I have a feedback regarding on setting up the correct listening volume.
The “official” suggestion is to use Frequensee apps and set up the volume so it falls around -50 dB.
or another suggestion is to set the iTunes volume to 75% and the system volume to 80% (for those who use macBook)
But I find that measurement is arbitrary and have so many factors.
In my case:
I use iPhone 7, and there’s no Free version of Frequensee app, So at first I tried to use different but similar app to measure. I found out that different app may show different measurement.
And then I borrow my friends Android phones. I use Xiaomi phone (forgot the model) and Oppo F5 phone to install Frequensee. But again, I found that the measurement is different. Maybe it depends on the microphone quality of the phone.
So I suggest that you provide a sound file as the calibrator. For example that this is a song with different volume range. To calibrate the proper volume for the ultrasonic subs, I should be able to hear the song at its lowest volume range and still feel comfortable at the loudest range.
Maybe I’m overthinking it
But still, this is just my 2 cents.