This contribution is from Kushimoto-san. Original video in Japanese is here.
This overcomes the problem of soft sound coming out of the THETA internal speaker.
USB Audio Class 1.0
Analog speaker with internal amplifier and battery.
This converts the USB DAC Type A USB connector to microB.
Successful Volume Increase
clip with audio
Earlier Tests by theta360.guide
Volume Tests with Internal Speakers
April 2018 test of THETA V playing music from internal speaker. This is a soft sound and the recording microphone is close to the THETA speaker.
Martin Luther King speech playing on internal speakers. This is also soft.
USB OTG Test with Ethernet
USB OTG Flash Drive Tests
This looks like the adapter Mr. Kushimoto was using. I have not tested it yet.