Ditto...Klipsch forums -
A short list:
Replace Crossover - Options include those by Al Klappenberg, Bob Crites, Dean Westcott and others.
Replace Tweeter Beyma CP25 is popular drop-in. Beyma CP385ND + TD250 horn (needs padding) is another alternative. I loved a padded Fane 2020 on my Scalas.
Major overhaul - Replace metal midhorn with Martinelli wood horn.
Replace wiring harness with better wire (I used DH Labs silver in my LaScalas)
If you're keeping the metal horns line them with Dynamat or a suitable substitute.
There's a start for you. Plenty of opinions on all of'em. YMMV. Use your own ears and all that.
Marco
