Just got a chance to swap out the cap and try the omni 603 on acoustic guitar.
It sounded great! That 7K thing definately dissapeared...very neutral and organic-sounding by comparison. I was very pleased with the sound.
It needs a BUTTLOAD of gain (66dB was barely enough for a picked guitar part about 2 feet above the players head, and I would've liked more gain on it.) I must have put it on the one that is about 10dB quieter than the other one out of my "matched" pair.
I'm excited to try them out on different sources now. I'll do drums next.
Thanks for the caps, Warren!