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ABSOLUTE POLARITY

Polarity or phase inversion  is an artifact of the recording and playback process. What it means is basically the positive and negative halves of the musical waveform have been inverted. It is rather insidious, however, and its musical ramifications are many and negative for the most part.

You will never hear inverted polarity in a real life situation.  It is an artifact of reproduced music. Everything live ( except for amplified music) automatically is in correct polarity. Inverted polarity often adds a harsh sibilance to the music, it blurs musical transients, making spoken words sound like the speaker is muttering. It blurs the fine detail and nuance, making a virtuoso player often sound like a student. The subtle nuance of a Stradivarius will be lost if the music is played back inverted in polarity.

Polarity inversion is everywhere, however. I would guess that the vast majority of my CD’s and DVD’s are inverted in polarity. In fact over the  years and various media (LD, etc.) the only two movies which have been  consistently correct have been Terminator 2 and The Abyss.

You can clearly hear the effects in video and surround sound. When inverted, often times the sound effects will drown out any dialogue. At such times, you have to turn up the center channel volume significantly. Strange how in a properly set up stereo (two channel system) you can get pin point imaging without a center channel at all. In fact, we urge all our readers to simply invert the black and red wires to their center channel (black to red and red to black on one side: either the amp side or the speaker side, but not both sides!) and audition the resulting sound. Chances are, intelligibility will be improved. If you like this, do the same for all the remaining channels including the back channels.

One of the major issues is that speaker designers  do NOT design their speakers to be phase and time aligned. More often than naught, they will invert the polarity of the midrange driver in relation to the tweeter and woofer in order to get a smoother sine wave. This ignores the fact that a musical waveform is not necessarily a sine wave, and generally has a much harder attack than the follow through.

Of course, having software out of proper polarity certainly sells a lot of center channel speakers….

REPRINT

This is a reprint from an article we originally wrote for Audio Reference Systems in Manoa. It was revised for ADL in Kaimuki. It eventually was also published by Martin Dewulf’s magazine Bound for Sound. Some revisions have recently been incorporated as the original article was written over two decades ago.

Absolute phase is an audio problem first brought to prominent attention by R.C. Johnsen in his book The Wood Effect. Although we are not familiar with this work, we, at Audio Direction, have been very aware of the effects of phasing ( we have since read the Wood Effect).

Absolute Phase involves the electrical polarity of the audio system electronics. To simplify, imagine your speaker wire leads. Normally the red speaker terminal is connected to the red coded wire lead, and the black terminal to the black lead. Since the vast majority of speaker designs use dynamic drivers, with a cone set into a sealed or semi sealed cabinet ( i.e. ported or transmission line types), this polarity is extremely crucial. A compression wave of high pressure can be thrown into the cabinet if polarity is reversed.

Given a rim shot, for example, the initial snap will create a large compression wave followed by the harmonic structure of the instrument. Incorrect polarity ( out of phase or inverted absolute polarity) means this initial snap will be thrown into the speaker cabinet rather than be directed into your ears. Music is not simple sine waves: with percussion instruments , for example, transient, staccato attacks mean means that the waveform may often approach that of a square wave. Out of phase components and recordings mean that sharp initial attack is thrown into a cabinet where your ears will not hear it.

While it is easy to illustrate and visualize polarity with speakers, the reality is that any component in your system may be inverting polarity. Denon 1500 series CD players were phase inverted: so were JBL ‘L’ series of speakers. Conrad Johnson latest preamplifier designs are also inverted in polarity: Apogee, Acoustat, and Martin Logan woofers are inverted in polarity to their panels (in their hybrid designs).

Some, like Conrad Johnson, deliberately design their preamps to invert polarity. In CJ’s case their quest for simplicity means that  leaving the preamp inverted in polarity eliminates an addition tube in the circuit path. Some pro amps invert polarity on their 1/4 inch jacks. so that in case of accidental unplugging speakers are not blown out. The speaker will move inwards where it will bottom out rather than go outward where they can rip out the voice coils.
These manufacturers are careful to note the polarity changes in their manuals however.

Inverted polarity is also deliberately done to disguise issues within a component. Hybrid speaker systems using ribbons or electrostatics with dynamic woofers often invert polarity on the woofers. Inverted polarity creates a sense of smear with diminished detail, and this often disguises the disparity  in speed between the panels or ribbons and the slower woofer. However, inverting the polarity of the woofer in relation to the tweeter never truly adds detail, and the schizophrenic quality of a speaker with mixed polarity rings to mind the Linn adage about rhythm and pace. Woofers out of polarity make the music sound like its dragging, like the bass players are half a beat behind: Jazz combos lose that “tight” feeling: classical performance sound inept and distracted.

These days, mixed polarity designs are increasingly more common and the designers have become more sophisticated. The vast majority of “audiophiles”  seem to have a predilection for highs and lows. Inverting the midrange driver of a three way design draws attention to the  tweeter and the woofer and many listeners believe that to be the ideal. In addition we have noticed that most males ( as most audiophiles seem to be) seem to like female voice, which of course places further emphasis on the tweeters.

