Ultimate Ears Reference Remastered

CK Moustache

100+ Head-Fier
Link to my review and measurement index thread where one can also find a full review overview, more information about myself as well as my general-ish audio and review manifesto: https://www.head-fi.org/threads/956208/

I only give full stars. My ranking/scoring system does not necessarily follow the norm and is about as follows:

5 stars: The product is very good and received the "highly recommended" award from me.

4 stars: The product is very good and received the "recommended" award from me.

3 stars: The product is good/very good, but not outstanding/special enough to get any of my two awards. ["Thumbs Up"]

2 stars: The product is only about average or even somewhat below that and somewhat flawed/flawed in some areas. [neither "Thumbs Up" nor "Thumbs Down"]

1 star: The product is bad/severely flawed to outright bad. ["Thumbs Down"]

Ultimate Ears Reference Remastered to-go


Review sample.


Three BA drivers per side, three acoustic ways, triple-bore design.

Great to see Ultimate Ears finally offering their CIEM models as UIEMs, especially for those who prefer the fit and handling of universals over customs (myself included) due to not having any fit, seal or positioning issues with most UIEMs.

Came with Ultimate Ears’ new, compact round storage case compared to my UERMs’ large “Roadie Hardcase”. While of high quality, padded on the inside and nicely compact, I wouldn’t mind if it were just somewhat taller as the ear tips can get deformed depending on how the IEMs are positioned inside the case.
Decent unboxing experience.

Good ear tip selection (they appear to be similar to those that came with my UE900 and UE900(S)) and typical accessories such as adapters (6.3 to 3.5 mm as well as impedance adapter) and a cleaning tool. The ear tips could be a bit stiffer, though.

I like the UERR to-gos’ standard design that is clearly an homage to the UERM, but with inverted colours.

Just like on my UERM, I like the transparent inner halves of the UERRs’ shells that reveal the three drivers, crossover components, internal wiring, dampers and sound tubes.
Comparing both, one can see that the driver layout and internal sound channel architecture is different from the UERM which had a dual-bore design whereas Ultimate Ears have opted for three bores on the UERR (most likely to better match the midrange’s and especially treble’s frequency response to the target they aimed for).
What I like as well is that the nozzles’ collars sit further in the back wherefore the ear tips don’t really protrude, which should reduce the acoustic affection that the ear tip material has on the sound to a minimum.

Build quality is very good.

Nicely soft and flexible quad-conductor cable with 2-pin connectors, although ultimately a bit less flexible than the (nicer and more premium looking) factory silver cable that I went with for my UERM.


Largest included silicone ear tips.


Neutral leaning very slightly towards the darker and warmer side. Nearly similar to the tuning of my InEar ProPhile 8. One could also simply say “just like the UERM but with a flat, linear treble without that >10 kHz peak”.

The bass is very flat and extends flat into the real sub-bass without any roll-off, and is slightly lifted by around 3 dB to my ears when listening to music, sine sweeps, noise signals as well as when compared to my Etymotic ER-4S. This leads to just a bit of “body” added to the sound, with an ever so slight spill into the midrange but without necessarily colouring it as the UERR are ultimately still some of the flattest sounding in-ears on the market.

Midrange timbre is mostly correct to my ears, with the upper midrange and presence range being just slightly more on the relaxed side, just like that of the UERM, which gives the UERR a still very revealing but somewhat more relaxed, less “brutally” revealing character compared to in-ears with a more diffuse-field-oriented midrange tuning approach, such as the ER-4S.
That said, what I hear is a still accurate sounding midrange that is ultimately however somewhat closer to a “prosumer neutral” than “studio neutral” tuning, with a slightly warmer and less direct approach in the presence range, but ultimately still very accurate.

The treble is, except for the ~5 kHz range that, just like on my ER-4S and many other in-ears, a bit more recessed than flat-neutral to my ears, remarkably flat, even, smooth and neutral, which also applies to the super treble frequencies above 10 kHz where the UERR sound flat and accurate compared to the UERM that had a peak which added quite a bit of brightness to the sound when a note hit it exactly; extension in the super treble is excellent and reaches past 17 kHz.
Therefore, the treble reproduction and timbre is accurate and realistic to my ears, but, as a result, at the cost of also being less “exciting” or “fresh” when compared to the UERM, which makes the UERR objectively the more linear, more accurate sounding in-ears.

Frequency Response:


Unlike most other in-ears, the UERR to-go showed to be super critical to insertion depth and angle in the coupler, reacting with strong frequency response changes in all areas depending on how they were positioned. The plot above is probably the closest to my actual perception, although with less bass shown on the graph compared to what I actually hear in a side-by-side comparison with my UERM and ER-4S.
The graph below (PP8 compensation) is from the same measurement.

ProPhile 8-Compensation


While the UERR have an additional sound tube over the UERM, it doesn’t show in terms of raw resolution.

Generally, the UERR are mostly similar to my UERM as in having high resolution that is definitely flagship territory, although somewhat below “summit-fi”.

The biggest difference compared to the UERM is in the bass where the UERR, while still having a quick and tight attack with high control, appear a bit softer and with a slightly more lingering, longer decay compared to the UERM, which results in a perception of more “body” at the cost of some perceived tightness.

Midrange details and speech intelligibility are on a high level, and it is rare that one would desire “more”. Speech intelligibility is high.

Treble details are on a high level without faking details with peaks, and the whole presentation is very natural and coherent, with great coherence. While ultimately similar in terms of actual resolution in the highs when compared to my UERM, the UERR definitely have the advantage of sounding more realistic due to being tuned more even here.


The UERR, just like the UERM, will not have the largest soundstage in the range of high-end in-ears. Models like for example the now discontinued UE18 Pro are more expansive and create a deeper, wider and even more layered field of sound. This however doesn’t mean that the UERR have a small soundstage, nonetheless it appears a bit smaller than that of the UERM.

Due to a bit less spatial width than my UERM, the UERRs’ stage appears circular to my ears.

