Phase Inversion, to flip polarity or not

I put a system up in another room using an older Bruce Moore Companion 2c Preamp with upgrades and a PS Audio HCA-2 amp with full blown Reference Audio Mods. The Bruce Moore just like the Audible Illusion recommends invert phase. I tried both ways and like both ways for different reasons. Without inverting phase it sounds fuller, drums sound bigger, horns have a little more meat on the bone.  With invert phase there more detail, drum a little tighter but still has slam, maybe little more information, the PS Audio does help as it's pretty good at information retrieval. Anyone's insight or explanation to what I'm hearing please let me know. When dealing with a preamp recommending inverting phase which route do you go, just haven't decided which one is best, there both good.

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When the image snaps into place in the center of the soundstage (between the speakers), that would be in phase.

It's determined by how many stages are in the preamp.

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Yes, of course it's polarity. My preamp also inverts polarity.
My bad.

It all depends. If the system is in Correct Polarity (phase) and the recording is in Reverse Polarity the sound will be in Reverse Polarity. There are no Standards for Polarity or requirements that CDs or LPs must conform to some standard for Polarity. Plus, the system can be in Reverse Polarity for reasons other than an inverting preamp, e.g., a pair of cables connected incorrectly. Gasp! Or one channel can be in Correct Polarity and the other Reverse Polarity. There is the additional issue that one speaker can sometimes be wired incorrectly. Also, some tracks on the same recording can sometimes be in opposite Polarity. One way to find out whether your system is in Correct Polarity is use the out of phase track on a TEST CD like the XLO Test CD or TEST LP. Channelization should also be checked. As Bob Dylan says at the end of all his songs, good luck to you.
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Now I am even more confused, drums in one phase guitar in another. I'm going to get out of this hobby and go into butterfly collecting. I do have a phase switch on remote on phono stage so that helps. What are most people hearing when polarity is switched. I can only pick one and leave it and deal with it I'm not going to flip cables for the song this hobby is crazy enough. What phase do most people pick.

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Unfortunately the elephant in the room is the fact that there is no absolute standard for polarity through the recording/mixing/mastering chain. Some albums are released in "correct" polarity, many are not. But like Elizabeth says it really doesn't matter if it doesn't bother you. If it does, flip your invert polarity switch on your preamp or swap speaker cable ends (on one end only). I can tell a difference so that's what I do.
Thanks for your insight, that helps a little, I listen to 80% records so I'm good there. Reversing polarity in this system does change things and not in a small way, I'm just going to have to give it more time just set everything up last night.

OP- you are very welcome. For decades I never thought to reverse speaker cables at one end. Then one day I did and it sounded better reversed. My focus is on imaging and soundstaging and that's where I noticed most of the differences. Good luck on your quest and post some more findings. As always, YMMV...

