Mellow speakers

I have the same sensitivity as you. I cannot stand that edginess because it hurts my head and ruins the musical illusion for me. I have spent years fixing it and i finally have a system that sounds amazing and more like real music than ever before. As you may have discovered each component can contribute to the problem or the solution. I have found there are detailed/harsh speakers (most audiophile speakers sound this way to me partly because i am sensitve to it, and partly because too much treble detail is what many audiophiles want, because they equate that with a more live and realistic sound. Then there are more balanced speakers, like vandersteen or old Proacs or Snell Type A1 (one of the most amazing speskers ever). But even they dont fully remove the edge, especially if you listen to recordings that are not perfect. This is all, of course, just my opinion! 
So, in answer to your question I will give you one unfailingly mellow speaker, the Spendor S100. It is incapable of sounding harsh and has a magic midrange. I found over time is was almost too dark, even for me... But it fits your bill. The other speaker is my current reference and will be for years: Quad esl-63. The quads are so musical, have the best midrange i have ever heard, and for some reason the way they reproduce treble is different that any speaker i have heard. They just seem to avoid that edge but still present treble energy is a convincing, real way. I bought a newly refurbished pair from Electroststic Solutions in Kansas City three years ago and they are amazing. I recently bought a pair of Audio Note AN-J spe speakers to possibly replace the quads amd after head to head listening the darned quads won again. I kind of wanted the Audio Notes to win because they mate better with my Shindo amp and look better too. But as wonderful as are the Audio Notes in terms of dynamics, tonal balance and musicality, they still have too much treble energy for me and sounded like hifi moreso than the magical Quads. I am afraid some of the dynamic speakers like vandy and quad may sound mellow to many people, but may not do enough to solve your need, if you are like me.

Anyway, feel free to send me a private message if you would like to talk more. I have thoughts on other components like DACs (I was thrilled to find out none-oversampling dacs like Audio Notes take away much of the digital edge, for example).
Stu

Time sensitive info: Just received an email from Ohm yesterday (9/2/16) http://http//ohmspeaker.com/speakers/walsh-tall/#wt-1000 Walsh 1000 Talls for $749 each and http://http//ohmspeaker.com/speakers/walsh-tall/#wt-4000 Walsh 4000 Talls for $2099 each (the link says $2199 each; I don't know what the deal is with that!). If you are interested in the 4000s, write to John@ohmspeaker.com and ask him about the $100/speaker difference between his email and the link. Here's what the email said: "More Than 25% OFF On Two Models of Walsh Talls: These Walsh are built for you -- brand new. The veneer choices are unlimited. The Walsh 1000s are for small rooms and the Walsh 4000s are for large rooms. Both work well with Home Theater systems using subwoofers. They all come with our 120-Day Home Trial. The Shipping and Handling charge is just $50 per pair. This SALE ends on Tuesday, September 6, 2016 at 11:59pm EDT. No trade-ins accepted at these SALE prices."

Meanwhile, back to my comment:

Yes, the only "upgrade" I've ever regretted was selling my big Vandersteen 4 speakers to replace them with something newer and more than twice as costly. With their huge brown (alt. black) nylon sock coverings, they would be vulnerable to Beastie, but that would be true of anything, assuming you'll leave the grilles on any pair of floor standers you purchase to protect the drivers. Also, the Vandersteen 4 have a nylon-covered opening in the oak cap-piece that made a perfect "hammock" for our British Shorthair cat, who thankfully left the socks alone (most of the time). When I sold the Vandersteen 4 and delivered them to the new owner's cavernous great room overlooking the rugged pacific cliffs and ocean, she wanted them tucked under the stairs at the side of the room not even facing the "listening area." I hooked them up to her mediocre mid-fi electronics and was utterly floored by the glorious sound filling the entire room! Since she hosts a music academy in her home and is a concert pianist, I felt I had done a service to her and her students, but I'd gladly buy them back. I'm happy with the newer Genesis III speakers I have, but I still miss that old pair of Vandersteen 4.

My solution to the "mellowness" issue was to put together a second system in our bedroom based around an old pair of ProAc EBS, and they sound great, even on terrible digital recordings that would make my ears bleed in our main system. The "secret" of my contentedness is Wadia CD players, Audio Research LS15 and 16 tubed preamps, and Levinson solid state amps. I've tried vastly more expensive CD transport and DAC combinations, but settled on the cheapest Wadias (the 23 in the bedroom and the 830 downstairs) and I forget about gear and just enjoy the music. Best wishes to you on your quest.

With kind regards,

Mark

Sorry for typo ... ". I am afraid some of the dynamic speakers like vandy and quad may sound mellow to many people"

I meant vandy and audio note.

One thing the old designers knew was that if you extend frequency on top it needs to be extended on bottom. Today many loudspeakers are voiced hot in treble. Toss in small drivers running off high power thermal compression sets in and you have a recipe for listening fatigue. Why so many systems sound great for about 45 mins after its hard on the ear.

I am selling a pair of Thiel 1.6 floor standing speakers because they are strong in higher frequency range, and cause ear fatigue. Although they are dynamite in terms of accuracy, I do not consider them mellow.