Back when I worked for RCA Records in NYC I picked up 3 LC9a, and then picked up 3 more of just the empty cabinets when RCA dumped the remaining inventory from their warehouse in Camden NJ. Two of the new cabinets got built up (don't remember what drivers I used) and sold to the film department at New York Institute of Technology on Long Island.
Only one of my systems came with the passive crossover, but if I recall correctly it was 3rd order for both high and low pass.
The original woofer was made by RCA themselves in Camden, and had a very large ceramic magnet. Community Light and Sound (now Community Loudspeakers) bought the magnetizer used for the woofer magnets from RCA and used it for the magnets of their M4 mid range driver (which may just be the most efficient driver ever made).
My favorite way to use these speakers for sound reinforcement was stacking two with the top box upside down. This placed the HF horns right next to each other, the LF horns further apart, and the LF ports even further apart. The result was significantly increased directivity vertically, but no change in the horizontal plane. I drove these with McIntosh MC40 for the highs, and a MC2120 for the lows, and a custom modified UREI crossover.
Unfortunately two of my LC9a were lost in a move, but I still have and use the other two.
To my ears the weakest link was the HF drivers. I replaced the original JBL made, RCA labeled drivers first with the larger magnet JBL drivers. Later these were replaced with Emilar EA175 drivers. The Emilar drivers on the RCA HF horns were dead flat up to 12 kHz, but got ragged above 12 kHz.
Tom Danley suggested I replace the HF drivers with BMS 4550 and the original RCA LF drivers with JBL 2226H. I have a pair of 2226H but they need to be reconed, so I used a pair of JBL 2225H instead. The results have been wonderful. They have never sounded better, and the highs are the best they have ever been. Current amp configuration is a Crown Macro-Tech 1200 for the HF and a Crown Macro-Tech 2400 for the LF, with a Peavey original X-Frame serving as the crossover and (minimal) EQ.
I drag these out at least once or twice a year for outdoor sound reinforcement events and get complements on the sound. Yes the drivers have been updated, but these are still the same 1950 vintage loudspeakers still going strong.