Don’t have anything against the rest of the propositions Kosst offered, but- regarding the physics: ".....decompressing air certainly has its limits. No matter how fast the cone moves, it can never create less than 0 psi of pressure......" Ever heard of something called, "vacuum" and how it’s measured? (May seem rhetorical, but- facts are facts) Below, "0 PSI" the rarefaction of atmosphere pressure(or vacuum) is measured in Inches of mercury(inHg, or- millibars/mbar). YES; there’s a limit of 29.92". No perfect vacuum has ever been achieved, to man’s knowledge. At rest; a cone(or diaphragm) produces no pressure(0 PSI), at it’s front(just like a compressor’s piston). It’s forward motion will cause compression. It’s rearward motion; a rarefaction. The amounts of energy, to achieve either, are equal, or- you’d notice a difference in overall volume with polarity reversed. The result of a reversal in absolute polarity, has been termed, "The Wood Effect"(a highly contentious subject). As mentioned, recordings can vary widely, regarding absolute phase, both in overall recording and individual voices/mics. This CD: contains polarity tests, that enable one to tell whether the, "Effect" is audible to them, in their system. Here’s another, that I’ve found useful: It doesn’t mention at what point the polarity is reversed(on track 8), challenging you to find it.(if you can). Both incorporate music, with attention payed to correct polarity throughout. Having phase reverse available, in both my analogue and digital sources, I’ve marked the media I own, that sound better to me with a particular phase setting.
I own an acoustic guitar that's in reverse phase, but I find that if I play things backwards it sounds fine. 
I’ve been told, my guitar playing causes rarefaction(sucks). Reversing the strings, end to end, didn’t help.  
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Hello Kosst- Like I said; I didn’t have a problem, with your other propositions. There are many phenomena, without clear cut, cause and effect solutions, surrounding us. I too notice, as a result of the Wood Effect, what seems too tight a focus(as you say, "...a hyper-real, artificially forward sound."), that hinders what some call, "bloom". If that’s the correct term, for how sound naturally expands, from a source, into the sound stage’s ambiance(which also seems stifled). At least; that’s what I notice, on the media that’s recorded with attention to phase, voice to voice, by the recording techies.  Then too, over the years I’ve noticed with speaker systems, in which everything’s not properly phase/time aligned, whether the drivers, in a multi-way system, or- subs not aligned with mains, most of the ambient material is lost in the first place. If a system doesn’t recreate images, within a sound space to begin with, the listener won’t hear a loss(The Wood Effect is of no effect). Also, the kind of interference/distortion you mention, perhaps. Have you ever used the LEDR test, available here: and on some test CDs, like this one: It’s an excellent way, to hear whether a system is actually recreating, what’s on well recorded media. Happy listening!
I use to use a preamp that allowed for polarity inversion by remote control so that one can easily A-B the difference.  In my system, the effects of flipping polarity varied greatly, depending on the particular recording.  In most cases, the change is subtle and whether one or the other polarity was better was not clear cut.  For example, even in one particular cut, one polarity may make the vocalist sound more "present" but the piano might sound slightly "phasey."  It might well be the case that polarity is not consistent between different parts of the same recording.  My preferred polarity, when I bothered to listen for this, varied from recording to recording, so it would make no sense trying to set up a system to consider polarity; if that is important to you, a switch of some sort would be needed.  

You can buy test CDs that have music presented in two different polarities so you can hear for yourself it matters.  One example is the Jazz sampler/test CD from Chesky Records.
One of the reasons I stuck with planar speakers, for so long(Acoustat Model III’s, were my first, in 1981/Magnepan, until 2017), was the knowledge that they were inherently time/phase aligned. The obvious/audible benefits of which were learned, through mirror imaging a few customers’ DQ-10s, back in the day. I’d always actively bi-amped the planars, with my own bass units, physically aligning the acoustic centers of the drivers and panels and enjoyed excellent reproduction. Things certainly became easier, when TacT/Lyngdorf came out with their DSP/active crossover systems, relaxing the need for exact placement. Again- SO MUCH depends on the attention paid, by the people laying down the tracks. It’s nice to know(once one tests and confirms that their system is doing it’s job correctly), if something’s askew; it’s the recording.
Not to mention the drivers in your speakers may not all be in the same polarity- phase. Some speaker designs change polarity for different drivers. 
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 Interesting analysis kost_amojon, I  will have to think about this.  For my part when I have had a phase switch I seemed to notice changes on transients such as cymbals.  Otherwise I haven't ever noticed much.  I take notice about the observations that recordings may or may not be in or out of phase anyway. 
  1. There are innumerable stages in the recording chain that may or not be polarity correct.
  2. In a multitrack recording, there may be tracks [drums, guitar, bass, etc.] with correct polarity and tracks inverted.
  3. Selections recorded in one studio may be inverted relative to another studio on the same album. Compilation albums are notorious for this failing.
  4. Some loudspeakers invert polarity between drivers.
  5. Almost every device in the chain introduces phase distortion, i.e. a time shift between fundamental and harmonics. Coupled with loudspeaker polarity, this can make it impossible to achieve correct polarity across the audio spectrum.

Given the above, it is almost impossible to use most recorded material to determine polarity.

In decades past, I marked LPs as to preferred polarity, but now I just enjoy the music.

Bottom line, set it to how it sounds best for the majority of material. 

The Polarity Test track on the XLO Test CD is in Correct Polarity. But wouldn’t it be funny if it wasn’t? 😬
The Polarity Test track might have been a prank, I heard.