feature request: add 300hz - 3400hz and -6db bandpass filter

[hbjonsson]

Currently SRS implements two bandpass filters:
1 - low 560, high 3900
2 - low 100, high 4500

Would like to request this to be changed or added as an option:
1 - low 300, high 3400 ( -6db) assuming that represents 300hz-3400hz.

This is what the specs are on aviation/mil std mic's are and test results are promising.

[ciribob]

I'll have a test 👍

[obfuscoder]

When adding radio FX to audio I also apply the band 300 to 3400 which sounds most realistic to me.