Search This Blog

Wednesday, February 20, 2013


I'd like to thank James for letting me analyze this unique IEM. 

Introduced in 2011, JVC HA-FX700 is one of those IEMs made with off-axis driver configuration in order to accommodate a large-diameter micro dynamic transducer.

Although HA-FX700 is equipped with several technical innovations, they all have already been implemented when HA-FX500 was first introduced:

1. A wooden dome
 - Minimizing harmonic distortion in the low frequency range, while suppressing the mechanical resonance in the high frequency range.
2. Dual-hybrid structure
 - Preventing energy loss due to vibration & stabilizing transient by enclosing the driver in a brass chamber.
3. A wooden housing
 - Inducing natural tonality from wood's eigenmodal properties.

According to JVC, a thin film of birch/maple is first stacked on top of a sheet of Japanese paper, impregnated with thermosetting polymer together, and then bonded on a PET diaphragm by thermocompression.

As the dome becomes more rigid, its characteristic motion breakup is effectively reduced. Such oscillation controlling technique has been adapted by various manufacturers, including Beyerdynamic(Varimotion) and Sennheiser(Duofol) as well.

PRO: Very unique tonality, perhaps on par with that of Final Audio Design.

CON: Excursion-induced distortion is quite gross. It is obvious that none of the "innovations" are working the way they are intended to.

ON SECOND THOUGHT #1: Regardless of the insertion depth, the tonality remains pretty much the same.

ON SECOND THOUGHT #2: HA-FX700 is heavily tuned with acoustic vents. While the front vent deals with the sub-bass range, the rear vent equalizes the mid range.

ON SECOND THOUGHT #3: A simple dust filter will not change the sound of this IEM.

ON SECOND THOUGHT #4: Interestingly, whether it is due to insufficient frontal venting or the wooden dome's low acoustic impedance, a small amount of leakage tames the low frequency range quite nicely.

ON SECOND THOUGHT #5: If anyone's interested, here's my recommendation on JVC HA-FX700. It is extremely hard to control the mechanical resonance at 5 kHz, but long-stem sleeves, such as Meelec triflanges, will do the job by pushing the IEM's resonant frequencies upwards.


  1. 1 question about"ON SECOND THOUGHT #3: A simple dust filter will not change the sound of this IEM."

    How you perform such measurement? Just made a hole in sound tube and install different acoustic resistor to the outside?

    As I understand this IEM made for loose ear-canal insertion. This recess the bass profile and smooth overall frequency response?

    1. 1. I simply add a 3/16"-wide annular sheet of either a non-woven cloth, which is equivalent to the HiFiMAN's stock filter, or a microfiber handkerchief, which is equivalent to Sony MH1C's stock filter, at the tip of the nozzle. There needs to be a reference acoustic resistance to compare to, for the accuracy assurance.

      2. While acoustic leak caused by loose insertion helps to tame the bass, shallow insertion will definitely even out the high frequency peaks/dips.

  2. Sorry I mistake on the pictures. I askin about how you perform front leakage with different acoustic resistance?
    I think it is best to try more leakage material in front cavities which goes outside the year. I mean a foam material in front of the driver.
    It can reduce the sub-bass region and dont breack any else..isn't it?

    1. I made a coupling jig, which had a small opening for dampers to fit in, and connected the IEM to the occluded ear simulator. Otherwise, you will have to crack open the frontal housing.

      Introducing additional leakage slightly increase the distortion level in the low frequency range & shorten the decay, but the pro simply outweighs the con.

  3. Look here:

    The frontal ring damper acts like additional resistance from driver to the outside of the earphone body. This item is responsible for such a boomy sound of FX700.
    If anybody remove this damper the bass response will be reduced. Possibly the thd curve will be more good without great acoustic impedance in front of membrane and much less in the back (asymmetrical 3rd harmonic is much bigger then 2nd)
    What you thinK?

    1. Once the annular damper blocking the frontal vent is removed, the IEM will simply lose all the bass response due to radiation impedance caused by huge amount of leak, behaving like an open-air earbud. In addition, the harmonic distortion will be increased tremendously as well.

  4. It won't be opened at all. There is a damping foam layer stays there...The same acoustic impedance as to the ear wave guide ...

    1. Puncture a hole on the front vent mesh, and you'll know what I mean. Of course, I won't take responsibility for any possible property damage. :p

  5. I personally prefer the RE272 as the best in sound and comfort at ones. But the HX700 wonder me in unusual micro-dynamics. I think it is outperforms the 272 in this aspect.

  6. Great Blog!!
    Any others ideas on how to improve the FX700 sound quality?

    1. Please refer to "ON SECOND THOUGHT #5", as that is the best I can possibly do with the IEM which I do not own. Otherwise, I'd decrease the air flow in the rear cavity for tighter bass & enlarge/elongate the nozzle for linear treble.

  7. Thanks for the help.
    Ive already ordered the tri-flange tips. Gonna try to reduce the air flow.

  8. Hi, not sure if somethings is wrong or not but my fx-700 have had very distorted bass since i bought it and I have had it replaced yet sounds the same, tried diferent buds as well. I thought given your knowledge you may be able to tell me what it fould be or if i can mod it to fix it.

    The bass isnt as deep as expected and it sounds very overdriven as well as being distant to the highs. The massive soundstage of the highs is what i was expecting but the bass certainly is not

    1. That sounds like a stock FX700 alright, LOL! Try to block the rear mesh with a masking tape, and make a pinhole with a needle. This technique will somehow dampen the overall bass level, and prevent it from being over-driven. If the bass quality still bothers you, you need move on from the IEM, and start searching for your perfect match. :)

    2. I like the bass volume, its something i look for but the quality.. it was awful. I have now covered up the ear facing ports, which increase the bass and the distortion seams mildly better.

      I will try your suggestion.

    3. FX700 has a lot of harmonic distortion in the bass range, indicating the driver has well exceeded its excursion limit. Tempering the rear vent will decrease the flow of air and dampen the driver.

  9. Is it possible to tame the resonance at 5khz using an EQ? I'll be using Rockbox's EQ settings, if so, what would be your recommended settings? TIA