I did this for myself but someone else might find it useful:

It's the measured effect of the +/- 13 step Bass, Mid and Treble controls on the Vauxhall Insignia Navi 900 (Intellilink RF900 Navi) system.

https://docs.google.com/spreadsheets/d/e/2PACX-1vRM-9G-Bdt7Tzi7EdLQ...