Small Bluetooth speakers often compensate for tiny drivers with an artificially boosted bass, which can leave the rest of the sound feeling thin by comparison.
If the sound feels bass-heavy and muddy, try cutting the low band a few dB. If it feels harsh at higher volumes — common with cheaper drivers — a small cut in the high band can make longer listening more comfortable.
Bluetooth audio compression (especially the basic SBC codec) can soften fine detail before your speaker even receives the signal — EQ can shape tone but can't recover detail lost to compression, so extremely aggressive boosts may just amplify compression artifacts.