Stereophile Magazine publishes in their test measurements an impulse test. This applies a basic square wave leading edge to the speaker under test ( you can read about this on their website). An ideal waveform is basically a right triangle with a sharp initial rise and a slow tapering back down to the zero point. John Atkinson , the editor, who performs these tests reports that  over the years he has come across only ten models from 5 manufacturers which exhibit this practical ideal  waveform. The manufacturers he lists include Vandersteen, Spica, Thiel, Dunlavy, and Quad. Spica and Dunlavy  are no longer in existence.

That’s a sad commentary on the state of speaker design. As one noted designer (he’s is on the list, BTW) has stated, “if perfect phase alignment, perfect phase alignment, and full range frequency response was the goal of every designer, you would think that at a certain price point speaker designs should sound more and more alike.” The fact that even at price ranges of tens of thousands of dollars speakers can sound very different indicates that most designers are NOT interested in perfection.

A good test is to listen to both female and MALE voices. Also, a piano piece is highly recommended. A piano covers a wide spectrum, not quite the ten octaves human hearing is supposed to encompass but more than any other instrument. In addition, it is percussive ( hammers hitting the strings) and will have complex harmonics. Remember that each note on a piano actually comprises three strings not tuned in perfect unison. A piano from the lowest notes through the highest should sound like one instrument and not like different instruments in different registers.

The issue with individual component inversion can be easily corrected by simply changing the leads of your speaker terminals, so long as your speakers are phase aligned. A major issue these days is that recordings themselves may be inverted in polarity. As audio electronics reaches higher degrees of clarity, the polarity issue becomes more evident. For ADL polarity can be heard even on a relatively inexpensive AV receiver (we can hear it on a $400 receiver).

What is frightening is that few designers and fewer salesmen and retailers can identify the issue. We have been to many trade and specialty shows and few have shown any knowledge of the issue. Many of these people are well known designers, so do not be intimidated if you can’t hear polarity inversion at first. For myself, it took  me personally about a decade to recognize it when I hear it. With practice, though, it becomes fairly obvious.

Returning to the software problem, on some recordings, typically modern ones, the effect is used to create a certain mood. Julee Cruise’s album “Floating Into the Night” featuring the soundtrack from Twin Peaks deliberately inverts polarity on her voice to give an ethereal effect in keeping with the mood of the theme of the TV show.

Vocalists using the Aphex Aural Exciter, a voice synthesizer, have their voices inverted in polarity. These artists include Barbara Streisand, Linda Ronstadt, and Neil Diamond. The women, in particular, had very clear high voices in their early career, but now have a deeper husky, throatier quality. It is the Aphex which gives them that quality with a bit of EQ. Inverting polarity on those recordings reveals a voice much more akin to their early recording quality.

The effect can clearly be heard on the American Tail soundtrack. Linda Ronstadt sings the title tune Somewhere Out There. With the system in correct polarity, Ronstadt  has a lisping quality and her attacks on consonants and her phrasing are rather vague. The orchestra sounds good, though.

Invert polarity and Ronstadt’s voice takes on a brilliant sheen and her breath support and phrasing becomes easily heard. Her voice control is easily discerned. The backing orchestra sounds horrible, however.

In the classic movie, the Commitments, director Alan Parker had an interesting comment in the director’s cut version of the DVD (highly recommended, BTW). The singer playing the lead, has a great voice, but in order make his voice sound even better, Parker, who insisted that all the actors play their own instruments and sing, recorded the back up group and inverted polarity when the lead vocal was added in order to really make the singer sound great. Curiously, the CD’s and LP’s of the soundtrack preserve all the playing in correct polarity to each other, and the voice simply does not stand out as in the movie soundtrack.

In the Michael Crawford CD MC sings Andrew Lloyd Weber, Crawford does several duets with some great singers, Barbara Bonney among them. I do notice that the singers he partners with are inverted in polarity to Crawford, so that they do not sound quite as good. Barbara Bonney has perfect pitch and, even though inverted in polarity, the quality of her singing still comes through, just not as well if you correct for the polarity.

The famous Phil Spector “wall of sound”  incorporates polarity inversions. The lead singers are kept in correct polarity and the background musicians are inverted. The vocals are sharply focused, but the vagueness afforded by the inverted polarity makes the background musicians very vague and they seem to be spread across the soundstage. This technique  then becomes widespread in the pop music industry.

Some two way speaker incorporate this effect. Tweeter is kept in correct polarity and woofer inverted. The highs then give a sense of directionality, and the vagueness afforded by the inverted woofer seems to give a much larger soundstage. This is very evident in speakers like KEF LS-50’s, and JM Labs Mini Utopia’s.

With training and practice, inverted polarity can easily be  recognized. We used to routinely mark our recordings, at least until we could recognize polarity inversions by ear. Be aware that some recordings, particularly best ofs can have individual tracks in inverted polarity. Some recordings, recorded in different studios also show this effect. One example is the last Buddy Holly LP. About half the recordings are done with orchestra in one studio, and the songs with a simpler back up in another. One studio is inverted to the other, and they are not in any particular order, but randomly scattered\, making it rather frustrating to listen to (unless your preamp has a polarity switch).

