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Thursday, November 22, 2012

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.


  1. " 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?"

    they also share similar impedance curve!

    1. Is it a coincidence, or not? :p

    2. It might not be a coincidence (and I don't think it is), since the xo's of the 2 are very similar. The only difference is the UERM's woofer is filtered by a 6.8u instead.

  2. When you say "Adding any amount of resistance to the UERM is not really a good idea", you added a 100ohm resistance adapter like this one?

    I am getting the UERM but am not sure if my Little Dot MK IV SE would work well with the UERM and a 200ohm impedance adapter.

    1. You'll end up with almost no treble, if you hook up a 100, 200 or even 33 ohm adapter to your UERM. Here's the rule of thumb for UERM: The less source impedance, the better.

    2. Thanks, I will probably end up getting a Asgard 2 when I get my UERMs.

  3. Hey Man Thanks for this amazing test !

    I'm looking to buy a high-end pair of in-ear monitors, this seems to be the best most linear option out there, would you recommend it ? or is it better to buy another brand/model with better specs ?