I spent more time testing the FiiO FH5s than any other set of in-ear monitors to date, which is also why there is an extra page in total and two pages of results and discussion. There was a lot to test, especially with the custom tuning options through the three sound-tuning switches in each of the two ear buds. This meant first measuring and plotting out the frequency response for both channels, doing the same with the three modes of bass, mids, and treble boost, normalizing the results to a set frequency, and making sense of it all. But all of this took a day at most, with the rest of the ~2 weeks spent dealing with the strong recommendation from FiiO to burn them in for 200 hours before objective testing. I strayed on the safe side and burned them in for an extra 50 hours on top only to find out that there was indeed an appreciable change in favor of the listening experience with these, including a reproducible frequency response change.

I am reaching out to FiiO to see if they have an answer as to why, but, more importantly, why the end user is supposed to do this at all. I have already seen first-hand how multiple owners of the FH5s were left disappointed after the FiiO hype machine worked overtime prior to launch a few weeks ago. Reviewers generally were left unimpressed, and then came the burn-in part a conspiracy theorist might well say was chosen deliberately long for users to get used to the IEMs and decide to stick with them rather than do a return. Had it all been psychoacoustics, I would agree, as I still don't completely believe in this, but other things seem to have contributed, too.

Take the design, for example. FiiO is using a fairly novel semi-open design as part of a dragon scale motif on the face plate. This is complemented by a hidden pressure relief valve closer to the sound tube itself, which combined ensure a balanced air pressure throughout the acoustic chamber housing two dynamic drivers for increased bass and vocal representation without compromising on soundstage, as well as a dual-unit balanced armature driver that is arguably the bottleneck in getting a stronger recommendation. Be it burn-in, consistency across channels, or even comparing the ideal case scenario with the artificial head to the human ear mold, it was the treble response that consistently let down the rest. This continued with actual listening where things are certainly better now than when I first started, but I still find the need to tweak things from time to time.

The sound-tuning switches are great for this, especially for the treble range. I don't see myself using it for the bass boost since I get enough already, and the mid boost causes the treble range to worsen, so maybe in specific use cases only. The genre-specific ear tips are also quite novel, at least to me, and the whole customizable aspect of these semi-open IEMs is why I am awarding the innovation award even though I can't generally recommend the FiiO FH5s across the board.