Took the time to go through all the filters this weekend after
@ExpatinJapan 's call to action. Hiby R6--->iBasso PB3 Mockingbird (SE)---stock cable.
To start filter 1T is the darkest sounding filter of the bunch. The top end is very much subdued while the low end is front and center. The strong bass presence bled into the mids leading to less refinement than the other filters but but a benefit to crowded tunes that could use some smoothing over. I found most of the Heavy hitting needle piercing dubstep I listen to paired well with these or compressed tracks.
The 2T cleans up the bass a bit by releasing some of the sub-bass for upper bass/lower mids reducing the bleed and increasing instrument separation. There is also a noticeable increase in clarity and presence in 1k - 5k area that really brightens up the presentation.
The 3T seems to turn back towards the 1T in regards to sub-bass but with a full clean, clear, and crisp bass presentation. The 1k - 5k jump seems slightly recessed for those who prefer a darker sound,
The 4T is very similar to the 3T but the 1k - 5k presences is back making it a brighter sound.
And all natural lessens the bass slightly in comparison to the 3T and 4T but leaves a crystal clear balanced tone between the mids and highs.
My personal choice is 4T. it adds just enough bass without taking anything away. Having five sound signatures to choose from is such a luxury; I can't say enough good things about these headphones.