I have to agree with Pete. Any horn that you are used to playing will automatically be more comfortable. I think noth your Selmers have radically different serial numbers, neck tapers/flare, and dimensions resulting in the middle register feeling more focused or spread. Are key heights the same on both horns? Late SBA versus early SBA will feel different from behind the horn while upfront it might sound the same. Middle D on the tenor is a nice note to test. Sounds like you may have been standing a bit closer to the mic on the SBA clip resulting in the "louder" responses. The height of the ceiling in the room where you are playing (acoustics) and how much natural reverb in the room will also have an effect on how you hear the horn. I'd play the same notes at extreme pianissimo and fortissimo at the same mic distance. This test wouldn't be much fun as playing a Bird head but at least you would eliminate the expressive/inflections aspect of playing a melody and only evaluating the horn.