I usually use symphony orchestra music Beethoven's symphonies or Dvorak's "New World " 9th symphony by the Chicago Symphony with Fritz Reiner conducting. I will also use David Crosby's first album to listen to the chiming guitar sounds and how they linger and fade away .
If one feels that your Thiel's are to bright then the adding of a .01uf cap on the tweeter solves the problem , the violins now reach the highest levels without sounding bright or brittle , the hall sounds larger than ever , and this was done after installing Mills resistors and Clarity Purity 15uf caps on both the tweeter and mid crossovers .