Out of Phase

[spiral scratch]

I was over at at a friend’s place listening to music and thought I heard his speakers out of phase. We played some test tracks and confirmed that the speakers were out of phase. i suggested we switch the + and - terminals and we ran the test again but the speakers remained out of phase. We did a bit of internet sleuthing and followed the recommendation to switch only one terminal rather than both, so essentially we have one speaker with correct polarity and another with reversed polarity to create proper stereo. This corrected the problem.

I’m confused by this as I had thought that both speakers out of phase meant that both speaker were connected with reverse polarity.

Another wrinkle is his pre amp runs the mains out in a reverse polarity configuration. Within the manual is states that in order to compensate for this both speakers should have their polarities reversed. Unfortunately this arrangement put the speakers out of phase.

Just wondering if anyone can help me understand what is happening with my friend’s stereo.

Thanks

 

[MaxwellsEq]

Out of phase means one speaker is out of phase with the other. You only need to correct one. If you do both, they will both still be out of phase with eachother.

Imagine a drum beat. If they out of phase, the left speaker may push outwards whilst the other is pulled inwards . You want them both to push outwards at the same time

 

[DVDdoug]

Another wrinkle is his pre amp runs the mains out in a reverse polarity configuration.

That's not unusual. It is unusual for the manufacturer to publish it. A lot of electronics reverses the polarity. It happens in recording & production too so you never know the original polarity. With multitrack recording, some vocals or instruments can be inverted and others not.

Audio is AC so it doesn't actually have a "polarity" and we generally can't hear the difference. But if the left & right are out-of-phase with each other the bass soundwaves cancel almost completely and the mid-frequencies can partially cancel in "strange ways" and sometimes you get a "spacey-phasey" sound and sometimes a perception of stereo widening.

Within the manual is states that in order to compensate for this both speakers should have their polarities reversed.

Since we don't know the phase through the whole recording & playback chain, you don't need to do that. And for all we know, your power amplifier may be inverting it back.

 

[Rednaxela]

I’m confused by this as I had thought that both speakers out of phase meant that both speaker were connected with reverse polarity.

Reversing both speakers’ polarity is unlikely to be audible. Out of phase or not. Note that you can test this yourself, by reversing the polarity of both speakers one more time so that only the other speaker’s +/- are swapped. I bet it would still sound corrected.

Unfortunately this arrangement put the speakers out of phase.

If your speakers were out of phase, it was not caused by this arrangement. As you found out yourself by reverting it.

To be honest I don’t really understand the preamp manufacturer’s recommendation.

We played some test tracks and confirmed that the speakers were out of phase.

Could you describe this in more detail? Did you conform this by ear or with measurements? How can someone know how out of phase sounds but not what it means? No offense at all. Just asking because maybe it was something else you heard that would need a different fix altogether?

 

[spiral scratch]

But if the left & right are out-of-phase with each other the bass soundwaves cancel almost completely and the mid-frequencies can partially cancel in "strange ways" and sometimes you get a "spacey-phasey" sound and sometimes a perception of stereo widening.

Yes, this is pretty much what I was hearing and what was confirmed by listening to the "In Phase" and "Out of Phase" test tracks. There was no perceptible central stereo image, no "phantom centre" and the sound had that widening effect. There was also a loss of bass. The test tracks listened to sounded the opposite of what they were meant to as in, the 'in phase' sounded wide without central image and the 'out of phase' had a clear representation of the central image without the widening effect. There was also a noticeable shift in volume.

Could you describe this in more detail? Did you conform this by ear or with measurements? How can someone know how out of phase sounds but not what it means? No offense at all. Just asking because maybe it was something else you heard that would need a different fix altogether?

This was all done by ear using a test recording for stereo set up. I've heard out of phase speakers before and I was able to check and correct the terminal connections. Maybe there is something else going on, but switching the wires on one set of speaker terminals made a correct central image for the 'in phase' listening test.

Anyways, we switched the + and - of one terminal and everything seemed to be sounding OK. I'm guessing that somewhere within the gear the polarity is not correct in one channel because the + and - wiring from the amplifier to the speaker terminals is not consistent now.

Thanks for the info!

 

[Doodski]

The best method of checking for proper speaker phase is to use a 1.5v AA battery cell on the speaker wire going to the speaker terminals. When the battery positive is on the positive speaker wire the woofer will move outwards a little bit. It is easily visible and makes a little tick sound. Do this for both speakers and proceed accordingly. If there is a phase issue reverse ONE of the speakers wires and that will solve the issue and make for a proper operation. Do not leave the battery connected for extended periods of time. Just use a small time frame of connection and all will be goody goody.

 

[AudiOhm]

Depending on the associated equipment with many interconnect cables, it is possible that one of the cables is incorrect.

Example an interconnect that has the +/- reversed in the connector...

