Just posting some new measurements from the B&K 5128
Raw
Compensated
For those unaware, there’s an air gap between the driver and the housing on the Sundara, which gives it a subtle bass boost compared to other open-back planars. The tradeoff is that you lose sub-bass at 20hz due to the dropoff below the resonance frequency (Fs).
When sealing up the driver gap but putty (Funtak here in Canada), it drops the bass boost and provides extension all the way down. I don’t recommend doing this, since perceptually it’ll sound like there’s more bass if you just leave it open. But it is the explanation and conclusion to the curious case of the Sundara’s missing sub-bass below 30hz.
