What is the best way to tame a slightly bright speaker?

Jim Smith Book on better sound, felt, revisit excessive toe in and or tilt, room treatments and then hardware changes

No joking the Zobels networks I have advertised in Loudspeakers will reduce the upper frequency noise and your system will sound better .if not  money back .i just spotted this in the forum .
that  is the easiest way ,or you can solder  in new capacitors.

I have a pair of VMPS RM40 ribbons speakers that have 40" of ribbons drivers per speaker. They are very detailed, transparent, and dynamic with good bass. They have a tendency to get a little thin and maybe hot sounding with some recordings. After a couple friends came over with their ICs they liked a lot, we listened to my system using my Darwin Ascension and some Amadi Maddie Signature ICs that I have used for a few years and really liked. Both of these have silver wires. I’ve never thought they were etchy or hot in the highs, but when we switched to Teo GC ICs, we were all in agreement that the sound was much improved in the organic sound of live instruments and made a big difference to the overall sound. They also were every bit as detailed as the prior ICs. Later in this year, Doug Schroeder of Dagogo online reviews, told a couple of us about the doubling up of Teo ICs to each component and the 3 of us did the same listening test at a later date to hear the difference. I had bought a couple pairs of Teo GCs to run from the CD to pre and from the Phono to pre. The result was even more impressive than just switching to the Teo GCs. There was VERY noticeable improvement in ALL ways compared the single. The sound of the RM40s was now about as good as could be desired and definitely the best I’d heard from these speakers. And I used to be a VMPS demonstrator for the last 5 years the company was in business.
These cables could be just the ticket. Whatever you end up doing, the doubling up of ICs, now called the Schroeder method in the Forum, will make a quantum jump in the performance of yours or any other system. The Teo’s will take them in the direction you want to go. I now have a pair of Vapor Audio Joule Black speakers and the Teos still sound fantastic with these speakers, and the Joules are much more organic and natural sounding than the VMPS’.

Bob

I own the TAD Evolution system with the E1s, C2000 pre and M2500 stereo amp. Source is Aurender N10 going Nordost Heimdahl 2 AES to the pre. Everything is connected to three dedicated lines via older PS Audio power cords, amp to the wall and other gear into an older Shunyata Hydra 6. Room was recently updated and all walls are still bare of wall hangings at this time. E1s are about 2.5' off rear & side walls and are around 8' apart. Floors are medium density carpeted. Sofa is cloth and about 10' away and five feet from sofa to rear wall.

In my room, I'd say that the sound is never bright unless the recording is subpar. There is plenty of snap and sparkle when the recording has it. I've been listening for a few months with very little setup performed so far. My dealer will come around when I'm ready and we will finish dialing them in then. Speakers are toed essentially to the center of the listening position.

I've heard the E1s with Luxman, Pass, Burmester, and maybe one other I'm forgetting. I preferred them with the matching TAD gear and voted with my wallet. I can't remember them sounding bright but they are very revealing and realistic. I'm no speaker setup professional, but maybe toe them in a bit to get rid of sidewall reflections. Play around with pillows and blankets to see if that may help as well. I've also used some plastic vases my wife had in her office to good effect.

I have heard the D'Agostino Classic Stereo amp but not with the TAD gear. It was with the Wilson Sabrina. My take was that amp was like a vice grip with mechanical-like bass control and the midrange/treble was nice but it was not of the usual refinement of the other D'Agostino gear I'd heard and I guess at the lower delta it shouldn't be. I wish I could add more but I just don't have any experience with your speaker/amp pairing. You didn't say what source you are using but that may bring the brightness you are speaking of. Good luck in your journey; I hope what I've described may be of help. IMO, the TAD E1 is very fine loudspeaker.

Tubes or class A amplification. I heard those speakers with an octave tube integrated and I started to cry. I hope you will also.