sounding too bright.
      Fourth, the music itself from the M6 is not spectrally balanced properly as the ear/brain perceives it from the maximum lobe axis, and this makes the tweeter output sound too bright overall, even though the M6 measures substantially flat on this maximum lobe axis. As noted above, the ear/brain perceives the M6's midrange (the region near the 2300 Hz crossover) as being tonally weak and recessed because the M6's total radiated power into the room is markedly less in this midrange region (due to the deep nulls in the radiation pattern here). But the upper frequencies, in the upper midrange and treble regions, are not as tonally recessed, since the M6's lobing pattern has its deepest nulls only in the vicinity of its 2300 Hz crossover. So, already in terms of total radiated power, the M6 has less energy in the midrange than it does at higher frequencies, so it sounds too bright.
      Furthermore, the midrange region around 2300 Hz contains music's lower overtones, and some fundamentals, all of which are usually (from most musical instruments) much stronger in energy than music's upper overtones (in the upper midrange and trebles). But the M6 reverses this natural musical relationship, making some of music's higher overtones sound stronger than music's lower overtones. Hence, the music sounds unnaturally too bright. In effect, the lower overtones, which are supposed to be the foundation for the upper overtones, are not strong enough to support the amount of upper overtone energy heard along the M6's maximum lobe axis.
      The relative contrast, between too little of music's natural overtones around 2300 Hz and too much at higher frequencies, is made starker and more obvious by the fact that the amount of energy change is sudden and takes place over a small spectral span. The midrange and upper midrange are immediately adjacent regions spectrally. The M6 puts out too little tonal balance total energy in the midrange (around 2300 Hz), and then suddenly jumps up to full radiated power output in the nearby and immediately adjacent upper midrange (beginning at 3000 Hz and extending upward). Our ear/brain's are very tolerant of non-flat tonal balances if the change is gradual over a wide spectral span, but very intolerant if as in this case the change is sudden over a narrow spectral span. This sudden jump in the M6 calls extra attention to the unnatural surplus of energy from 3000 Hz upward, relative to the immediately adjacent midrange region around 2300 Hz, thereby further making the M6 sound too bright when heard along the maximum lobe axis, even though that maximum lobe axis does measure flat.
      Incidentally, if you do want to listen to the M6 as we initially did, from the angle that puts you in the maximum lobe just as the manufacturer's design intends, you need to make a small correction to the instructions in the owner's manual. The owner's manual tells you to point the M6 straight ahead with respect to the room, with the tweeter side inboard. The normal listening angle to a loudspeaker location is about 22 degrees to 45 degrees, since for good spread of spatial imaging you normally place the loudspeakers about 45 to 90 degrees apart from each other (total included angle), as seen from the listening seat. But the maximum lobe of the M6 is actually merely 15 degrees off axis (on the tweeter side). Thus, if you wanted to position yourself in this maximum lobe and had installed the M6s pointing straight ahead with respect to the room as instructed, then you would only have 30 degrees included angle between the loudspeakers, not the 45 to 90 degrees needed for good spatial imaging spread. The solution is to locate the M6s about 45 to 90 degrees apart, as you would for other loudspeakers, and then disobey the manufacturer's instruction to keep them pointing straight ahead with respect to the room. Instead, toe them inward about halfway, so that they are pointing not directly at the listening seat but rather 15 degrees outward from the listening seat (you can sight along a protractor to easily do this).

Getting Better Sound from the M6 Drivers

      At this point in our evaluation process, we were disappointed, chagrined, and unhappy. Here was a very promising loudspeaker system, featuring innovative (indeed brilliant) systems engineering, great flexibility, and very good performance in some aspects, but distinctly mediocre performance in other aspects, the latter caused primarily by driver spurious misbehavior. Since we couldn't change drivers, there was nothing we could do. Or was there?
      We put on our Sherlock Holmes cap, and started letting our creative imagination run free. We had set up the Evolution system in accordance with the manufacturer's instructions. What if we tried constructively disobeying these instructions? In exactly what manner would we disobey them, and what sonic benefit could perhaps be accomplished by each such tactic?
