With modern 5 channel systems, the center channel does most of the vocal duties and is often neglected in its performance. I believe it is important for the speakers in a surround system to have the same quality aka the same type of tweeter. This aids in the realism as sounds sweep around the veiwer. My surround sound system utilizes the Allison CD9s as the left and right towers with Allison CD6s as the rear speakers. Sadly the CD6s I ordered secondhand had a damaged tweeter and needed to be replaced. I found a pair of undamaged tweeters on ebay and used those to replace the damaged ones. I ended up with an extra tweeter. With the leftover drivers I had, I decided to make a center channel for my surround system.

The original PC 60 had a crossover point at 2khz but I couldnt find any indication of order or slope.

The Allison CD7 is designed for a 2khz crossover point as well for a 2 way system. With a first order low pass filter on the woofer and a 2nd order filter on the tweeter.

After the initial construction of the cabinet, I utilized my active crossover amplifier to estimate the crossover and balance the drivers by ear.

The final crossover is 2nd order focused around 2khz with a -5db L-pad on the tweeter.