It looks like you're new here. If you want to get involved, click one of these buttons!
Don, you should take a look at the Purify 6.5inch'er if you haven't already.https://hificompass.com/en/reviews/purifi-audio-ptt65w04-01a-midwooferlook at that stupid low HD performance! Only other commercially available cone transducer with harmonic distortion that low that I've ran into is the Beyma 8LW30 (save for Accuton's that are stupid expensive with those ceramic cones!)
Initial measurements of a stock RT-4001 taken, with initial conditions (relative drive level, mic distance) notated. Diaphragm modified. Patient is resting in ICU, expected to make a full recovery in 24 hours. Next measurement tomorrow. This one's for you Don!