What is phase inversion and what do I do about it?

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decofan
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What is phase inversion and what do I do about it?

Post by decofan »

While researching bi-amping with my CJ 17LS I looked up the specs at CJ and it said "Phase: inverts phase of all inputs at main output". So If I have understood this correctly, to correct for phase inversion I should reverse the connections at the amps or the speakers?
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Re: What is phase inversion and what do I do about it?

Post by admin »

Yup, just switch the positive/negative speaker cable attachments on one side.

Both my preamp (PV-12) and amp (Evolution 2000) are phase inverting so my speaker wires are standard. But if switch any single component out (to a non-phase inverting unit) I have to change the speaker cable connections.
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Re: What is phase inversion and what do I do about it?

Post by pstrisik »

Just a slight clarification. Speaker leads should be reversed on both speakers for absolute phase inversion. Switching only on one speaker would change relative phase and negatively affect bass response and imaging. I suspect you meant to switch both cables but only on one end of each cable.
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Re: What is phase inversion and what do I do about it?

Post by admin »

pstrisik wrote:Just a slight clarification. Speaker leads should be reversed on both speakers for absolute phase inversion. Switching only on one speaker would change relative phase and negatively affect bass response and imaging. I suspect you meant to switch both cables but only on one end of each cable.
Yes of course your right. I meant that you can switch them on either the speaker connection side of the cable, or the amp connection side of the cable. Both left and right channels would need to be changed (either at the speaker connector or the amp connector).

Each speaker should have the same phase.
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decofan
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Re: What is phase inversion and what do I do about it?

Post by decofan »

Thank you - I was not precise but that is what I meant. I did switch them on the amp side for both amps. I can't tell if I can hear any difference. I guess if I really wanted to hear it I could just do one and compare?
System 1: CJ 17LS, CJ Premier 280 monos, MIT Shotgun 2, Rega RP6, Talon Ravens
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Re: What is phase inversion and what do I do about it?

Post by admin »

decofan wrote:Thank you - I was not precise but that is what I meant. I did switch them on the amp side for both amps. I can't tell if I can hear any difference. I guess if I really wanted to hear it I could just do one and compare?
Out of phase sound should be rather apparent, so I am little surprised you are not hearing the difference. When the phase is reversed the music generally sounds rather poor with lack of spacial definition. Here is a website which give examples of what in phase and out of phase music sounds like:

http://www.audiocheck.net/audiotests_polaritycheck.php

And here you can download some test tones that you can burn to a CD:

http://www.eminent-tech.com/music/multimediatest.html

Hope this helps.
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Re: What is phase inversion and what do I do about it?

Post by eagle6014 »

I bought a Nordost System set-up and tuning disc from Music Direct when I was setting up my pre. It has a track on the disc which will help you make sure your in phase. It's also got plenty of other tests you can conduct with pink noise, white noise, frequency checks, and a burn in track. It was very helpful to me because like you, I had no idea what phase meant when I started out in tubed equipment. It's been a valuable tool for me because I need all the help I can get. G'luck, Pat.
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Re: What is phase inversion and what do I do about it?

Post by rthomeint »

I always make the phase change at the speaker terminals at the amp. This keeps you from getting confused about the phase because you tend to see the cable at the speaker end more that the amp end. a get disc for phase check is the XLO disc if it can still be found. Also some og the Sterophile test disc has phase checks also.
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Re: What is phase inversion and what do I do about it?

Post by pstrisik »

Almost all of the test discs you will see will have relative phase test tracks, but not tracks for testing absolute phase. I have seen one absolute phase track, but can't recall on which disc it was. I have a DAC that has an absolute phase switch. I sometimes don't hear a difference, sometimes slight. With relative phase change, it is immediately and unmistakably noticeable.

Relative phase tracks will play something in phase and often say something like, "the dog's bark (or voice, etc.) should sound like it is coming from between the left and right speakers, be easily localized, and sound coherent. For the out of phase sample, it will say something like, "the dog's bark should be difficult to localize, sound diffuse, and bass quality should diminish.
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Re: What is phase inversion and what do I do about it?

Post by Ian Millar »

As long as the left and right speakers are connected the same way around it does not matter whether the preamp or speaker wires invert the phase.

Both active and passive crossovers cause phase shifts and inversions right across the audio band and there are dozens of additional phase inversions as the sound reflects off room boundaries. C-J talks a lot about phase inversion in its pre-amps and seems to like the term "phase correct" which is meanigness given that nobody knows what phase inversions might have occurred in front of the microphones or indeed during the mastering process. It is also irrelevant as soon as you move back from the speakers to pick up a few of the wall and ceiling reflections.

I use Linkwitz Riley 4th order crossovers in active systems. An LR24 is known to be phase aligned at all frequencies. This does NOT mean that the phase is the same at all frequencies. It just means that the phase to one driver is the same as the phase to the next for proper summing. Indeed the mid-point of the midrange passband is inverted at line level. Switching the phase 180 degrees at the preamp would "correct" that, but there will be an inversions at other frequencies.

None of it matters. What matters is that at the speaker crossover points there be some designed correlation between the drivers for correct amplitude summing which phase misalignments can play havoc with. This includes physical as well as electrical alignment of drivers.

Immediate phase flipping (by a switch at the input side of an opamp in a preamp say) can be heard by some people with some music such as saxophone, but walk out of the room and back in again and they could not tell you if you flipped it back again while they were out of the room.
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Re: What is phase inversion and what do I do about it?

Post by jacktoz »

I have to second Ian's comments.

