I think my last picture is a momentum of the played music, it only shows reproduced frequencies with a level of SPL.
It does not tell very much about the average accuracy ot the reproduction, but the app give you this possibility by observing the changes and graphs while playing music.
Video would be much better of course.
Oh off course my mistake , but if you play for example a 20 hz - 20 khz pink noise over your system you can do a FR measurment , you might find such a test signal on a special CD or on you tube
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