We know of no way to switch ON the JBL Go 2 low frequency mode. But if this were possible, it would make the speaker vibrate a lot more. Plus, it would add a louder bass quality to the content playing. But if JBL ever adds this feature, it might work something like as follows…
How to Switch JBL Go 2 Low Frequency Mode OFF and ON – Proposal
Firstly, by default, the Go 2 would have its extra bass mode turned ON. This mode would add more treble and lots more low frequency bass to the audio output. Very much like the Loudness control on older stereo systems.

How to Turn JBL Go 2 Low Frequency Mode OFF, and then ON Again, Proposal
Find the Bluetooth and Volume Down buttons on the top of the speaker, as circled in the picture above.
You could turn this extra bass mode OFF by pressing the Volume Down (-) and Bluetooth buttons. Then hold them in for about ten seconds. Finally, you would release when the pilot lamp on the front blinks a few times. See this in the next picture.

Finally, to turn low frequency mode back on, again, you would press the Volume Down and Bluetooth buttons. Then keep holding them in until the light again flashes a few times. Finally, you would release the buttons after that.