Try to flip the passive radiator to upsidedown because on my kingone k5 Bluetooth speaker has a strong bass and has a upsidedown passive radiator. Please, try that for us.
JBLs are way to exspensive, I got a completely waterproof, dust proof, and kind of shock proof speaker, that has a 1.25 inch tweeter, and a 8inch sub. For the same price as a Flip 4 and it sounds amazing, brand: Altec Lansing