What the UERR can do well is reproducing proximity, and in this regard their soundstage in general appears a bit closer to one’s face than the UERMs’ although both in-ears feature around the same amount of spatial height as well as spatial depth that is definitely well present wherefore the UERR also manage to layer well and create a good imaginary room with quite precisely placed and separated instruments as well as good spatial scaling abilities depending on the recording.

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Ultimate Ears Reference Monitors:

Bass quantity is pretty much similar while subjectively, the UERR appear slightly warmer, fuller in comparison, which is most likely due to the lack of the super treble peak that the UERM have whereas their successors do not. As a result, they definitely sound less analytical.
When it comes to the midrange, the UERRs’ appears closer, more intimate in the mix, with just a touch more perceived lower midrange body while still maintaining a mostly correct, neutral timbre.
In terms of the rest of the treble, both are pretty much similar to my ears, however the UERR do not have the UERMs’ 10 kHz to 13 kHz peak, wherefore they sound smoother, more realistic (“correct”) and more linear in the highs to me, which is a definite plus and, in my opinion, also a rather substantial improvement, however due to that, they are also perceived as “warmer” in comparison and lack that “UERM magic”.

While both in-ear models are on a very high technical level, the UERM appear a bit faster and tighter in the bass compared to the UERR whose lower notes seem to linger just a bit more, which is why they ultimately come across as somewhat tighter, faster and better controlled sounding than their successors that seem to have somewhat more body and decay despite not having any more bass quantity.

Directly compared, the UERMs’ soundstage appears to be somewhat more spatial and wider to my ears, with the UERR presenting the imaginary stage closer to the listener, which makes them appear more intimate.
Layering, precision and separation are pretty much equally good but as the UERRs’ bass appears a little “slower” in comparison, they come across as slightly blurrier/less precise on fast and dense tracks.

As a result, the UERR have an edge over the UERM in terms of tuning because of their more linear, more realistic treble response, whereas the UERM are somewhat above the UERR in terms of technical performance when it comes to bass quality and also a bit when it comes to soundstage, wherefore I would position the UERR higher than the UERM in terms of tuning but somewhat below when it comes to technicalities.

Etymotic ER4XR:

The two in-ears’ sound signature is not exactly similar but still heads into a rather comparable direction.

Both in-ears have got about similar levels of “warmth”, if one wants to call it that, in the root, with the ER4XR being a little more forward in the mid- and sub-bass, making them sound ultimately slightly “bassier” than the UERR.
When it comes to the midrange, the Ety are slightly more forward, with the somewhat closer vocals due to more energy in the presence range, while midrange timbre and balance are comparably accurate.
Both in-ears feature a treble presentation that is among the most even and accurate out there, with the ER-4XR having just slightly less energy with cymbals.
The UERR outperform the ER4XR a bit when it comes to subtle air and extension in the super treble.

In terms of resolution, precision, bass speed and tightness, the UERR appear like the higher-end upgrade to the ER-4XR, with an overall somewhat higher level of minute details and a bit more control.

When it comes to perceived soundstage, that of the UERR is, to my ears, about four times the size of the ER4XR (i.e. twice the width along with twice the depth) and also appears somewhat cleaner and somewhat more precisely layered on complex and dense, fast tracks, with a cleaner and more accurate reproduction of “emptiness” between and around instruments and tonal elements.

InEar ProPhile 8:

Both are tuned remarkably similar to my ears, featuring a “natural neutral” kind of tuning in contrast to the more “studio neutral”-like sound that the ER4SR and my ER-4S have to my ears.
To my ears, the ProPhile 8 have got pretty much exactly 0.5 dB less bass than the UERR and UERM, are slightly less “warm” in the fundamental range/lower midrange, and sound otherwise pretty similar to the UERR in the treble.

In terms of resolution though, I would position the ProPhile 8 a bit over the UERR. The InEars’ bass is even tighter, faster and better controlled in direct comparison to the UERM, and even a bit more so when compared to the UERR, with the generally somewhat higher resolution and note separation, wherefore they have somewhat of an advantage in very dense, fast and complex music passages.

In terms of soundstage, just as with the resolution, the ProPhile 8 are somewhat above the UERR when it comes to imaging precision and note separation with very densely arranged recordings.


Natural-neutral tuning with remarkably linear and realistic treble response.

While the tuning would definitely warrant a “Recommended” award, they are ultimately a bit behind the UERM when it comes to technicalities, especially in the bass that appears a bit softer in comparison (which also somewhat affects the perceived soundstage precision), and then there are the overall very similarly tuned but technically more proficient InEar ProPhile 8, which leaves the UERR to-go “only” as being “very good”, with a “thumbs up”.



Headphoneus Supremus
Pros: •now finally available as "To-Go" universal fit version
•widely linear tuning
•"Reference Remastered" very fitting name compared to the UERM
•more linear and therefore realistic treble tuning compared to the UERM
•good detail retrieval, separation and realistic imaging
•no "fake" details
Cons: •die-hard UERM fans will likely miss a bit air and sparkle

Originally posted on my German audio review site, the "Kopfhörer-Lounge", here comes my review of the Ultimate Ears Pro Reference Remastered To-Go - yes, the UERR are now finally available as universal fit version!


For an audio lover, there might be some reasons to pick universal fit in-ear monitors over the custom fit variant, such as handling/cleaning/comfort preferences, better resale value or just the preference of how they feel in one’s ears. Whatever it is, there are definitely people who would rather pick the universal fit option if an in-ear was available with custom-moulded or universal fit shells.
I am one of those people (my reason is mainly the handling and that I pretty much never have fit issues with universal fit in-ears), and have encountered several other like-minded people over the years.

For the majority of time, Ultimate Ears’ Pro in-ears were only available with custom-moulded shells – while this fact was not matching my personal preference, I purchased the now discontinued UERM (reviewed here) anyway. They fit very well and seal immediately, but I would have still picked the universal fit option if it were available at that time. And I heard of others who would have done the same and were wishing that Ultimate Ears would also offer their in-ears for sale with universal fit shells, since the more recent universal fit demo models that are available for demo at their partner stores and distributors have got excellent comfort and ergonomics.


