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Thursday, June 6, 2013

Suyama Fit Ear F111

Disclaimer #1: This opportunity has been provided by Bryan, who is a frequent contributor of this blog. Had there been no support from my fellow contributors, I would've long given up on this blog. Thank you again!
Disclaimer #2: Measurement has been carried out right at the reference plane of the occluded ear simulator, using a pair of stock single flange sleeves.

Originally named as TO GO! 111, Suyama's FitEar F111 was first introduced in July of 2012, and later released in February of 2013. As a single-BA transducer driven IEM, F111 has a lot of competitors, such as ER-4 of Etymotic Research, and SE420/e4c of Shure. And of course, in order to keep their product competitive in the game, Suyama develops a proprietary technology once again. Made in titanium, F111's テーパードポートステム(Tapered Port Stem) delivers great airiness and elegant treble, according to the manufacturer.

PRO: A well-matched pair, flat frequency response, low distortion & nice built quality as expected from Suyama.

CON: Inverted polarity

ON SECOND THOUGHT #1: Although insertion depth-induced resonances are minimized due to Suyama's  テーパードポートステム, shallow insertion is still recommended for F111.

ON SECOND THOUGHT #2: If anyone feels F111's treble to be somewhat recessed, adding a serial resistance to the IEM may help resolve the issue. A resistance value of 33 Ω is recommended, as 100 Ω seems to be an overkill.

ON SECOND THOUGHT #3: Unfortunately, because the diameter of  テーパードポートステム's inner opening is smaller than that of an acoustic damper, damper modification can not be carried out with F111. And as expected, even a microfiber handkerchief does not dampen the IEM, due to high acoustic output impedance of a balanced armature transducer.

ON SECOND THOUGHT #4: As observed in above data, Suyama's テーパードポートステム, which is an acoustic horn, lowers acoustic output impedance of the transducer, making the IEM relatively free of insertion-depth/sleeve bore related acoustic interference. In short, the horn plays a roll of an acoustic impedance transformer. According to Dr. Harvey Dillon, the director of research at the national acoustic laboratories of Australia, an acoustic horn has following effects:
"By gradually changing the diameter of a connecting tube, and hence its impedance, there is a more gradual transition from the high impedance receiver to the low impedance canal, and hence less power is reflected...Consequently, the response is less peaky, resulting in improved sound quality."
Such technique is extremely useful for taming high frequency peaks/amplifying the treble acoustically at the same time, and it has been utilized for the optimization of Westone 4 previously by me.
In order to fully understand the overall effect of  テーパードポートステム, the inner diameter, the outer diameter, and the length of the horn portion must be figured out.

The horn's gain is obtained via above formula, which calculates to ~6 dB boost.

And the 3 dB cut off frequency turns out to be approximately at 18 kHz, at which the driver hits the upper bandwidth limit. It is clear the technique has been utilized to offset F111's electroacoustic limitation caused by its single driver configuration.

ON SECOND THOUGHT #5: Compared to its quad-driver brother, To Go! 334, F111 has both advantage and disadvantage. While F111 lacks linearity in the upper frequency range, it has better fidelity in the low-mid. This is quite awkward, since To Go! 334 is supposed to cover the lower frequency more tightly with its multi-drivers.

ON SECOND THOUGHT #6: F111 is quite versatile, as it can be tuned to coarsely fit both of the references: the Olive-Welti target and the conventional diffuse-field target, which is my recommendation. The former is achieved by simply equipping the IEM 3mm away from the reference plane, and the latter is done the exact same way, but with a 33 Ω resistance added in series.


H. Dillon, Hearing Aids, Boomerang Press, Turramurra, Australia, 2001.


  1. Thanks, nice writeup! I've been eying the F111 and its successor Parterre for quite awhile all because of their horn design.

    There've been several people reporting the significant improvement over the ER4-S, which the F111's based on, in terms of soundstaging regardless of their identical FR. Can the horn be the cause here?

    Also you are saying that the horn design will cure canal resonance which is insertion depth dependent? I don't entirely get this part though, doesn't resonance have more to do with tube length rather than acoustic Z?

    1. You're welcome! I won't go that far to call F111 as an ER-4 equivalent, as it is lacking linearity in the treble. But it is indeed a solid-built, versatile IEM.

      An acoustic Horn boosts treble without introducing additional distortion. but the public opinion could be due to a slightly damped mid range & a long decaying sub-bass.

      Insertion-depth induced resonance is caused by the 2nd wavelength resonance of a closed ear canal, and becomes more prominent when the transducer is of a constant volume velocity source. (Zo > Zi)

      An acoustic horn is an acoustic impedance transformer, decreasing the high acoustic Zo of the transducer. When this is equipped on a balanced armature driven IEM, it will effectively decrease the level of acoustic interaction, such as reflections and standing waves, caused by impedance mismatching, hence minimizes the insertion-depth related interference.

      Personally, though, I prefer Sennheiser's D2CA more :p

  2. Is it just me or it feels a lot like HF3??

    1. If you can obtain a deep-insertion, and decrease the mid-range slightly with EQ, Yes.

  3. I'm a bit confused. If I fit the f111 correctly I can lower 16khz with my eq and easily hear the drop out. From your graph it looks like it doesn't even go past 11khz? If I boost the treble as well, I can only go 1-1db past 12khz before it sounds to "sharp" to me. I'm used to the er4s and pfe112, so I know what flatter and brighter phones sound like, however even though this is a "less bright" earphone, I seem to be getting better extension. However, with certain fits I defintely hear a cap around 11khz. So is it possible you didn't get a "perfect" fit for your measurements? I know you tried different distances, but for me it has to do with the seal and distance being perfect.

    1. By looking at the Olive-Welti graph, which is the realistic subjective tonal quality of the IEM, its relative level difference is about 10 dB compared to the lower range. The notion of "short bandwidth" applies when the frequency response is "conservatively" referenced to the diffuse-field target of ISO 11904-2.

      However, the high frequency extension of 16 kHz is still way too short to be considered as Hi-Fi IMHO.

  4. Would inserting one of the cables the other way correct the inverted polarity? I'm interested in these headphones as a replacement for the ER-4P, would you recommend them? Thanks