[UPDATED ON 1/14/2012] After having a nice little chat with Mr.Sead Smailagic in regards to his designing philosophy via email communication, I am convinced Mr.Smailagic really tried everything he could in terms of electroacoustic design in order to make customers happy with their purchase. If everything clarifies, I awe Mr.Smailagic, and to him only, a big public apology. I've thought all this time, MH1C is worth only a couple of dollars in terms of sound, but this will be changed in no time. And the data deviation listed here is possibly due to manufacturing error. Once I obtain the original version MH1 along with MH1C version, I will post a separate entry with everything newly analyzed. Before that, please keep in mind all the information below is preliminary and inconclusive!
[UPDATED ON 11/29/2012] Reworded the part# 2, the role of MH1C's top vent to make my point clearer.
[UPDATED ON 11/28/2012] Added possible explanation on why Mr.Smailagic's and my data are different in the low to mid frequency range. I didn't know there were two different versions! Also added some new datasets.
Sony MH1C has been causing quite a stir lately among users who fancy budget-fi, partly due to the designer's voluntary background check. Unless very confident with their products, it is exceptionally rare for original designers to submit themselves for public verification.
According to the designer, Mr.Sead Smailagic of Sony Mobile, MH1's acoustic signature revolves around the very basic; how the human hearing system works. He mentions that all kinds of factors related to a human HRTF(head related transfer function), including the missing 6 dB effect, the directional notch of a free-field response, and finally, the equal loudness contour, are accounted for designing the IEM.
First of all, the missing 6 dB effect has been debunked.
Second, when MH1C is compensated with a free-field target, the mid-high frequency range becomes very linear.
So it seems Mr. Smailagic's approach works. But then again, it shall be noted that the free-field reference has been long gone ever since it was challenged more than 30 years ago by Germans. On top of lack of a natural interchannel leakage, due to much interpersonal variations, this approach simply introduces a linear distortion in the high frequency range.
Third, according to Toole, as long as the output volume is well above the realistic hearing level, this kind of equal-loudness compensation is not preferred for a high fidelity reproduction.
"The curves tell us that different frequencies at the same sound level may be perceived as having different loudness. This is not a message that anything needs correcting. We live with these characteristics from birth, and they are a part of everything we hear, whether it is live or reproduced. That is why audio equipment must exhibit flat-frequency responses—uniform output at all audible frequencies—so the sounds we perceive have the correct relative loudness at all frequencies, assuming they are reproduced at realistic sound levels."It can be argued that the compensation is to maintain a spectral balance at lower volumes as well. Even if the boost is relative to the contour, due to the +20 dB with such small Q factor, the argument will not hold water at all.
IMO, his explanations are commercially oriented excuses to sell a product. not to mention that there is an affiliated blog blatantly advertising the IEM. Is a bad excuse better than none? No, I don't think so. (to whom may it concern: I have no interest in bashing anybody with the above statement, absolutely no reason to do so. To my standard, whether there's a monetary transaction involved or not, if a blog is in close relation with a representative of a special interest, then it's as good as an affiliation. AND if the blog actually shows off the product with manufacturer bias, then it is an advertisement. Even I had a phone chat with Mr.Jonathan stewart of Etymotic Research, thus I should be affiliated as well with Etymotic Research in a way.)
CON: A lot of uncontrolled bass. This bass will simply mudify the overall perceived fidelity.
ON SECOND THOUGHT #2: There is a vent on top of MH1C, which works as an acoustic filter, although the low frequency drops down only to a few decibel when the vent is blocked.
Since depressurization is occurring elsewhere (most likely at the strain relief), excursion caused by over-pressurization should not be of an issue here. However, as the sonogram on the left clearly shows blocking the vent actually worsens the sub-bass response by causing more delay, it may also contribute to a better transient characteristic of an IEM within the ear canal.
Let us not even talk about measurement accuracy, as it's right on target.