absolute phase

[MoodyDragon]

Been watching this debate develop.... I have a Sonic Frontiers Line 3 Preamp that has a phase switch in the remote. I have used the headphone output of this (apparently a very high end unit with its own dedicated power supply and a HeadRoom licenced design) and used the phase switch to see if there is a difference.

It seems the difference is slight but present on certain disks. That is, there are a whole bunch of disks that do not seem to sonically change when I throw the switch. However, others do>

One in which I found a very audible difference was Eva Cassidy's Live at Blues Alley. Definitely the phase switch appeared to be more 'correct' one way and 'wrong' the other.

You know the problem now? I am trying to listen for phase induced changes on all the cds that I now play. This hobby is an illness.....

 

[gaboo]

Have you people even considered that the analog circuitry that inverts may actually sound slightly different? It's trivial to do the inversion error free in the digital domain at the source! Well, unless it's SACD or encrypted DVD but that's another matter.

I'll bring a phase inversion CD sampler at the next meet.

 

[smokey]

IIRC There are several "test" disks that will help you make sure your system is set up correctly as to phase.

BTW Do we now add "Phase Rolling" to tube and Op Amp rolling in our sonic bag of tricks?

 

[MoodyDragon]

Quote:

Originally Posted by smokey IIRC There are several "test" disks that will help you make sure your system is set up correctly as to phase.

Absolute phase disks? I think not... I think you are talking about reversed phase between the two channels.

 

[Edwood]

My SAC AKG K1000 amp had an inverted phase. It sounded just plain weird. It was like the sound stage was "inside out". Sounds that normally sounded like they were coming from just in front of my head, sounded/felt like they were coming from the back of my head. Is this the same thing as absolute phase being inverted?

-Ed

 

[gsferrari]

I am trying to imagine what inverted phase will sound like...no luck.

Is it possible to do this simulation on the computer? Get a plugin that will play foobar music in inverted phase?

EDIT : http://pelit.koillismaa.fi/plugins/dsp.php

He he...time to screw around with the phase inversion plugin

For those who cant do this via hardware - this should be a good simulation.

[EDIT]I just downloaded the plugin and it works. You can simulate how the phase change will affect the sound. Add the "CHANNEL SEPARATION" control in the DSP Manager and go to its settings menu. There you can invert each channel. The difference is PHENOMENAL

But this is software...how far it translates to hardware is debatable.

Try it folks...[/EDIT]

 

[smokey]

Moody Dragon,

I could certainly be wrong. I'm not an audio engineer, I don't even play one of TV.

However, in looking at my XLO Reference Recordings Test & Burn-In CD, I noticed a number of tracks dealing with phase.

Track 2 - Voice In-Phase
Track 3 - Voice Out-of-Phase
Track 10 - Mono In-Phase
Track 11 - Mono Out-of-Phase
Track 12 - Stereo Out of Absolute Phase

I think track 12 is what we're talking about here, but again I could certainly be wrong.

 

[gsferrari]

 

[MoodyDragon]

Smokey, my apologies. It seems you are right. Now I need to get that XLO disk and satisfy my neurosis

 

[Sugano-san]

Quote:

Originally Posted by smokey IIRC There are several "test" disks that will help you make sure your system is set up correctly as to phase.

That is correct. I own the Cardas Sweep Record, which features, inter alia, tracks that serve precisely this purpose -- absolute phase setup.

The common argument against phase reversal is the following: When the absolute phase is correct, the "attack" of an instrument (e.g. a trumpet) will result in the speaker's diaphragm initially moving towards the listener. That is seen as the "correct" way of reproducing a trumpet. When the absolute phase is inverted, the attack of the trumpet will cause the speaker's diaphragm to initially move backwards, i.e. away from the listener. Apparently that effect can be quite irritating.

The same applies mutatis mutandis to all other sounds, in particular explosive ones, such as "p", "t", "k", etc., i.e., sounds where the listener subconsciously expects attack that's "in your face", wheras the phase reversal creates the opposite effect of "sucking out" air in the moment of attack.

However, given that some amplifiers are designed to revert the phase as a matter of course, many people may have gotten used to reversed phase sound without even being aware of it. This does not mean that such people would not notice a change or even an improvement when listening to non-reversed sounds. I was too lazy to pay attention to the test record. Possibly I've never in my life experienced how how correct phase sounds...


BTW: I just double-checked this with Helmut Becker of audiovalve -- the RKV is a non-inverting amplifier.

Does anybody know if the Stax 007t is a phase inverter?!? Kevin?

 

[GWN]

In the end chasing absolute phase is an exercise in futility. You do not know the absolute phase of the recordings, let alone each track that can be recorded at different times, in different locations. On multi tracks recording, the tracks may have been laid down in three different recording studios then mixed at a fourth location. At the extreme you can have the singer and the band in different absolute phase, if they used different brands or types of microphones, and the routing of the signal thru expanders, compressors, ADC, DAC and mixing console was different. So in that case if your ears are fine enough to notice the difference, in-phase would cause the singer to sound great and the band to sound lousy, the reverse would cause the band to sound great and the singer lousy.

A final note, absolute phase of a piece of gear has nothing to do with the fact that its Solid State or Tubes. Absolute phase is determined by the number of output stages used.

 

[Sugano-san]

Quote:

Originally Posted by GWN In the end chasing absolute phase is an exercise in futility. You do not know the absolute phase of the recordings, let alone each track that can be recorded at different times, in different locations. On multi tracks recording, the tracks may have been laid down in three different recording studios then mixed at a fourth location. At the extreme you can have the singer and the band in different absolute phase, if they used different brands or types of microphones, and the routing of the signal thru expanders, compressors, ADC, DAC and mixing console was different.

I completey agree with this assessment, in particular relating to multi track recording, etc. What you CAN do, however, is double-check and correct the absolute phase of your own stereo system, just to be on the safe side. In his first post Kevin mentioned: "Certainly many of the record companies go thru great effort to maintain correct phase, especially on classical performances so there must actually be something to this." Consequently, there's a realistic chance that a certain percentage of publicly available recordings are phase-correct, which is encouraging.

 

[Hirsch]

Quote:

Originally Posted by Edwood My SAC AKG K1000 amp had an inverted phase. It sounded just plain weird. It was like the sound stage was "inside out". Sounds that normally sounded like they were coming from just in front of my head, sounded/felt like they were coming from the back of my head. Is this the same thing as absolute phase being inverted? -Ed

This was not incorrect absolute phase (almost). The channels were not in correct relative phase. Actually, one channel had correct absolute phase, while the other was phase-inverted. The trick is figuring out which one was correct.

 

[Earwax]

Quote:

Originally Posted by gsferrari Is it possible to do this simulation on the computer? Get a plugin that will play foobar music in inverted phase? EDIT : http://pelit.koillismaa.fi/plugins/dsp.php

That plugin only inverts the right channel, making left and right out of phase, it doesn't seem to have a setting to change left and right together.

 

[gsferrari]

Quote:

Originally Posted by Earwax That plugin only inverts the right channel, making left and right out of phase, it doesn't seem to have a setting to change left and right together.

Im still searching - there has GOT to be a plugin to invert phase on both channels...i'll post if I have luck finding something...