Does PHASE matter on a single source?

CoolCat

Well-known member
What is my "phase button" doing to change the sound on the DI?

I been reading and dont really get it.
I understand two mics on a snare on-top and below is what seems the most common discussion/example....but when I plug something into my preamp DI or Mic...the PHASE button has two distinct sounds. One has more bass /low freq the other less low freq.

Any inputs appreciated...
 
I assume you mean the almost universally mislabeled polarity switch. In most cases it would be nearly impossible to tell the difference. With some sources you might feel a difference on initial transients.
 
The manual says nothing, I dont even know if its IN= LED is ON, is it IN Phase...and when its out=led off the polarity is out,,,,,

seems I heard some difference, oh well. its a mono preamp, with DI.

yeah...its labeled PHASE...typical clone manual which means it has nothing, as compared to designers like Ted Fletcher whose manuals are like a history thing coffee talk.. and each component purpose is described...or the old JVC JBL manuals...

thanks.
 
The audibility of "Absolute Phase" has been debated forever in audiophool circles but, like so many of these claims such as 'One way cables" none of the people nor firms that claim these effects are audible have ever put money where gob is and paid for independent, double blind tests.

I am certain "AP" is "BS". From first principles, if my ear is 10 ft from a big drum when struck, yes the struck skin will initially move inwards, the pressure wave will move through the drum and cause the outer skin to first deflect toward me (and if we say it is a BIG big drum a foot from skin to skin, the P wave will take 1mS to get there*)

Thus a pressure wave is launched at me, followed closely by a rarefraction. Now, I will only get the positive pulse IF I am some exact multiple of the distance from the skin (which is itself DELAYED by 1mS from the 'real' beater hit!) And of course, I must not move!

"Phase" can only be detected in conjunction with another source, e.g. the comb filtering you get from poor microphone placing.

The other claim is the ear can detect the polarity of asymmetrical waveforms? Might be true for electronically generated signals but music signals are shifting shape mS to mSec, as anyone who has ever used a 'scope will attest.

*The pressure wave cannot move faster than the mean particle velocity of air molecules which is of course about 1100fSec (340mSec)

Dave.
 
Even the big brands with mega R&D departments never sorted the polarity vs phase labelling, and often talked themselves about phase, but I guess it really stems from the concept of phase rather than absolute measurements of it because in everyday life nothing is ever chase coherent. Probably the closest we get is a DI'd instrument with IEMs in your ears. Yet - we all argue endlessly about latency, which is of course a phase linked phenomenon. 9ms in the latency department is a phase delay. I guess that practically fiddling with the phase switch is a starting point and then you can delay or advance your tracks even further to cure or enhance?
 
but when I plug something into my preamp DI or Mic...the PHASE button has two distinct sounds. One has more bass /low freq the other less low freq.

This will be the case if you're monitoring yourself whilst playing because the audio you hear through speakers/headphones will be interacting, to some extent, with what you hear from, or feel through, the physical instrument.
If you just record and play back solo bass and use a plug to toggle polarity there should be no audible difference.
 
I thought this was just for reducing noise. Like a ground switch on a DI. Not needed most of the time but can help reduce induced RF or something. Dave?
 
ok, the head-internal skull thing,

yes I was using headphones and pushing the button in and out and it was much more drastic with the microphone. like a bass freq boost.

so the real DAW track isnt really going to capture any sound difference, only my ears due to headphones and some weird physics.

ok, I was just wondering if it was miswired or something. thanks
 
I thought this was just for reducing noise. Like a ground switch on a DI. Not needed most of the time but can help reduce induced RF or something. Dave?

Polarity switch is there because audio is recorded as positive and negative voltage swings. If you capture the same thing with two microphones but one microphone, or cable, or preamp (or combination) is resulting in reversed polarity,
then one capture is going to have negative where the other has positive, and vice versa.
In perfect conditions that'll mean total cancellation when it comes to playing the two tracks back together - In reality with differences in mic position and equipment accuracy it means heavy/partial cancellation and a thin sound.

Flipping polarity literally just inverts a the signal so positives become negatives and vice versa. It's not destructive.


Balanced audio technology uses polarity, and comparison, as a means of removing noise that may have been picked up along the way - Spikes from lights being turned on, hum from a transformer, etc.
If you send a sine wav through some cable but are also sending and inverted copy then, in theory, the two combined at the receiving device should cancel each other out..
Any noise picked up along the way is going to affect each conductor equally (same polarity on both) so combining the two signals at the other end will cancel intended signal and leave then unwanted noise only.
Armed with that, picked-up noise can be removed from the signal.
 
