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High shelf and low shelf filter slopes. Does anyone use them?

sigbergaudio

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Well, you can, but not with these conventional IIr filters. A FIR filter with enough filter taps can remove a single frequency with enough precision and depth. Alternatively a route via FFT and iFFT would do it, but similar caveats apply.

But to what end? :)
 

voodooless

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But to what end? :)
Because you can :cool:

For audio production tools, this can be useful if for some reason the recording was contaminated with some kind of sound that should not be there. If these consist of a handful of frequencies, it can be a useful tool.
 

Mart68

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This is my first day using PEQ. Gone with the smiley face for now. Still trying to figure it all out:

 
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Shadrach

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It's not possible to just remove one single frequency (like removing for instance 1259hz) surgically, but you can use a very high Q filter to reduce a very narrow range. Why are you looking to do this again?
I've tried to be polite; pressed the like button etc. The thing is I know you're wrong. You can remove a single frequency. I've seen it done.
One can also create a notch filter, if that is the correct terminology, that will produce a flat topped shape with vertical sides. I've seen this done as well.
It seems from reading below that someone agrees with me.

Perhaps it's not me that "@Shadrach I think you've misunderstood a thing or two. :)" that hasn't understood a thing or two.

No worries, you've learn't a couple of things today.;)
 
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Shadrach

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I find the phase shift on shelf filters is much less objectionable (less likely to cause unwanted cancellations) than low/high pass filters.

But that is during song editing and mixing. My speakers, JBL 308P, have their crossovers done in fixed DSP which I have never needed or wanted to alter. My room correction uses only peak/cut PEQ filters.
I assume the differences are audible then. Interesting. I'll have to experiment.
 
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Shadrach

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Well, you can, but not with these conventional IIr filters. A FIR filter with enough filter taps can remove a single frequency with enough precision and depth. Alternatively a route via FFT and iFFT would do it, but similar caveats apply.
Indeed. However these are not options with the parametric equalizers I've used. But with a decent production suite just about any filter shape is possible incuding the removal of individual frequencies.
 
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Shadrach

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This is my first day using PEQ. Gone with the smiley face for now. Still trying to figure it all out:

There is a lot to learn on the topic. I started with presets and moved on to trying to establish a curve that suited my equipment and room. I think there are other possibilities that I need to learn more about. Whether they prove to be practical solutions to say room nodes, particularly in the lower bass regions is another matter.
 

sigbergaudio

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I've tried to be polite; pressed the like button etc. The thing is I know you're wrong. You can remove a single frequency. I've seen it done.
One can also create a notch filter, if that is the correct terminology, that will produce a flat topped shape with vertical sides. I've seen this done as well.
It seems from reading below that someone agrees with me.

Perhaps it's not me that "@Shadrach I think you've misunderstood a thing or two. :)" that hasn't understood a thing or two.

No worries, you've learn't a couple of things today.;)

Where / When did I offend you exactly? Not sure if I learned anything, apparently you didn't either.
 

Mart68

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There is a lot to learn on the topic. I started with presets and moved on to trying to establish a curve that suited my equipment and room. I think there are other possibilities that I need to learn more about. Whether they prove to be practical solutions to say room nodes, particularly in the lower bass regions is another matter.
I've yet to measure so no concrete notion of what needs fixing. I think there's a slight mid/top emphasis so I'm trying to correct that by shelving down the mids but I think I might need to narrow the bandwidth a bit more.

Just playing around with it at the moment really trying to get a handle on what it does and can do in practical terms. There's only three bands as it's a vintage unit from 1989. Maybe that will prove to be a limitation. But it's all good fun.
 
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Shadrach

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I've yet to measure so no concrete notion of what needs fixing. I think there's a slight mid/top emphasis so I'm trying to correct that by shelving down the mids but I think I might need to narrow the bandwidth a bit more.

Just playing around with it at the moment really trying to get a handle on what it does and can do in practical terms. There's only three bands as it's a vintage unit from 1989. Maybe that will prove to be a limitation. But it's all good fun.
Three bands is a bit of a limitation. It is interesting. I got a fairly flat response to start with. I tried a few curves but allthough they generally improved things I was still left with some low frequency problems. I started constructing my own curves using various equalization graphs to get an idea of what might work well. I like a bit of bass.
:)
 
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Shadrach

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This is an informative video on what one can do with a parametric equalizer.
 

thewas

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I use rather shelving filters when a transducer (loudspeaker or headphone) deviates on a wide frequency range from the target then several peak/notch filters as its also recommended by REW, Genelecs GLM does that too.
 
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Shadrach

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I use rather shelving filters when a transducer (loudspeaker or headphone) deviates on a wide frequency range from the target then several peak/notch filters as its also recommended by REW, Genelecs GLM does that too.
Have you tried comparing the shelf and notch filters to the standard bell curve filters centred on the same frequencies? The differences are measurable but sometimes I'm not certain they are audible to my ears.
Changes in transition slopes I've found easier to hear.
 

voodooless

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Shelve filters are typically useful for bass boost, creating a sloped-down high-frequency response, or for adding baffle step compensation.
 

thewas

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Have you tried comparing the shelf and notch filters to the standard bell curve filters centred on the same frequencies? The differences are measurable but sometimes I'm not certain they are audible to my ears.
Changes in transition slopes I've found easier to hear.
From signal theory point of view the result should measure and sound the same if the total curve is exactly the same and they are both IIR filters but often it is harder and more tedious to do so with bell filters.
 

gnarly

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I find the phase shift on shelf filters is much less objectionable (less likely to cause unwanted cancellations) than low/high pass filters.

But that is during song editing and mixing. My speakers, JBL 308P, have their crossovers done in fixed DSP which I have never needed or wanted to alter. My room correction uses only peak/cut PEQ filters.
Yep. And if the DSP has 2nd order shelving with variable BW/Q, a low shelf with a big gain cut can make for a fine high-pass filter substitute for the speaker itself..
With less comparite group delay that a traditional hpf.

As folks have said, first order shelving makes for great one controls, either on the low of high end. I like to use linear phase shelves for a frequency response "tilt-control".

Last thought...I think a notch filter is just a parametric EQ with narrow bandwidth technically, but in practice a notch filter is typically very narrow....beyonfdthe range allowed by normal PEQ's. Live sound use notches all the time for feedback control.
My DSP allows a notch filter to have a maximum bandwidth of 0.10 octave, and a minimum bandwidth of 0.01 octave...

notch.JPG
 
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