Starting my work on the Earfun Free Pro 2 (Patreon)

I want to finally start my work on the Free Pro 2 and did some first measurements which I would like to share with you. These are compensated for my own target, thus the Free Pro which you can see in black will measure as a flat line. Blue is the factory tuning for the Free Pro 2 and red the raw unequalized tuning. You can see there are some issues, especially the overwhelming bass which will be hard to tame with just a single filter like I managed on the Free Pro. Treble alone will require most of  the filters, thus I am not sure I can really manage the same quality despite the better hardware overall.

I also wanted to ask if there is need for additional tunings higher than 7000Hz? I could still try to prepare tunings for 7200Hz and maybe even 7400Hz, but I am not sure if there is someone who would need those except maybe my son. I was actually surprised that so many seem to prefer the 7000Hz tuning. 

With the Free Pro 2 I hear the peak at exactly 6000Hz, thus it seems to be a bit lower than what I get from the Free Pro, you can also see that peak in the measurement (I always try to reproduce what I am actually hearing on my own, not doing some generalised measurements like everyone else does with some fictious resonance frequencies which no human being would get except maybe a newborn).

I could maybe post a first result for my own resonance frequency within some days, but it will take quite a bit longer to get all other tunings finshed. Fingers crossed I can manage something decent, because I really like the Free Pro 2 hardwarewise.

Update: Fooled around for about 1 hour now, used 8 filters so far and I think it already sounds great. AutoEQ towards my target sounded off and needed 18 filters, tried to start with that one trying to adjust it better but was still not satistied so I started completely from scratch without even trying to follow my target too strictly and wasting filters for some small details. I am surprised that this led to a much better result.  It's not perfect but already better than most other IEM I know. There seems to be some magic to get the tuning right, there must be some particular ratio between various frequencies that needs to be correct in order to fool the ear that the sound is good, while concentrating too much on absolute values will sound off. Unlike with the Free Pro the Free Pro 2 has slightly more bass in ANC mode, thus this mode will always sound slightly different and a bit more boomy, I will try to balance it out to have neutral bass with normal and ambient mode and more bass with ANC, which makes sense to me.