Earfun Free Pro 2 - reference tuning

I would like to post my first result of the new reference tuning, which replaces all previous tunings I did in terms of fidelity or neutrality or however you would like to call it. After weeks of trial&error and endless hours of listening sessions I have finally a setting for my own ear canal resonance frequency which I would regard as satisfying enough to be shared with you. It should work well for resonances close to 6000Hz, mine is slightly higher now and closer to 6150Hz but it sounds and measures well at my standard 6000Hz. Over time I will add all settings optimised for other frequencies, as soon as they are finished. Below you can see the new tuning in bold black, with lots of earlier variants I tried and rejected during this time. It would seem as if there were just small differences but actually all these tunings sound completely different, with some sounding way off although they all measure with a very similar tendency:

My goal was to get a true sounding tuning with as little as possible coloration still to some degree interesting and impressive sounding, outperforming most other headphones I own. It should sound similar to the HD600 equalized with my own EQ which I posted here.

Below you can see a measurement overlaid with my earlier tunings like "neutral" in green and "RC2" in blue:

A big change compared to before is some upper bass increase which was necessary to really make it "true" sounding. These measurements show more bass than in reality, with deeper insertion the bass as well as mids will be measured with a lower amplitude, this is a limiation of the measuring coupler. According to my measurements I would be way above the Harman target, but with a more standard insertion also mids follow the Harman target better. In green you can see exactly the same EQ setting just measured close to 7k with the 6k filter adjusted accordingly: 

The green graph represents the real bass response much better, also mids are closer to the target now, although it would seem there was a lack of response between 2-3khz. I tried filling this up, but it sounded wrong to me, therefore only relying on some measured curves won't tell you anything about the real sound, which has way more body now without sounding boomy, as lower bass even decreased compared to my previous tunings. But listening to a lot of neutral references, I discovered that the stronger upper bass was always present to a similar degree on my neutral or equalized to flat headphones, this made the result sound less hollow than before. I tried to capture the timbre up to 1-2khz as good as possible with the overall bass to be as natural as possible, although depending on your unit you may want to decrease bass even slightly more, I highly doubt it will be necessary to boost it, as most other units I tried had rather too much bass compared to my reference unit, I use -10.4dB on my other unit, why my reference unit has it at -10dB. This setting works well with normal and transparency mode, unfortunately with ANC it will become too bassy now, because ANC boosts upper bass which was missing in my previous settings. You can try to change to another ANC mode from within the Airoha app like it was suggested before, but with my old app version I have no access to additional ANC settings and cannot try out any other modes.

Apart from bass I think that mids and treble sound also way more natural than before, at least to my own ear. I was monitoring with pink noise but also performing sine sweeps all the time to get sure that I have no area boosted or recessed. When sweeping above 5khz, I get a pretty constant amplitute with just minimal changes in amplitute and rather dips than peaks up to 16khz. I cannot judge the result above 16khz as due to my age I have my limit here, therefore I would need your help to find the most neutral and satisfying setting above 16khz. The treble area is also the one which changes most depending on ear canal length or even insertion. Below you can see various measurements inserted as exact as possible at 6000Hz still the treble range above 13khz varies between all measurements, which I cannot trust just by judging the measurement and need to rely on my ear up to 16khz. Right now performing a sine sweep I get a constant amplitute to around 14.5khz which starts to slowly roll off above that and dies around 16khz. I could extend this range with some stronger upper treble boost but this may lead to an excessive treble boost for those with better hearing ability.

The current tuning has some issues though, which I may want to address before doing all further work. The tuning became quite loud and is much louder than my previous RC2 tuning as the filters are created completely from ground up. Now I am usually listening below half volume to get decent listening levels. Let me know what you think about the current loudness curve and if it's an issue for you. The problem I had with my previous tunings was that due to continuous filtering the final result became quite soft leaving the lowest and highest frequencies untouched at the same time, thus there was a raise towards high and low frequencies with no control over it. Shown is a measurement of a previous version compared to the new reference tuning also overlaid with the Harman target and you can see a strong raise towards 20khz, which now shouldn't be an issue now because I follow the target more closely: 

The rebuilding of the filters allowed for an own "air"-filter at 16k which gives you the option to control upper treble to some degree depending on your ability to hear high frequencies. 

My standard setting should be quite faithful up to highest frequencies I think, and I would like to ask those who still hear up to 20khz how this sounds to them checking the response with some sine sweep. I would also like to add an alternate setting which leaves everything more or less the same up to 12khz and only boosts above that. This setting sounds definitely more airy but at the same time may changes the treble timbre a bit and may be too much for those with younger ears. Measurements of both shown below:

The standard setting: 

Setting with additional upper treble boost keeping everything else at the same level:

I would welcome everyone to try it out and give me your feedback which I can work into the final setting. The raw response has 3 distinct peaks which the shown filters are correcting for. Listen to pink noise and adjust the shown filters to get rid of any harshness as long as your resonance is not too far away from mine. These 3 filters are the most important ones to get a smooth response. If pink noise doesn't sound natural to you, try moving the 6K filter slightly up or down in frequency until pink noise appears natural and smooth to you and do the same for the other 2 filters. This works best in realtime if you load my EQ into EqualizerAPO and adjust the settings there:

My goal would be to create a basic setting which adjusts the rough response with the other 3 filters simply correcting for the ear canal resonance (red) and its upper harmonics (green), I am not sure where the 2nd blue peak comes from but this will also shift depending on ear canal length etc. This is not easy to achieve as so far I was simply trying to at least get a general response that would satisfy myself in all regards, I would need to rebuild my complete filter set and do some experiments if a basic setting with only flexible filters for the peaks would still lead to usable results. My current setting should work well up to 6500Hz and maybe down to 5700Hz if the peak filters are adjusted accordingly. Above or below that the overall response will simply change way too much with the current filters, that it would need more detailed adjustements of the remaining filters as well.

