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Tuesday, October 23, 2012

Ultimate Ears UE900 part3: In-depth analysis


Introduction

Ultimate Ears UE900 set the definition of Logitech's new reference in IEM acoustics: Low distortion, wide bandwidth, and linear impedance characteristic. More importantly, there are never-seen-before technologies implemented as well.

1. A pinhole bore
2. Knowles TWFK damping
3. Logitech: The pioneer of triple-bore technology?


A pinhole bore


Perhaps the most intriguing part of UE900 lies in its unique dual-bore configuration, with the large bore dedicated to the tweeter (Knowles TWFK), and the small bore dedicated to the woofer(Possibly Knowles CI-22955? Possible candidates are Knowles DTEC variants or Sonion 3300/3700/3800, according to one of my blog readers, Tom). My initial assumption is that the pinhole bore has something to do with an acoustic constriction action, which is a widely used low pass filtering technique in audiology for taming the frequency range above 5 kHz; the thinner the bore, the less output in the high. Moreover, as long as the bores are separated, the technique may help further eliminate any type of phase interference issues which may arise when a high frequency transducer is connected to a low frequency transducer in parallel.

from Wikipedia

So I did some constriction action calculation with that in mind.


However, the calculation attempt fails to yield anything valid- the measurement just does not match the numbers at all. Rather than cutting the high frequency, the pinhole actually amplifies the low frequency. What's going on?

So upon close examination of the frontal nozzle cap of UE900, I figure those four transducers actually share the same acoustic chamber within the nozzle. Thus, the dual bores do not really act as bores, but more as an acoustic enclosure with two ports working as Helmholtz resonators. (I guess the phase offset correction has been implemented only physically, by shifting the distance of the transducer from the outlet) Since the larger bore only affects the high frequency range due to its size(wavelength), the working principle of the pinhole is more of a concern here.


With so many acoustic filterings along the sound transduction path, no wonder the polarity of UE900 is so skewed up! Still, this approach is the first of this type of IEMs, so I shall give some credit to Logitech.


Knowles TWFK damping

There have been some speculations of UE900's high frequency transducer unit being a Knowles TWFK within the community. Even the damper configuration is identical, though UE900 uses 2200-Ohm red dampers instead of brown ones. Regardless, since there is enough room for a damper to be inserted on the larger bore, here you go:


Even with a slightest acoustic impedance drop, UE900 will lose all the frequency response above 16 kHz, since it is amplified by the larger bore's high pass filter, just like any other TWFK equipped IEMs. Try not to clog this bore with your bodily fluid!


Logitech: The pioneer of triple-bore technology?

Now we all know the dual-bore configuration techniques that are implemented on Triple.Fi 10 Pro and UE900 come from US7263195 & US7317806, issued on August 2007. While going through a bunch of research materials, I stumbled upon a patent document, US8116502, issued on February 2012. This patent deals with Logitech's all-new triple-bore & multi-layered bore configuration, both for generic and custom IEMs.

And it literally means that all of the custom & generic IEM manufacturers will have to acquire a permission from Logitech in order to manufacture devices with such bore configurations. You may call Logitech monopolizing the industry, but I know many companies haven't got the license, and made products anyway. Hopefully this will effectively eliminate whole bunch of random IEM companies with no objective design philosophy in mind.


In conclusion

Ultimate Ears UE900 is a well-made, class-defining product. It is free from the effect of electric damping, low in harmonic distortion, and reaching up to 20 kHz. Ultimate Ears really got their homework done, thinking about how bad Triple.Fi 10 was in those criteria.

The only thing UE900 is missing is the diffuse field linearity, and..


If someone is interested in a neutral tonality from UE900, hook up a 100-ohm adapter, block the pinhole, and insert the IEM nice and deep. That will yield the flattest, and widest frequency response, on par with electrostatic headphones! Really? Try it for yourself!




Appendix


There has been quite a talk going on in regards to this data. Perhaps it would not hurt to mention that Innerfidelity's data are in good agreement with mine, under a very specific circumstance.

25 comments:

  1. Interesting analysis. I knew there was something different about that side port, but I didn't have that much time with the UE900 to make any real conclusions. It's nice to see some data.

    I'm curious what you think of the design of the Ocharaku Flat-4 (http://ocharaku.jp/sound/service/) design; you've probably already heard of it, but just in case, it's essentially two ATH-CKM55 transducers glued back-to-back, with a tube coupling the two housings, so that the back driver seems to act as a bit of an 'active' Helmholtz resonator. Well, at least that's how I understand it.

    I know Sonove did an analysis on it, but I can't really understand technical stuff through Google Translate...