For phono sections we can make a junction box with a four pole double throw switch. That way you can change polarity with the flick of a switch.

The most obvious manifestation of inverted polarity is the rounding of the leading edges of transient attacks. Dynamic contrasts are subdued. Vocal attacks, particularly on the hard consonants, P’s, T’s, K’s, become soft and lose some of that explosive initial attack. Percussions lose their snap. With strings, the effect is much more difficult to hear since the instruments are typically bowed. The effect is more evident with wind instruments, particularly the brasses. There should be a very clear delineation between a tongued attack and a breath attack.

Wind instruments are also interesting because of their differences in harmonic structure. Brasses tend to accentuate the even order harmonics. Some woodwinds, in particular the clarinet, emphasize the odd order harmonics. Inverted polarity tends to emphasize the harmonic structure over the fundamentals. Clarinets will typically sound much more shrill than in real life. Inverted polarity in emphasizing the harmonics also tend to emphasize the sibilants in vocals.

Inverted polarity also destroys the precise lateral placement in recordings. With classical recordings, this may be difficult to hear on the more modern multi miked recordings. Because of the number of microphones used, the physical relationship between the musicians is destroyed as the distance of the performers to the microphones will vary greatly.

Try to use a good minimally miked recording. Old Mercury Living Presence recordings used only three mikes: so do the first three RCA LSC recordings: Zarathustra, Gaite Parisiene, and the Daphnis and Chloe. The Decca classical recordings although multi miked used the famous Decca “Tree”. Although the tree used multiple microphones they were placed relatively close to each other (within three  feet) so phase interaction between mikes were minimal. They have a relatively good sense of three dimensionality as a result.

It should be noted that the Decca/Londons are usually phase inverted to the RCA’s. The Decca recorded LSC’s such as Witches Brew and the Royal Ballet are likewise inverted in polarity. LSC LP’s are often problematic in terms of polarity. I have a Reiner Scheherazade with a 1s/7s stamper on different sides. The 7s side is inverted in polarity to the 1s side. When RCA decided to reissue an SACD of the Reiner Mahler, it was discovered that the two tapes used to splice the working master were inverted in polarity to each other (maybe  why that particular Reiner was not acclaimed for its sonics even though Mohr and Layton were the recording engineers). Apparently recording technology in terms of the tape decks used back then did not have a polarity standard or perhaps the microphones were not standardized.

Proper polarity should give pin point accuracy in terms of lateral placement and a tremendous increase in the sense of depth.  The Webber Phantom of the Opera, the complete London edition, is an excellent illustration of this. In correct  polarity, the recording, particularly in the opening scene, takes on vividness and immediacy which can be rather startling. The striking of the auctioneer’s gavel has an attack which is very real  and an extremely good test of system dynamics.

Another test is the Fantasy LP of Miles Davis Blue Moods. In normal polarity, the recording sounds like it was recorded underwater: everything is blurry and unfocused. Placed in correct orientation, the members of the ensemble stand out in sharp contrast and the sense of space is quite nice and realistic. Thank heavens I didn’t throw that LP out.

For some reason we find that the vast majority of our digital recordings, including DVD’s have their audio inverted in polarity. In the laser disc era the only two movies we had which were correctly phased were T2 and the Abyss (curiously two James Cameron movies, although later Cameron movies are also inverted). We do know in early CD copying software (EZ CD creator) when the data was placed into the hard drive and later extracted, the resulting recording was inverted in polarity to the original.
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For LP’s, almost all Columbia, Decca, DDG, and Philips are inverted. RCA’s are a mixed bag, some are and some are not. Mercury, at least in the early pressings are pressed in correct polarity. So are majority of the audiophile labels  Chesky has a quirk, though. The CD’s are correctly phased up to  catalog number 63. After that. they are inverted, including their second test CD. This coincides with the switching of their CD mastering to George Kaye electronics.

POLARITY OF A FEW RECORDINGS

Some Correctly phased recordings:

Rickie Lee Jones            Pop Pop
Julia Fordham                 Swept
Enya                                Watermark
Bela Fleck                        UFO TOFU
Three Blind Mice CD’s
Reference recordings CD’s
Sheffield Lab CD’s
Mercury Living Presence CD’s produced by Sir Dennis Drake
East Wind Silver CD’s ( not the gold  discs)

Some inverted CD’s

Mary Black                   No Frontiers
Babes in the Woods
Terri Garrison               Only Love ( Waterlily/Vandersteen recording)
Fourplay                        Fourplay
Ray Lynch                     Deep Breakfast ( interesting that a fully synthesized recording can exhibit polarity differences)
Sarah K                         Gypsy Alley
Closer than They Appear
Harry Connick, Jr           25
Julia Fordham                Porcelain
Mary Chapin Carpenter Come on, Come on
Enya                               Enya
Shepard Moon
Radka Toneff                 Fairytales
Ella Fitzgerald                Clap Hands here Comes Charlie
Holly Cole Trio               Temptation (voice and bass are inverted, piano is correct)
Don’t  Smoke in Bed ( see note above)
East wind Gold CD’s

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