klipschorn modifications

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

Wouldn't lining the horns narrow their geometry (or is that part of what's good?)? Any benefit from lining the outsides of the horns for damping?

You line the horns on the outside, not the inside. You can use Dynamat, or you can get much cheaper alternatives at Parts Express. The Parts Express stuff is a bit easier to apply.

Yes, the CP25 is a "drop-in" in terms of its output (no padding necessary, just wire it up and play using the same crossover). Physically it is larger and must be located on top of the cabinet, or an adaptation to the cabinet needs to be created. I used a Fane tweet and located it on top of the cabinet. It worked GREAT! Big improvement over stock. The two horns do not depend upon the cabinet for sound (just support and position). Having the tweet slightly higher did not create a handicap in my experience.