Change how much rumble you get on the JBL Xtreme, by turning on and off its low frequency mode. When ON, this mode makes the passive bass radiators vibrate much more. It indeed adds a low rumble quality to the playing program, that travels pretty far from the speaker.
JBL Xtreme Low Frequency Mode: How to Turn OFF
By default, the JBL Xtreme 1 has its bass mode turned on after a reset. This adds a bit of treble and lots more bass to the audio output.
You can turn this mode off by pressing the Volume Down (-) and Bluetooth buttons. Then hold them in for about ten seconds, until the Power and Connect buttons light up white. Find all these buttons on the top of the speaker.
JBL Xtreme Low Frequency Mode: How to Turn ON
To turn low frequency mode back on, again, press the Volume Down and Bluetooth buttons in. Then hold them in until the Power and Connect buttons light white. Then release the buttons. When the buttons inside the oval above light white, the low frequency mode is active once again.
Warning
The drivers really thump when you enable low frequency mode. So use caution in how loudly you play this speaker with the resulting extra bass. That way, you’ll avoid damage to the speaker drivers. If the bass is crackling, tapping, or otherwise distorting, turn it down !