New System Photo Explained

The previous living room system photo was very outdated.  Taken in mid 2010, it showed the Krell, Acoustats, Elac supertweeters and SVS subwoofers.  The speakers are the same but the Krell is now offline (and to the side, still visible in new photo), having been functionally replaced by the Aragon 8008 BB.  The listening position has been moved up to 3 1/2 feet from speakers, the most important change of all.  Normally facing straight ahead, the listening chair is rotated in the photo to avoid hiding all the equipment, but is otherwise in correct spot.  And now there are additional piles of equipment to the left and right of the two center components.  From left to right and top to bottom, here are the electronic components:

Far far left:
120VAC to 240VAC hammond stepup transformer (for KT-6040)
Radio Shack Remote Extender

Far left:
Jenson Iso-Max...used to isolate ground from Kurzweil K2661 cables and convert to unbalanced
Behringer DEQ 2496...used to equalize output of Kenwood KT-6040 tuner from Europe.
Classe CP 35...used (sometimes) to amplify output of Kurzweil providing 10dB more gain
   Could also be used for transformerless input and conversion to unbalanced
Pioneer F-26...classic analog super tuner, used for living room system only
Kenwood KT-6040...digital remote tuner used whole house through Sonos
Sony CDP-507...original CD only player used for guest CD's

Left:
Aragon 8008 BB...amplifier for Acoustats full range above 80 Hz

Right:
Sonos ZP 80 zone player
Behringer DCX 2496...3 way digital crossover with delays and eq
Tact RCS 2.0...main system preamp, selector+level+eq, room correction not used

Far Right:
dB systems 5 way selector with teflon jacks
Lavry AD 10...digitizer for F-26 and Denon 5900
Denon 5900...universal DVD, DVD-Audio, SACD, HDCD player
Acurus A250...power amp used for super tweeters
Belkin UPS and audiophile power conditioner...used for all except Aragon

RTA not working on Samsung Galaxy S4

Literally, the application named RTA does not work correctly on the Galaxy S4.  It is unable to show an interesting graph of pink noise response from my living room audio system (pictures below, sorry they got turned upside down somehow automatically).  Furthermore, the response shown doesn't vary much with orientation of the phone from the listening position.  Whether I point the front of the phone at the quite directional electrostatic speaker or not makes very little difference.  (That lack of directionality might be good for some things, like measuring actual noise exposure, but bad for measuring specific sounds or system responses.)  In case you are prepared to argue the problem is the ultimate SPL limit, which may well be around 90dBA as it is for other Android phones or so I have read*, I tried measuring at two different system SPL levels, which were around 75dBA and 65dBA, and they showed the same uninteresting picture, simply having an enormous peak around 8kHz and rolling off dramatically above and below that by 10's of dB's.  (Tthe left is 75dB upside down and the right is 65dB turned left.  And, strangely enough, it matters little which way the phone is turned, just as the pictures might suggest, but actually I had the phone laying flat in the same direction for both pictures.)

In contrast, the application named RTA on my iPhone G3 shows a very interesting and plausible frequency response of my living room system, broadly flat through the mid to highs but with a few peaks and dips below 600Hz, and then rolloff at the very lowest and highest frequencies.  I'm sure the rolloffs at the top and bottom are iPhone limitations, I have 16Hz-25kHz nearly flat response, but I think the rest is fairly accurate, or if not, it's simply the result of 4 and a half years of smartphone wear or careless measurement technique resulting in minor reflections.  The picture changes in interesting ways depending on orientation--notably the extreme highs get flatter when the bottom of the phone is pointed right at the speakers.  That's what I mean by an 'interesting' picture, when you make changes, you can see their effect reflected in the graph.

A different Android app running on the Galaxy S4 gives an equally plausible but different picture.  This is from AudioTool, the paid version:

Because AudioTool does show plausible response, I suspect the problem is that the default calibration of the free version of RTA isn't good for the Samsung Galaxy S4, and unfortunately you can't change the calibration on the free version.

(*I don't know why Android phones are limited to 90dB.  Tiny capsule microphones usually have a much higher limit, something like 110-140dB.  The iPhone SPL app can measure up to about 105dB, but that could be because the app is automatically compensating for known microphone compression.)

Types of Listening

1) Annoyed listening (e.g., neighbor's dog barking).

