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Non-Minimum Phase IRs

FractalAudio

Administrator
Fractal Audio Systems
Moderator
So I've been doing a lot of critical listening the last couple months and have come to the conclusion I like non-minimum phase IRs better. The difference is subtle. They don't really sound that different but there are differences in the attack and in the feel. They just sound/feel a little more open and realistic.

Another thing is that they mix very differently. It's less predictable but more natural. The caveat is that it's like mixing real mics, you need to experiment moving each mic in and out whereas with minimum phase you can usually just leave one mic at zero and move the other in and out.

So here's a zip file of my favorite IR session, the Wellspring session, in non-min phase format for use with the Axe-Fx III. My suggestion is to put them in one of the user banks and compare with the factory min-phase versions. Note that names are a bit different but you should be able to figure it out ;).

www.fractalaudio.com/downloads/firmware-presets/axe-fx-3/Wellspring_NonMP.zip

I hope to release all the factory cabs as a non-min phase download in the coming months. We're just very busy with a bunch of other things so it's low on the priority list.
 

lqdsnddist

Axe-Master
Very cool and the relentless pursuit of perfection is always unmatched in the industry.

I’ve always been a fan of the phase effects you’d get from multiple mics. It’s not always desirable, but when it works, it sounds fantastic and adds a certain “real-ness” which sounds like what I’m used to when mic’ing cabs, as it’s hard to totally avoid some phase issues.

Will be fun to a/b them
 

yek

Moderator
Moderator
So here's a zip file of my favorite IR session, the Wellspring session, in non-min phase format for use with the Axe-Fx III. My suggestion is to put them in one of the user banks and compare with the factory min-phase versions. Note that names are a bit different but you should be able to figure it out ;).
The file contains a selection of IRs from Wellspring session 1 as well as session 2, is that right?
 

greiswig

Power User
I vaguely remember working with some aftermarket IRs and thinking that something got lost in converting to minimum phase, but it really didn’t seem like it was enough to worry about at the time. I appreciate the opportunity to have some direct comparisons from this session.

Is there an opportunity here to change the way the minimum phase conversion works to get the best of both, or is that just technically not feasible? I like being able to mix IRs and not worry about them causing issues with one another.
 

yek

Moderator
Moderator
Some commercial vendors supply non-MPT WAVs/IRs. Didn't hear the much of a difference back then. I guess I have to listen again.
 

WhiteSpace

Inspired
I’ve done a quick search but am not sure of the answer. Could these be used on AX8 or converted with CAbLab lite?
 

xpenno

Power User
I've always left that option off in cablab, it seems to result in more space/room in the sound, hard to describe but it kind of takes up less sonic bandwidth.
 

edo

Power User
This sounds very interesting! So if one is using his own ir’s (made with cablab3), how does he make the non minimum phase versions to try out?
 

VegaBaby

Fractal Fanatic
I've always left that option off in cablab, it seems to result in more space/room in the sound, hard to describe but it kind of takes up less sonic bandwidth.
same here. in fact, I convert my third party IRs into two versions, on and off, in case I should need the minimum version which is rarely the case...
 

ben ifin

Inspired
.... am I right in saying that this only applies to a Cab IR that was "shot" with 2 mics or more ie: no impact / change with 1 x Mic IR's (?)

Ben
 

AlbertA

Power User
Thanks :) My ignorance of course , but I had absolutely no idea that when miking up a cab with 1 Mic that you could have a phase issue. Learn something every day :)

Ben
Phase issues are a different topic - that indeed occurs if you are trying to mix more than 1 IR.
It's easier to avoid phase issues with minimum-phase (MP) transformed IRs as they are all time aligned. However, the MP transform essentially throws away the phase information from the original capture and instead derives it from the amplitude response alone.

Speakers are fairly close to a minimum phase system that's why the difference is subtle, but in my experiments the MP derived phase deviates as the frequency increases. The caveat is that removal of the time-of-flight delay from the original capture is not as precise as with MP transform - so mixing these IRs requires more care, as multiple IRs won't be exactly time aligned.
 

ML SOUND LAB

Cab Pack Wizard
Vendor
Many times you'll compare RAW vs MPT and think you hear something but then you don't and then you do again. I don't really believe in making IR mixes in post anyways because it's extremely unrealistic but even when doing that you'll get very different results when using RAW vs MPT and this is where it's easier to notice the differences. Me and some other IR producers have had chats about this and I believe the consensus is that you'll get different sounds but who's to say one is better than the other.

That being said I know some people very high up in the industry that said that my real life mixes that are MPT'd in post "are the best of both worlds". It's not a fake multi-mic-mix made out of multiple MPT IR's but just one MPT process. I personally prefer RAW for everything for the sake of wanting everything to be as realistic as possible but I'm sure that if I posted clips with soundcloud compression comparing MPT vs RAW the majority would have a hard time saying which is which. It's more of a feel thing for me and just like Cliff said if you do the criminal act of mixing separate IR's in post then it'll act more like real mics in real life.
 

ben ifin

Inspired
My brain hurts :) ..... so if you are using 1 x IR only and that 1 x IR was mic'ed with 1 x Mic only ...... the issues Cliff mentioned in the OP still apply (?)

Ben
 

AlbertA

Power User
My brain hurts :) ..... so if you are using 1 x IR only and that 1 x IR was mic'ed with 1 x Mic only ...... the issues Cliff mentioned in the OP still apply (?)

Ben
Cliff just posted a subset of the factory IRs with no minimum phase transformation applied. They sound subtly different.

The second paragraph is about mixing these no minimum phase transform IRS. If you are just using 1 IR, yeah it doesn't apply.
 
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