      We realized that the radiation pattern lobe maximum we were sitting in, per manufacturer instructions, was boosting the problems from the midrange driver, especially because this lobe had its maximum boost in the 2300 Hz crossover region, just where the driver's spurious misbehavior seemed to be worst. So, we reasoned, if we simply rotated the M6 to get out of the radiation pattern lobe maximum, we would at least reduce the boost of the midrange's problems. Also, if we rotated the M6 to get farther away from the tweeter's frontal axis, we might ameliorate the sonic problems from its misbehaviors.
      But then an even simpler possibility occurred to us. Rather than rotating the M6, and conducting repeated experiments to find the best listening angle, we could simply keep the M6 pointing straight ahead (without rotating it) - and instead simply flip it upside down. Following the same reasoning as above, we realized that this might possibly provide even greater sonic benefits.
      Instead of merely curing the boost of the midrange driver's misbehavior above the nominal baseline, as wrought by the radiation lobe maximum, this tactic might even work to reduce the listener's perception of the midrange driver's misbehavior, to a level below the nominal baseline. That's because flipping the M6 upside down would reverse the relative horizontal positions of the midrange and tweeter, thereby reversing the relative time delay between these two drivers. This would place the listener at or near a usable regional null or minimum in the radiation pattern, instead of at the radiation pattern maximum, in the region of the 2300 Hz crossover where the midrange driver's misbehavior was worst (there are probably other minimums in the radiation pattern, but they are too far off the frontal axis to be useable as listening axes). In this radiation pattern minimum, the output from the tweeter would be effectively working to cancel a lot of the misbehavior garbage output from the midrange driver, in exactly that 2300 Hz region where the midrange driver's misbehavior was worst, because of the now reversed relative time delay in direct arrival paths to the listener from these two drivers.
      Simply flipping the M6 upside down could also provide other sonic benefits. It would place the tweeter on the outboard far side of the M6, so we'd be hearing the tweeter from farther off axis, which might ameliorate the hard brightness and aluminum coloration heard on axis, and also heard when listening closer to the tweeter axis as was the case when the tweeter was on the inboard side of the M6.
      Furthermore, flipping the M6 upside down might also improve spatial imaging, in two ways. First, it would dramatically reduce the hot spot localization effect that had effectively collapsed the projected image to just the loudspeaker locations. Second, it would aim that maximum radiation pattern lobe at the side walls. So long as the side walls are reasonably far away from the loudspeaker (to avoid problems from the Haas effect), the side wall reflections and reverberations thus created can do wonders to widen the portrayed stage width, so that it extends far beyond the loudspeaker locations, and even beyond the side walls of the room itself.
      Additionally, since the bulk of the peculiar driver misbehavior colorations would be aimed at the side walls, they would become part of the room's reverberation pattern, so their obnoxious nature would disappear amidst the random mixing effects that room reverberation accomplishes.
      So we tried simply flipping the M6 upside down, in situ. Wow! The M6 was utterly transformed, into a totally different loudspeaker. Of course, the sonic difference most immediately noticeable was the M6's drastically different tonal balance when flipped upside down. Instead of being aggressively bright, its tonal balance became very mellow. But that's OK. We humans easily adapt to and accept different tonal balances.
      Even when we go to concerts to hear live music, the same orchestra will have a drastically different tonal balance in different halls (an old plush hall vs. a bright, modern concrete hall), and indeed will have a dramatically different tonal balance when heard from different seats in the same hall (near vs. far seat, down low vs. overhead side balcony seat). We accept all these very different tonal balances as still representing the genuine sound of live music, so we can be similarly accepting of such different tonal balances in our playback chain. You might personally prefer one tonal balance or the other (bright or mellow), just as you might prefer one concert hall or a certain seat location in a concert hall, and that's fine. But we can become accustomed to both, and both can be acceptable.
