Install the JBL Connect app (not JBL Portable or JBL Headphones). Older versions of the app may be required for the original Xtreme—if the latest version doesn’t detect your speaker, try an APK for JBL Connect 3.0 or earlier.
Launch JBL Connect. It should detect your Xtreme automatically. Tap on the speaker icon. jbl xtreme update firmware
Turn on your JBL Xtreme and pair it with your phone via Bluetooth (Settings → Bluetooth → JBL Xtreme). Install the JBL Connect app (not JBL Portable
If an update is available, tap “Update”. The app will download the firmware and transfer it to the speaker. This takes 3–10 minutes. Do not turn off the speaker or close the app during this process. jbl xtreme update firmware