RTA 12C driver and passive question

geppy1

I have RTA 12cs that came with 6501 drivers and a passive that has a smooth surface.. I saw a 1985 ads for the 12C that specify the 6600 drivers and show a passive with a rough surface. I have 6600s laying and could swap them but then would I have to change the passive also?. I do have a pair of the rough ones also. I guess the questions are. What is the difference between the rough and smooth surface passives? The 6501 seems to be a one fits all driver verses being specialized like the 6600. That would led one to think the 6600 is better and the 6501 was made to cut down on to many drivers and save money?? Anyone have early 12Cs with the SL1000 tweeter?? The 84-85 era of the 12s is an exercise in frustration as it appears anything in the parts bin would go into them Thoughts welcome.

jon s

I have a pair with the smooth surface passives and the SL2000 tweeters...

tx_polkhead

my C's have the SL2000 tweeters, the smooth PR and the same mid driver as my 7 and 5jrs, I thought, I could pull a driver and check if it would be of any help.