      The second big sonic difference was that the excess quack and brightness that was previously so bothersome simply went away. And, remarkably, it went away from both the midrange and tweeter drivers. The excess quack from the midrange driver was due to its spurious misbehavior in the 2300 Hz region, and that was now being largely cancelled by the tweeter's output in the same 2300 Hz region. That's because the tweeter's output was being delayed just enough along this listening axis, so that it arrived at the listening position in inverted polarity relative to the midrange output within the 2300 Hz region. As to the tweeter, its excess brightness (for the rest of its operating range above the 2300 Hz region) went away because we were now listening to the tweeter farther off axis, with the tweeter now being located on the far side of the M6's front panel instead of the near side.
      Incidentally, because the M6 has this deep 2300 Hz valley in its total radiated energy, it is necessarily confined to being a polite or recessed loudspeaker in this presence spectral region that gives up front immediacy to other loudspeakers. Thanks to the M6's flexibility, you can change its tonal balance personality in other spectral regions - at higher frequencies, in the upper midrange and treble regions, and at lower frequencies, in the warmth region (and bass regions as well with the flexible Evolution system subwoofers) -- but you cannot change the midrange politeness and recession due to the depression in total radiated energy around 2300 Hz.
      You could try to compensate for this by listening on the manufacturer recommended axis, 15 degrees off axis on the tweeter side (and at tweeter height), so that at least the first arrival direct sound is boosted in the 2300 Hz region to have measurably (but irrelevantly) flat response. But this 2300 Hz boost at this axis largely consists of spurious misbehavior from the midrange driver's dust cap, so it sounds artificially foreign, as noted above. And, as noted above, this also severely degrades spatial imaging, creating localizable hot spots at the loudspeaker locations, since this boosted lobe around 2300 Hz is not also fed to the room's reverberant field, so the ear/brain locks in on the location of the source of this inconsistent excess of direct first arrival sound, and also since the ear/brain is attracted to the locations of these spurious breakup misbehaviors that are obviously coming from the driver locations and not from the portrayed image as reproduced from the recording.
      If you wish, you can utilize the M6's flexibility to crank up the M6's warmth region (choose 0 setting for Boundary Switch) and upper frequency regions (choose inverted polarity connection, and sit at tweeter height in maximum lobe with tweeter inboard), so that these spectral extremes are much louder than this recessed 2300 Hz region, to turn the M6 into a boom and sizzle loudspeaker, as many other home theater loudspeakers inherently are.
      Or you can choose (as we did) to make the M6 a flatter, more neutral sounding loudspeaker, by using the flexible M6 choices to dial down the spectral extremes, the warmth and upper frequency regions, until they more closely match the tonally recessed 2300 Hz region. This choice makes the M6 a mellow loudspeaker, but this is consistent with its polite tonal recession in the midrange, and it is a generally well liked and accepted type of sonic personality for a loudspeaker (the so-called New England sound).
      In other words, since we must live with the M6's tonal balance politeness in the 2300 Hz midrange region (due to the total radiated power from its total radiation pattern being depressed here), we might as well make all our other choices, with respect to the M6's admirable flexibility, such that the M6 becomes as tonally consistent and uncolored as possible, by making the M6 into a mellow loudspeaker that plays real sounding music. We think that this choice is far preferable to trying to boost the 2300 Hz region by listening on the axis where the drivers' misbehaving colorations are the worst, since that tonal boost in the 2300 Hz region energy (as well as at higher frequencies) is largely composed of obnoxiously artificial sounding colorations, thereby changing the M6 into a loudspeaker that plays its own artificial colorations instead of playing just the music.
      Which brings us to the third, and most important, sonic difference: with our new listening axis the M6 dramatically morphed into a loudspeaker that played music, and only music, instead of being the loudspeaker that it had been, a loudspeaker that also loudly played its own misbehaviors. All the various sonic problems that we had previously heard from the drivers' spurious misbehaviors (both the midrange and tweeter drivers) were audibly, incredibly, almost magically, simply gone. The artificially added foreign material colorations (crinkling plastic dust cap from the midrange, breaking-up metallic aluminum dome from the tweeter), that were previously so salient, magically were audibly gone. The ugly time smearing of the music, from the lingering of these spurious misbehaviors, was audibly gone. The seeming modulation distortion, caused by this spurious misbehavior garbage being modulated by the music signal, was audibly gone. All that was left was the music. Suddenly, with one stroke, the M6 was transformed into a loudspeaker that played only the music, instead of also playing its own obnoxiously irritating misbehaviors.
