Since writing the original query, and only just recently, I've done a couple of major changes to the studio speakers (LaScalas). I was finding that in the much larger space of the studio, and with the very loose wood floors sucking up much of the bass, that they speakers occured to me to be out of balance. I went back to the ALK crossovers which allow some tweaking in the form of varying attenuation in the Squawker. In the smaller room in my home that the speakers were once in (see my system pics) I preferred the AA crossover with the ALK sounding less 'musical' to my ears there (for lack of a more authorative description - I did go back and forth extensively). In the hayloft that is my studio, the ALK's worked wonders and actually sounded better than the AA's. I found also that the recording in question, which remains a favorite, sounded a bit better, but still displayed similar, albeit less pronounced, breaking up at those highest notes. OK, so recently I tried switching tweeters from the stock K77, to a pair of Fane tweaters (English made, used in Edgarhorns - very sensitive. Huge magnet. Slot tweeter). Initially I thought the new tweets sounded a bit hot (110db efficiency was a bit too much), but they did display a remarkable improvement in smoothness and clarity in the high end. I contacted Al Klappenberg, who was kind enough to consider the specs on the Fanes and run the figures through his filtering program to suggest a pair of resistors to pad down the tweets about 6db. He'd nailed it and, with a slight bit of tweaking with the Squawker settings they now blend in seemlessly, and that clarity is remarkable. So the other upshot of this is that I put that very CD on as a test just the other day and low and behold, those highs are no longer distorting anywhere nearly as much. In fact, I can barely perceive any at all. I have to listen again to prove this to myself, but I was quite amazed the first time round. I've also changed amplifcation sources at home since posting this and have yet to try it there. More to come......
Marco