Martin Logan Mikros 7

According to Wikipedia, Martin Logan is an American company producing a variety of floor-standing hybrid, wall-mounted, and in-wall speakers using electrostatic loudspeaker and planar magnetic thin film loudspeaker technology, as well as conventional subwoofers.

In September 2012, they introduce their first IEM, Mikros 70, which is "inspired by the clarity and detail
of MartinLogan’s legendary high-end electrostatic loudspeakers", and should deliver "realism, richness, and purity" to listeners, according to their claim. It will certainly be revolutionary if a dynamic driver's electroacoustic performance is close to that of an electrostatic driver.

PRO: Very clean transient, Super-low distortion, and planar driver-like impedance linearity, which yields no frequency-dependent attenuation. What, no resonance?? Just feels like orthodynamic from 30 years ago.

CON: Absolutely flat. No sign of diffuse-field in its sound, similar to an unmodified UE900. A slight channel mismatch in the mid frequency range. The high frequency bandwidth is up to the specification, but with a large downward tilt.

ON SECOND THOUGHT #1: It is a good idea to insert Mikros 70 deeper into the external ear canal, since the frequency response above 10 kHz and below 19 kHz notches down as insertion depth becomes shallower. (IOW quarter-wavelength resonances shifts) The IEM's acoustic output impedance is quite for a dynamic type.

ON SECOND THOUGHT #2: Other than stock sleeves, Martin Logan also includes a pair of tri-flange sleeves in the package. As you can tell, its longer stem changes the quarter-wavelength resonance of the IEM, and cuts off the output in the high frequency range, while boosting the mid-frequency. If you can insert the IEM deep with stock sleeves, don't even bother with the tri-flanges.

Westone 4

Again, this is owned by an Austrian Head-Fi user, James444. Much appreciated for your contribution, James!

Last time I encountered Westone products was when I attended the Canjam 2009, held in Los Angeles, California. I had a nice little chat with the representative, and auditioned Westone 3 along with UM3X. He even gave me brand-new sleeves for better fitting! IMO UM3X sounded little more neutral, but I did not find either of them to my liking. And in 2011, Westone introduced a new model with quad-driver configuration, Westone 4.

PRO: The overall distortion is below the threshold of 1%.

CON: Polarity inverted. A brick-wall high cut at ~12 kHz.

ON SECOND THOUGHT #1: In terms of tonality, Westone tuned this IEM to be electrically linear within the ear canal, as JH Audio and Ultimate Ears do all the time with their products. Still, Westone 4 still keeps somewhat neutral tonality due to its slow mid range, which would have been unseen without my newly established waterfall & ETC & GD plots. It basically prevents the sound to be overly emphasized in the low and high frequency range. Moreover, the subbass delay gives nice natural "thumping" sensation- I just wish it was less boosted and had more response over 12 kHz.

ON SECOND THOUGHT #2: The high frequency peak at 10 kHz won't go away, whether the insertion depth is deep or shallow.

ON SECOND THOUGHT #3: What a pleasant surprise with Westone 4's impedance characteristic. Adding a 100 Ω resistor will turn the tonality quite linear, while suppressing the peak at 10 kHz & pumping up the response above 10 kHz. This modification is highly recommended. The IEM shall be fully underdamped with a 250 Ω resistor, with about +6 dB @ 2.5 kHz.

ON SECOND THOUGHT #4: How does the acoustic damper affect the sound of Westone 4? As acoustic impedance of the damper increases, the high frequency drops down. Unless more bass is desired, this modification should be avoided.

ON SECOND THOUGHT #5: The sleeve analysis with Westone 4 will be discussed on a separate blog entry. Stay tuned! Meanwhile, here's my 2 cents for Westone 4 users: Add a 100 Ω resistor, equip a pair of Phonak's stock sleeves, and insert the IEM shallow, but with a tight fit; a great neutrality & high-frequency extension achieved. 

Location : 1033 N Loara St, Anaheim, CA 92801,

Posted via Samsung Galaxy Note

HiFiMAN RE-272

I first met Dr.Fang Bian of Head-Direct.com at Canjam 2009 held in LA. It was when his all-new HiFiMAN HM-801 was first introduced, and I auditioned it along with some of the YUIN earbuds. Well, to be honest, I was not impressed at all with the quality of his products at that time. I simply disregarded HiFiMAN brand as one of those random Chinese products.

And at the end of year 2012, I come across HiFiMAN once again, with the help of good friends!

PRO: Flat frequency response, on par with Etymotic Research ER-4P / modified UE900. The overall impedance is so linear, even a 100 Ω resistor does not hinder RE-272's damping characteristic. Also, the amount of decay is nicely even along the entire frequency range.

