Just wanted to introduce myself and say hi. I've been a polk fan for a long time. I have owned a set of 10B since the late 80s. At that time I got a chance to hear a set of SDA SRS, but the price was way over my budget. I recently picked up a set of 5Jr off ebay for use as either rear speakers or maybe a center, but my daughter installed them in her room. So I then picked up a set of SDA 1C. All I can say is wow!!
The top caps had some issues, I sanded them and put a couple of coats of urethane on them. I am really happy with how the caps look now. The SDA cable was missing so I put in new binding post for the SDA signal and made a 12Ga sda cable. Also made some new speaker cables while I was at it.
I have been looking over the crossover schematics for a bunch of the SDA speakers. I think I have a pretty good understanding of the low frequency section. I will need to spend some more time before I have a good grasp of the high frequency section. Changing out the electrolytic caps seems obvious. It looks like the symmetry could be improved between the stereo and the dimensional drivers. On the 1C (and most early SDA) the wire gauge of the stereo inductors is the same as the dimensional inductors. This causes the dimensional circuit to have a higher DCR than the stereo circuit. In the later TL series the dimensional inductor used a heavier gauge than the stereo correcting this issue. I noticed the TL series also used a higher cutoff frequency for the low pass filter, I need to look at the tweeter sections before I form any opinion on that.
I'm probably not as critical a listener as most hear, hopefully I will be able to hear the difference when I get around to modding the crossover.
I feel myself entering the rabbit hole, already on the lookout for a set of SRS 1.2.