Fast forward, Ultimate Ears, who definitely don’t really need an extended introduction since pretty much everybody who is into the in-ear hobby/passion knows them and their story, now offer the UERMs’ successors, the Ultimate Ears Pro Reference Remastered (UERR), as universal fit “to-go” version, which makes me and those other people who prefer universal fit in-ears really happy.

Rather new is also Germany’s new Ultimate Ears partner, “Hearing Berlin”, located in Berlin, who just opened a second branch, “Hearing Dortmund”, located in Dortmund. They don’t only have a full physical showroom where customers can demo the in-ears, but also a laboratory for servicing defective in-ears.

Now how do the new UERR sound, especially when compared to the UERM? That is what this very review is all about.

Full disclosure: The UERR to-go in-ears were sent to me free of charge for this review. As always, my words are nonetheless true, unbiased honest and written without any guidelines or requirements for the review, no matter how it would turn out.

Technical Specifications:

Price: $999/€1229
Available as: CIEM and “to-go” UIEM
Type of Drivers: Balanced Armature, three drivers per side
Acoustic Ways: three acoustic ways, triple-bore construction
Sensitivity at 1 kHz, 1 mW: 100 dB
Frequency Response: 5 Hz – 25 kHz
Impedance at 1 kHz: 35 Ohms

Delivery Content:

I was a bit surprised by how small the delivery box of the UERR to-go in-ears I received for review was, compared to the large box my UERM came with. This is because the UERR in-ears come with Ultimate Ears’ new, compact round storage/carrying case whereas my UERM arrived with the large “Roadie Hardcase”.

Just as with every Ultimate Ears Pro in-ear, one will also find a sticker on the outside that says who the in-ears were crafted for, what’s inside, along with the serial number and the initials of the person who inspected the in-ears.

Inside that cardboard case, one will find a holder for the universal fit silicone and foam tips that obviously come included with the universal fit to-go version, a round, black transport/storage case with the in-ears inside, and last but not least a 6.3 to 3.5 mm adapter, impedance adapter and a combined cleaning tool/brush.

Looks, Feels, Build Quality:

The standard design of the UERR consists of white faceplates with a black UE logo on the left shell and black Capitol Studios logo on the right shell, which is the exact opposite of the UERMs’ design with black faceplates and white logos. Personally I also think that this design option is the best-suited for the UERR, resembling the UERMs’ iconic appearance but with inverted colours, however options for custom colours, materials and designs do exist too and the buyer has got full control over that during the order process, but it’s important to note that then the Capitol Studios logo would be replaced with a UE logo when choosing a different faceplate design than the standard one.

The body of the shells is clear and transparent wherefore one can see the three drivers, crossover components, wiring and acoustic dampers. Comparing the inner layout to the UERMs’, one can easily see that the UERR feature a different driver layout and internal sound channel architecture. This also becomes obvious at the end of the nozzle where the UERM have a dual-bore sound output whereas the new UERR feature a triple-bore construction with each driver getting its own sound tube and output bore.

Quite clever is the nozzle design of the universal fit to-go version, since the collar on the nozzle sits further in the back wherefore the tips don’t really protrude, which means that the ear tip material will have as little influence on the sound as possible.

Build quality of the shells is really good and I cannot spot any air bubbles.

The custom fit version would have two initial letters as well as a serial number printed on the inside of each shell, with red for the right and blue for the left side.

When you order the in-ears, you can choose between various cable lengths, colours, and lately also material. Bluetooth, digital and microphone cable options were recently added as well, along with the option to go with MMCX connectors instead of the proven Ultimate Ears 2-pin connector type.

Not much surprisingly, the black, twisted quad-conductor cable is very soft and flexible (although the silver cable that I chose for my UERM is even a little more flexible), with proper strain relief near the angled 3.5 mm plug, as it should also be expected in the professional and high-end sector.

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The compact, threaded carrying case that is made of metal on the outside and plastic on the inside has got a softly padded lid and bottom. For absolute perfection, solely bolstered or rubberised walls on the inside are missing.

This new carrying case is definitely a nice addition in Ultimate Ears’ line-up compared to the other, larger cases that were offered as only option in the past.

The universal fit to-go version’s silicone and foam ear tips are nicely soft and colour-coded. People who also own the UE900S will definitely recognise them.

Comfort, Isolation:

The fit and comfort of the custom-moulded version will of course highly depend on the quality of used ear impressions, while the universal fit to-go’s fit and comfort will depend on one’s individual ear anatomy.

Shape-wise, the UERR to-go are quite ergonomic and feature a size that should make them fit quite well if your ears are at least averagely sized. In my large and deep ears, fit and comfort are very good and I really appreciate that Ultimate Ears broke with their old tradition and finally offer some of their Pro models, such as the UERR, as universal fit to-go version.

Cable noise is pretty much inexistent, which is due to the over-the-ear fit as well as flexible cable.

Provided you get a properly tight seal with the universal fit version, noise isolation should be about on the same level as when you are using an acrylic custom-fit in-ear, and this also is the case when I compare my custom-moulded UERM to the universal fit UERR to-go monitors that feature a level of passive exterior noise reduction that is very high and just marginally lesser than the custom fit in-ears’.

Neutral = Neutral?

Before I head over to the “Sound” section of my review, I will take a short discourse and look at the theory and research of neutrality with headphones and in-ears and give a very brief introduction to this topic.

With loudspeakers in an acoustically treated room, it is quite easy to define what a measurably neutral frequency response should look like. The case is different in the headphone realm: A headphone or in-ear that would measure exactly like a flat speaker in a raw measurement would sound different directly at the eardrum – this is because our ears, ear canals and upper body amplify certain areas of the frequency range, which is a totally natural and normal thing. With headphones and in-ears, these natural reflections and amplification disappear when the source of sound is directly at the ear, respectively inserted into the ear, wherefore the ear canal is closed on both sides and the “Open Ear Gain” disappears.

