the silk dome tweeters can make a HUGE difference... i auditioned a pair of boston acustics that were their top end model, they were using a titanium tweeter, they sounded alright, but like your saying the highs were just to bright for me... next i auditioned a set of Dynaudio speakers.... with a silk dome tweeter... the Dyn's sounded WAY better to me, and thats what i ended up buying. It was ALL because of the tweeter, so like someone before said, maybe the m60's just aren't for "you" or aren't for you anymore.. maybe you would be happier with a pair of ERT-8.3's..
one has to keep in mind this hobby is VERY subjective... you can show a bunch of charts to someone, but at the end of the day, EVERYONES ears are different, so no matter what the numbers say.......
on the M60's one thing you might try... get a piece of tissue paper and some scotch tape, and tape a piece of tissue paper over the tweeter, see if that does anything... I do realize this is not the most scientific approach, but I'm sure you have these items lying around the house, and it would only take 5 minutes.. worth a shot right?
In a previous post I stated that earlier I had actually taken a shop towel and tri folded it and taped over both tweeters, left and right and that knocked out quite a bit of the shimmer that seems to get to me. It was a lot more than just tissue
