Phase as an issue in audio.

[StanleyB]

First you have to be able to hear the problem before you can say it exists in the signal that you are listening to at that moment in time.

[Marco]

Croft preamps are designed to phase-invert the signal, therefore in order for them to perform optimally, the Left and Right output terminals at the back of the partnering power amp (or speakers) must be swapped round.

There is a very clear audible difference when that arrangement is not so!

Marco.

[MartinT]

I used to use JBL L100-T speakers that inverted phase, so I always connected them reverse polarity from the amp and they sounded best that way.

More recently, I've been playing with Tellurium Q cables. Their primary goal is to make cables which preserve phase coherence across the audio band. My findings are ongoing and I am awaiting delivery of their Ultra Black speaker cables for evaluation, but so far their claims are upheld as the XLR cables are very good indeed.

[PaulStewart]

OK here's my twopenneth, one of the problems I identified when I was a record producer was lack of absolute phase integrity. At the most basic level, when a drummer plays the kick drum it creates a pressure wave moving forward which is picked up by the mic and hving been recorded and played back, the reproduced sound should logically cause the speaker one to move forward. Sadly this is not always the case, at Village Way Recorders in Harrow, I was confused by the fact that the JBLs in the control room never gave as precise a feel as the much less well positioned Tannoys in the main studio. We swopped the monitors and the problem remained in the control room. After a lot of head scratching I realised that although the speakers were in phase with each other the absolute phase was 180 degrees out in the control room. Having corrected this, the room always sounded right after that. When I went to cut after that I always checked that the phase of the repro was correct. As we know that leading and trailing edges of transients are important in our perception of the reality of the reproduction, this would all make sense to me and phase and time domain correctness have always been paramount when specifying systems.

[f1eng]

There is probably a significant difference between the 2 discussions here, absolute phase and phase shifts with frequency.
There are very, very few phase coherent speaker designs, so it is quite likely nobody on the forum has ever listened to phase coherent reproduction.
OTOH testing absolute phase is easy, and particularly trivial in the kit made by companies which believe it to be important, since they will have provided a phase reverse switch. Sometimes remote controllable, both my Goldmund and DeVialet remotes have a phase button, for example.

[jandl100]

Whilst I do hear a difference (as in my previous post) I don't really understand why ...

At a midrange frequency of say 1000Hz the speaker driver is zinging backwards and forwards a thousand times a second.
Does it really matter if it's going inwards rather than outwards on each of those zings? There's 0.001 seconds difference ...

Or have I lost the plot?

[MartinT]

It's more to do with the leading edge of transients, Jerry. Does a drum kick pressurise the air or 'suck' on the initial kick?

[jandl100]

Hmm.

I'm not trying to be difficult, just trying to understand something that doesn't seem to me to be logical, even though I happily admit to hearing it!

It seems to me that even a transient like a drum kick (or a violin pizzicato, or whatever) is actually a very complex waveform, generated by the motion of an extended diaphragm (or taut wire), and would have a time extent far greater than 0.001 seconds (0.0001 seconds at 10KHz!!), and so such variations would be lost in the grand scheme of things. I doubt the ear can perceive differences down at that level. It just doesn't seem to be mechanically sensible!

I'd sure like to know what is going on here!

[DSJR]

By the time you're three metres away from the speaker, phase gets screwed up by the room interaction anyway, but in the bass, the difference can be quite large I've found...

Phase coherance in speaker cables? new one on me, since we're not talking rf or microwave frequencies here, just very low audio ones which a heavy enough gauge wore should conduct without alteration.. Sounds like snake-oil shiite to me, despite any subjective differences these wires may or may not have. Would love to read documented proof of the claims

[jandl100]

Yep, Dave, bass freqs fair enough - 1/50th of a second say, may well be a significant portion of a transient and so easily discernible - but I'm hearing plain and obvious changes to the soundstage and perceived detail well into the midrange freqs and above!

As to proof of cable differences --- let's not go there! (says me, a buyer of expensive foo cables! )