The original eq suggestions in version 1 of this post has been deleted, because we found a better way.
As stated in several reviews, e.g. by NymPHONOMania, FH7 has great potential, but there is a harshness in the presence area that kind of destroys the fun. In the referenced review, one source of this is the original cable. This is exactly what we found ourselves as we per coincidence got another 40cm cable from the Norwegian agent of FIOO. Its length wasn’t that usable, but its sound was much better. More refined, not so harsh, all in all a much better experience. We are two persons who had this experience and we are both into “audiophile sound”, so to speak.
The other day, we were testing Unique Melody´s MEST, comparing. And using the original cable, the difference was large enough in favour of MEST to justify the higher price level, due to that haunting FH/ harsness. It is not a good thing. However, we started investigating, and found an older cable from a left-over; the completely unusable AudioFly AF1120 top model. (Unusable because there is simply no bass, and amazingly strange construction).
We replaced the factory FIIO cable with the AudioFly, and what a shock. The whole device just calmed down, and started to produce smooth treble and a MUCH better soundstage. Believe me, and you will if you try, but it is like night and day. The enhancement is on the level that “all known” music must be played again for confirmation, and we got it, on track after track.
I add that this is with the green (treble emphasis) filter, the soft earpads and the AudioFly cable. Problem solved.
It migh sound odd that a treble harshness is solved with adding a treble filter, but treble is many things. The green filter is distrincly more smooth than the two other filters in the bag. We have tried withe black (natural) filter, and this also works well, but presents a somewhat coarser treble. You will hear distinct differences when listening to fine recordings of female choirs, well done violin recordings, etc.
Compared to the MEST, at the double price, MEST IS better, but our new arrangement is closing the gap in a significant manner. What mainly remains, is the total blackness in the MEST, resulting in more “air” and more seperation between the instruments. Therefore, we have kept our original measurements of the FH7, as the 3rd harmonic distortion in the midrange could be the reason. Other options are better internal configuration of drivers in MEST, or better drivers. Who knows…
Conclusion: FH7 has gotten critics as above, and right fully so. Therefore, FIIO could consider replacing the original cable with another, more aligned the examples found in the linked review and here.
A harmonic distortion issue
There ARE errors here, e.g. too much level in certain regions of the bass range creating a “FH7 signature” (= bass perfumed), a little too “massive” treble, etc, so there are definitely things to work on. But compared to RAW FH7, this EQ in our ears represent a giant step forward in audio quality.
As there is always “a worry” left in whatever tweaking process, this time it is the harmonic distortion of the midrange driver; Knowles DFK BA said to be based off the classic 30017. We are not sufficiently competent on the normal level of distortion on IEMs, but on normal loudspeakers we know a lot, as we work with that. On those, these levels, in particular the 3rd harmonic, would cause concern. Whether it is at all audible, we suppose we will find out along the way. Here is the measurement, though not following any world standard for measurements of headphones. We have a home-brew arrangement. The distortion holds a higher level on FH7 than several other IEMs that we have here. The third harmonic is often related to mechanical misfits, so it could be a design “flaw”, or a production issue. We are going to ask Fiio.
If you are reading this without knowledge of harmonic distortion, just know that 3rd (in particular, but also all odd numbered) harmonics are your aggressive enemy, while even order harmonics are not THAT critical. Those are not aggressive, but can cause pitch changes, and distortion is distortion.
Look to the 300 – 1kHz area. The two upper curves are the FH7 (measurement is notorious), at the bottom Focal Elear and BGVP MDG (at 20% of the cost of the FH7). In the middle (the purple) it was injected a broad EQ dip on the FH7 to make it look more similar to the BGVP MDG, to check if a reduction of the peak in that area would calm down the 3rd harmonic. Problem not quite solved by that coarse test. It may possibly be that it is the said Knowles driver that deserve to be subject to further 3rd harmonic investigations. (But could be a million things causing it).