Absolute Polarity Revisited

 I am a critic of the idea that absolute polarity is readily audible or particularly important.  A friend of mine has been a leading proponent not only of the idea that absolute polarity is audible, but key to musical enjoyment, and that the recording industry has deliberately reverse-polarized 92% of all CD's to sucker us to buy more and more with less satisfaction.

I've long cited the unsurpassed Lipschutz double blind testing published in JAES in the 1980's.  Lipshutz showed that polarity is not audible in complex music period, but that it is audible on test tones and certain solo instruments like trombone using headphones more easily or speakers in some cases (and Lipshutz used the speakers with unmatched phase coherence, near perfect square wave reproduction, the Quad ESL-63).  However, Lipshutz said it normally costs little to keep polarity correct, so that should be done when possible.  (My friend discounted this research immediately.  "Electrostatics can't do bass, and if you can't do the bass, polarity is moot."  Even though he mostly found the effects of polarity in the midrange and highs.)

The lack of audibility of absolute polarity seems to also be the prevailing view among audiophiles I have met (other than friends of my aforementioned friend) so much that few even bother to get the absolute polarity correct when connecting speakers.  If the speakers are out-of-phase, they simply reverse one to match.  (I always track down where the error is and correct it, to preserve absolute polarity.  I also use an up-to-date acoustic testing app and manufacturer provided audio files to verify the polarity on systems when I've completed setup.  Or sometimes my own constructed audio impulse signals and an oscilloscope.)

I have conducted 3 double blind tests on my polarity-theorist friend, and he has failed to reject null hypothesis p < 0.05 on every one.  All three were of a designs (changed each time, often taking years to construct) he was certain he could pass, as in piece of cake (he was going to market a polarity test kit).  None of this altered his POV of course (it would be plausible to continue to maintain that polarity is somewhat audible, but not so much that it's obvious and therefore a big deal).  Nor does the fact that he has sometimes changed his strong convictions about which recordings are correct (less so with equipment).  Most of his judgements are subjective, though he sometimes also uses (incorrectly, I have many times explained) a schlocky polarity check gizmo, or "simultaneously" starting CD players.

My friend has very often asked me to test polarity subjectively (I have done so only a few times) and criticized me for buying equipment, such as the Oppo BDP-205, and Emotiva XSP-1, which lack a absolute polarity reversal switch.  For a long time he only purchased CD players which had absolute polarity reversal switches for single ended (which are extremely rare, like a few NEC models).  He also criticized many of my purchases as having reverse polarity by default (I tested them and they didn't, then he said they were tricked out to pass polarity correct for test signals only).  To date, the only device out of 100 I have objectively tested having reverse polarity was an iPod at the headphone jacks.

If such switches even exist on CD players they don't control the digital outputs, which is all I ever use.

It has infuriated me that neither the Emotiva XSP-1 nor the exceedingly flexible (but now discontinued) Behringer DEQ 2496 have ways to control absolute polarity either.  I believe there is such control in the miniDSP OpenDRC, but only if you connect a computer device to the miniDSP...there is only one physical rotary selector switch on the OpenDRC, which is used to control "settings" (you could make two otherwise identical "settings" with only polarity being different--what a hassle--but I use the "settings" differently than that anyway).

But I have long, long, long, overlooked the fact that I CAN control absolute polarity using the Tact 2.0 RCS preamps I use.  I just have to press the menu button, scroll to the polarity control, and then the polarity screen comes up.  From there, I can set the polarity of each speaker independently.  This makes instant A/B testing impossible, which is why I have long, long, long overlooked it.  When I first got the Tact I was hoping to do the polarity experiments my friend was asking me to do right away, but finding that I could not do instant A/B tests, I lost interested, and disparaged the Tact as having "no absolute polarity control."

But yet it does have absolute polarity control, it's just not "instant."  It takes about 5 seconds to do the operation.

