Old 02-14-2020, 06:49 PM   #1
Johnny Chandler
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Default Add EQ to existing cabinet IR to remove boom

Hello all! I am wanting to add some EQ to some IR's I purchased. I want to EQ the IR and then load it onto a microSD card to use with a Shift-Line Olympic MKIIIS. Basically there is just a little bit extra in the low frequencies that I want to remove so that it is not as boomy. I may also try to remove some high end for use with distortions so they are not as harsh. Is this possible in Reaper? If so, how do I do this?
Thanks in advance!
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Old 02-15-2020, 11:20 AM   #2
ashcat_lt
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Pretty sure you can just bring it into Reaper like any other audio file, add the EQ, and render.
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Old 02-15-2020, 11:46 AM   #3
Johnny Chandler
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Quote:
Originally Posted by ashcat_lt View Post
Pretty sure you can just bring it into Reaper like any other audio file, add the EQ, and render.
I have tried this a few times and it has resulted in very weird results. Possible phase issues(?) that sound very honky in the midrange, no bass at all even when setting a HPF as low as 20hz or whatever the lowest possible setting is. The way I tried was dragging and dropping a 48k 24 bit IR in as a track. Then adding ReaEQ to that track and rendering at 48k 24bit. Is there a different way I should be doing this? Thanks!
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Old 02-15-2020, 11:55 AM   #4
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Let me add that I am using these in a Shift-Line Olympic MKIIIS. I will try again and see if the rendered IR sounds weird in Reaper also, or just when loaded into the SLO.
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Old 02-15-2020, 11:59 AM   #5
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Try using a linear phase eq. I wonder if the phase shift from using a non-linear phase eq (e.g. ReaEQ) would then interfere with the dry signal and cause cancellation. Seems likely, by my understanding of convolution math is shaky.

ReaFIR can be linear phase. I like QRange. SplineEQ is nice, too.

Edit: ReaFIR needs to have "Reduce artifacts" enabled to be linear phase

Last edited by clepsydrae; 02-15-2020 at 12:50 PM.
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Old 02-15-2020, 01:03 PM   #6
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Quote:
Originally Posted by clepsydrae View Post
Try using a linear phase eq. I wonder if the phase shift from using a non-linear phase eq (e.g. ReaEQ)
I would definitely recommend against linear phase EQ in this case. A LP EQ will dissipate energy before AND after the attack of the IR. In order to preserve the pre-attack energy, you'd have to delay the whole IR (latency) or chop off the front end of the IR (incorrect).

Top-to-Bottom: Original IR, Minimum Phase EQ, Linear Phase EQ


Clipped to better show pre-ringing:



Normal EQ is the way to go and should work as easily as AshCat says. Make sure you're not somehow mixing the original IR with the EQ'd one before rendering. Make sure you're not clipping.
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Old 02-15-2020, 01:20 PM   #7
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I think a chop would be pretty harmless in this case (and AFAIK it would chop automatically anyway since the IR would be processed at 0:00 and the plugin/DAW isn't going to insert data back in time when the rendering happens), but it's a valid point.

Also, transients pre-ringing with linear-phase is usually only audible in low frequencies anyway, and OP is eq'ing those lower anyhow?

AFAIK IR's capture frequency response and phase response? (Correct me if wrong.) So it would make sense to me that if you have a very wet blend of reverb and original signal, messing with the phase response of the IR would at the least change the results (i.e. for better or worse -- if this is an IR of a space it probably doesn't matter, but if it's e.g. a guitar cab it might be harmful if the OP is mixing dry/wet).
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Old 02-15-2020, 06:33 PM   #8
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Well the weird honky tone results whether I use ReaEQ or ReaFIR and when it is loaded into the SLO. Doesn’t sound crazy in the DAW. The IR’s don’t sound as boomy when used in ReaVerb on a track either. Maybe it has something to do with the file type. From Shift-Line: “The supported impulse format is 24bit 48kHZ WAVE PCM1, uncompressed.” I am rendering at 48K and 24-bit PCM. Is PCM different than PCM1? I am also not doing anything to compress it, should something be done to ensure they’re not compressed?
Hopefully you can help this experience lacking guy out!
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Old 02-15-2020, 07:51 PM   #9
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Quote:
Originally Posted by Johnny Chandler View Post
“The supported impulse format is 24bit 48kHZ WAVE PCM1, uncompressed.”
Never heard of PCM1, and can't find anything on google... can you upload the un-modified IR file somewhere so we can diagnose?

Quote:
I am also not doing anything to compress it, should something be done to ensure they’re not compressed?
You should be fine there.

Does the unmodified IR sound normal in the DAW as well? So, normal both before and after you modify it? And in the SLO, normal and then weird after it's modified? That's a pretty weird pattern, and does start to point gently in the direction of possible user error/misinterpretation :-). Are you testing the DAW version by running a signal back out to the bass amp, or just listening through headphones/monitors? When you make the EQ changes in the DAW, same question: adjusting EQ based on what you hear through the amp, or through the DAW monitors/headphones?
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Old 02-16-2020, 06:53 PM   #10
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If you edit an IR you get a mashup: The time of an event in an IR has a complex nonlinear relationship to frequency response (EQ). You can easily see this by creating a handful of EQ curves, and make an IR of each one, then examine the resulting waveforms of each.

If you insist on using an IR to create the EQ, you'd be better off to create the EQ you want, capture a separate IR of that, and insert that IR into the same instance of ReaVerb (you can do more than one at a time).

It'd be simpler to just add an EQ plug after ReaVerb, and save the pair as an FX chain, though.
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Old 02-16-2020, 08:35 PM   #11
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I disagree with everything you've said.

Quote:
Originally Posted by Philbo King View Post
If you edit an IR you get a mashup: The time of an event in an IR has a complex nonlinear relationship to frequency response (EQ). You can easily see this by creating a handful of EQ curves, and make an IR of each one, then examine the resulting waveforms of each.
Applying EQ directly to the IR .wav and rendering is equivalent to the EQ being applied before the original deconvolution. Ask and I'll prove it.

Quote:
Originally Posted by Philbo King View Post
If you insist on using an IR to create the EQ, you'd be better off to create the EQ you want, capture a separate IR of that, and insert that IR into the same instance of ReaVerb (you can do more than one at a time).
ReaVerb loads IR's in parallel so you'd be mixing the original IR with an EQ'd dry signal, not EQ'ing the IR itself like he wants.

Quote:
Originally Posted by Philbo King View Post
It'd be simpler to just add an EQ plug after ReaVerb, and save the pair as an FX chain, though.
He needs the IR to be EQ'd and rendered to work in a hardware IR loader.
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Old 02-16-2020, 09:51 PM   #12
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Meh. Opinions do vary. You may be right.

Like a good percentage of DAW forum questions, it's simpler and faster to do than to post endless opinions snd speculations about it. Plus doing it holds potential for learning something new.

Peace to you.
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