MotherSky

Phase inversion

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13 hours ago, chris217 said:

This is the technical forum. I am only asking for experimental evidence to support your claim.

The OP was asking why some preamps phase invert.  That question was answered.  But as to whether it is audible, I have documented my experience, unlike anyone else here.  If you wish to conduct your own experiments, in whatever manner you like, that would provide the experimental evidence you require.  My own (accidental) experiment showed me that in certain circumstances polarity inversion can be audible.  A powerful amp and sealed box loudspeakers are a good starting point.  As for the double blind nonsense, as far as I am aware we are not talking about a cure for cancer or an important scientific discovery.  I even suggested a possible mechanism as to why suck and blow could be different, but that of course was ignored, just the usual knee-jerk responses.

If you want to be scientific, as opposed to "I don't understand it and I don't like it, so I will argue against it, without actually DOING something." do your own tests.  But that is less fun than just ranting or forum point scoring, eh?  And if you HAVE already done such tests, post a link to the results.  But of course, not hearing something is not proof that it isn't audible.  Just that YOU didn't hear it.  And it would seem that actually hearing it isn't accepted as any kind of proof either.  So do your own tests, or you are just flapping your gums.

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3 hours ago, rabski said:

That's really interesting. I suspect that possibly it is crossovers casuing the difference, though I have to confess that I don't see how. Of course, it depends on how you took the measurements. If you're using a calibrated microphone, then the difference between two speakers will still have more to do with the room acaoustics than anything else. The real interest here is in the difference between reversed phase for one speaker, assuming everything else remained unchanged.

Yes, no other changes. Put the mic tripod in usual spot. Mic is a calibrated UMIK-1 which without any changes would just overlay however many measurements I took with no difference reported. Believe me I've tried.

Connected everything up. Run a sweep. Then reconnected speakers with opposite polarity and run another sweep. 8verlaid the results in a graph.

Still same room acoustics, mic and speaker position and equipment and cables. I approach it this way if there was no difference why would speaker manufacturers put + and - on terminals?

I'm speculating below. 

When you change the polarity speaker pulls when it's supposed to be pushing. This impacts on impulse response and as such phase. Phase measurements look nothing alike by the way.

Of course the simplest explanation would be the speakers I've measured are crap :) I might be tempted to see if I can either find any old measurements or measure my main speakers. 

1 hour ago, Speedskater said:

One problem with doing repeated in-room measurements is: Moving either speaker or the microphone just a fraction, can change the response. Same goes for moving the furniture or the humans.

That's partially correct but that's not what happened here. Mic is on a tripod. I could run a sweep without me in the room and the difference would be negligible. 

2 hours ago, bigfool1956 said:

I suspect 1db changes could be created by standing/sitting in a different place in the room for the two measurements, or changes in external noise at those frequencies.

I've been measuring anything and everything for over a year and never found it to be a significant factor. At least not one where I could account for difference like this. A lot of the time I don't see any measured differences when it comes to frequency response. 

------

As an overall note. I don't really have any agenda here.But would be happy if anyone could explain what's happening. As far as I'm concerned in second instance I've eliminated as much as possible and conclude differences come from the only variable which is reconnecting speakers with opposite polarity. I invite anyone who has the facility to try for themselves. 

How speaker design contributes to this is anyone's guess. As to how obvious the sonic differences will be? Really depends on how intently you're listening to. Voicing remains the same so they may not be obvious.

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Worth adding just done some some measurements. It was with a mic on tripod at around 1m from a speaker. Run 3 sweeps on each polarity. There was no difference in frequency response. I believe when there are differences they are down to phase and speaker room interaction. 

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Super Wammer

I'm thinking a sweep shouldn't show any differences, whereas impulse response might.

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4 hours ago, bigfool1956 said:

impulse response 

That ought to show absolute phase!!!!!!!

Oh go on, I'll put my toe in. I made a remote control relay phase switching box for a guy who was obsessive about it. He even listed the phase he thought was best for each track of an album. 

I made a single ended amp (one output transistor and a choke) for my bass guitar once, it was, er, not optimised electricaly shall we say. It's output was highly unsymmetrical, but it sounded lovely. On a tinkering impulse I put in another (phase inverting) stage with adjustable gain. That totally killed the sound. I think by random fluke the first iteration's unsymmetric behaviour was somehow in sympathy with the guitar's not particularly symmetrical (depending on how and where it was plucked) output.

