This blog may rightfully be regarded as a “rambling” as it is attempted to gain in knowledge and understand how to apply an optimal set of EQs to the FIIO FH7, but in case of discussions on this matter, it could be of value. You are really reading a log of progressions. There will be at least a part three of this blog as we crawl slowly in the direction of a perfect EQ for the fabulous FIIO FH7.
For the record, we (in HD SoundLab AS, Norway) are normally developing products like SoundPimp audio enhancer; “headphone soundstage on speakers”, but there is a need for a properly tuned IEM or two, for normal usage and for monitor use in development of advanced loudspeaker systems. The goal is clear: EXACT sound reproduction, as close to reality as possible. Perfumed treble to tempt you in the short run? Not interested. So:
Below subsequent suggestions for EQ for the FIIO FH7. The result is already the best monitoring transducer we ever had on ears. The Focal Elear is here too, but is put aside and must be subject to EQ upgrade later on. Compared to this EQed FIIO FH7, Focal Elear is now a disappointing transducer.
Let us know if you come up with something better. See email address in footer (preferred) or make a comment below. Even a flying thought could be of value. This is still an immature attempt, but song after song is heard like never before. We use LG V30, with its superb (in our opinion) high-end DAC. Fantastic combo with these corrections:
This EQ focus on improving the treble, rather than the overall balance and tonality. The reason is the limit of the Equalizer at hand for this version. It is attempted to straighten out the peaks and dips of the FIIO FH7 specifically in the 3kHz to 9kHz region. The Harman “standard” curve was used as “the truth” (true or not, too early for us to tell) about how this region should look like.
Note that we had to simplify a little as ToneBoosters in this Android version (an extension to USB Audio Player Pro) only offers 6 EQ positions. Therefore, additional EQ was added using the other EQ tool included in Android USB Audio Player Pro. Both are running. They will be merged using other methods later on.
There is still a tint (but no more) of hiss somewhere in the upper treble. And some other imbalances in the treble region overall. And some imbalances when listening to the totality. IOW, more work is in the pipeline.
This version has a better tonal balance than version two, but, after a while, we started to notice a certain “greyness” in the treble in the below version. Albeit, it is still quite good compared to the RAW FIIO FH7:
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).