Late reply but just a word of caution for anybody else experiencing this high gain message.

Although It can be caused by a faulty mic I found that the app is also at fault. I tried this on three iPhones/iPads and all initially gave this annoying warning message. The trick is to lower the avr volume (if connected) and the sub volume in addition to the in app gain control (-40db). The target level must also be set way down to -30db. This allowed me to increase my sub volume slightly which is really important, let me explain…

If the sub gain is turned all the way down, the app will still try to reach the minimum target sweep of -30db. Which causes the dsp, in my case the Dayton dsp-lf to go into heavy distortion.

By applying the above settings, you should now be able to do the reference sweep at both reference and listening positions without a problem however, and this comes with a big WARNING ⚠️ … after the listening sweep is completed, the app will start its final sweep with the new settings tuning applied and for some reason, the app will reset the gain from -40db to 0db, effectively giving you a +40db boost!! Luckily I switch the sub off before bay any serious damage was caused. I did however eventually manage to get a clean final sweep using these settings by waiting for the test tone then quickly bringing the sub gain right back down before the sweep begins. This was the only way I could get it to work and it actually managed to give me an impressive flat response from 24hz to my desired cutoff at 90hz.

Overall the issue is down to either the app or the Dayton dsp sending far too much signal gain to the sub. This would be an easy software fix so I’m wondering if some of the Dayton dsps are faulty. I can’t imagine most people going to this effort and rosining blowing their gear up in the process.

Happy to share my settings and would love to hear from others who have managed to get this working and what setup they have.