Approval from Etymotic Research!

Today, I had a conversation with Mr. Jonathan Stewart, the Engineering Manager, Quality & Regulatory Affairs at Etymotic Research, on the phone, and he verified & approved my blog article regarding the proper insertion depth of insert earphones. After sending a crap load of emails to college professors & audiologists, DIYing a coupler, reading through journal articles & industry standards, my few years worth of effort has finally payed off!

And this also means that most of the IEM manufacturers have been hiding the most vital part of the equation in using IEMs- proper coupling of the earphone and the ear itself! Usually, conventional IEMs, especially custom-moulded ones, reach no deeper than the 1st bend due to technical difficulties & safety reasons. This kind of shallow insertion would not secure the residual ear canal volume of 0.5cc, and cause some degree of linear distortion on IEMs.

Thus, I blame *erry Har*ey, the founder of *l*im*te Ea*s & J*au*io and Wes*one, for causing all these! (At least Etymotic Research and Shure have long eartips available for deeper insertion)

The mystery of a fortune cookie

Today, I was eating at a Vietnamese restaurant, and stumbled upon a fortune cookie with some bizarre fortune paper in it.

Hmm..

I can neither decipher nor understand what it means even though it's written in English. Maybe it's some kind of a secret message from a government agency, handed to me for some reason..?

Also, verbally in Korean, 'bó zi' means ...

"Do not let what you do not have, prevent you from using what you do have." 

- a fortune cookie

Ultrasone's headphone technologies

Sometime ago I started a post at hydrogenaudio.org regarding what Ultrasone claimed upon their headphone technologies:

http://www.hydrogenaudio.org/forums/index.php?showtopic=73327

It's still an ongoing discussion, and I am waiting for someone professional who can verify all the electromagnetism related mumbo-jumbos Ultrasone has claimed.

Guess who's using Etymotic Research

Barrack H. Obama - ER4

Hillary Clinton - ER4

..Yes these folks are down with Etymotic Research- and you know they deserve some of those tea-party shit for sure.

George W. Bush - ER6i

Oh.

How is a balanced armature different from a dynamic?

From the Acoustic Society of Japan..
(sorry for my clumsy translation)

Source: http://www.asj.gr.jp/qanda/answer/183.html

Q: It seems a balanced armature type has been more utilized on insert earphones lately- how is it different from a dynamic type?

A: A balanced armature transducer is a type of electro-magnetic transducers, and is fundamentally different from a dynamic transducer in principle. An electro-magnetic transducing mechanism is an adaptation of Flemming's left hand rule, which is a product of the force of magnetic field, current, and the length of a coil, caused by the perpendicular force generated when current is applied to the coil set in perpendicular to the direction of the magnetic field. The force, which is in proportion to the change in current, drives a diaphragm, and generates acoustic pressure.

Meanwhile, an electro-magnetic type utilizes any changes of magnetic pull, by alternating magnetic field generated at the magnetic gap. Consequently, since magnetic field strength B is proportional to its force B², an electro-magnetic transducer must contain some second-harmonic components inevitably. In order to minimize this harmonic distortion, a balanced armature type has been developed. As Figure 1 shows, the design of a balanced armature consists of a magnetic armature in the center of the magnetic gap stabilizing the pulling force of direct current, while canceling the second harmonics that are proportional to square of the pulling force. Because the direct-current magnetic field and the signal magnetic field on the one side of the gap are in same direction, while it is in opposite direction on the other side of the gap with the force in opposite direction as well, the force square of driving pressure on the armature nullifies. Moreover, using magnetic ferrites, or other rare earth materials with less magnetic permeability, might slightly change the size of the magnetic gap, but the acoustic sensitivity should be enhanced around 6 dB with driving force now doubled, while the value of B remains pretty much constant. In practice, by comparing the sensitivity of a dynamic transducer and a balanced armature transducer (in reference to IEC 60711), the former type is 102 ~ 106 dB, while the latter type is 112 ~ 116 dB. Due to its high sensitivity, a balanced armature type has been used in applications in which more volume is required with less amplification, such as hearing aids, but recently, it has became the subject of interest to audiophiles. It seems there are only upsides, but of course, there are downsides as well.

1. Compared to a dynamic type, a balanced armature is high in cost due to more strict limitations in designing. Normally it is 3 times more expensive.

2. As the vibrating system is made out of an iron-related material, its mass is heavier; Thus, normally acoustic sensivity beyond 7 kHz range decreases.

