So after several months of searching I got lucky on eBay last week
and happened upon an original cone K120 about 20 minutes after it was listed. Score! Anyway, the speaker arrived today and I just got through putting it through its paces. It's different than the E120 I've been playing through, and I'm still trying to figure out the adjustments I'll need to make to get the most out of it. I'm curious if my brief observations are consistent with other's experiences, or if I'm off in the weeds?
As an aside, I'm using a SSP 1X12 cab and my home/practice amp, a Mesa TA-15 that's been re-tubed with JJ's: an ECC803S in the V1 (clean) position and JJ ECC83S in the V2, V3, and V4 positions, and JJ EL84s in the power tube positions. The ECC803S is a lower gain version of the ECC83S, so the TA-15's first channel is fairly clean, warm, and "full". It isn't as sweet sounding as my SMS CTP & MC50, but it's a lot smaller and easier to live with in the house, and as I just got it I haven't had the chance to play it with the bigger setup yet.
I had the Mesa dialed in pretty well for the E120, but after changing speakers and plugging back in, I was immediately struck by how much more efficient -- and brighter! -- the K120 is than the E120. Settings that permitted me to get a nice tone from the E120 at bedroom-to-loud-bedroom levels made the K120 sound rather shrill. Some of this may be that the K120 is exposing more of the true tone of this particular Mesa (and these JJ tubes), but it was really surprising to me just how radically different these two speakers sounded. I'm sure the warmth is in the speaker, but I'm still figuring out how to get it out.
Is this a "typical" experience with a K120? I was expecting a sweeter, less shrill sounding speaker, but as I said, I think some of what I'm hearing is just the Mesa being very accurate/sterile, and perhaps the JJ's being a little harsh? I guess I'll know more on the weekend when I'll have the time to play through the SMS, but I'd enjoy hearing from others who have played their rig with both speakers, and what adjustments, if any, you needed to make?