Hi All, I'm a newbie and just discovered this site. I have a set of Heresy's that I bought new in 1977 and they have in storage for years. One of the tweeters isn't working so not sure if it's the diaphragm or the crossover and I haven't had a chance to put a meter on them. The serial# are 25P006/7, not sure what series these are but the tweeters are K-77, serial # 51685 on the non-working one. Reading an old forum here about the same subject and people replied with upgrade suggestions and sources. Any information would be greatly appreciated, thanks in advance, Peter.