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Why is De-Phase necessary?

dbun

Experienced
I've been trying to find some more info on De-Phase, but I'm curious as to why it makes a difference.

If an IR is simply a capture of a cab mic'd up, what is going 'wrong' with the process that De-Phase becomes necessary?

I'm sure one of the threads had some info around this, but I'm struggling to find it again. I know it's one of those things where "use your ears" is the rule, but I'm always curious to know the technical reasons behind stuff.
 

USMC_Trev

Fractal Fanatic
This is what I have worked out in my mind. Cliff will raise the BS flag if I'm off-base.

Think about sound as a wave (since it is). You are the observer, and your ear is at some point along the length of the wave as it oscillates up and down, but not necessarily right on the wave. Since we never sit or stand perfectly still, this position changes from moment to moment in relation to the source (like a guitar cab), as we look around and listen, so these tiny shifts in position are what make the sound real and alive to you. Also, unless you're impaired, each ear has a slightly different position in relation to the sound source. This might be what they call Doppler shift. An ir captures an "image" of that wave at a fixed close position, using a microphone (simulating a single "ear"). It is by definition perfectly in phase, that is to say the ir capture process normalizes whatever position it was in to the original wave. Therefore, wherever the mic was becomes the zero point for the source of the sound wave since it now becomes the sound generator.

The de phase somehow reintroduces the variability of observer position that gets removed in the ir capture process, recreating the "amp-in-the-room" characteristic.

Just a guess.
 

ChrisCG

Experienced
Hopefully we will get a De-phase article in the tech notes section. I have personally learned a bunch from those posts very, very helpful.
 

Stratoblaster

Fractal Fanatic
I tried the Dephase control for the first time tonight and absolutely love it's effect on the tone/IR...this is an amazing parameter and one the I think a lot of people who use a real cab as they cannot get a satisfactory sound with IR's/FRFR will find immensely useful and valuable if/when they explore IR's/FRFR tones.
 

Eliju

Experienced
This is what I have worked out in my mind. Cliff will raise the BS flag if I'm off-base.

Think about sound as a wave (since it is). You are the observer, and your ear is at some point along the length of the wave as it oscillates up and down, but not necessarily right on the wave. Since we never sit or stand perfectly still, this position changes from moment to moment in relation to the source (like a guitar cab), as we look around and listen, so these tiny shifts in position are what make the sound real and alive to you. Also, unless you're impaired, each ear has a slightly different position in relation to the sound source. This might be what they call Doppler shift. An ir captures an "image" of that wave at a fixed close position, using a microphone (simulating a single "ear"). It is by definition perfectly in phase, that is to say the ir capture process normalizes whatever position it was in to the original wave. Therefore, wherever the mic was becomes the zero point for the source of the sound wave since it now becomes the sound generator.

The de phase somehow reintroduces the variability of observer position that gets removed in the ir capture process, recreating the "amp-in-the-room" characteristic.

Just a guess.
Doppler shift is a change in the frequency of a wave, not the phase. I'm guessing dephase has to do with interference waves.
 

dbun

Experienced
The point of how we listen to a guitar speaker makes sense.

In the purpose of recording or direct to FOH where you are close micing an amp anyway, does De-Phase then apply in this context?
Is De-Phase really just about getting the direct mic'd sound more 'room like'?
 

USMC_Trev

Fractal Fanatic
The point of how we listen to a guitar speaker makes sense.

In the purpose of recording or direct to FOH where you are close micing an amp anyway, does De-Phase then apply in this context?
Is De-Phase really just about getting the direct mic'd sound more 'room like'?
I think it really comes down to trial error and preference. I myself haven't played guitar outside of my own house in 18+ years. I'm not in a position to experiment. I would think the parameter could be one of several used to accentuate positive or mitigate negative qualities of a specific space, especially in a direct type situation.
 

USMC_Trev

Fractal Fanatic
Doppler shift is a change in the frequency of a wave, not the phase. I'm guessing dephase has to do with interference waves.
Yeah you are correct. Doppler shift is frequency change due to movement of the source.

What's the term for the phenomenon caused by change in position of the observer...?
 

dbun

Experienced
Yeah, I'll need to give it a go next time I play. I'll setup a CAB with X/Y switching to compare.
I only play with mic'd amps, so I'm used to hearing the direct tone.
 

solo-act

Fractal Fanatic
I've been messing with it today. It reduces that immediate, ear-against-a-speaker direct sound, if you're trying to get away from that.

It's also like Nasonex for cab IRs that have frequency congestion but otherwise sound good.
 

steadystate

Fractal Fanatic
Why is De-Phase necessary? In layman's terms; because so many IRs sound like shit (IMO) due to excessive comb-filter-type artifacts. Too much of this character can make an IR sound hollow/nasal/sucked-out (for lack of an accurate term to describe what a comby IR sounds like). Too little can make an IR sound lifeless and one-dimensional (think Palmer, Red Box, or standard lowpass filter). De-Phase lets you dial down this quality in even the most extreme IRs until you achieve the perfect balance.

I can't stress just how much I love this parameter. It allows thousands (literally) of IRs I once found unusable to be quite usable for my taste. I've bitched and moaned since day one about my difficultly in finding IRs I really loved, especially after dropping money on cab packs from various companies. De-Phase changes everything for me. It might be the single most important parameter for me in the Axe.

So we now have a parameter that Cliff has described as both computationally demanding and yet very simple. Whatever it is, I LIKE IT.
 

PacoCasanovas

Fractal Fanatic
I wouldn't call RedBox or Palmer lifeless, because what they did is to recreate the sound we hear on recorded guitar amp by designing a circuit that fit for most tones out in the field.

Dephase (what ever it does in detail) is just a statement, that reaching for ultra high amount of accuracy might not be the only key to simulate analog sound forming. ;) Whatever they say, technology brought us to the point were we can explain it in detail, now finding out that life takes a even more simpler way than our calculations were based of..... ;)
 

Kent

Inspired
Without getting a more detailed answer from the developer, I've come to assume that it is basically something like this at heart:

ll_ibp_sq.jpg

A phase alignment tool. One can read more about what these do over here at Little Labs.
 

Kent

Inspired
It could still hold true as both units do this and we don't know the method behind Fractal's implementation.
 
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