This is also exactly my experience unfortunately
My previous phone was the one x with beats audio + headphones, I'm now using the beats headphones with the Z2 and the bass leaves so much to be desired... I've tried all the settings to no avail, as mentioned above the bass specific setting seems to lower mediums and highs instead of pumping bass.
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There are some audio hacks out there that rely on root, so providing you ate either able unlock your bootloader and root or an exploit is found so you can root, then you might have some luck yet!
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