CON: Slight channel mismatch in the upper frequency range.

ON SECOND THOUGHT #1: The shallower you insert RE-272, the less peak you will get, while the bandwidth remains more or less the same. This is an engineering wonder of in-ear acoustics.

ON SECOND THOUGHT #2: Other than regular stock sleeves, RE-272 also comes with biflange ear sleeves, which boost the response above 10 kHz. Combine these biflanges with shallow insertion, and the frequency response will become even closer to the diffuse-field reference.

ON SECOND THOUGHT #3: There is a removable acoustic damper within the nozzle, effectively controlling peaks in the mid to high frequency region. Unless peaks are desired, removal of the damper is not recommended. Moreover, the vent is merely a depressurizer- blocking it is not recommended either.

The electroacoustic performance of RE-272 is simply outstanding, eventually changing my preconception on HiFiMAN brand. Chinese manufacturers really have improved over the years, and I can now confidently recommend HiFiMAN and Vsonic products to anyone! (No, I still won't recommend Heir Audio.)

Ultimate Ears Custom In-Ear Reference Monitors

A fellow Head-Fier, who lives in Austria, generously let me borrow his Ultimate Ears Custom In-Ear Reference Monitors(UERM). As it must take a lot of will to lend such an expensive equipment overseas, I truly appreciate James for the trust. (Not to mention Inks did all the diplomatic works! This could have never been possible without his support)

In a collaboration with Capitol Studios, Ultimate Ears developed this custom IEM for studio engineers. The manufacturers claim that the IEM has been meticulously tuned to be flat, in order to match any type of professional recording/mixing/mastering conditions.

Since I've never measured a custom IEM before, I had to build a special jig to suit them. Now I can confidently measure any customs with an air-tight seal!

PRO: Very low distortion at the frequency range where the human hearing is most sensitive. Aesthetics-wise, such a great craftsmanship by UE.

CON: Unlike what the specification states, the UERM does not cover up to 20 kHz. There is a slight channel mismatch in the lower frequency region. Its impedance characteristic varies greatly over the entire frequency spectrum- making the IEM hard to be driven effectively.

ON SECOND THOUGHT #1: Since the exact location of the reference plane can only be determined via either a CT-scanning or equivalent volume measurement of the ear canal, a slight shallow insertion is inevitable.

ON SECOND THOUGHT #2: Adding any amount of resistance to the UERM is not really a good idea, as it loses good amount of high frequency response, as much as -10 dB or more. The lower the output impedance of the amp, the more high frequency retained.

ON SECOND THOUGHT #3: According to ITU's definition, a studio monitoring headphone should provide a flat diffuse-field response within very narrow tolerance limits. While the UERM shows some signs of diffuse-field in the mid frequency range, it is too far off from the reference target. Rather, its response is close to JH Audio's tuning philosophy.

ON SECOND THOUGHT #4: Is it just me, or the frequency response of the UERM really resembles that of good old Triple.Fi 10 Pro?

You be the judge, but as far as their frequency responses are concerned, the deviation here is a matter of a simple crossover circuit / acoustic damper modification. Of course, above response of TF10 can only be achieved when it is situated at the reference plane, meaning when it is custom-molded. Still, there is a chance for reasonable doubt when the price difference is x10. Just sayin', that's all.

SONY MDR-7550

AFAIK SONY MDR-7550 is an international version of MDR-EX800ST, specifically tweaked for a monitoring use unlike its brothers, EX600 and EX1000, which are tuned for a personal listening.

PRO: Very linear impedance characteristic, and almost non-existent distortion figure.

CON: For some reason the channel balance is little off with this unit, as if the left channel has been slightly clogged with wax. The frequency response can be a lot more flatter IMO. 7550's high frequency extension is little too short. Not really a desirable tonal balance for monitoring purposes, as suggested by the ITU tolerance.

ON SECOND THOUGHT #1: As expected, just like MDR-EX1000, the insertion depth does not play much role here, partially due to the fact that it does not have much high frequency content to be altered with, and partially to its low acoustic output impedance.

ON SECOND THOUGHT #2: Even a 100 Ohm resistor does not alter the frequency response of MDR-7550. Don't expect much from its electric damping characteristic.

ON SECOND THOUGHT #3: There is an acoustic vent on MDR-7550's housing, working as a depressurizer, just like that of Sony Ericsson MH1C, or that of AKG K3003. Blocking the vent will greatly boost the sub-bass, along high frequency extension.

However, it is worth to note that not only the vent prevent the drivers from getting damaged, acoustic vents sometimes contribute to a better transient characteristic of an IEM within the ear canal, especially when the diaphragm is of a high compliance.