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    1. According to 図8 on http://ocharaku.jp/sound/technology-2/, Flat-4's funky design is intended for a selective-equalization using phase-cancellation. If data were good, I would've been convinced. Unfortunately, that is not the case. IMHO, rather than simply evening out peaks, Ocharaku need to focus more on a human HRTF.

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  2. You should probably correct this section:

    "Perhaps the most intriguing part of UE900 lies in its unique dual-bore configuration, with the large bore dedicated to the tweeter (Knowles TWFK), and the small bore dedicated to the woofer(Possibly Knowles CI-22955?)."

    The CI-22955 is a single driver unit, which means that it can't possibly be inside the UE900. The size is not the same. The woofer used in the UE900 is more akin to the Knowles DTEC, its new high-output variant the HODTEC, or the Sonion 3300 series, which has many variants as well.

    While it's likely that the mid/high unit of the UE900 is indeed a TWFK, it's likely a completely proprietary-spec version designed solely for the UE900, with different internal dampening.

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    1. That was just my speculation, nothing solid about the statement. I definitely need more info in regards to identifying what the woofer unit is. Has anybody crack-opened their UE900 yet? LOL

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  3. Well, it's definitely NOT the CI.

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  4. BTW, No one needs to crack open their UE900... they won't find anything more helpful than what they can see from the outside, unless you want them to crack open the BA units themselves. The point is, the woofer unit is a dual driver unit. It is two drivers welded together back to back to output to a single port. If UE decided to go with all Knowles, then it'd be the DTEC/HODTEC, with its own dampening specifications. If the decided to continue with mixing/matching, then it'd be the Sonion 3300/3300U/3700/3800, unless UE commissioned them to produce a whole new design, which is unlikely. All proprietary drivers, no matter how different, are variants of existing designs.

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    1. I see. Since there ain't many dual BA models around dealing with bass, we may be better off just rounding up with those two. Thnx for the info, Tom.

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  5. How would you suggest blocking the pinhole?

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    1. Makes the bass tighter. If you make even a smaller pinhole, that will lower the resonant frequency. IOW it will only boost the lowest sub-bass. Highly recommended for bass-heads.

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  6. and how does this IEM compare with the ER-4?

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    1. Worse for phase skewing.
      On par for frequency response & distortion.
      Better for high frequency extension.

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  7. so the sub bass gets stronger when the pin hole is block and the logo portion of the ue 900 came off so i got to see the ba inside and you cant really tell what they are unless you crack them open like someone mention above

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    1. Sub-bass becomes more "controlled" when the hole's blocked. It's good to know somebody actually opened up the UE900 LOL JK, I hope someone takes a picture of the drivers!

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  8. so the sub bass becomes more controlled and the overall bass becomes tighter, but at the same time the presence and the impact is diminished? lol I was tempted to take the ba out but i knew that would void my warranty. I sent my 900s back to Logitech, there sending me a new one. Hopefully this dost become a repeating issue with the 900s.

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  9. How did you managed to block the pinhole? Cos it is so small that it is almost impossible to put anything in it

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    1. Get a duct tape and a scissor, cut out a tiny piece which is small enough that can only fit the pinhole, and apply it. I'd use a head of a needle to give a firm pressure to it.

      ..Or apply a tiny amount of silicone gaulk.

      And FYI, if you make even smaller hole on the tape, it will only boost the sub-bass range below ~50Hz, which is quite nice.

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  10. How well would a 33-Ohm resistor work on this IEM? Does a 100-Ohm resistor offer greater improvement than 33-Ohm. Also, what ear tips do you use in order to manage a deep insertion?

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    1. 33 Ohm should do it too- only less than a few dB short compared to 100 Ohm. I'd recommend using UE biflanges or MH1C stock sleeves for deeper insertion.

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    2. If I wanted to use a 100-Ohm adapter, where would I get an inexpensive one? Preferably a flexible one, similar to Cowon's "Sound Capsule" adapter.

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    3. I don't think they sell flexible ones.. I'd rather modify one of those Radioshack's volume attenuators.

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    4. Where would I be able to purchase a pair of UE bi-flange ear tips? I'm not getting much luck on Amazon...

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    5. The generic ones on Ebay are as good as stock! Kudos to Chinese sleeve manufacturers :)

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  11. Hey, really appreciate the in depth analysis even if I don't understand any of the technical stuff. I own a C&C BH that's equipped with two outs, one is 0.1 Ohm output impedance and the other is 100 Ohm output impedance. Would the second out yield the result you're talking about? Because on one point you stated that it changed with the output impedance and here at the end of the article you said to hook up to a 100 Ohm adapter. Is that really the same thing?

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    1. Ok! Thanks a lot, now it will be really hard to resist buying the UE900. My wallet curses you but I admire what you do.

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