2) Enjoyable Background Music Listening

This is fine, even if audiophiles consider it inferior to the point of condemning it altogether.  One can't always devote full attention to music, in fact, for most of us it's rare to have both the time and inclination together.  So having pleasant background music can be one of the greater joys in life, if done well.  I prefer the absence of talk altogether, but can listen to non-commercial radio also if there is minimal talk.  One of the radio programs I used to love to hate was "Adventures in Good Music" which seemed to be more talk than music.  Whole house music systems like the Sonos I use are helpful, as were auto-reversing tapes, and FM radio.  Internet radio based on lossy compression--I don't like it much.

Background music listening can't provide the intense pleasure that serious listening can.  But because it is something can can be done over a relatively larger proportion of one's time, and I'd say in principle the more the better, it can constitute a large part of audiophile enjoyment.  It should not constitute ALL of the enjoyment, for that would be saying that NO serious listening was being done.  But taking up about 95% of one's total system playing time, and providing about 50% of the total enjoyment, sounds like it would be about right for a working person with many other interests.

3) Serious Listening

You can't be doing much else while doing this.  Drinking a wine or beer, maybe, but even that's pushing it.  But rather than concentration, the goal is relaxation, relaxation into the music, not thinking about much else, letting thoughts go away generally, including thoughts about the qualities of music systems.

4) Comparative Listening

Listening to more than one system variation with the aim of determining differences and establishing relative or absolute quality levels.  This is most definitively "Comparative Listening" when done in one listening session or a planned series of sessons.  But long term comparison is possible also--so basically what determines whether listening is comparative or not is the degree to which thoughts about audible differences arise in the mind at the time.  So while I do little but long term comparison anymore...I'm still guilty of comparative listening, though to a lesser degree than some.

This is what audiophiles are known for.  However, contrary to some self-appointed categorizers, there is no essential need to do this to be 'an audiophile.'  As stated in an earlier post, 'an audiophile' need only be enthusiastic about music reproduction, not necessarily dedicated to the labor of improving audio systems through comparative listening, component substitution, and/or tweaking with accessories or special treatments.  I'd suspect that too much of those latter things, and one is well on the way to audio burnout.

Besides which, comparative listening as it is usually done should not be taken seriously.  At minimum, comparative listening should be done Double Blind, where even the experimenter doesn't know which equipment has been chosen.  And level matched.  Any results other than those from a level matched double blind test should not be taken seriously at all, ignored, or not even thought of if possible.  It is very easy to be wrong, our expecations and pre-conditioning (including, the previous playback) can easily dwarf actual equipment differences, and usually do IMO.  Unfortunately, most audiophiles I have met seem to lack the mental compartmentalization to doubt their own hearing sufficiently, in which case I'd suggest they'd be better off not doing comparative listening at all, because any judgements made are likely wrong, and after awhile a large set of wrong or random judgements may cascade to very wrong audio configuration or (just as likely) audiophilia nervosa, when one can't enjoy listening to anything anymore because of the feeling it needs improving somehow.

The reference is double blind testing (which includes ABX type) in a full trial of at least 30 trials, testing to a 95% confidence interval.  This is a lot of work and very hard to do well.  I have conducted 3 full blind tests in my lifetime on a well regarded audio guru.  Not one of those tests came close to the 95% confidence interval.  The audio guru chose the tests because he felt he could not fail on even one choice.

I make Comparative Listening a special category of listening because...it is fundamentally flawed.  Thinking of the need to make comparative judgement not only takes out much of the inherent pleasure in listening to music, it makes itself impossible.  A correct comparative judgement can only be after the fact of listening.  It need not be long after, it could be mere seconds, and that may be the best for some kinds of tests.  But once comparative listening is the goal, it becomes impossible NOT to think about the ultimate conclusion, and such thinking makes it impossible to feel the inherent pleasure, which is what the comparative judgement should be all about.

Ghostly Heifetz sound made real

Just before breakfast on Monday May 27, 2013 (Memorial Day Observed) I decided to do no work not urgently needed.  So while I would wash underwear (urgently needed) I wouldn't bother mowing the front and back lawns, let alone thinking about any of the other million-and-one chores that were still undone (and mostly still are).

I like to make this 'no work' rule from time to time when I can, a virtual sabbath, since I often find myself dreading the endless-weekend-work even more than my job, and don't have the organization and whatever-it-takes to get all my infinite household chores done during the "week" (M-F) itself, something that some lifestyle coaches say is a very good idea (leave the weekend to socializing and fun).