By that point, 5 seconds on the music has moved on, and is not directly comparable to the preceding music.  Plus your short term direct audio memory is lost, all you have left is whatever memes you encoded from the music previously.  The comparison is far harder...and virtually certain to produce false positives if you believe you must be able to hear differences.  This is even more true if you play something all the way through, or just a few dozen seconds, in each condition.

But this is the type of thing "serious" audiophiles often do anyway.  Including gray hat near-objectivists like me.

So I finally got around to playing with the Tact polarity control on New Year's Eve 2021.  And my first subjective result was that being out-of-absolute-polarity sounded a trifle smoother.  I might add that I am very skeptical I could hear this effect double blind.  It's probably an artifact of the fact that I can't switch instantly.

Other than the likely null effect I am glorifying, I theorize something very different from my friend.  In fact, it was one of many reverse arguments I made to him.  I suggested his all-cone speaker system had magnetic distortion that caused more distortion when transients were played one way vs the other. 

Notably, my friend did all of his actual double blind tests using headphones, which he considered most sensitive to everything...the best window on the recording.  But it may well be that the headphones didn't have the asymmetrical distortion that his speakers may have had which made him believe so firmly in the importance of absolute polarity in the first place.  However, he no longer listens to speakers but only headphones and continues to maintain the uppermost importance of absolute polarity and that most recordings get it wrong.

I don't have an all-cone system...but I do have a cone subwoofer going up to 125 Hz (crossed with linear phase LR8 implemented with FIR DSP).  So, the woofer is important, and it's magnetic, and years of leading transients which tend to do one way could (I imagine) cause a slight magnetization inducing increased distortion.  I imagine the distortion would tend to be reduced, and eventually undone, using reverse polarization.

So, taking my position that reverse polarization will diminish distortion immediately, and in the long run de-magnetize the woofer system, I've decided to try running my system in reverse polarity for awhile.

If I'm wrong, well polarity didn't really matter anyway.  And if that is wrong, and my friend is right, 92% of CD's will sound better anyway.  He taking this very seriously for over a decade now, and he finds reverse polarity nearly always sounds better.

My theory, that dynamic speaker magnetization causing distortion is involved, is objectively testable.  I am doubtful I will find it, though I'll add that to the list of experiments I want to do in 2022.

According to my theory I will continue to get lower distortion in reverse polarity until I have operated the subs for the same number of years in each absolute polarity.  Then I should reverse them again.

Come to think of it, electrostatics could have a long term "memory" distortion effect too,  in both the transformers and the diaphragms too.

 

Audio Achievements for 2021

 1.  I programmed an automatic playlist generator, now called "mplay" (but possibly renamed for distribution so as not to be confused with other things with same name).  I am now planning to "release" it to the public within a few months, I just barely started thinking about a release package in the last week of 2021.  It is likely to be useful only to computer geeks like me who like music.

This has made programming background music from my wonderful album collection a snap.  It also means my vast collection (800 albums and more being added all the time) is actually being used, and not just my top 10 favorite albums.

I was working on this on and off during 2021.  In the last week of 2021 I finally got around to fixing some major bugs.  It actually works as intended now, I think, for the most part.  Previously it had a tendency to keep getting stuck (and never finishing), ignoring all my latest albums (which I hadn't realized), and repeating the same things far more than intended (which I long suspected, but I worried would it be hard to figure out and fix, but in fact only took a few hours of concentrated effort).

I never thought I would do such a thing.  I now wonder how I ever got along without it.  Why did I bother collecting so many albums I hardly ever actually played?

2.  Improving the home automation control of the living room stereo.  I already bragged about this last year, but the job had not been finished.  I added home automation control of the Oppo (just in time for use by mplay generated playlists).  Considerable work was also done making the programming and reprogramming the home control system to make control of the audio system more convenient.

3.  Keeping the local Classical Music FM station sounding good.  Twice this year KPAC developed audio problems.  I reported them and they got fixed.  The first time, the problems didn't get fixed for months.  The second time, in late December, they got the problem fixed in less than a week after I reported it, and I even got a friendly call from the station engineer.  The audio problems were identical on both FM and streaming.  The station engineer said it was a network problem.