To imitate the natural amplification of the lack of this Open Ear Gain, a headphone should ideally show a boost in this area of the frequency response when an uncompensated frequency response chart is viewed (roughly speaking, the boost should be seen between ca. 200 and 15000 Hz, with the climax around 2.7 kHz with an elevation of up to around 15 dB here). Measured directly at the ear drum, this would result in a flat and neutral frequency response (important and related key words on this topic are “HRTF” and “Open Ear Gain”).

Of course the ear anatomy will slightly differ among individuals, wherefore the perception of the averaged diffuse-field target might not be perceived equally by everybody, especially when it comes to the perception of the upper midrange and presence area, wherefore some people might perceive an in-ear that measures flat in the presence area and lower treble according to the diffuse-field target as exhausting or even shrill whereas many other individuals would hear the same frequency response as acoustically flat and neutral. This is rather the exception than the norm though.

Most frequency responses of headphones one can see in magazines and large online sites are therefore usually shown with a compensation target, usually the diffuse-field target, already applied to the raw measurement and show the frequency response that is perceived directly at the ear drum instead of the raw measurement that might be confusing at first if one is used to loudspeaker measurements and doesn’t have much experience with the theory of headphone and in-ear tuning.

Apart from the existence of the Open Ear Gain, there is one thing that has also caused some inconsistency among researchers about what the ideal neutrally perceived frequency response for headphones should be: Listening to music, we don’t only hear the sound waves that reach our ear drums, but also feel the mechanical vibration/body-borne noise with our whole body, especially at higher volume levels. With headphones however, there is obviously no mechanical vibration/body-borne noise anymore, wherefore some people might find a diffuse-field neutral headphone to sound too thin in the lows although a neutrally measuring loudspeaker in a highly treated might not perceived this way by the same person.
Some people and researchers are therefore convinced that the lack of mechanical vibration/body-borne noise when listening through headphones should be compensated by adding a (usually) slight (!) emphasis to lower notes in order to get a headphone to be subjectively perceived to sound equally neutral as a neutrally measuring loudspeaker.

As one can see, the subjectively perceived neutrality with headphones and in-ears is a topic where there is no 100% unity even among famous researchers upon what the ideal frequency response should look like, and of course the individual ear and body anatomy might as well contribute to individual variance although major researches have come to the same conclusion of what the averaged HRTF looks like.


My main sources for listening were the iBasso DX200 (AMP1 module), Cowon Plenue 2, and last but not least the Shinrico SHD5 or my Pioneer PD-S701 connected to my Chord Electronics Mojo & Leckerton UHA-6S.MKII stack.

I solely used the included silicone tips for listening.


The original Ultimate Ears Reference Monitors were already among the more/most neutral sounding in-ears in the high-end in-ear territory, featuring a mostly uncoloured and neutral presentation (with just a tiny pinch of warmth compared to an in-ear that is even closer to the diffuse-field target in the lows, such as the Etymotic ER-4S/SR) with lows that extended flat into the sub-bass, a flat and neutral midrange reproduction, and an upper treble peak that added some extra air and clarity but could sometimes come across as just slightly unnatural and was the UERMs’ only shortcoming.

The new UERR follow this route, being among the more/most subjectively perceived neutral in-ears in the high-end range, but focus on a slightly smoother, more linear approach compared to the UERM, which fortunately also means that Ultimate Ears got rid of that upper treble peak, which, at least to my ears, is a great achievement as it makes the whole presentation even more accurate and realistic.

Their tonality is mostly “flat” and “unexcited”, which is something you want a perceived neutral in-ear to be, although not exactly “boring” or “sterile” – nothing really sticks out, nothing is really masked. Everything in terms of tuning is coherent and nothing is especially highlighted, in contrast to what you would usually find in an in-ear that still sounds balanced but is not tuned for neutrality.

The UERR claim to be studio reference monitors – and they are.

Apart from regular music, listening to white noise and sine sweeps with the UERR is a true delight – no peaks, no valleys, just an overall very smooth, linear and even frequency response with marvellous flatness and evenness, especially in the treble, which is something that definitely not every in-ear achieves. In this way, in the treble, I definitely see an improvement over my UERM that have a peak in the upper highs that makes their presentation sometimes too sharp and artificial if a single note hits that exact spot even if the recording isn’t mastered that way.

In that way the UERR highly remind me of Etymotic’s ER-4 line of in-ears that is around for a very long time and has got, in most parts, a very even, accurate and realistic tuning. Speaking of Etymotic’s reference models, the discontinued ER-4S and its successor, the ER-4SR, there still are some slight differences that can be found in the UERR and are worth to be mentioned. For example in the bass – while the UERR, just like the UERM, are among the flattest and most neutral in-ears in this area, they still have a gentle lift of ca. 3 dB compared to the Etymotic in-ears that are tuned for a diffuse-field neutral bass presentation. Definitely not much and a bit less than the, for Etymotic-standards, somewhat bass-elevated ER-4XR, but still enough to give the UERR just a little more warmth and body in the lows compared to 4S/SR, and to deliver a little of acoustic compensation for the lack of physically felt mechanical vibration and body-borne noise you would get from actual instruments or flat speakers in an acoustically treated room, since the UERR are miles away from being a remotely bassy or even mildly bass-elevated in-ear – it isn’t even “mildly balanced” but quite neutral in the lows and tuned for accuracy and linearity.

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Extension in the lows is really good – just as the UERM, the UERR don’t really have any roll-off in the sub-bass either, but also, not surprisingly at all, won’t give you an impactful, heavy sub-bass.

Midrange timbre is accurate and uncoloured, just as the UERMs’, however the UERR appear to have ever so slightly more body and their vocals seem a bit more present and forward in the mix, with greater proximity.

When it comes to evenness and naturalness in the highs, the UERR deliver a really high level of accuracy and won’t bother the listener with any dips or peaks – just a very smooth, linear, even and harmonious presentation.