Polarity flips can also be useful to combat feedback in a mic/speaker PA setup.

Set gain so the systems is just at the ring point then flip the mic phase/polly. The ring should get better or worse. If possible repeat the exercise for the speaker polarity (rarely have the option these days) You can often get up to 6dB more gain before ring with this technique.

If you cannot decide which is "flipping best" go for the lowest ring note.

This reminds me. I did some tests with mics a couple of weeks ago and I suspected the Behringer 8500 dynamic was OOP with the rest of my mics? Must check into that.

Dave.
 
There is no such thing as phase with a single source. Phase is a relationship between two or more signals. If hitting the button makes a sound difference, you are monitoring at least two things. Either you are changing the phase relationship between the bass and the other instruments in the song, or you are monitoring the bass live and recorded.
 
Polarity flips can also be useful to combat feedback in a mic/speaker PA setup.

Set gain so the systems is just at the ring point then flip the mic phase/polly. The ring should get better or worse. If possible repeat the exercise for the speaker polarity (rarely have the option these days) You can often get up to 6dB more gain before ring with this technique.

If you cannot decide which is "flipping best" go for the lowest ring note.

This reminds me. I did some tests with mics a couple of weeks ago and I suspected the Behringer 8500 dynamic was OOP with the rest of my mics? Must check into that.

Dave.

This is exactly what i meant.
 
I remember my old Fender amp had a 'phase' power switch (old amp with a only an ungrounded 2-prong power plug), so it was used to quiet hum, just reversing the + and - connections.
A phase switch on a DI is to stop feedback, as Dave said. The reason it can make the sound seem different is the signal coming out of the speakers/headphones is now either (almost) perfectly in phase (increasing some frequencies' volumes) with the original sound you are hearing, or out of phase, reducing some of those frequencies due to phase cancellation. Did I mention I hated Wave Physics in college? :rolleyes:
 
I would say that a polarity switch on a DI is for whatever use one might need a polarity switch. I would most likely use it to make the DI work with a mic on the amp.
 
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I have done the checks and the Behringer is definitely wrong polarity when used against a Sontronics LDC and a Prodipe TT1.
I then made up a polly flipped XLR-XLR cable and that sorted the XM8500. I shall buy another one soon just to check mine isn't a Friday afternoon lemon.

Dave.
 
One thing I have experienced concerning phase on a single source occurred on an acoustic/electric Epiphone Guitar with volume, bass, mid-range, and treble sliders on the guitar's body. It also has a "phase" switch which, according to the instructions, can be operated to reduce feedback when the guitar is close to the amp. That switch somehow changes the phase between two pickups or something like that to cancel feedback. It's more complex than simply reversing the polarity or phase on a single pickup, since such a simple reversal would immediately go out to the amp and do us no good for cancellation of feedback. I'm sure that this matter is more involved than I understand, so I will be interested in hearing more about it.
 
I'm sure that this matter is more involved than I understand, so I will be interested in hearing more about it.
No I’m sure it’s far less complicated than you’re trying to make it. It’s the same thing ecc83 talked about above. Flipping polarity might help with gain before feedback, but only kind of accidentally, probably only at certain frequencies, and definitely only until you move either the guitar or the amp.

I read a thing a while back where Brian May talked about using his pickup phase switches in a kind of interesting way. Now, if you’re playing through just one pickup, the absolute polarity is pretty much arbitrary and doesn’t matter. Flip it one way, record, flip it the other way, record, compare the two, hear no meaningful difference. BUT if you’re playing in front of a loud amp, and you hit a note and hold it and it goes off into that self-oscillating feedback thing, and you flip the switch, it might just cause the held note to break to a harmonic. The harmonic mode of an eBow is very similar. The driver is opposite polarity to the sensing coil, so it is kind of driving against itself, which magically causes the first harmonic to jump out.

Now, if you happen to be pushing an asymmetrical waveform into an asymmetrical limit, the polarity of the input does make some difference. If the higher side of the wave goes one way, it hits the limit sooner than if it goes the other way. It’ll be noticeably more distorted. But if the limits are symmetrical, then it doesn’t matter, and if it’s not hitting the limit in either direction anyway, then it doesn’t matter and won’t be audibly different either.

But yes sometimes polarity matters between different sources. A kick drum and a bass, or even a bass guitar and a guitar might work better together one way or the other. It’s pretty much accidental again, and if there’s any amount of timing slop, it could be different for each hit, but bass waves are long enough that it could be a matter of degree rather than full reversal from note to note.
 
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