Cool! Very interesting, actually. Here's what you are getting with your K12s....
First, I normalized the frequency response curves as close as I could get, so they are all at the same relative levels, then I looked at them in pairs, to see what each control is doing. First, the "Vocal Boost" control: Red is "flat" response, green is "Vocal boost". As you can see, the "flat" setting is really more like a vocal CUT! And with it set to "boost", that's actually flatter.
As I suspected, that returns some of the missing upper mids. So I would keep that "vocal boost" switch on for now, for all future measurements. It gives you flatter response, with a roughly 3 dB increase, centered around 2.5 kHz, and covering a range of about 4 octaves. That solves one mystery: the missing mids are not a room problem, but rather an EQ problem.
The other interesting thing you can see there is that, even with the LF set to "flat", there is actually a pretty big LF boost! It's roughly 4 dB boost at 71 Hz, with fairly tight EQ. That's probably the bass reflex ports, and there is some low-level ringing going on there, so that makes sense. You can see that here too, in the waterfall plot, below...
Notice all the low-level "muck" between about 50 Hz and 100 Hz: that's typical of bass reflex ports: in order to do their job, they have to resonate... but sometimes they resonate too much: That's WITHOUT the bass boost on. When you apply the bass boost, this is what you get: A massive boost around 68 Hz, with an even more massive increase in ringing, in the reflex ports. This amount of air "chuffing" in the ports also introduces some distortion. Here's the "bass flat" and "bass boost" THD graphs:
So, what does all that say?
1) Only use these with the vocal boost ON, to get the mid range flatter.
2) These speakers don't go down low enough to properly trigger the room. Here's the final comparison, Green is "bass flat", orange is "bass boost". The cursor marks the point where the FR crosses over the average SPL level, at 44 Hz... with the bass boost turned ON! And below that, it rolls off very steeply. At 30 Hz, it is 24 dB down. By 25 Hz, it is down into the noise floor... nothing at all down there. So there's no "bottom end" to these guys.
3) It looks like you are going to need to borrow a sub to excite the low end of the room. Hopefully something that is reasonably flat down to 30 Hz.
That low end, below about 80 Hz, is the only remaining mystery in your room: that's what we need to see, to complete the picture.
- Stuart -