Emulating the total phase response of a recording system, or at least understanding it.

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MaxDM

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I have a free plugin, in its basic form, which alters the phase of any audible frequency band by +/- 360 degrees.

I've been toying with it to see if I can get some effect which will make digital tracks sound more 'analog'

Now, I was wondering, considering a pre-1980's studio, with transformer balancing throughout and tape recording: if someone were to measure phase response by sending a test signal at the microphone input of a mixing console, then measure at the tail-end of the recording system (Vinyl record or Master tape) what would the TOTAL phase response look like?
 

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As the relative phase response is just the "flipside" of the frequency response, it's easier to think of it that way.

I don't think you'd gain much by doing this that isn't already caught as impulse response library - but it's worth trying for the fun of it anyways

/Jakob E.
 
Now, I was wondering, considering a pre-1980's studio, with transformer balancing throughout and tape recording: if someone were to measure phase response by sending a test signal at the microphone input of a mixing console, then measure at the tail-end of the recording system (Vinyl record or Master tape) what would the TOTAL phase response look like?
You'd probably be very disappointed. You would see phase increasing as LF goes lower and decreasing as HF goes higher, but not much in between.
The typical recording chain is constituted of Minimum Phase elements, where the phase response is the conjugate of the frequency response, as gyraf said.
In simple words: flat response=no phase shift.
It is admitted since long that absolute phase is almost undistiguishable, unless there is a non-linear element (distortion in the chain or there are two different paths.
Since you have this plug-in, what can you say about what you hear when you rotate phase? Not when you're changing it, because it creates selective interference, but when it is stable.
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Well, it does some interesting things to the bottom end, similar to what you might associate with a tube compressor, if you anticipate sub 50 Hz frequencies, compared to the mids.

It also can create the feeling of distance.

I noticed the highs lose their hard edge if you play with the phase.

I was initially attracted to such a plug in because I was looking for a way to rotate the phase.

Phase Rotators are used in broadcast to make waveforms symmetrical, for modulation purposes, if I remember correctly.
 
Well, it does some interesting things to the bottom end, similar to what you might associate with a tube compressor, if you anticipate sub 50 Hz frequencies, compared to the mids.

It also can create the feeling of distance.

I noticed the highs lose their hard edge if you play with the phase.
Are you sure these are the effects of phase only? Isn't there some alteration of the frequency response, even minute? OTOH, loudspeakers and ears are somewhat non linear, so it is quite possible that the change in crest factor results in an audible effect. Until now, all research made on the subject points the audibility to some non-linearity in the chain.
Phase Rotators are used in broadcast to make waveforms symmetrical, for modulation purposes, if I remember correctly.
Indeed, they are (were?) used in AM transmission to avoid excessive negative modulation, which results in carrier loss, and in FM for spreading transients in an attempt to reduce the crest factor.
 
Are you sure these are the effects of phase only? Isn't there some alteration of the frequency response, even minute? OTOH, loudspeakers and ears are somewhat non linear, so it is quite possible that the change in crest factor results in an audible effect. Until now, all research made on the subject points the audibility to some non-linearity in the chain.

Indeed, they are (were?) used in AM transmission to avoid excessive negative modulation, which results in carrier loss, and in FM for spreading transients in an attempt to reduce the crest factor.
Yes, the frequency response isn't affected. Consider that the plugin can vary up to 360°

If I switch the phase from +360 to -360 from 50 to 100 hz and back to 360 at, say, 300, you can hear quite a (bad) effect in the bass. Shifting below 50 Hz can be interesting

I suspect that what some people say about vinyl having 'better bass' (which is impossible, in terms of fidelity), may be partly due to the phase shift of the RIAA eq etc. in the bass, and the quality of the playback preamp filters etc.

It's easy enough to download it and try it out.
 
While it may be an interesting 'toy' it is difficult to understand what you might really achieve with this except as an effect.
Human (and almost if not all animals hearing) is remarkably good at processing directional information based on phase and timing, meaning with your eyes closed you can locate pretty accurately the location of various sounds through 360 degrees and varying vertical elevation as well as appreciated in full 'surround sound' attempts at recording. Of curse in the 'multitrack' recording realm, the important issue is how the various sources combine in the mind of the recording engineer (the person wiggling the faders) and they determine what is or isn't the 'best' performance. In the hope if creates revenue of course!
 
