I use 1More's quad drive earbuds and it's taken me a while to get the full range of sound to really come out on Rockbox.
I have the Bass at 6.0 dB
Bass Cutoff at 3
Treble at 9.0 dB
Treble Cutoff at 2
Stereo Width at 120%
Crossfeed, Dithering, and Haas Surround OFF
Perceptual Bass Enhancement 0% [when I tried playing with it the enhancement sounded to artificial and didn't create a clean crisp bass]
Without the EQ on the sound was missing a lot of mid-range and didn't have the full bodied sound I was hoping for.
I've created my own EQ Preset which is as follows:
eq enabled: on
eq precut: 110
eq low shelf filter: 32, 7, 91
eq peak filter 1: 64, 10, 82
eq peak filter 2: 125, 10, 68
eq peak filter 3: 250, 10, 56
eq peak filter 4: 500, 10, 70
eq peak filter 5: 1000, 10, 80
eq peak filter 6: 2000, 10, 90
eq peak filter 7: 4000, 10, 102
eq peak filter 8: 8000, 10, 91
eq high shelf filter: 16000, 7, 82
After adjusting the EQ I can now hear clean crisp sounds with full body and can hear all levels of each instrument instead of them sounding 'flat' or each instrument seeming a bit monotone. They now have the full range and tones have dimension!
I can no get crisp highs, full bass sounds (like round bass), and clear (not muted) mid range like vocals etc.
Finding the right EQ was a bit tricky at first. I actually took the Hip-Hop preset from
https://gerrit.rockbox.org/r/#/c/rockbox/+/401/ and modified it to replace the Rock preset as the settings on those presets seemed WAY off and the sounds they gave me were very muted at best!
The type of settings I use when setting up a device for listening is done such that you get the best overall sound for ALL styles of music!
With these settings I get clear Rock guitar for instance, or crisp crunchy high end rhythms like are used in Industrial music. This is great for Electronic music like EDM or Techno because you get very clear treble and bass signatures on all sounds. You also get very clear and full bass like in Reggae and R&B etc - It's great for Classical and Acoustic instruments because you can hear the full range of string instruments for instance.
I tend to try to push the bass and treble limits while still getting clear mid-range while avoiding distortion. In other settings I often find that sounds struggle to compete with one another instead of sounding clearly separated. When they compete they tend to get 'muddied'. When they are separated they sound more crisp and full bodied etc.
I'm curious if anyone else is willing to try these on other devices and/or headphones or even external speakers and let me know how it sounds in comparison to the other presets available for download at the link above. I personally find that you usually do NOT need a lot of different presets for different genres of music though once in a while slight adjustments can help for things that are more bass heavy but are often unnecessary overall.