How to make the Focal Kanta No. 2 speakers sing?

Just a reminder that technically "warmth" is associated with ~ 150-250hz frequency range which is the upper range of what is considered bass. Worth noting if one is to attempt to add "warmth" . A sub or two properly mixed in might be called for otherwise perhaps some simple equalization or DSP.

Also 2-6 khz range is high midrange and  associated with "crunch and edge" so too much of that is not a good thing.

I’d take a sound meter or good sound meter app to the problem with some streamed white noise to determine what is really going on. Adjectives alone may not be the best way to properly identify and resolve the issue.

+1 to the OP for the detailed question!  I have a good deal of experience with Focal.  They can sound quite good, very lively, in a properly treated room.  One thing that is too often overlooked is the point of reflection off the ceiling.  Untreated this yields an unwanted point of reflection of the highs which causes phase issues and thins the mids.  To get more out of the mids you might want to reposition the speakers to get more room gain.  I demoed the Kanta 3's  and thought they sounded fantastic.  They were being driven by tube/ss hybrid McIntosh MA352 and the pairing was lovely.  If you would like to keep the speakers I would look for a used MA352, they are usually available on the second hand market, and try your Eversolo analogue out into the amp.  Cheers and good luck.

Hi OP,

I haven’t had the Kanta’s but I have older Focal Towers 816V’s that I now use as my surround sound speakers, I have the 800v center.

I had the Electra 1028BE’s which prior to Focal revamping their line up was the trickle down speaker that had the Woofers / Tweeters found in their top line options. 
 

I struggled with what you are right now.  Highs were very pronounced, could be eerily smooth with the right recording but fatiguing with most.  Mid’s lacked, bass was there, deep, fast, punchy.  You’ll find Focal’s tend to lean toward the highs, fall into the more analytical camp.  They are also tougher to drive, especially if you want to get the most out of them, a better blend of Mid range to go with the Highs and lower region bass.  If they are slightly bright to you but you really love the sound signature, room treatment and changing your Amp will do the trick.  If you are further away from loving the sound signature than feeling like a few small tweaks will do the trick you’ll likely need to change your speakers.  I spent a lot of time and money chasing the right Pre / Amp / DAC combo and I still moved on from the Electra’a which many will hail as a tremendous speaker in the Focal line, blending in their top tier materials into a more affordable overall package.  Did I improve the performance of the speakers, mainly through amplification changes, absolutely, did it change the tweeter / tuning of the speakers being fatiguing, nope.  
 

If you are sure you want to keep the speakers, they’ll need amplification that isn’t all about Watts but impedance / handling difficult swings, loads.  Brands like Pass, Parasound, Coda, Music Fidelity, Mac, Krell, Hegel.  Naim is also often paired as they are owned by the same parent company.  You can find Amps today that won’t heat your room.  If you want to keep costs down, look for used Integrated units, Parasound Hint 6, Music Fidelity, a little pricier but a step up amplification / Pre wise, Coda, and the latest Krell would be fantastic fit, you can get it with a DAC.  You could also go all in one streamer, DAC Pre / Amp with Naim or Hegel, the Hegel 390 would be a great all in 1 solution. 
 

Amplification will make the biggest difference in performance followed by Room Treatment.  I tried those plus Room Correction andEQ’d things via Roon, still moved on.  A great recording that focused on vocals, I have never heard a speaker speak to me like the Electra’s with their BE Tweeters and I’ve cycled through some speakers, but I only loved them 10 % of the time as when I moved onto poorer recordings, rock and other genres they were fatiguing.  
 

So, I’ve lived what you are going through, you can warm them up, bring the mids more into the equation but that won’t change the highs, if they are really fatiguing now, that fatigue will still be there to a lower degree but there.  Best advice I got that I ignore for too long was only your ears matter, if the sound signature isn’t for you on a particular speaker you won’t be able gear or room treatment your way out of it.  

Good tips from everyone. I'm, taking them all in consideration.

@rick_n Yes good, point. The ceiling is the weakest link here, plasterboard... It's a living room so I can't put anything up there for diffusing either.

@mm1tt77 Wise words. Great to hear you experience. Thanks. This is really what it boils down to.

An easy next step as pointed out is to mess around with the Yamaha AVR and see how far EQ:ing takes me. In combination with REW and the Umik perhaps. If that turns out well it might be a path to walk down further. And after a proven concept, perhaps later on getting a better performing device with EQ / room acoustics tools built in.

What about putting a pre amp, be it tube based or not, in front of the Class D amp. Has anyone done that in a case like this to achieve a welcoming warmth to the sound? Some sound tuning possibilities is also good to have.

I have not really planned to invest more than a like 2000€-3000€ on gear at this moment. On what would that money best be spent in this case?

I’d try to demo a tube preamp at home if at all possible.