Spectrogram versus Frequency and Angle

Angle-dependent amplitude response divided by Bark-smoothed average response to be used as the basis for design of time-varying, angle-dependent equalization to be applied after $H_0(z)$

Spectrogram view of the angle-dependent amplitude responses of the horn with $H_0(z)$ (Bark-smoothed curve divided out. This angle-dependent, differential equalization is used to design the filters $H_{0L}(z)$ and $H_{0R}(z)$ in the Leslie simulation. Note that below 12 Barks or so, the angle-dependence is primarily to decrease amplitude as the horn points away from the listener, with high frequencies decreasing somewhat faster with angle than low frequencies.