ERDI calculation

[joentell]

Question about the ERDI smoothness: On the D&D 8C, what would cause the ERDI smoothness to be only a .65 compared to the SPDI which shows as .87 even though the deviation looks similar on both? https://www.spinorama.org/speakers/Dutch%20Dutch%208C/ErinsAudioCorner/index_eac.html