I suspect that what some people say about vinyl having 'better bass' (which is impossible, in terms of fidelity), may be partly due to the phase shift of the RIAA eq etc. in the bass, and the quality of the playback preamp filters etc.
RIAA does not produce phase shift, since it's a complementary process. The signal is encoded when mastering and decoded at playback., with two perfectly complementary transfer functions.
 
Human (and almost if not all animals hearing) is remarkably good at processing directional information based on phase and timing, meaning with your eyes closed you can locate pretty accurately the location of various sounds
You're talking of binaural hearing that is based on phase/timing differences between the left and right ear.
Here the subject is audibility of phase-shift from the source. This phase-shift is added equally to the acoustic waves that reach the ears.
 
If I switch the phase from +360 to -360 from 50 to 100 hz and back to 360 at, say, 300, you can hear quite a (bad) effect in the bass.
I've tried that, and many other things, I can't hear any difference (the meters register some difference in peak-level, though, which is to be expected).
I'm not really convinced in the pertinence of it, even in the context of trying to time-align sources.
 
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I've tried that, and many other things, I can't hear any difference (the meters register some difference in peak-level, though, which is to be expected).
I'm not really convinced in the pertinence of it, even in the context of trying to time-align sources.
I think that it comes down to source material and how attentive you are to some aspects of sound.

I hear a difference, especially if I zig-zag the phase response at extreme settings.

A very cleanly recorded, or synthesised, percussive sound will be perceived differently if the phase is off. Not as incisive and forward-sounding.

But my girlfriend can't hear the difference, for example, so it's very subtle.
 
I hear a difference, especially if I zig-zag the phase response at extreme settings.
In that case, you don't hear the supposed effects of absolute phase. You hear distortion due to the displacement of the waveforms. If you changed the phase at a rate of 1 Hz, for example, you would create sidetones, one 1Hz above and one 1Hz below the original tone; this is an audible effect. If you changes phase very slowly, the sidetones would be so close to the fundamentals that they would not be audible.
But if you change the phase and leave it, after the first moment of transients, you won't hear a thing, unless the signal path is non-linear, because changing phase often results in changing the crest factor.
A very cleanly recorded, or synthesised, percussive sound will be perceived differently if the phase is off. Not as incisive and forward-sounding.
Percussive sounds are very likely to put one or more elements in the signal path to behave non-linear.
 
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You're talking of binaural hearing that is based on phase/timing differences between the left and right ear.
Here the subject is audibility of phase-shift from the source. This phase-shift is added equally to the acoustic waves that reach the ears.
In human audition our brain is sensitive to arrival time differences between both ears. In addition comb filtering (pinnae transform) caused by our outer ear horn structure provides sonic cues to up/down (above /below) discrimination.

JR
 
Personally the phase response of a single signal wouldn’t interest me as long as I got the mix right

but didn’t SSL consoles used to have phase meters that did this?

seems like if it were truly useful the idea would have stuck around
 
When mixing for vinyl, large phase differences between L and R low frequency content could exceed cutter/playback tracking capability. In the old days some cutting lathes would short L to R with a huge inductor, crude but effective way to insure low bass was panned mono.

Modern recording media is not sensitive to low bass phase relationships.

JR
 
but didn’t SSL consoles used to have phase meters that did this?
So-called phase-meters (actually correlation meters) evaluate the correlation between two signals. Ther is no instrument that can measure the phase of a single signal, because phase is a relative value, between two time-varying entities (voltage, speed, force...)
seems like if it were truly useful the idea would have stuck around
As others said, they were useful for cutting vinyl discs and for FM broadcast, not so much for digital media.
 
I’m not saying it wouldn’t be cool but as abbey said, phase is relative to other signals

maybe a multi input oscilloscope would work, it’s popular in the eurorack world

depends on what you actually want to measure
 
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