Here are four files useful for tuning audio systems i subwoofer test. Some frequencies may not be reproduced properly by audio system, but these frequencies while not subsonic, may cause damages to your system if the volume setting is to high.
Track 1 – 10 ~ 14 Hz :
Track 2 – 15 ~ 19 Hz :
Track 3 – 20 ~ 24 Hz :
Track 4 – 25 ~ 29 Hz :
Enjoy!