Headphones not reproducing bass under GNOME

I have a 2012 Retina MacBook Pro running Arch Linux with GNOME. Normally, I listen to music using the analog audio I/O interface -- the 3.5mm socket.

Recently, I had to attach a USB microphone to the laptop. While doing that, I used the microphone's built-in 3.5mm socket to monitor the sound I was recording with lower latency and less distortion than what the laptop's internal amplifier, and the backing software, would produce. Because of this, I went into GNOME's sound options and updated the audio output profile to digial, which allowed me to pipe system sounds through the mic and into my headphones while I was monitoring the audio received by the microphone.

After switching back to using the 3.5mm socket on my laptop and reverting the audio output profile to analog (the only option available without the mic), the outputted audio's really distorted. After some tinkering using the ALSA mixer and reproduction of the issue on the laptop's main speakers, I've concluded that the issue is that outputting audio to my headphones now results in the bass part of the spectrum being cut off completely, resulting in a tinny, distorted, and almost downsampled effect.

Unfortunately, I haven't found any settings allowing me to tweak the bass response for the 3.5mm out.

Where can I do this system-wide?

Perhaps a simple solution would be to use pulseaudio-equalizer. It'd allow you to boost the bass a bit.

However, it seems to me that this is a driver/PulseAudio issue, and the workaround would be to grab the equalizer with Pacman:

sudo pacman -S pulseaudio-equalizer.

I'll fiddle around on my machine to see if I can reproduce something similar to figure it out. I'll reply if I work it out.

I had exactly this issue when running Gentoo on my Broadwell laptop - all the music was tinny, scratchy and oversampled. It turned out that, for whatever reason, I had to use PulseAudio instead of ALSA. Switched over to that and audio's been fine ever since.

I had an similiar issue and fixed it using pavucontrol. There you can specify many settings for PulseAudio. For me I used the HDMI output and afterwards there was no sound on the 3.5mm socket. Try some time to get the settings right.