And I find a virtual sabbath helps focus the mind in a strange way.  If on the other hand, I decide to mow the lawn on a weekend day, that does usually get done, but little else worth speaking about.  What little time there is for relaxation on such a day generally gets spent on the easiest and least spiritual forms of relaxation.  Yes there are lots of things easier than sitting down and seriously listening to a full disc of music--a task so difficult, in fact, that many audiophiles never do it, I am finding.

Having acquired a rule-bending personality, I don't like to make my virtual sabbath a day that must be spent doing uplifting things....like listening to entire discs of music.  That would be a very tough rule, and I'd never follow it.  Rather, I let things happen.  Eventually, given that I never have to something physically demanding, I will eventually get around to the spiritually uplifting things.  After doing everything else, as it were.  And this Memorial Monday, I actually did.  I got around to doing these uplifting things:

1) Watched four 30 minute lectures from The Great Courses on Complexity.

2) Read the preface and first two chapters of J.M. Keynes' masterwork, The General Theory of Employment, Interest, and Money.

3) Listened to the Heifetz Concertos disc from the RCA Living Stereo series on Hybrid SACD.

OK, #3 was the very last thing I got around to.  By 12:30 AM (actually Tuesday Morning if you follow the rules) my eyes were blurring to the point where no more reading or watching would be possible.  At this point, listening to music with eyes closed would be the best thing to do.  And indeed it was!  I enjoyed the entire disc, only falling asleep a few times...

Unfortunately, I didn't listen very critically at first, mainly focussed on my obsession with the center of the image, which requires small left and right movements of the listening chair to correct.  After that, it was a long time before I noticed something about Jascha's violin.  It was sounding ghostly.

Thinking of that had me laughing, and helpfully helped wake me up a bit.  Of course Heifetz sounds ghostly, he's been dead for decades!  But while the thought might have been funny, I clearly wasn't getting the best sound.

The fix was simple.  I turned up the level.  These classic recordings are recorded at a very low average level...allowing incredible dynamic range, and also (I am guessing the engineer's intent) hiding the analog noise level.  Turning the volume all the way up to about -1dB relative to 0 (actually, the Tact showed 92.1 and 0dB is 93.8) made it sound just right.

I am running the output of the Denon 5900 into a Lavry AD10 set to maximum gain.  I think this leaves about 2dB of analog headroom, thus my -2dB was actually -4dB relative to the recoding.  But still, even -4dB is an impressively high volume level for my system.  Most of the time I have the Tact set to something around 80.0, which would be -13.8dB.

After cranking the level, I was thinking how this compared to modern recordings.  Modern recordings would most likely sound cleaner, clearer, more transparent.  This recording has a warm fuzzy glow.  However, the warm glow compliments the music and makes it soaring, never edgy.

Polymer Audio Research Speaker

On May 12th, I attended the demonstration of the Polymer MKS loudspeaker by Polymer Audio Research at a meeting of the San Diego Music and Audio Guild.  I was glad to be able to attend this meeting if for no other reason than it was the first audio society meeting I have attended in over two decades.  At one time, and for about 9 years, I was the President of the San Diego Audio Society.  That was from about 1982 to 1991, and I haven't attended an audio society meeting since.  Not by choice, though arguably by laziness.  I moved to San Antonio Texas in 1992 and there hasn't been an equivalent organization here that I was aware of.  The only purist audio store in San Antonio is that of Galen Carol, who opens his home to prospective audio shoppers by appointment only.  The local Bjorn's dominates audio and video storefront space at the high end, but is primarily oriented to home theater rather than audiophiles.  There was a purist store called Concert Sound from which I bought a Linn turntable in 1998, and the owner expressed interest in having me operate an audio society here, but the store closed sometime not long after I bought the turntable.  Speaking of laziness, even when I was an audio society President (I think I was chosen or chose myself by default as the original organization created by Ike Eisenson was otherwise crumbling) I did very little, mainly just printing announcements for meetings that were mostly arranged by Bruce of Stereo Unlimited, one of the most well known high end audio stores in San Diego.  Even then, I rarely talked to Bruce directly, but instead had details provided to me by my friend and brother-in-law George Louis.  After I left San Diego, my friend George has retained ownership of the San Diego Audio Society name, but the more functioning successor volunteer organization is the aforementioned Guild.  So for me this was a reunion of sorts.