Ohms

 

[spiral scratch]

Thanks again. I do/did think I understood phase correctly. I liken it to the speaker drivers moving like a pistons. When the speakers are in phase the left and right channels move in and out in tandem. When they are out of phase they move in opposite directions which cancels each other out and leads to a loss of proper imaging and energy output. Kind of a generalization but all of these other things mentioned are really helpful in nudging my brain in the right direction and troubleshooting.

I think the reverse polarity pre amp kind of muddled my brain a bit, but it's all good.

 

[Doodski]

Thanks again. I do/did think I understood phase correctly. I liken it to the speaker drivers moving like a pistons. When the speakers are in phase the left and right channels move in and out in tandem. When they are out of phase they move in opposite directions which cancels each other out and leads to a loss of proper imaging and energy output. Kind of a generalization but all of these other things mentioned are really helpful in nudging my brain in the right direction.

You are totally correct and the battery test method I gave to this thread is exactly what is occurring. The pre-amp phase relationship stuff is bit more convoluted and sophisticated and requires more mental somersaults but it is the same thing.

 

[spiral scratch]

Depending on the associated equipment with many interconnect cables, it is possible that one of the cables is incorrect.

Example an interconnect that has the +/- reversed in the connector...

Yeh, I can pretty much attribute 99% of my stereo problems to a loose RCA connector or a reversed + and -, but of course my brain always wants to go to the worst case scenario. He has some esoteric speaker wires with banana terminations so maybe there's a wire flipped in there.

My friend has a stereo vendor pal so maybe he'll come by to give him a hand troubleshooting. I also offered to help troubleshoot, but it's a pretty expensive set up so I'm not sure my friend's too comfy futzing around with it. Anyways we flipped a connector, I didn't think there was any danger in correcting the phase that way and he seems pretty happy to have some slam and proper stereo back.

Thanks for the info and assist!

 

[krabapple]

Yes, this is pretty much what I was hearing and what was confirmed by listening to the "In Phase" and "Out of Phase" test tracks. There was no perceptible central stereo image, no "phantom centre" and the sound had that widening effect. There was also a loss of bass. The test tracks listened to sounded the opposite of what they were meant to as in, the 'in phase' sounded wide without central image and the 'out of phase' had a clear representation of the central image without the widening effect. There was also a noticeable shift in volume.

This was all done by ear using a test recording for stereo set up. I've heard out of phase speakers before and I was able to check and correct the terminal connections. Maybe there is something else going on, but switching the wires on one set of speaker terminals made a correct central image for the 'in phase' listening test.

Anyways, we switched the + and - of one terminal and everything seemed to be sounding OK. I'm guessing that somewhere within the gear the polarity is not correct in one channel because the + and - wiring from the amplifier to the speaker terminals is not consistent now.

Thanks for the info!

Maybe it's too elementary, but did you carefully check that that the system was wired correctly in the first place, i.e., the + outs from the amp channels went to the + terminals of the speakers, the - outs to the - terminals? With generic speaker wire it can sometimes be easy to get the +/- wires mixed up along the way from the amp to the speaker.

 

[spiral scratch]

Maybe it's too elementary, but did you carefully check that that the system was wired correctly in the first place, i.e., the + outs from the amp channels went to the + terminals of the speakers, the - outs to the - terminals? With generic speaker wire it can sometimes be easy to get the +/- wires mixed up along the way from the amp to the speaker.

Thanks. Yeh we checked all the cabling before we did anything else. It was all hooked up in the correct manner. The speakers were the most difficult to check with tiny colour rings at the very base of the posts and barely legible embossed +/- indicators but it was all done properly. We did have to switch the +/- connectors at one of the speaker posts to get proper phase, but it's the opposite of how the other speaker is connected from the + and - colour coding on the cable perspective. He has some fairly expensive looking cables with large colour coded spades on the amp end and colour coded bananas on the speaker end. The wires run inside a jacket so maybe they got mixed up. As AudiOhm mentioned it's possible there's a mixed up wire somewhere. Maybe we'll check the cable continuity at some point, but everything seems to be working OK now.

 

[coonmanx]

Thanks. Yeh we checked all the cabling before we did anything else. It was all hooked up in the correct manner. The speakers were the most difficult to check with tiny colour rings at the very base of the posts and barely legible embossed +/- indicators but it was all done properly. We did have to switch the +/- connectors at one of the speaker posts to get proper phase, but it's the opposite of how the other speaker is connected from the + and - colour coding on the cable perspective. He has some fairly expensive looking cables with large colour coded spades on the amp end and colour coded bananas on the speaker end. The wires run inside a jacket so maybe they got mixed up. As AudiOhm mentioned it's possible there's a mixed up wire somewhere. Maybe we'll check the cable continuity at some point, but everything seems to be working OK now.

Seems like the only other possibility would be that a speaker is internally wired out of phase. So yeah, it would be a good idea to check continuity of the cable as well.