Joegi:
...but to build a two band peak-meter with one band going from (roughly) "0 to 1kHz" and the other going from "1kHz to 16kHz" I could use this formulas:
Band1: (peak_63Hz + peak_160Hz + peak_400Hz + peak_1kHz) / 4
Band2: (peak_2,5kHz + peak_6,25kHz + peak_16kHz) / 3
- right?
If that is what you want to do you are using the wrong chip, while this would give you something it would not have a very smooth frequency response, in other words there would be lots of pass band ripple. You would be better off just using a high order high pass and low pass filter.