      Of course, we knew intellectually that these driver misbehaviors were still occurring. But, because they had been dramatically reduced in perceived amplitude along this listening axis, they were no longer audible in relationship to the main music signal.
      When we previously had listened along the horizontal axis of the M6's maximum lobe, these driver misbehaviors had been boosted above the amplitude of the main music signal (whose loudness is determined by the overall energy radiated into the room from the loudspeaker's whole radiation pattern), and unfortuitously the biggest boost came in the 2300 Hz crossover region, precisely where the dust cap of the midrange driver exhibited its worst misbehavior. But now we were hearing the M6 along a different horizontal axis, an axis where there is a minimum instead of a maximum in the radiation pattern, especially in the 2300 Hz region. Heard along this axis, the midrange driver's spurious misbehaviors in the 2300 Hz region were now reduced to an amplitude below that of the main music signal, whereas before they had been above the amplitude of the main music signal. Evidently, their new, reduced amplitude was enough below the main music signal so that they dramatically became substantially inaudible, relative to the main music signal.
      Note that even the best, most expensive drivers still exhibit spurious misbehaviors, since all real physical materials do misbehave at some point, in the stressful driver environment. The best one can hope for, with even the best and most expensive drivers, is to tame these misbehaviors so that they are far enough below the main music signal in amplitude so as to be substantially inaudible. And that is what we were able to achieve, in one simple stroke, with the M6 drivers.
      Incidentally, it's interesting to note how this dramatic sonic improvement involves a literal reversal of fortune. Back when we were considering rotating the M6 to get out of its maximum lobe, we suddenly realized that, by instead simply flipping the M6 upside down, we could literally flip its fortune upside down, changing bad luck into serendipitous good luck, and thereby changing a lemon into lemonade.
      Recall that it was the M6's unfortuitous bad luck that the spurious misbehavior of the midrange driver's dust cap was in the 2300 Hz region, while by unfortunate coincidence the M6's crossover frequency was also the same 2300 Hz, which meant that maximum lobe of its radiation pattern also had its greatest emphasis in the same 2300 Hz region, thereby emphasizing most the very region where the midrange driver was misbehaving its worst. We suddenly realized that this same unfortunate coincidence could be completely flipped around to become a great advantage, simply by flipping the M6 upside down. With the M6 flipped upside down, we were now sitting in a minimum (instead of a maximum) of the radiation pattern, and that minimum, like the maximum, had its greatest effect (here attenuation instead of boost) in the 2300 Hz crossover region.
      Thus, the coincidence, that the midrange driver has its worst spurious misbehavior in the same 2300 Hz frequency region as the M6 crossover happens to be, was flipped from being an unlucky coincidence into being a lucky coincidence. The fact that the crossover frequency is in the 2300 Hz region means that the radiation pattern minimum is most effective at its attenuation in this 2300 Hz region, and that just happens to luckily be exactly the same 2300 Hz frequency region where the midrange driver's worst spurious misbehaviors need the most attenuating.
      The ugly, artificial colorations from the tweeter also vanished along this new horizontal listening axis. In this case, the sonic improvement was due primarily to the fact that we were now listening sufficiently farther off the tweeter axis so that its misbehaviors were no longer audible. At this new horizontal listening axis, the tweeter no longer sounds excessively hard and bright, and the ugly artificial aluminum coloration is not audible. Instead, the tweeter now sounds sweet and polite, giving just a gentle ting or sheen of upper treble overtones to triangles, strings, etc.
      The fourth, and also very important, sonic improvement from flipping the M6 upside down was a total transformation of the M6's spatial imaging. The quality of the M6's spatial imaging improved so dramatically that it went from a mediocre rating, rocketed past pretty good and good ratings, and became very good. Suddenly, the hot spots at the loudspeaker locations were simply gone. This improvement was due mostly to the fact that the spurious misbehaviors of the

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