my pair of CDM1 - bought in 1998, seldom and always played with low levels - has a very weak treble response.
Testing with white noise shows a sharp frequency cut off below 8 kHz, whereas nominal cross-over is 3 kHz.
A German B&W-group manager told me the tweeters' ferrofluid might have become thick so the coils would not be able to swing easily enough.
He told me this would be the result of thermal overload due to too high amplifier output.
But I never listened to the speakers with high levels, so misuse cannot be the reason for the problem, which now occurs since 1 year on both tweeters.
Believe me the speakers' sound is awful.
After purchase they sounded much brighter and clearer, only the upper bass region was too much emphasized.
If the reason is thick ferrofluid it must be a failure by manufacturing, have you heard about such problems ?
If it's not the bipolar electrolytic capacitors - do they relly use such cheap stuff ? - might have lost some capacity that may increase the crossover frequency considerably.
What do you think about this ?
I would deeply appreciate your postings.
Many greetings from football crazy Germany (good luck for both the English and the German team).
Peter from Wolfsburg (Germany, the Volkswagen town)