The location was an incredibly beautiful home at an incredibly beautiful spot on the shoreline at the southern edge of La Jolla, having a commanding view of Pacific Beach to the south.  The meeting was held in the living room which was joined with the kitchen and dining area in a unified space surrounded on two sides with large windows showing the surrounding views.  Virtually all the exterior wall space was covered with large super premium unscreened windows with no curtains or blinds.  I would guess the room to be about 40x25 feet or so, nearly as large as my entire house.

As George and I arrived just before the official starting time, the people from Polymer Audio Research were busy trying to get decent sound by slight adjustments in the speaker position, and removing hum apparently apparently picked up or caused by the speaker wire, which was two large separate conductors for each wire.  By the time the meeting started, the hum problem was mostly fixed, but the sound had not been well optimized.  As Roger and I agreed, they probably should have allowed a whole day for proper setup.

While the overall presentation had some good points, and the speaker itself seems to have many virtues, the sound was far from perfect.  It varied a lot by position in the room.  During the setup phase, somebody said that the best listening position was standing behind the sofa, and that was later repeated.  Well that position did seem to solidify the bass a bit, though the bass was irregular everywhere in the room (surprising for such a large room).  But the behind-sofa position on the center axis was one of the worst locations for a pleasant midrange.  From that position, the midrange was hazy, ill focussed, recessed, and slightly edgy.  The midrange was much better sitting on the sofa itself on the center axis, or even leaning forward a foot or two.  One of the key factors seemed to be the listening height with respect to the tweeter axis.  On or below the tweeter axis, the midrange was best, it quickly became unpleasant above the tweeter axis.  And all the listening positions from the center of the sofa on back were too far back for correct imaging, an proper listening triangle would have been about 4 feet in front of the sofa.

The bass had a different set of irregularities at each position, being slightly more forceful overall behind the sofa, but not really better overall.

My take was both a problematic room and a not-quite-perfected speaker.  I suspected the speaker had crossover and baffle related issues that tend to give it high frequency irregularities above the tweeter axis and edginess.  Notably the baffle seems truncated at the top, diffraction might be improved by extending the box (and the inward curvature) up by another 3-9 inches, more of an egg-shaped top.  About the crossover I don't know what needs to be done.  I suspect physical driver time alignment would help, or anything that improves performance above the tweeter axis without compromising it elsewhere, and perhaps adjusting tweeter level lower.  The people from Polymer audio said the crossover was intended to be very steep, but implemented with few parts.  Perhaps they chose the wrong tradeoffs here.  Crossover design is an art, ultimately like violin making.

While making these guesses, let me say that the room was unremittingly hard, with all ceramic, glass, wood, and plaster surfaces, and that huge number of identical windows.  Such a room might be better designed with each window to be slightly different to eliminate shared resonances, acoustic absorbers at key points.  I see the homeowner has a room correction system, which was not used for this demonstration; Polymer audio brought their own playback system including amplification--Linn amplifiers no less or more.  The amps might have contributed a tiny bit of edginess to the sound.  Further, a key factor was that the vaulted ceiling reached a peak in front of all listening areas.  This reflects all manner of delayed sounds to the listeners, smearing the image.  Vaulting running along the axis of the speakers is *much* better because it lacks this problem.  All manner of damping at the peak is possible (but maybe not visually acceptible) and also, what I did(!),  move the listening position in front of the peak.  That also combines with a flattened listening triangle, subtending about 75 degrees from the listener to the speakers, and a 4 foot listening position to 8 foot high speakers...so the speakers (not the room) dominates--that's what I did to mitigate my transverse vaulted ceiling.  Well the owner of this home could do something like that by ditching the coffee table and putting chair much closer to the speakers.  Actually...his speakers were further back (up against the back wall) and farther apart, subtending a better angle and possibly getting some useful bass augmentation.

Polymer Audio Research made the point over and over of using the best parts available in this speaker, and I don't doubt it.  But always, it's always the design that counts foremost.  Polymer Audio Research is a relatively new company, and perhaps they haven't learned the best way to design yet.  I'm not saying I know the best way either, but I know I've made a lot of mistakes, and it took even longer to realize I made mistakes, so at least one principle is...it takes time and experience.

On the plus side, the speaker was clearly undistorted even in this large room, a testament to the driver and enclosure quality, which IMO is worth the price in that you are getting what you are paying for (you are just not getting the performance it should be capable of, IMO, but this was not a fair test either).  In such a large room, it's nearly a miracle for such a compact speaker, with two small woofers, to fill it as well as it did (pretty well, with noted room-related irregularities, and not sub 30 Hz).  I don't think a speaker like this should be used without subwoofer in such a large room, but a test like this shows it should be able to handle smaller rooms with ease, if you can stand (or better, sit) the way it sounds.

