sorry, just a different amount of boost on the EQ showing how boost affects the curve - was in a hurry, could have left those off…
The bottom line is this is not an odd or even uncommon thing to do.

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moofi
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Post 11 Nov 2021

Thinking about it I at least guess it would have been more clear if the purple line was red aswell.

PhillipOrdonez
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Post 11 Nov 2021

I like that OP checked the music first to see if they would listen to the advice given. Now if everyone did this with everything things would be much better. Just came to say this, moving on. 🤗


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miscend
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Post 11 Nov 2021

I just stumbled across this video and I thought it would be relevant to this discussion. There are no rules in audio, but its good advice to keep the amount of filtering and EQing of sounds to a minimum as there are trade-offs with EQ. Each time you use filters you degrade the sound quality of the source and you lose some headroom. So rather than using a HP on the bass and then next boosting with bell, it's better to use a low shelf to control the low frequencies.


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Ottostrom
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Post 12 Nov 2021

miscend wrote:
11 Nov 2021
I just stumbled across this video and I thought it would be relevant to this discussion. There are no rules in audio, but its good advice to keep the amount of filtering and EQing of sounds to a minimum as there are trade-offs with EQ. Each time you use filters you degrade the sound quality of the source and you lose some headroom. So rather than using a HP on the bass and then next boosting with bell, it's better to use a low shelf to control the low frequencies.

That's actually really interesting! Thanks for sharing the video.
I did the test myself with GQ-7 and on some material it does indeed increase the peak slightly when I just cut out some of the insignificant lows. Had no idea this would happen without some sort of gain compensation involved and I think everything he brought up is good information to have

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miscend
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Post 12 Nov 2021

Ottostrom wrote:
12 Nov 2021
miscend wrote:
11 Nov 2021
I just stumbled across this video and I thought it would be relevant to this discussion. There are no rules in audio, but its good advice to keep the amount of filtering and EQing of sounds to a minimum as there are trade-offs with EQ. Each time you use filters you degrade the sound quality of the source and you lose some headroom. So rather than using a HP on the bass and then next boosting with bell, it's better to use a low shelf to control the low frequencies.

That's actually really interesting! Thanks for sharing the video.
I did the test myself with GQ-7 and on some material it does indeed increase the peak slightly when I just cut out some of the insignificant lows. Had no idea this would happen without some sort of gain compensation involved and I think everything he brought up is good information to have
If you have some time you should check out the other videos, it's part of a three part series.

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selig
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Post 13 Nov 2021

miscend wrote:
11 Nov 2021
So rather than using a HP on the bass and then next boosting with bell, it's better to use a low shelf to control the low frequencies.
While I totally agree to using the least amount of processing required for each task, I can’t wrap my head around using less than needed. In the initial example I cannot think of a way to reduce the low frequencies around 40 Hz while boosting the frequencies above (around 100 Hz) using only a low shelf. I’m a fan of the Einstein quote: “things should be made as simple as possible, but not simpler”.
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selig
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Post 13 Nov 2021

Ottostrom wrote:
12 Nov 2021
That's actually really interesting! Thanks for sharing the video.
I did the test myself with GQ-7 and on some material it does indeed increase the peak slightly when I just cut out some of the insignificant lows. Had no idea this would happen without some sort of gain compensation involved and I think everything he brought up is good information to have
This comes up from time to time and is good to remember - many processes add gain, and if you follow best practices that include compensating for processing gain changes (up or down), you would likely already have compensated for that change. The idea that you loose “headroom” is nonsensical IMO, since you have literally hundreds dB of dynamic range beyond what is needed - you could theoretically “loose” close to 1400 dB dynamic range and still have enough dynamic range to accurately reproduce a 24 bit signal., so loosing 1-2 dB is not a problem.
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AnotherMathias
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Post 13 Nov 2021

miscend wrote:
11 Nov 2021
So rather than using a HP on the bass and then next boosting with bell, it's better to use a low shelf to control the low frequencies.
If you want to filter out the sub 40Hz, and also get a bump at 100Hz, I guess the easiest way is to use an EQ that has an HP function that lets you set a Q-value, for a bit of a resonance peak right above the cutoff point. No stock Reason EQ will do this, AFAIK, but you could use a synth-type HPF for this, using a device like Sweeper.

But you can also use a low shelf EQ that has a Q setting - M-Class is one. Use it to CUT your lowest bass frequencies, then crank up the Q value all the way up to get your bump. The M-Class graphic display illustrated this fairly clearly.

But really, for all but the most critical, delicate work, just stack EQs and filters all day long - if it sounds good, it sounds good!

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Ottostrom
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Post 13 Nov 2021

selig wrote:
13 Nov 2021
Ottostrom wrote:
12 Nov 2021
That's actually really interesting! Thanks for sharing the video.
I did the test myself with GQ-7 and on some material it does indeed increase the peak slightly when I just cut out some of the insignificant lows. Had no idea this would happen without some sort of gain compensation involved and I think everything he brought up is good information to have
This comes up from time to time and is good to remember - many processes add gain, and if you follow best practices that include compensating for processing gain changes (up or down), you would likely already have compensated for that change. The idea that you loose “headroom” is nonsensical IMO, since you have literally hundreds dB of dynamic range beyond what is needed - you could theoretically “loose” close to 1400 dB dynamic range and still have enough dynamic range to accurately reproduce a 24 bit signal., so loosing 1-2 dB is not a problem.
Yeah I'm not gonna worry much about the slightly increased peak level, but the quite drastic phase distortion caused by LP/HP filters is something I've become more aware of. From my previous understanding this would not be an audible issue unless I have a parallel channel of the track running as well but in the video he mentions that this could even be a problem for a single track, and that it can "ruin the mids". I don't expect this to be a big issue but maybe I could be a little more mindful of where I use my filters

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