I'm not sure absolute phase means much with the state of engineering being what it is. Years ago I had a list of record labels, It might have been from grammophone, but I'm not positive, showing how the various labels treated phase. It was all over the map. Some companies adhered to absolute (not relative,) phase, others were always out of absolute phase, and some had no rhyme nor reason. If you have the album "Kind of Blue" by Miles, listen to the first track, "So What?" The piano is out of absolute phase with the rest of the combo. If the piano is in sharp focus, the rest of the band is slightly soft, reverse both sets of speaker leads and you'll find the piano a bit diffuse and the rest of the band nicely focused. If memory serves, Columbia was listed as having absolute phase change between different tracks on a single disk.

Remember...this refers to absolute phase, not relative phase. Chasing true absolute phase is frustrating and will interfere with the enjoyment of music. Believe me, I've tried, I also tried adjusting SRA for every record I played back in the lp days. My suggestion is to try your system both ways and see if you have a consistent preference. If you do, leave it and start listening to the music.

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Re: What is phase inversion and what do I do about it?

Post by Ian Millar »

Hi Jack, I bet the album to which you refer could also trick the mind. Flip the switch and walk out of the room and back again and you may not know whether "the phantom" switched it back. The inversions would be listener position-dependant. I.e. what some might consider "diffuse" and "focused" might depend on where the listener is positioned in the room. But it doesn't really matter too much if you are several metres away from the speakers since minute head movements can shift your ears across several higher frequency phase flips anyway.

Check this out. The first image is an SPL and phase plot which I made of my own midrange driver in an active 3-way system with separate amplifiers connected directly to the respective speaker drivers. The crossover is at line level in front of the power amplifiers. I simply turned off the bass and tweeter amplifiers (leaving the midrange amplifier on) to find out why the midrange sounded so terrible in the room. The first plot is with the microphone right AT the midrange driver:

Image

You can see the SPL looks nice and symmetrical (that nice round "mountain" in the middle) and there is one phase inversion in the midrange (this one is actually caused by the crossover at line level and is passed through by the power amp) . All those inversions over to the right are not relevant as they are out of band anomlies.

Now see what happens when the microphone is pulled back into the room by about 1 metre or so:

Image

You get the horrid baffle step response in the SPL (that 6dB "land slide" to the left), but look at the dozens of phase inversions right there across the mid band. That's what you get.

Of course I fixed the baffle step response with a simple compensation circuit, but nothing can be done about the inversions. They're a fact of life.

Next time someone tries to baffle us with so-called "absolute phase" stories, maybe suggest that they consider some simple physics.
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Re: What is phase inversion and what do I do about it?

Post by Good Dog Jocko »

Phase inversion is best investigated after you have had at least half a bottle of Talisker or similar libation. You should also throw the subjective review audio magazines in the far corner and ..........

What you do about phase inversion is either switch your speaker leads and decide which way your like it best, or you drink enough Talisker or similar libation and switch your speaker leads and decide which way you like it best. You can also smoke something and decide which way you like it best.

That is about all you need to know about phase inversion.
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Re: What is phase inversion and what do I do about it?

Post by jahatl513 »

Admin,
On the PV12 w/ phono, I heard It is phase correct for the phono stage, phase inverting for the line stage. So am I to understand that I have to switch speaker wire every time I use the phono? Can I just reverse my R/L leads from my Turn Table? What is your thought, take, solution? Is this true?
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Re: What is phase inversion and what do I do about it?

Post by admin »

I always took that to mean that the PV12 is phase inverting regardless of source (including phono stage). Meaning that the phono stage input will still be phase reversed when sent to the amp via the PV12 outputs. Hence, the phono stage by itself is phase correct, but the output from the PV12 will always be phase inverted.

You may want to read this thread on audiogon as they also talk about it: https://forum.audiogon.com/discussions/ ... ng-problem

Here is the PV12A manual for reference: http://conradjohnson.com/owners-manuals/PV12MAN.pdf
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Re: What is phase inversion and what do I do about it?

Post by roberto »

Hola...
All of you do know that some recording manufactures like Sony/Philips, Deutch Grammophone, etc, do invert the absolute phase. When your stage is too big, voices are too big or the soloist instrument is really big...the stage has a thickness of a pancake, and musicians are located just between the speakers. When you have this, just invert the polarity on both speakers and take a listen again. You will notice the difference right away. Some of you might like to listen the music phase inverted, and this is OK. I do believe it is a matter of liking. Your music collection usually the 50% has abslute phase inverted. The standard industry believes that we can not hear the difference. Also, on some recordings, you can find some instruments out of phase and other with the right phase. Yes, those recordings are the ones that no matter what we do, we can´t get all the instruments right!. We do get their sound, but not the phase right.

When we have right the phase, everything snaps in a wide and nice stage, with truly sense of 3D. Instruments and voices are projected into a truly virtual space on our speakers.

So, because right now I am only into digital, my software keeps the recordings with the absolute phase right. Audirvana Plus has it, and HQPlayer has it too. My system is setted with the right phase in mind. So, usually, my stage is wonderful, and I am enjoying all the musicians and the quality sound of Conrad Johnson. This is a truly Nirvana.
Happy listening!
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Re: What is phase inversion and what do I do about it?

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phase (1).docx
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ML CLX BF-210 Stage X Motion 4. CJ 120SE amp ET7V2 pre, Holo May Kte Dac. Mac Pro. Power Cond. BPT Signature+ 3.5, Gaia II Feet. USB Lush^V3. Nordost SPM IC and Spk. Shun Mook, BCanto CD2 CD3. Linn LP-12/Unitrack tonearm/Denon DL103R MC.
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