Earfun Free Pro 2 - work in progress (Patreon)

I wanted to keep you updated about what is happening right now. I spent the last days concentrating on getting something usable out of the Free Pro 2. For the start I tried to tune it towards the same response of the Free Pro solely by matching both responses which didn’t lead to any usable results. With more or less the same measured frequency response for both the Free Pro 2 sounded off, with some perceived peak which I didn’t hear from the Free Pro. I don’t quite understand the reason but it just proves that tuning solely by looking at some graphs won’t be successful henceforward I didn’t pay too much attention to measurements anymore but kept tweaking and improving by ear instead and ended with various versions until I finally settled for a particular tuning which I used as base for further adjustments. You need to keep in mind that this procedure is really exhausting and takes hours of concentrated work, listening to pink noise, reference tracks and comparing back and forth, I am not an expert at this and I am sure others can achieve better and faster results, but if it was that easy, all headphones out there would sound great. I was always coming back to this particular version if my further “improvements” didn’t turn out successful. I also started to depart more and more from my original target but still tried to get the overall response smooth with no obvious harshness. When I finally performed a measurement to see what I was actually doing, to my surprise the result resembled the Harman target quite closely:

I always criticised the Harman target because it never sounded right to me with all headphones which were tuned towards it but obviously there is more to this than just some line. The balance between all frequencies must be right, if some upper treble is missing you will perceive lower treble as too harsh, gettting this balance right is really the hardest task because when I tried to “improve” the tuning by smoothing the response based on the measurements the result became worse, it sounded worse and I had to always get back to my starting point and try improving from there. I finally settled for this temporary tuning and wanted to give it a longer try. I was listening with it since yesterday and although I can still hear some slight issue with room for further improvement I am to some degree impressed at the same time. I wouldn't say it sounds necessarily better than the Free Pro, but the sound became extremely spacious sounding. I am not sure if this is just due to a different tuning or if there is more to this, but Free Pro 2 with this tuning sounds extremely open and broad, it easily competes against the HD800S regarding sound stage, I was blown away by that effect, despite the remaining minor issues I can still hear with treble, I assume the dip around 13khz could be the main reason why I am still not fully satisfied as the Free Pro rather peaks in this region, here both side by side:

I quickly tried "filling up" this dip with a filter, but was not successful so far, as the result became again worse sounding, you can immediately notice any issue by listening to pink noise. Sometimes just listening to music doesn't reveal all differences. A particular track can sound great on its own, but by playing pink noise you start to hear that there are problems. 

My current status is that I am still listening with this tuning right now as it has some particular magic to it, and although it sounds different to the Free Pro, they both have their own flavor and I cannot settle for one or the other. This just proves again that tuning a headphone can be really tricky as it's not the absolute values that matter, but the balance of all frequencies to each other. Changing some frequency in the upper treble range will also affect the timbre of lower treble a lot. You always need to keep the entire image in mind.

Before posting some first values I still need to listen and optimise it until I am fully satisfied only then I can  start my work on all further resonance frequencies. This can take again a while, as I also need give my ears some rest after longer sessions I will keep you updated as soon as I have further news. But for future I even came up with the idea of offering further tunings simulating the responses of other popular headphones like the HD800S for example. There won't be any need for buying new headphones again, as I can simply transform the Free Pro 2 into something completely different if wanted just taking the limit of 10 filters into account. Please let me know what you think about that idea. Of course it's going to be lots of work thus I won't be able to release new tunings every week but if there was enough interest this could in fact become my main occupation instead of reviewing some mediocre sounding highend end-game flagship headphones, although I would definitely need more supporters that would allow me to invest into new measuring equipment and finally to have enough money to get a new PC or new studio monitors for owning an even better neutral reference...