Solely the 4 and 5 kHz range takes a slight step back when listening to sine sweeps, just like the UERM, but this area is still more present and neutral than the majority of in-ears on the market that have a dip here to generate a more relaxed middle treble.

The UERRs’ upper highs are where they differ the most from the UERM that had a peak somewhere around 10 kHz. Not so the UERR that are flat here, probably even just a tad too polite with cymbals, and never give you the feeling of too much sharpness but instead realism and tonal accuracy. Too hot mixes are still reproduced that way, but not as aggressively as the UERM (that were however also sometimes too aggressive while no aggressiveness should be reproduced).

Past 10 kHz, in the super treble, the UERR quite easily extend past 17 kHz.

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When there is one thing that I could change about my UERM, it is the upper treble peak that leads to some unrealism and artificiality at times. This is exactly where the UERR come in and deliver almost exactly the upper treble the UERM should always have had in order to be more even and homogenous in the highs. Therefore the name “Reference Remastered” is spot-on and describes what the UERR are – “Reference” in-ears that are based on the UERM but feature an updated, more realistic, linear, “Remastered” upper-end presentation.


High detail retrieval that only rarely leaves you wanting even more is also what one finds delivered by the UERR, just as one already did with the UERM.

Transparency is on a high level without faking details with peaks, and the whole presentation is very coherent and every part of the frequency spectrum appears integrated instead of separated. Here I even see a slight advantage in the treble for the UERR compared to the UERM.

Midrange details and speech intelligibility are on a high level and no part of the frequency spectrum really has an advantage or disadvantage compared to the others; the distribution of details is very coherent.

The bass has got a quick and tight attack and excellent control, however just a bit of added softness in terms of decay to give the UERR a bit more body without affecting control with fast and complex tracks and/or bass lines in any way. Indeed, the discontinued UERM decay slightly quicker and are a bit tighter in comparison, but control is similarly good.


The UERR, just like the UERM, will not have the largest soundstage in the range of high-end in-ears. Models like for example the now discontinued UE18 Pro are more expansive and create a deeper, wider and even more layered field of sound. This however doesn’t mean that the UERR have a small soundstage at all, since this is simply not true.

In terms of width, the UERRs’ soundstage somewhat leaves the base of my head and stops just about one centimetre before where my shoulders’ outer edges are. Therefore it certainly doesn’t lack lateral expansion at all although the UERM carried even a bit more with. This however also means that the UERRs’ stage is a bit more circular compared to the UERMs’ that is a little more oval.

What the UERR can do well is reproducing proximity, and in this regard their soundstage in general appears a bit closer to one’s face than the UERMs’ although both in-ears feature around the same amount of spatial height as well as spatial depth that is definitely well present wherefore the UERR also manage to layer well and create a good imaginary room with quite precisely placed and separated instruments as well as good spatial scaling abilities depending on the recording.


In Comparison with other In-Ears:

Ultimate Ears Reference Monitors (custom fit):

Tonally the two in-ears aren’t even all that far apart – both aim for a quite neutral, reference tonality. Both approach neutrality differently though – the UERM with a slightly cooler, airier character that could be considered “analytical”, and the UERR with a slightly smoother, less “exciting” (in terms of upper treble “bling”) character.

Objectively, both in-ears don’t really differ when it comes to bass delivery – both have got pretty much similar quantity in the lows and root. Nonetheless the UERR appear subjectively slightly warmer and (, which is probably not the right term to use since it not really is what describes the UERR,) “fuller” in comparison, which is because that upper treble peak the UERM had and that gave them their analytical character is gone.

When it comes to midrange, the UERR appear more direct, with more proximity in the mix compared to the now discontinued UERM that have a slightly more distant midrange presentation in comparison. Vocals on the UERR have got just a touch more body compared to the UERM, while still maintaining a correct, neutral timbre and high accuracy.

Where both in-ears differ the most is the treble, and the UERR feature the more realistic (although slightly de-fused) upper treble while the UERM are just somewhat more exciting in the upper highs (at the cost of less accuracy), which leads to a more vivid sound reproduction.

People who loved the UERMs’ tonality to the last bit might therefore miss a bit of sparkle and air from the UERR at the top in the upper treble/beginning super treble, while those who thought that the original UERM were tuned really well but could become a bit too sharp at times at the very top will likely find the sound signature they always wanted the UERM to have right in the UERR. Therefore I would definitely describe the UERR as more correct sounding in the highs, and to my ears the gained realism and refinement in terms of tuning is definitely a plus and rather substantial improvement.

Both in-ears resolve very well, on a pretty much similar level, and have got pretty much similar note separation, too.

The UERM have got the slightly tighter and faster bass in comparison while control on fast and complex tracks is identically good. Due to that, the UERR gain a bit more body and decay, which might be perceived as more natural.

Due to the more even and harmonious treble response, the UERR have somewhat of an advantage when it comes to coherency.

Both in-ears scale well depending on the recording, the UERM probably even more so, which could however also be related to their somewhat more pronounced spatial width in comparison, while depth and height are comparable with the UERR having the slightly closer presentation. Layering accuracy, precision and separation is where the two in-ears are about on the same level.

HiFiMan RE2000:

The UERR are the more linear, neutral sounding in-ears out of the two with somewhat less bass quantity and less warmth in the lower midrange. The RE2000 has got the more impactful bass that, while just around 3 dB more present, appears more impactful and energetic.

The HiFiMan has got the slightly airier/brighter upper mids at the same time (the UERR are flatter and a bit more authentic here), and places them a bit further in the back as a result.

The RE2000 is a good bit more pronounced around 5 kHz where the UERR are just slightly recessed (when regarded by diffuse-field standards and when one is listening to sine sweeps) wherefore the HiFiMan sounds a little more metallic and brighter here.

Cymbals on the RE2000 are splashier but also appear a bit more “spread” instead of spot-on focussed and are a little unnatural.

Generally, the UERR have got the flatter, more linear and correct tuning, but also especially the more linear highs wherefore they sound a bit more realistic and authentic up there.

