Why does my system now have shrill top end.

OCOS cables are pretty old ( around 1997 or so).  If I remember correctly, they were designed with OCOS standard terminators (Red), but when used with dome tweeters or a speaker with a rising impedance curve, they needed to have the HFC (Black - nobel) network installed on the speaker end in place of the Red ones.  They also came in VERY specific lengths (9'10"/13'/16'6",etc) which I have to assume was a performance benefit or to correct a design/engineering issue.  I would try and borrow some newer speaker cables and hear if that "fixes" the problem.  Those OCOS cables might have oxidized over the years and/or the connectors might have issues.  I also suspect that the Black HFC needs to be used for the Endeavor speakers.

Awww... Looks like Geoff got butt hurt again for having is snake oil called out. I think I need another tactic. I think I'm just going to report every single snake oil post I come across so threads like this don't get derailed by these clowns.
Happy posting!

Tis probably best to think of snake oil as the lubricating liquid that makes the engine go. It also separates the MidFi from the High End, you know, just judging from the responses here. No offense if MidFi is your thing. Everyone has to be somewhere.

You two guys need to get room. You're beyond foreplay.

Jea48 Huh? I wasn’t addressing anyone in particular. Thanks for the image anyway.