4.  Tracking down a peculiar distortion problem.  I figured out that sometimes Sonos attempts to add digital gain when it shouldn't.  A Sonos Update appears to have fixed the problem.  But I mostly use the Oppo nowadays anyway, except for testing, and when I do testing I'll be aware that this issue could pop up again, though I'm taking some measures (like not fiddling with the volume change buttons on the Sonos Node) to prevent it.  This problem might or might not affect some earlier results, such as the miniDSP seeming to need 6dB extra headroom.  I will be aware of that next time I do serious testing.

5.  Fixing a low level buzz.  I discovered I had a buzz about -55dB from normal levels, or -80dB from peak levels.  This was fixed by cutting the shield and ground pin on the AES digital cable feeding the Emotiva DAC.  Funny I had just written a post arguing that audiophiles shouldn't be much concerned about -110dB distortion potentially being added by jitter or other digital anomalies, while often ignoring -60dB noise and distortion.  It turned out that I was yet another person ignoring a -60dB noise.  The fact that this made no difference when I was comparing Hafler and Krell a few years ago suggests that if you can't hear a noise at the listening position, it probably doesn't matter much.

6.  Testing and adding a new digital recorder.  My biggest audio purchase this year was a brand new Tascam DA-3000 digital recorder, for making digital transcriptions of vinyl records and FM radio.  I tested this to be certain it is bit perfect when used with the Lavry AD10 analog to digital converter, and with a clock cable.  Without the clock cable, it is not quite bit perfect.  Unlike my previous recorder, the Marantz PMD-580, the DA-3000 allows the Sample Rate Converter to be turned off, so I am recording the exact bits produced by the Lavry.  I've already recorded a bunch of Sheffield direct-to-disc and Reference Recordings vinyl albums.

7.  Switching to XLD (X Lossless Decoder) for copying CD's to my harddrive.   Up until last year I had always used iTunes for copying.  But iTunes does not always produce perfect copies, and I was becoming disturbed by the errors from some CD's I had acquired from an estate sale.   XLD uses the Accuraterip database to ensure accurate rips.  I also find it easier to use since I can place files into a folder of my own choosing.  Before settling on XLD I also tried Poweramp CD ripper, but I didn't like it as much.

8.  Over 100 albums have been added to my harddrive, including new transcriptions from vinyl.  There are many hundreds more where those came from.

9.  I now use Audacity's "repair" effect to remove pops from vinyl transcriptions.

10.  Minor adjustments to the EQ since the last system crossover and EQ tuning work in 2020.  I itended to do much more work but never got around to it.  Anyway, the system sounds great, far better than anything I've ever had, mostly thanks to earlier work.

11.  Reworked how my Sonos nodes in living room and kitchen are connected.  I'm back to having two nodes in the living room, one dedicated to making HDCD decoding through the Denon DVD-9000.  I have a labeled switch in the Kitchen which determine which kitchen source plays thought the Sonos Line in.  Previously it seemed that always the wrong thing was connected and it was hard to change.  I changed to unshielded CAT6a cables for the Living Room nodes, eliminating another possible source of hum (as compared with using the shielded cables).

12.  Oppo now connected through Ethernet (with unshielded Cat6a cable).  I hadn't even realized I had the Oppo on wifi only.  That possibly explained a few (but very few) previously inexplicable dropouts.

13.  Upgraded my computer CD/DVD drive to a metal cased Other World Computing unit.  My old LG DVD drive started having problems.

14.  Leveled the turntable stand.  This required removing all the equipment from the stand--no easy job--and adjusting the feet on the stand to make it level, then putting everything back.  Previously I hadn't trusted the "wobbly" feet on the stand.  But once the stand is on it's feet, the wobble goes away.

