Add EQ to existing cabinet IR to remove boom

[Johnny Chandler]

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!

[ashcat_lt]

Pretty sure you can just bring it into Reaper like any other audio file, add the EQ, and render.

[Johnny Chandler]

Originally Posted by ashcat_lt

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!

[Johnny Chandler]

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.

[clepsydrae]

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

[ErBird]

Originally Posted by clepsydrae

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.

[clepsydrae]

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).