HEDDphone measurements done on the B&K 5128:
Raw:
Compensated:
Looking like the variable folds shows up similarly to driver modes in some planars (the jaggies), pretty cool IMO. Also interesting to note, the HEDDphone’s FR is practically illegible on the GRAS in the treble as it omits a ton of information up there with this one for some reason. This is one case where the 5128 is more than just slightly better.