One of the hardest tradeoffs when installing a non-Sense-based custom ROM on an HTC One is the loss of Beats Audio. Due to a patent restrictions from Beats and compatibility issues, it's currently impossible to port it to a non-Sense ROM, but with ViPER4Android you can get almost identical results, bringing life back to the BoomSound speakers on your device.
Founded by Euphy Wong, ViPER4Android is an audio-enhancing software that works both on Android and Windows devices. With ViPER Audio and Bass installed on your phone, you will have equalizers and audio effects that are equal to those of Beats.
In order to install and use ViPER4Android, you will need to root your HTC One if you haven't done so already. Also, because this app isn't available through Google Play, make sure to have "Unknown sources" enabled through your device settings.
Go to the ViPER4Android website and download the newest FX .zip file of V4A (I'll be calling it this for now to speed things up).
Once it's downloaded, extract its contents onto your phone using a file explorer like ES File Explorer. Head to your Download folder, select the FX .zip file, then tap the Extract button on the bottom panel.
Since your device is running an Android version over 4.0, you will install the file "ViPER4Android_4.x_2322.apk".
After the app installs, open it up and grant superuser permissions. It will then notify you that you have to install the V4A driver and will give you three option to choose from—for best audio quality, select Super Audio Quality.
After the driver installs, you will be asked to restart your phone to hear the changes take effect.
After reboot you will now have the option to use the V4A equalizer in all your favorite music apps, like Google Play Music. To activate it, go to the Settings menu in the Google Play Music and select Equalizer, then select ViPEr4Android FX as the default equalizer and enable it.
V4A comes with many features to improve your audio quality. These include ViPER Bass, which offers different bass modes, so that you can get the same result as you would by enabling Beats. There is also ViPER Clarity, which balances audio levels so that vocals never get drowned out by heavy bass.
There you have it, a legitimate alternative to Beats Audio, usable with any ROM you load up on your HTC One.