It is quite remarkable how close the RE2000 comes in terms of bass speed and tightness. The UERR still decay slightly faster, but ultimately bottom-end control is relatively on the same level. Due to the slightly slower decay, the HiFiMan has got that admittedly quite pleasant dynamic driver texture and layering.

When it comes to midrange resolution though, the UERR are a bit ahead and portray the somewhat superior speech intelligibility as well as minute detail retrieval.

Treble separation is almost a draw with the UERR separating single notes slightly sharper with busy and complex recordings. Treble resolution on the other hand is comparable, but as mentioned, the UERR win when it comes to treble realism.

Playing fast and busy recordings, the UERR are somewhat ahead when it comes to control.

In terms of soundstage, the RE2000 features the somewhat wider presentation that is also coupled with a bit more spatial depth, wherefore it generates the more open appearing presentation. Borders around instruments appear slightly cleaner on the UERRs’ side with busier recordings though, and their soundstage also scales better depending on the recording.

Etymotic ER-4XR:

The two in-ears’ sound signature is not exactly similar but still heads into a rather comparable direction.

Both in-ears have got about similar levels of “warmth”, if you want to call it that, in the root, with the ER-4XR being a little more forward in the mid- and sub-bass.

When it comes to the midrange, the Ety is slightly more forward, with the somewhat closer vocals due to more energy in the presence range, while midrange timbre and balance are similarly accurate.

Both in-ears feature a treble presentation that is among the most even and accurate out there, with the ER-4XR having just slightly less energy with cymbals.

Not all that much surprisingly, the UERR win when it comes to subtle air and extension in the super treble.

In terms of resolution, precision, bass speed and tightness, the UERR appear like the higher-end upgrade to the ER-4XR, with an overall higher level of minute details and an increase of control.

I would say that chances aren’t all that bad that if one really likes the ER-4XR but doesn’t mind a slightly flatter lower bass reproduction and a generally higher detail retrieval, that he or she might find exactly this in the UERR. The same goes for those who really like the ER-4S/SR but want a bit more bass than their diffuse-field flat bottom-end reproduction delivers, coupled with the somewhat greater detail retrieval and larger soundstage.

Speaking of the imaginary soundstage, the UERRs’ is about four times as large to my ears (twice the width along with twice the depth) and also appears cleaner and somewhat more precisely layered, with a cleaner and more accurate reproduction of “emptiness” between and around instruments and singers.

So altogether about the same things that I also already found when I compared my UERM to the ER-4SR and my ER-4S.


While die-hard fans of the UERM might miss some of that upper-end air and sparkle, the UERR feature a more linear and realistic treble reproduction, which, in my book, is definitely an improvement as well as an advantage over the now discontinued predecessor.

Should you switch to the UERR if you already possess the UERM? My answer is “only if you found the UERM to be sometimes too sharp around 10 kHz and therefore lacking the last bit of tonal realism and evenness”.

Well done, Ultimate Ears and Capitol Studios. Just as mentioned in the “Sound” section of this review, the UERR definitely deserve the terms “Reference” when speaking about general tonal accuracy and neutrality, and “Remastered” when comparing them to the UERM.


CanJam London 2016 Karting Champion
Pros: Resolving without adding Harshness, Musical yet Transparent, Sensible price.
Cons: Low bass impact at low volume, Pairing with poorer recordings can be hit or miss.
Thank you UE for supplying these review sample and Snugs for the excellent 3D scanned ear impressions.



Never before I have struggled so much to describe a pair of headphones, describing the Ultimate Ears Reference Remastered (UERR) custom in-ear monitor is like trying to describe a bottle of spring water water connoisseurs feel free to grill me on this. It’s natural, flowing and does not impart a distinct flavour to the sound. The UERR shows that driver counts should not be the deciding factor of getting a pair of CIEM.
For those who are looking for a pair of clear and natural sounding CIEM that is often over looked and want a real solid performer at the 1k USD mark, the UERR is well worth looking into.


Transparent, separation and resolution are what the most apparent character when first listening to the UERR. Unlike some detail orientated headphone, the UERR maintain the impressive detail presentation without reverting to boosting the treble.
The UERR does improve with a good source and shines with good recording.

Mids (9.5/10):
To my ears, the vocal of the UERR is the strongest strength of the rather rounded package. Vocal sounds extremely realistic and never drown out by the bass or treble.
Unlike my FitEar MH334, which sweeten and smooth out the vocal, the UERR doesn’t impart any extra flavour the sound but is extremely resolving in the midrange and have one of the most breathtaking vocals that I have heard from a pair of IEM.

Lows (8/10):
This is where opinions can divides. The bass of the UERR extends well, have surprisingly good texture and is lightning fast. However it does not slam anywhere as hard as the competition at the price range. It’s not unlike bass presentation of electrostatic headphones but the slam on the UERR is noticeably lower when stacked up to other in ears, especially when played at a low volume.
The predecessor of the UERR, the UERM have issues lacking in bass, especially outdoors.
The UERR have enough bass to not sound thin and bright in noisy situations but if big bass impact is vital, look elsewhere.

Highs (9/10):

The highs just simply extends and flow, it never shows harshness unless it is already apparent in the source recording. It is unlike the brighter predecessor UERM where the bright treble can be a bit too hot,
If you liked the overall sound of the UERM but the hot treble of the UERM made you looked elsewhere, the UERR should be on your list.

Soundstage (8.5/10):
Another highlight for me, the UERR have a relatively good soundstage depth forward and wide soundstage width for an IEM. It sounds precise and has enough depth to project sound in front, instead of an in-the-head sensation.

Packaging & Storage

Storage with the supplied “hockey puck” case is secure and classy, due to the metal construction it is a relatively heavy case and doesn’t comes with latches but uses an O-Ring to secure the top.