What is an Audiophile?

I like the Wikipedia definition, also found elsewhere, an audiophile is someone who is enthusiastic about sound reproduction.

A friend of mine, George, objected to this.  "That's a definition not written by audiophiles...what do they know?"  He had been trying to make the point that by not bringing a set of personal CD's to a friends house recently for an audiophile listening session, I showed that I was not an audiophile, or not like an audiophile, for certainly any true audiophile would have done so.  This was really a rhetorical argument which was part of another argument criticizing a mutual friend Roger for the way he hosted a previous listening session at Roger's house, starting with ten of Roger's own favorite recordings, rather than jumping into to trying other people's favorite recordings first.  George complained bitterly about having to listen to the whole tracks also.*  The next day George strong statements that of course I--Audio Investigator--am an audiophile, and it would have been ridiculous to say otherwise.

(*Actually, the very first track was interrupted to reverse polarity, at George's request, and likewise many other of the first ten tracks were played in both polarities, with as many as three partial track plays, with George asking many questions to all of us about the perceived differences.  So it was ridiculous that George was complaining...he directed the entire listening session nearly from the start, albeit playing Roger's recordings at first.  But George's urge to control is rarely satisfied. I ignore his demons when I can and love him anyway for his energy and charm.  BTW, he also well knows but usually ignores that I do not believe absolute polarity even makes an audible difference in most playback, let alone being a peculiarly important factor worth endless replays to get right, as it seems to him.  Nor do I believe that most quality players differ in their polarity (no CD players that I have tested differ, including a few specific models he still believes different), that most but not all recordings are wrong, etc., and his whole conspiracy theory about polarity obfuscation.  I've written my specific evidence and arguments before, and will get to that corpus soon when discussing George's most recent negative finding double blind test results submitted in 2012.  As a quick overview, I made some double blind tests for him, and a program designed to create more such tests at will, in 2010.  It took him until 2012 to submit his choices in a same/different test made to his specifications with music tracks he specified.  A significant relation between his choices and the actual polarities was not found.  He did get a slight majority of choices correct, but that would have statistically useful meaning only in a large number of similar tests.  It's also in direct contradiction to his questions, before submitting results, about what I would think if he got all answers correct.  George not only claims to know polarity with his own system and chosen recordings, he can hear it outside a building before entering, on a strange system with strange music.  He is questioning renowned makers of CD players, and recording engineers, about errors he hears with no other knowledge.  The prior from his standpoint should be near certain correctness, making every error count against.  So I think the results should be a big setback for perfect polarity punditry, not an incremental advance.  Admittedly, it doesn't do much for us critics, like me, who had the prior of 'he doesn't hear polarity consistently enough to be useful'.  Of course, George is free to try again with same or corrected paradigm. And I will keep this blog updated with results.  I will have to review old emails for the actual numbers on his official polarity test submitted in 2012.  BTW, I think George may be sometimes be hearing issues in system asymmetry, polarity may cause other effects in highly asymmetric systems.  But he has made certain errors, I am sure, in system reports, for example his saying the Oppo CDP-95 is out-of-polarity with classic CD players like the Sony CDP-507.  I have measured both, easily, as having the same polarity.  He fails to recognize those errors, and only quits arguing for time.  I have tried to argue with him many times that unless he is absolutely sure about his criticism of major players and recordings, he should say nothing.  Best not bear false witness.  He insists he is absolutely sure, despite my disagreements, he finds fault with my test signals, or my use of oscilloscope, and renders that his Cricket polarity tester agrees with him in these cases, though he concedes it is not perfect (I thought I once explained exactly why the Cricket makes the errors that it does).  I pity those equipment producers, recording engineers, and reviewers, who are subjected to this polarity folly.  But it is hardly the worst in the world, and one can hardly expect all audiophiles not to be cranks--in fact, if ever there were a world of cranks, it would be audiophiles..  George is just the clown who does it more perfectly than anyone else, shamelessly, and he claims to do both, but with all the science, there seems (to outsiders but extended family members like me) no time not for advancing the science, so business, apparently, comes first, enjoyment only shared with work.  A recipe for dullness.  Brilliance in defending his ideas, dullness in remembering your response to his repeated question, or from withdrawing from your unease.)