15.  Read the Linn LP12 Setup Manual.  I am hoping to get my LP12, whose suspension started becoming very erratic in late 2021 (probably after I wrongly but briefly flipped the turntable on edge) fixed soon.  But after trying unsuccessfully to fix it myself, I read the LP12 Setup Manual so I have some basic understanding.  I hope to have my LP12 expert, Mark, over here soon to fix and, and now I'll have a better idea of what he is doing.  I tried, unsuccessfully so far, to order a Linn Setup Jig from England.  I obtained a Linn Spindle Oil Cap from a Linn Dealer in USA.  (It's a black OEM one that the dealer claimed to hold tighter than the red original.)

16.  Discovered the source of occasional audio distortion in the bedroom system.  It turns out that I have sometimes set the audio level on the Mac to way over 100% by mistake...this is done simply by moving the scroll wheel while the mouse is over a VLT window.

17.  Got an actual SanDisk interface for reading Compact Flash cards.  This works about 100 times faster than the old Compact Flash reader I had from the 1990's (built into a floppy drive...).  What had been taking 6 hours is now done in 6 minutes.

18.  Copied all my Reference Recordings HRx high resolution discs to my harddrive.  I didn't even realize until recently that I could do this.  These are some of my favorite recordings, and now they are much more accessible as well as being available to my playlist generator.

19.  Labeled all the Surround controls on my Kitchen system.  I use two chifi preamplifiers and two Behringer DEQ's to adjust surround sound on the Kitchen system, and I could never remember which box or control did what.  Now they are all labeled.

20.  Verified acoustic response to 39kHz using M50.  I had a vast array of microphones and systems for measuring up to 40kHz.  Unfortunately, none of them were functioning completely, including my Mighty Mike, which needs a new capsule.  I need to create an usual adapter cable for my Bruel and Kjaer SPL meter which could properly power a few B&K capsules I have, but I've never gotten around to it.

So, in at least a second major purchase in 2021, I purchased my long time dream, an Earthworks M50.  I measured my system using that and my previous standard, a Dayton mike calibrated to 25kHz and compared the measurements.

It turns out my Dayton mike was essentially showing the correct response, with a few minor corrections in the very high end.

The HF curve is:  a dip to 17khz, a peak above 20kHz (the Dayton was showing that peak a bit lower than actual) and ultimately a steep decline in the upper 30's, but not going below the 17kHz level until 39kHz.  (The M50 shows about 4dB more response at 39kHz than the Dayton.)

I think a curve like this is fairly inevitable without a different supertweeter technology, such as my old ELAC 4pi, which could possibly be used now that I can create very steep phase linear crossovers.

Interestingly many of the highly regarded tweeters have peaks like mine in the 20-30kHz region.  Lousy tweeters have peaks in the 10-20kHz region, or steeply rolled off response at 15kHz.  The HF peak helps mitigate the loss of angular dispersion at the high end of a dome tweeter.

Of course, I do use a highly regarded cloth dome tweeter, I think one of (if not "the") best ever made for supertweeter usage, the Dynaudio D21AF, which the manufacturer rated to 40 kHz.  I only wish I'd bought a bunch more of these in the mid 1980's when I had the chance.

But the magic is also in my crossovers, etc.

Dynaudio's response curve doesn't show any peaks, however.  I think that's because it's an anechoic on-axis measurement.

Setbacks

1.  The Linn LP12 developed a terrible suspension wiggle.  I hope to have this fixed soon, but meanwhile I've been using the Mitsubishi LT-30, which isn't too bad I think, and this has also given me the opportunity to make transcriptions of 45 RPM records, which especially includes the ones from Reference Recordings.  I should also be fixing some of my other turntables.

2.  One of the two Emotiva Stealth DC Dacs used for amplifiers powering the Acoustat speakers failed.  This means I can no longer do A/B amplifier comparisons without changing cables.  I also hope to get this fixed soon.

Conclusion

Overall another excellent year for playing music and doing Audio Investigations and Improvements!