Fit & Isolation

The UERR have great long term comfort and typical isolation for a custom in-ear monitor.
The UERR unit I received is very well fitted. It is shallower fit and overall less tight than my FitEar customs, the looser fitting helps with maintaining a good seal when there is extreme jaw movement. In fact, I wasn’t able to break seal when fitted correctly.
However, the hollow shell on the UERR along with the looser fit does means that while the noise isolation level is higher than most universal in-ears, the isolation is inferior when compared to a fully filled CIEM or silicon CIEM.

Here are some of the characters/features that only might not be apparent in a short demo.
Source scaling (recording to source gear)

The UERR is not a flattering CIEM by any measures. To hear it at its best will require decent recording and capable source gear. I found the UERR sounded best out of the RNHP headphone amp connected to the Chord Mojo acting as a DAC, listening at moderate volume.
It’s not like the UERR will just fall apart when the user’s intention is to just use a smartphone and only really listen to poorer recordings. The transparent character will still shine through but compared to other IEMs that are tuned with a more flattering sound signature will perform better in this usage case.

Small diameter sound bores

Here is a topic that cannot be avoided if you wanted your CIEM to be in top notch condition, cleaning and maintaining!
I personally have easy to clean dry ear wax and not much of it, cleaning is a breeze but do note that 2 of the sound bores are very narrow in the UERR, care must be taken to keep it clean at all times.
The included cleaning kit (wire end) can only fit the largest of the 3 bores and the smaller bores will need to be cleaned out by the included brush instead of the wire tool.

Long listening sessions

As mentioned earlier, the UERR is still a very source dependent IEM compared to other IEMs tuned purely for music enjoyment. The blood of a professional mastering tool stills very much so flows within the UERR.
I found that if listening to well recorded music, the revealing character of the IEM is not an issue but adds a welcoming layer to the listening experience. I can hear details that were not revealed to me before, it is a pleasant experience throughout and it is when the UERR certainly shine the brightest.
However when listening to poorly recorded music, especially when straight out my phone, music sound less dynamic that most consumer focused IEM and flaws are ruthlessly ever so present. Depends on the quality of the recording and the playback chain, it can be a bit tiring to listening to for a long period of time on poor recording. A smooth and mellow IEM will be a better choice in this saturation, if minimal harshness with poor recording is a must.

Similar sounding system

UERR sounds detailed without the typical treble boost that a lot of the more detail oriented headphones tends to exhibit.

Here are some full size headphones that I think that sounds similar:
  • STAX systems, quite a similar presentation to the Lambda.
  • Sennheiser HD800S

The UERR is like a blank canvas, it relies solely on the music that is being played to bring out the colour and will shine brightest when quality recording is played through it. It also scales decently with source components but doesn’t sound bad when played straight out of a smartphone.

At just under $1000USD, it provides excellent value in the current market of CIEM, providing transparency and resolution are what really matters to your listening. UERR shows that getting good sound is not at all about chasing numbers!


FitEar MH334
Fostex TH-X00 Purpleheart
Audio Technica W3000ANV
Audio Technica AD1000PRM

Chord Mojo (Optical In or USB in with UAPP)
Neve RNHP with linear power supply


1000+ Head-Fier
Pros: (Probably) Most neutral equipment on the market. Amazing Separation
Cons: May be bass light for many. A touch less detailed than its competitors.
This is a duo review written by Eu Jin Ong (@ejong7) and Andre Moore (@shiorisekine). The main body of the review are general comments on the product that are agreed upon by both side. Personal opinions on the product by each reviewer are stated in separate dialogues, indicated either by EJ (Eu Jin) or AM (Andre Moore).
EJ:          The UERR unit was provided by the Ultimate Ears (UE) team free of charge in exchange for an honest review. Many thanks to Mike Dias and David Gutierrez who help expedite the entire process. Special thanks to Paul Best and Nick Bruce-Smith who both represent UE in the UK.
AM:        I too would like to thank Mike and David over at UE. They were able to arrange for a pair of UERRs free of charge just days after discussing this whole idea with them.
For anyone who is remotely interested in the custom in-ear monitor (CIEM) market, UE has been and continues to be one of the leading companies in the field.  Officially started in 1995, they have since maintained if not strengthened their standing in the CIEM echelon with the help of products such as the UE11 Pro, UE18 Pro, now revised with the brand new UE18+ Pro, and of course the famous Ultimate Ears Reference Monitor (UERM).
The UERM, first released in 2010, was an IEM that utilizes a 3 driver, 3-way crossover design which was specifically tuned for professional mixing and sound engineers for use in a studio. Known as one of the most neutral and revealing IEM in the market, it got itself many fans from both the professionals and personal audio enthusiasts while at the same time became a cult favourite among critics and reviewers as it allows them a natural reference or standard to evaluate other gear.
6 years down the road, UE and the recording engineers at Capitol Studios, who first worked on the UERM, came out with the sequel to the already legendary piece – the Ultimate Ears Reference Remastered (UERR). With its tuning design lead by Barak Moffitt from Capitol Studios, the intention is to fine tune a piece that is already held in such high regard, update the design to conform with the increasing availability of high resolution recordings regardless of the era which the music was produced in hopes of satisfying returning fans of the product and also attract potential new users to the foray.
EJ:          As I’ve never heard the previous rendition, my review should appeal more to the latter, which are new users who are trying to dwell into the well-respected UERM lineage of IEMs.
            AM:        I have heard the old UERM, so I can do a few comparisons based off what I remember.
Following the footsteps of its older brother, the UERR remains a 3 driver design using balanced armature drivers, with multiple passive crossover points and a triple bore sound channels incorporated into the design, as quoted from UE’s website itself. However, the drivers are all new proprietary drivers, which UE are calling True Tone Drivers that are able to extend the frequency range and deliver a flat response to 18 kHz.
As listed on the specifications page of the UERR, the frequency response is 5 Hz to 25 kHz, with the IEM being capable of isolating up to -26dB of ambient stage noise if fitted properly.
EJ:          To my experience, the UERR blocks out enough noise for me to comfortably use them as a pseudo passive noise cancelling headphone, notably when used on an airplane or a crowded café.
AM:        In my experience, the UERR blocks off enough sound for me to be afraid to use them when walking around outside and to make me have to take them out when I cross a street, as I cannot hear anything outside of what the IEM is playing.
The CIEM has an input sensitivity of 100dB @ 1 kHz, 1mW with an impedance of 35ohm at 1 kHz.
EJ:          Although it is not the easiest IEM in my arsenal to drive, that remains to be the Empire Ears Zeus-R, I have yet to find difficulty in driving it on most of my portable devices, including on my Samsung Galaxy S7 Edge.
AM:        I agree with Eu Jin here. When using the UERR on my iPhone 6S Plus, I only have to put the volume on 6/16 to be at a listening level and only ever have it at most 8/16 before it gets too loud. While plugged into an amp such as the Cavalli Audio Liquid Carbon 2.0, I have to have it on normal gain and can only turn the volume to about 7:30 on the dial.
Probably the biggest news is that UE has decided to maintain the price point of the CIEM at $999, which is a rarity in a scene that is regular to see waves of updates, improvements and refinements to a previously available product come with a significant price increase. This will surely help attract new users as they just have to fork out the same amount of money to get an updated product.
Sadly, with the release of the UERR, UE has decided that it was time to say goodbye to the UERM, and has since discontinued the UERM, so it will no longer be possible for anyone to experience the magic it once entailed on its listeners, unless you could find someone who has one in universal form. Good luck in finding one of those.
EJ:          The box that was sent over by the folks from UE, which contains the aluminium case that houses my UERR unit.
The UERR arrives in a medium sized cardboard box that has both the UE and Capitol Studios emblazoned on top. The box has a premium feel to it, something you would definitely expect from a no nonsense company like UE. The top cover uses a magnetic flip cover, which when open will reveal the CNC machined, anodized round case, made from aluminium with the users name, or preferred nickname, laser etched onto the case. It is slightly different from the generic case that you can purchase off the UE website, where the name is etched below the UE logo at the top and the Capitol Studios logo is etched at the bottom of the case.
EJ:          This is probably the best case I’ve received with my IEMs. It is sturdy and just the right size for me to carry around at 3 and ¼ inch diameter. CIEM companies have often supplied their IEMs with their personalized version of the Pelican case, which provides maximum protection for your IEMs but does not fit with my usage as I prefer a smaller, less cumbersome storage case. This proves particularly useful whenever I wear a top or jacket with a pocket, as I can just easily slip it into one to carry around. Do note that the case is meant to be directly lifted off and not twisted off like a bottle cap, as it will squeak like no tomorrow if you try to twist it off.
AM:          Having already owned a UE product, I have always enjoyed the carrying case over say a pelican style case as it is easier to put in my pocket and not something I have to put in my backpack. It still provides protection all the same but I guess if I go swimming with my case in my pocket it might not hold up. But who needs to swim when you have headphones.


