Try This

It occurs to me that the same reasoning (see my post above) shows that the two signals interfere constructively at double the frequency, so you'd get a boost at 9090Hz in addition to a notch st 4545Hz. Perhaps this is what's contributing to the apparent clarity with some IRs?
 
FractalAudio said:
If you have one our cab packs (say Cab Pack 14) try this:
Set the Cabinet block to Stereo UltraRes (or just Stereo).
Choose an R121 IR for the left.
Choose an SM57 IR for the right.
Set the right delay to 0.110 ms.

It probably works with ML IRs too but I haven't tried it yet.

The math says that this puts a notch at f = 1 / (2 * tau) = 1 / (0.22 ms) = 4545 Hz but I don't hear a notch just a marked increase in clarity.
Click to expand...

Well, what my (very) limited knowledge of math tells me is that this "notch" formula would work if both IRs would have flat frequency response. The very unevenness of cab IRs is what makes the math, well, (very) interesting and the resulting tone pleasing to human ear.

P.S. How this thread went so much below radar astonishes me. I found it by mere accident. Perhaps it should get moved to "Cliff's Notes" sticky...
 
I might try this. I just "pinked" my passive FRFR coaxial 15" with Smaart 7, and ended up using a medium "Q" PEQ to notch down where the crossover point is. I thought there would have been a null at xover, more likely a phasing issue is happening?
I have alot more linearity of EQ's and smoother high end response. Kill's the "harshness" so many complain about.
Sounds more like a guitar cab. I run in MONO..so will this work in my situation? Of course, 4K is way above the center where I need the most attenuation. Maybe you can do the math for me for the mic.delay differential?
 
hdurdevic said:
Well, what my (very) limited knowledge of math tells me is that this "notch" formula would work if both IRs would have flat frequency response.
Click to expand...
Flatness of the frequency response doesn't matter. A notch is still a notch.
 
hdurdevic said:
Well, what my (very) limited knowledge of math tells me is that this "notch" formula would work if both IRs would have flat frequency response.
Click to expand...

It's not clear to me what role flatness of this sort should play. If the IR doesn't monkey with the phase at the frequency in question (or more generally if the two IRs monkey with the phase in the same way at that frequency), then the formula will always calculate a notch frequency. The depth of the notch and its "Q" will depend on other factors (such as the relative strength of the frequency between the two IRs).
 
DrNick said:
It's not clear to me what role flatness of this sort should play. If the IR doesn't monkey with the phase at the frequency in question (or more generally if the two IRs monkey with the phase in the same way at that frequency), then the formula will always calculate a notch frequency. The depth of the notch and its "Q" will depend on other factors (such as the relative strength of the frequency between the two IRs).
Click to expand...

I did try to describe the dependency of the depth of the notch on the strength of the frequency of each of the two IRs, but, as I mentioned, my math knowledge is limited, so I did a poor job :/ When I mentioned "flat response" it was in reference exactly to the resulting notch depth (equal frequency strength would yield a deeper notch, different strength - which comes from using different mics - results in shallower notch).

But enough from me, I don't want to pretend I know anything about this...
 
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