I haven’t heard the Bird but agree that the one area the Isabellae might fall short is in staging, which is fairly intimate.
Thanks for saving my wallet from trying these. Intimate stage is one of my pet peeves on any transducer.
I suspect it is all relative. Would really like to see an Isa / IE900 direct comparison as that would help set some context, and both are far closer together in terms of being musically tuned single DD's.
If I do a DTB (direct-to-bird) comparison, the IE900 is also fairly intimate and markedly less wide and deep.