Devs bring Harmon/Kardon audio features to all HTC One (M8) variants - HTC Source
Disappointed that the new Sprint HTC One (M8) Harmon/Kardon edition has better audio than the standard model you’re sporting? Thanks to baadnewz from XDA-Developers, you can now mod your plan old HTC One (M8) with all the audio goodness that’s baked into the Harmon/Kardon edition. You will need root access and a custom bootloader to flash the mod to your phone, but those who have tried it seem extremely satisfied.
If you do choose to mod your standard HTC One (M8) with the Harmon/Kardon audio tweaks, let us know how the process goes and if you really notice a significant boost in audio quality. Keep in mind, you’ll probably need a good pair of earbuds or headphones to really notice the difference.