Tried this again. However, this time around, and to my surprise, the “Treble Cut-off frequency” challenge seems absolutely impossible. I can identify the first cut-off at 8.5 kHz, but the second step at 9 kHz is a “brick wall”. It would seem I’ve lost some of my treble hearing ability. It could be age, or it could be I’ve had a bad cold for almost a moth. For some reason I expect age. Anyway, I’ll give it another try once I feel perfectly healthy again. It does bother me.