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(
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?
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.
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!
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.