3. Since the location where the direct-current magnetic pulling is stabilized is at the center of the magnetic field, even a slight displacement would cause the armature to stick to either side of the magnet. Increasing the stiffness of the vibrating system definitely helps resisting the magnetic circuit's pulling force. However, due to the presence of the magnetic gap between the ear, low frequency playback becomes harder when there's an acoustic leak.

The practice of inserting earphones into the external ear canal has became more popular among manufacturers. And as a result, with better isolation, those earphones reproduce better bass. Maybe that is why you see more earphones with balanced armature transducers in these days.

Ōhira, Ikuo (Advisor at Ishda Sound Inc.)

CUSTOM•FIT ear sleeves for ER-4

Dr. Mead C. Killion, the founder of Etymotic Research, used to say: "Adding custom earmoulds to high-fidelity earphones could compromise fidelity." But recently he seems to have changed his mind on custom moulds: "but we found a partner in ACS that allows us to maintain the Etymotic sound signature while providing an extra level of customisation."

I trust Dr. Killion, so I've gotten my self a pair of CUSTOM•FIT ear sleeves, exclusively made for my ER-4B. ACS Ltd. (Or more precisely, DST Swiss) took care of the entire process. The cost was $100, which was quite affordable, but 2.5 months of waiting period was just little too long, IMO.

This is the result, and I AM VERY DISAPPOINTED with the quality of this CUSTOM•FIT ear sleeves. Yes, I am. Here's why:

As you can see, the insertion depth of CUSTOM•FIT is extremely shallow, causing a linear distortion mentioned previously.(insertion up to the reference plane, 13mm away from the eardrum, is a must) Due to the distortion caused by the insertion depth, ER-4B sounds like a hollow tin-can and does not work along with binaural recordings or any other HRTF synthesis.

Furthermore, the lengths of an acoustic tube on both channels are not matched, resulting in λ/4 resonance of the tubes at different frequencies. This skews the frequency response of ER-4B even further.

If someone is willing to pay $100 only for the sake of comfort of ER-4, CUSTOM•FIT is the way to go for. However, if you're serious about the fidelity of what you hear, stay away from it.

Of course, I've requested a re-make of my ear sleeves to the DST SWISS with detailed instruction, but I've yet to received an answer(price quote) from the DST SWISS. :(

Update on 11/09/2010: DST SWISS neither answers my phone, nor calls back though I left a message. Are they intentionally avoiding me? Dr. Kasper, from Etymotic Research, just called in and promised me to fix everything that went wrong. Even though I can't trust DST Swiss anymore, I can certainly believe in Etymotic Research. He said he will call back in couple of days, so I will wait for his call.

Update on 12/21/2010: On Dec. 9th, 2010, DST SWISS sent me another pair, by charging me $85 without my authorization. And the result was more or less the same to the first pair! So I contacted Dr. Kasper again on the same day to address the issue. On his email, he said DST SWISS is not affiliated with ACS USA anymore, and I can get the refund of $85 charge. (which I got on Dec. 15th) Dr. Kasper promised to send me another pair, this time made by the lab which is now 100% owned by ACS. THANK GOD I don't have to deal with those DST SWISS anymore..!

Update on 01/17/2011: Dr. Kasper forwarded my inqueries to Mr. Matthew Sinisi, Customer & Provider Relations Representative of the new ACS USA. Mr. Sinisi told me the UK lab got my ear canal scans, and they'll make the sleeves ASAP. After initial 2.5 months + later 3 months, I will finally be able to get the sleeves with quality that I originally expected from ACS.

Update on 02/18/2011: I finally got new sleeves, and they fit perfectly. Their physical built quality is top-notch; Yet, acoustically, they are more or less the same to the ones made by DST SWISS. Below is the analysis.

Currently, with a quick calculation, the right sleeve is 19mm away from the eardrum, while the left one is 22mm away. Considering the adequate residual distance of 13mm, new sleeves are way too far away from the eardrum. I contacted Dr. Kasper, and he said he will discuss the issue with the lab technician who manufactured my sleeves. I'll see how it goes. (I surely am a man of patience)

Update on 02/19/2011: Dr. Kasper informed me that new sleeves are in production now with above issues taken care of. Hopefully ACS get it right this time, so that ACS and I do not have to go through this kind of ordeal ever again.

Update on 03/14/2011: The 4th pair is here. Below is the analysis.