High Pass Filter problem

I am a professional live audio engineer and I tried using this app on my iPad Mini to monitor my mix. In my genre of music I mix very heavy to the low end and work the subs a lot. This app looks great but it doesnt give an accurate read below 250hz. Near useless for my application if I cannot defeat the HPF built into the mic software.

Eric Hoelter about Octave: An RTA for the iPhone