So my subjective opinion is that there is probably something in it, but how to tell what is "right" from microphone to speaker.... 

May try the drum experiment one day.

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6 hours ago, awkwardbydesign said:

The OP was asking why some preamps phase invert.  That question was answered.  But as to whether it is audible, I have documented my experience, unlike anyone else here.  If you wish to conduct your own experiments, in whatever manner you like, that would provide the experimental evidence you require.  My own (accidental) experiment showed me that in certain circumstances polarity inversion can be audible.  A powerful amp and sealed box loudspeakers are a good starting point.  As for the double blind nonsense, as far as I am aware we are not talking about a cure for cancer or an important scientific discovery.  I even suggested a possible mechanism as to why suck and blow could be different, but that of course was ignored, just the usual knee-jerk responses.

If you want to be scientific, as opposed to "I don't understand it and I don't like it, so I will argue against it, without actually DOING something." do your own tests.  But that is less fun than just ranting or forum point scoring, eh?  And if you HAVE already done such tests, post a link to the results.  But of course, not hearing something is not proof that it isn't audible.  Just that YOU didn't hear it.  And it would seem that actually hearing it isn't accepted as any kind of proof either.  So do your own tests, or you are just flapping your gums.

I did document mine. I have tried it more than once and heard no difference. I have also done so under controlled conditions with other listeners. Still no statistically evident difference.

You, as usual, choose to regard that as some sort of personal attack. Further, 'double blind nonsense'? Strange that it is an accepted methodology in many if not most scientific disciplines. However, your ears are obviously the ultimate test. Except, you offer no proof, documented evidence, or anything other than hearsay. And insults.

As always, I have done my own tests, whereas yours seem to be purely based on whay you claim to have heard, mine have been conducted properly, under controlled conditions and with a panel of listeners. Result? As above. No statistically evident difference.

I find it quite strange that you immediately go on the personal attack yet offer no evidence whatsover to support what you suggest. When anyone offers evidence to contradict your world view, it is always a 'knee jerk reaction', 'flapping your gums'.

You have documented your experience? Documenting your personal experience does not in any way at all constitute scientific proof. All it means is that you've stated your belief.

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Where is this documented evidence?  And what equipment was used?  I at least told you which speakers showed the difference, and the amp*.  And a possible explanation of why there is a difference. But you just claim to have conducted failed tests.  I have no need to provide what you like to call scientific proof, I simply told you what I (we) heard and you chose to disbelieve me.  Suit yourself, but don't try to pretend this is a "scientific discipline"; it's an online hifi forum!  And if you don't want what you call personal attacks, then stop sneering.

* It might possibly have been a Quad 606, I had both amps at the time.

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9 minutes ago, awkwardbydesign said:

Where is this documented evidence?  And what equipment was used?  I at least told you which speakers showed the difference, and the amp*.  And a possible explanation of why there is a difference. But you just claim to have conducted failed tests.  I have no need to provide what you like to call scientific proof, I simply told you what I (we) heard and you chose to disbelieve me.  Suit yourself, but don't try to pretend this is a "scientific discipline"; it's an online hifi forum!  And if you don't want what you call personal attacks, then stop sneering.

* It might possibly have been a Quad 606, I had both amps at the time.

Exactly the sort of response I would have expected.

I did not conduct failed tests, nor have I ever done so. I have conducted more than a few tests under controlled conditions that have proven some things do not seem to exist. That is not failed tests, that is successful tests, but producing the results you do not agree with. I have posted many times here the results of properly conducted tests which refute, with proper evidence, some of the daft claims that have been made, and not necessarily by you, before you take that personally.

By contrast, you told us what speakers and amp were used that 'showed the difference', but have provided absolutely zero evidence of any actual difference apart from the 'fact' that you heard it. You have given possible explanations. I accept those with an open mind, but that does not mean I necessarily agree.

It is pointless carrying on with this.

You are perfectly entitled to your point of view, as I am to mine. I don't 'disbelieve' you. I have no doubt you heard what you heard. However, you continually accuse me of 'sneering', when all I have done is to suggest that you have no evidence to support your suggestions. And you still do not have. I don't pretend anything. I have no need to.

If you feel you have no need to provide proper proof of anything, then simply state it as an opinion, which I have no issue with. To state it as fact, however, I do not accept.

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