After all, George's argument continued, how can you properly judge an audio system without playing CD's you are familiar with, he continued in an argument that lasted for quite a while.  I conceded that using personal CD's for comparison might be a good idea for doing comparisons, but there is no rule that audiophiles even need do such comparisons at all.  They might simply use equipment deemed by themselves or others to be sufficiently good for enthusiasm, and then enjoy how well such systems reproduce music.  Further, even if audiophiles do comparisons, there is no requirement that they always do so with personal reference recordings.  Audiophiles can and do in many cases make comparisons to the absolute sound, to how similar any given reproduction compares with live music they have heard at some time, or the sounds of particular instruments, etc., and not necessarily limited to the relative qualities of a particular recording.  Or they can simply react as pure subjectivity, how the reproduction made them feel, with no assertion regarding it's accuracy or general tendency to do so.

I like the Wikipedia definition because it gets right to the point and doesn't take sides.

Many audiophiles are constantly taking sides, and the world of audio is full of different schools of thought.  In my opinion most of this is pure waste, the result of endless commercialism among other things, and especially the commercialism regarding tweaks (cables, for example) that rarely make an audible difference IMO.  So each tweak maker, or critic of such tweaks, invents a new school of audio thought to explain and justify their ways, since they may relate in contradictory ways to commonly accepted audio engineering principles.  BTW, one of the best studies on the audibility of absolute polarity published in the Journal of the Audio Engineering Society by renowned engineers concluded that absolute polarity is not generally audible on loudspeakers with complex music, even though it can easily be discerned with certain test signals on headphones.

And it was ironic that George was making this argument at all, given the long history we've had of related arguments.  Way back long ago, maybe 30 years or so,  George made an argument that recording engineers who have pre-knowledge of what a recorded event sounded like at the time have no special knowledge beyond those of a discerning listenter, like himself, in judging a playback system.    After all, George argued, it was not the satisfaction of the recording engineer which was desired, but his  own, from the playback using his own system.  Therefore, only he, George, could be the judge, and he would be the judge using his favorite recordings.

More speaker fine tuning

Some of the response curves showed a bit of peaking above 6khz, that had me concerned that I was too much on-axis with the acoustats.  One needs to be slightly off axis for the best sound, this can be tuned best by ear, but measurement sometimes helps too.  I have felt quite often in the past few months that my close-up position was too much on-axis, having a slightly peaky sound.

So I moved both speakers slightly straighter, by first angling out the super tweeters about a half inch, then moving the speakers to match.

After doing this I also measured the speaker distances to the nose-position microphone.  I was very surprised to find how short the distances are now, about 40 inches to the center of the panels.  But the left side was clearly shorter, I first measured 36 inches but 38 seemed more accurate, whereas the right side was at 40 inches.

So I moved the left speaker back as much as I could, which wasn't much, hardly an inch.  When doing the full system response curves, there was still a slight gap between the impulse in the right and left channels, the left channel still seemed to measure about 0.03 ms faster as if it were about 6mm closer.  BTW, that is a fraction of an inch, about 1/4 inch.

I decided to fudge this one with the Behringer DEQ.  I dialed in short delay of 0.03 in the left panel and  added 0.03 to the existing delay for the left tweeter also, figuring it might be more delayed now.  It seemed that after I set the "unlink" option globally, I could set short delays separately for each channel. I had not figured that out before.

This yielded a measurement in which the impulses for the two channels exactly lined up.  But in listening, it seemed slightly skewed to the right.  So actually I reversed the DEQ setting, dialing in short delay for the right panels only of 0.03 ms, and undoing the delays I had previously added on the left.  That sounded correct.  I can't explain why, perhaps I don't have the microphone positioned correctly or my head is slightly asymmetrical.  In principle I could have moved the panels.  I chose not to do measurements after making this final tweak by ear, since the measurements seemed to steer me wrong on this one.

Another change I made was to reduce the bass levels on both sides.  The bass has been sounding a bit boomy, and the measurements showed  a rise in bass below 80 Hz and the left channel rising above the right in the bass below about 40 Hz, so I took about 1.5 dB off the right sub and 3.0 dB off the left sub.  That seemed to make both the measurements and the sound better, but I subsequently noticed that the Tact measurements are inconsistent, even averaging 40 trials, sometimes the right channel exceeds the level of bass in the left channel all the way down to 20 Hz, and other times left channel has more below 50 Hz.  So some additional relative subwoofer adjusting may be required, about a dB or two, but the current adjustment is an improvement in reducing the boominess if not level matching.