That’s it really. I know no-one cares, these haven’t been in production for years but I still use them and I was curious. People who have asked Sennheiser have got answers of mid 40ms and low 20ms values so I thought I’d just test it myself.
It’s worth noting that these use a different encoding/transmission system (Kleer) than the current generation which are quoted in the 40ms range.
Test technique was splitting an analogue metronome signal direct into a recorder, and via the headphones and a microphone and measuring the difference in initial waveform movement in Reaper.
Just to validate I did the same test with a set of wired headphones and the measured latency was under 1ms.