The measurements you are linking to are showing the level of distortion (HD3 v level) not dynamic range! The Y-axis on the graphs is showing the 3rd harmonic in dB in relation to the mV given in on the x-axis. This has absolutely nothing to do with dynamic range and it is also not the signal-to-noise-ratio. The fundamental frequency in those measurements was at 315 Hz. HD3 refers to Harmonic Distortion at 3rd level.