Both the ebony and rosewood headphones have a V-shaped sound signature, faithful to the original Foster design. The high frequencies are energetic and lively, the low- to mid-bass tight and powerful, and the overall presentation slightly vocal-forward. The teak headphones, on the other hand, have a more gentle V-shaped signature, with wide staging, excellent layering, reduced sibilance in the highs and mids, and responsive bass with fast decay.

In the frequency plot below, the blue line represents the ebony headphones, red represents rosewood, and black represents teak.