I will wait for your feedback especially from those with a similar resonance frequency as mine as all others will get wrong results with this setting. In the meantime I will try preparing a general basic filter setting which may only need additional adjustment of the 3 peak filters depending on ear canal length. I am not sure this is possible at all. Depending on the feedback I will be getting I will start to either optimise the current setting which I attached or start working on creating all other settings for lower and higher ear canal resonances than mine with the posting being updated as soon as a new setting is finished and uploaded here.

Update: thanks to a discussion I had with Francois who discovered that even when listening to sine sweeps over neutral speakers, the amplitude doesn't remain constant, but there are some dips, especially one at 7.5khz, I also hear another one at around 9.5. This made me have another look at the tuning and suddenly I could indeed hear the peak at 7.5khz, which I tried to correct for and changed the balance slightly. 

I think the updated setting gives an even better and smoother transition from mids to treble, you can see the previous setting in blue with the new one in black. You can see slightly more response at 5k while less at 7.5k now, at the same time treble is boosted slightly to add some transparency, thus my alternate setting with extra treble boost shown above is obsolete now, because the current adjustments made the overall sound more balanced and airy (attached is already the updated tuning).

Update 2: I tried to fix treble smoothness a bit more which maybe also fixes the metallic character many are complaining about. The transition from mids to treble appears smoother and more realistic to me now, this "Sssss" has gone now more or less while mids i in the 4khz region are slightly more pronounced more which seems to sound more comparable to what one would get from a speaker. I also replaced the attached EqualizerAPO config file with the updated setting here. Please let me know if it's some improvement for you as well. If it's still too metallic for you try reducing the 16k filter a bit more or increasing the Q-factor.

Update 3: I tried some further adjustments, and although minimal they can have a big impact on the overall smoothness of the sound but can also lead to different results depending on the used unit. I have 2 further variants and would like you to tell me which one sounds best to you on your unit. A is the recent one, B is with slightly reduced mids and treble which appears smoother to me, C is like B with upper treble reduced even more. From the measurements the difference appears rather minimal but when listening to pink noise the differences in smoothness can be significant especially depending on the unit. I want to start preparing all futher settings for additional ear canal resonances and try to stay as close as possible to my reference, but need to know which I should regard as template.

Update 4: I am currently trying to prepare EQ settings for other ear canal resonances but will need your help finding the right path. I created a setting for 6250Hz which follows my original 6000hz measurement pretty well:

I can achieve 6250Hz with deeper insertion but the result doesn't sound the same as my setting for 6000Hz although both measure nearly the same:

I sat down and tried tweaking this setting in order to make it sound similar to what I usually get with normal insertion and a 6000hz resonance and came up with this:

But this setting gives a completely different measurement compared to my original 6000Hz setting:

Maybe the angle of the nozzle becomes different when inserted deeper, which might affect treble response that I had to compensate for. But like this the result sounds closer to my own 6000Hz setting while measuring completely differently. I would kindly ask those with a resonance of around 6250Hz to try both settings out and tell me which sounds more normal to you. 

The 6500Hz setting would look like this:

Looking at the measurement you see less bass and less mids compared to my original 6000Hz setting, although only the resonance filters were adjusted. Please let me know how those affected perceive this setting, as I need to know how to proceed and if I can still rely just on measurements or if these settings need to be corrected by a trained ear, which unfortunately I cannot do on my own, but would need others for that:

Update 5: After lots of further hours of listening sessions, I think i managed to smoothen the sound even more compared to B which was favored by most, some still complained about some remaining harshness which should be gone now more or less. I think the sound gained some additional transparency compared to before, the balance changed a bit as seen from the measurements, with black being the new and hopefully final tuning which I will use as base for all other ear canal resonances. The dip at 7.5kHz is on purpose as this definitely elimnates some of the remaining harshness. We also gained a bit of lower bass compared to before and the tuning became slightly softer which is not bad, as the previous one was too loud anyhow. I would say this is the most realistic rendering up to date I managed in terms of naturalism:

Those who are close to 6000hz please let me know if this tuning is an improvement for you and I will immediately start preparing all other settings after your approval:

I also prepared a playlist with some outstanding recordings for you to check. It should sound balanced and detailed with the new tuning: https://music.apple.com/at/playlist/reference/pl.u-DdAN0YeTaMKYpd

https://open.spotify.com/playlist/2aWDszMTsGzXhbLA4SUjiu?si=HEitHdMXTBGAaR2MCZPNGA