I just installed Dynamat and replaced my door speakers with Infinity Kappa 62.9Is. The speakers sound wonderful--a huge improvement over the stock Infinity's. They also have a built-in tweeter, delivering some additional highs that the stock setup lacks. I have plugged everything back in as it goes and if I'm not mistaken, I am getting little to no noise from the stock tweeters. If I place my ear to them, I can get a slight hiss, but nothing distinctive. What gives?

 

Dunno - they are wired in parallel to the door speakers, so if one works, the other should too

 

I believe you have two sets of tweeter sets with crossovers wired in parallel. Thats effectively cut them out. Thats my guess!