Good for basics after tweeks

I bought this app to properly set the levels on my new home theater. By default the readings were way low in comparison with my RadioShack meter. After tweaking the trim extensively it matches up pretty well. However even when calibrated and using c weight and slow response my iPhone 4s with this app was completely incapable of picking up my subwoofer test tone for subwoofer level setting.

Joe Astorino about SPL Meter, v5.2