big_greg - I’d like to address your brightness problem. It is odd that the Thiels alone are bright among good company. It seems reasonable to assume a speaker problem. I don’t know the 2.3s, but hear that the original tweeter could be heard as ’strident’ and the vented replacement 'fixes' it. I do know 3.6s and the only brightness, stridency, etc. I have found is from a baffle surface propagation phenomenon which is greatly reduced with grilles in place, and is being addressed in my present work.
There is the possibility that something has gone wrong in the XO which is disabling a shaping network in a tweeter or midrange. A physical XO inspection might be in order. But such an instance would be rare, and becomes statistically next to impossible in more than one speaker.
So here's another thought. I’ve had an interesting (disorienting) experience since getting my Benchmark front end yesterday. First of all: it seems phenomenally good compared with the PS Audio Stellar gain cell / DAC and S300 amp. BM is better in every way. The ’interesting’ part is how much more obvious are the cabling differences. I have some Straightwire, Audioquest, Morrow, Mogami, and the standard Benchmark / Canare that came with the stack. Hard for me to believe that the ’normal’ $35 BM interconnects seemed so much more ’right’. Same goes for the speaker cable (with not as much comparison.) I’m in cognitive dissonance since I’ve been doing wire for nearly a half century. I am presently evaluating execution levels in the 3.5 equalizer within two driving systems. The big tip-off was the Bass & Mandolin cuts. I have played the mandolin and was involved in the development of the Collings line. The nuances of chop and gulp, box and ring are in my ear and under my skin. I stopped blaming the equalizer when I added ’straight wire’ to my protocol. When I got to the all-BM / Canare cables things settled into that remembered musical reality. It sounds right and good and I’m not missing those audiophile traits that might be artifacts.
My point is that before you give up on the Thiels, you might make some comparisons with BM cables. The phase / time coherence of all Thiels puts the ear-brain in a different hearing space than do non-coherent speakers. I’ve addressed this idea before, and I admit it can sound hoaky, but my consistent experience over these many decades is that when the system gets right, the speakers disappear. Something smells wrong about your Thiel brightness problem. I hope you can fix it.
Good luck, and keep up posted.
