When & How to apply Min Phase/MPT and Low & High Cuts?

Prince

Inspired
Vendor
Hi y'all, I am in the process of mixing my massive stash of OwnHammer IRs for my FM3's User Cab Bank. Before before I go all in and make 1,024 IRs, I want to make sure I'm understanding these two steps correctly, so that I don't have to repeat this process. Yes, I have read a ton on this already, but it seems that my specific concerns about methodology and when to apply certain steps haven't been sufficiently addressed.

I. Min Phase (MPT)

In Cab Lab, my current methodology is:
1) Create "Single Speaker + Aux" (SS+Aux) IR consisting of:
1a) (Raw/Non-MPT) OH1, OH1F, or OH2 (#'s 01,03,05,07,09) file @ 0.0 dB
1b) add (Raw/Non-MPT) Room & Mid each at @ -12.0 dB
1c) add (Raw/Non-MPT) Rear at @ -15.0dB
2) Export SS+Aux IR .SYX & .IR files
3) Create a "Speaker A + Speaker B" (A+B) mix of two SS+Aux IRs from the same OH cab pack.
3a) Speaker A @ 0.0 dB
3b) Speaker B @ 0.0 dB (occasionally @ -3.0 dB)
4) Export Speaker A+B Mix .SYX & .IR files.
5) Load SS+A IRs & A+B mix IRs into FM3.

Questions:
-When do I apply MPT? During Step #1? Step #2? Step #3? During Steps #1+#2? #2+#3? #1+#2+#3? etc..
-Is it possible to overapply MPT/Min Phase? Or would it just be redundant/cancel itself out if I did it during steps #1+#2+#3?
-When loading IRs into the FM3 Cab Bank, which have had MPT applied in Cab Lab, should I set the Cabinet Import IR Processing to "None" or "Min Phase"?

Should the work flow be:
6) "Min Phase->None->None"
a) Load Raw/Non-MPT in Cab Lab -> Processing Mode = "Min Phase" -> export SS+Aux IR
b) -> reload SS+Aux IR's -> Processing Mode = "None" -> export A+B IR
c) FM3 Cabinet Import Processing "None" -> Import new IRs
or
7) "None->Min Phase->None"
a) Load Raw/Non-MPT in Cab Lab -> Processing Mode = "None" -> export SS+Aux IR
b) -> reload SS+Aux IR's -> Processing Mode = "Min Phase" -> export A+B IR
c) FM3 Cabinet Import Processing "None" -> Import new IRs
or
8) "None->None->Min Phase"
a) Load Raw/Non-MPT in Cab Lab -> Processing Mode = "None" -> export SS+Aux IR
b) -> reload SS+Aux IR's -> Processing Mode = "None" -> export A+B IR
c) FM3 Cabinet Import Processing "Min Phase" -> Import new IRs

Side Question
I read another user speaking about mixing the Room IR, stating that since the Room IR isn't near-field, that it should be mixed in it's raw/non-MPT state with MPT versions of the near-field IRs. Is this true? If so, how/when would I apply MPT in this process?

II. HPF + LPF & Low Cut + Hi Cut
-Are the High Pass (HPF) and Low Pass (LPF) Filters equivalent to the Cab Blocks Low & High Cuts? If not, differences? What is the slope of the HPF & LPF?
-Is the main benefit of the HPF & LPF that you can "bake in" your Low & High Cuts into the IR, thus allowing the user to not have to use the Low & High Cuts and can keep them at the default values of 20Hz & 20kHz?
-Is it redundant, harmful, or beneficial to use the HPF & LPF and Low & High Cuts simultaneously?
-Or is this an "Either / Or" scenario?

---I've experimented with this some and there does seem to be slight differences:
ex) a) Apply HPF & LPF of 100Hz & 7.5Hz in Cab Lab -> Import to FM3 -> Load into Cab Block with Low & High Cuts of 20Hz & 20kHz
b) Take the same IR but with HPF & LPF of 20Hz & 20kHz -> load into Cab Block with Low & High Cuts of 100Hz & 7.5kHz.
Result: they sound slightly different.

-If one were to apply both HPF & LPF and Low & High Cuts, Should:
c) The HPF & LPF be "tighter" (ex. 100Hz & 7.5kHz) and the Low & High Cuts "looser" (ex. 50Hz & 15kHz)?
or
d) The HPF & LPF be "looser" (ex. 50Hz & 15kHz) and the Low & High Cuts "tighter" (ex. 10Hz & 7.5kHz)?
or
e) use either Cab Lab's HPF & LPF or the Cab Blocks Low & High Cuts, but not both?
---Of c) or d), I'm guessing that d) would be the better practice. Since (I'm assuming) the IR file (and it's contained HPF & LPF) is in the signal path before the Cab Blocks Low & High Cuts, it would have the primarily influence on shaping the tone. By keeping the HPF & LPF "looser" (ex. 50Hz & 15kHz), you're just doing some edge trimming rather than lawn mowing/tree removal. By going the "looser" route, it would still allow you to utilize the Cab Blocks Low & High Cuts more so than you could with the "tighter" approach. This is all assuming there are no negative consequences of layering differing or equal values for the HPF & LPF and Low & High Cuts...

Thanks for y'alls wisdom and guidance. Even after 5 months with the FM3, I'm still a total noob!

(Mods, if this needs to be transferred to Cab-Lab Products sub forum, so be it. I posted it in User Cabs & IRs as there is a LOT more traffic over here.)
 
Yea, this stuff can get a little confusing...

You might find this Ownhammer guide useful:

https://www.ownhammer.com/tutorials/fractal/

I'd reach out directly to OH as to if/when you need/should apply MPT to process his IR's.

My understanding is that if the raw IR files are properly aligned you don't need to apply MPT, and the merits of applying MPT to them seems to be somewhat subjective from discussions I've read.

I'd think that just creating two IR's of the mixes of the raw files as a test would be enough:

-presuming the raw IR's are aligned (which I'd imagine they'd be, but verify), apply MPT to one IR mix in Cab-Lab, leave the other IR mix raw , upload them directly from Cab-Lab, and see if you prefer one over the other via A/B testing.

I'd also think that you'd not need to test all the permutations you've indicated...the one test of two IR's mixed with only one having MPT applied in Cab-Lab should be enough to guide you one way or the other...I cannot say for sure though. Myself, that's all I'd likely do and go with the best result if there were differences.

https://forum.fractalaudio.com/threads/ir-length.155295/post-1848701

Raw is technically "better" but the difference between raw and MPT is minimal. The disadvantage of raw is that you have to manually align them if you are mixing IRs.
 
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