You can change the amount of bass on the JBL Flip 5 Speaker, by turning ON and OFF the bass boost. When ON, bass boost makes the passive radiators on each side of the Flip 5 vibrate a lot more. Plus, it adds a low rumble quality to the playing program. So, for you boom lovers, we explain bass boost here. Further we show how to get that extra umph.
JBL Flip 5 Speaker Bass Boost: How to Turn it OFF
By default, this speaker has bass boost mode turned ON after a factory reset. This adds a bit of treble and lots of extra bass to the audio.

You can turn this bass boost off by pressing and holding in the Volume Down (-) and Bluetooth buttons.
Hold them in for about ten seconds, until the Power and Bluetooth buttons light up white.

JBL Flip 5 Speaker Bass Boost: How to Turn it ON
To enable bass boost once again, press the Volume Down and Bluetooth buttons. Then hold them in until the Power and Bluetooth buttons light up gray-white. Finally release them. Then, once the buttons start glowing, bass boost is again in effect.
Warning
The drivers really thump when you switch ON bass boost. So be careful in how loudly you play the Flip 5 with bass boost. This helps avoid damage to the drivers. If the bass is crackling, tapping, or otherwise distorting, turn it down !