EJ:          Inside the aluminium case is my UERR unit, in the ‘classic’ UERR design, which came with a UE buffer jack and a ¼ inch stereo adapter.
Inside the case are your UERRs, along with some accessories such as the typical cleaning tool and a ¼ inch stereo adapter. Something that will surprise new UE customers is the inclusion of a buffer jack, which UE claims will ‘lower audio signals on airplane entertainment systems and buffers electrical impedance mismatch. In other words, it will help allow your UERR to play nice with audio gear that is typically used for higher impedance headphones and earphones.
EJ:          I have successfully used the buffer jack with a number of sources to date with continued success on its original intention but I would highly recommend that you get a source component that will instantly play well with the UERR’s impedance rating as I found the sound quality to just slightly decrease when using the buffer jack. Specifically, I found it to be less clear and revealing in nature, with just a slightly boosted lower end that may cause you to have the wrong perception that the UERR or the source component to have the described sound signature.
The UERR is standardly equipped with a 48’’ long cable, which is connected with a 2-pin connector and a 1/8 inch headphone jack as its input connector. The cable supplied was of acceptable quality and users should not experience any microphonics. If you wish to obtain a longer cable or a different input connector such as the 2.5mm balanced connector, the cables could be purchased off the UE site. You could have them custom made by a number of custom cable manufacturers but do note that the 2-pin connector slightly differs from the industry standard to fit with the recessed sockets used by UE’s CIEMs, hence you will not be able to easily chop and change your cables with your other IEMs that uses the regular 2-pin connector.
EJ:          Although I find this to be a little unwieldy as it would mean that I have to make a new set of cables for them rather than use my previously available cables, I found the UERR’s recessed connectors to be particularly sturdy among my IEMs, and provides a sense of an extra level of tightness or security to the connection. However, if you do break the 2-pin connector by handling it with excessive force, you probably have to send it back to UE to get it fixed as I have seen a couple users who got their connectors stuck in the recessed socket.
AM:        However, if you do somehow break the sockets on a UE IEM, UE has a very fast turnaround rate which I had experienced with my UE18s that ended up breaking before I got the UERR. I got them back within 2 days of UE receiving them.

EJ:          My UERR unit, in the ‘classic’ UERR design with the stock 3.5mm cable.
As the UERR provided was a custom piece, one’s ear impressions are needed to construct it. This is where UE differs from many of its competitors. Rather than just using physical impressions, also known as silicone ear moulds, UE offers another option for their customers: digital impressions. With the help of a firm called United Sciences, they use a 3D digital scan to obtain one’s ear impression, which aims at improving the accuracy of the ear impression of a customer that will potentially reduce the already low return rate of UE’s products. To learn more about this intriguing process that may revolutionised the CIEM industry, please refer to this video.
The process is not made available worldwide yet but do contact your local UE dealer to enquire about its availability as it was made known that UE’s intentions are to have the process widespread in the near future.
EJ:          Personally my impressions that were sent in are digital and were taken by a UE representative that was present in an event that I attended. The impressions were taken with my mouth closed, which I ever so slightly regret, with details to follow.
AM:        My impressions were taken before UE started to use the digital scan impressions so mine were made with the old way of making impressions - silicone molds. I did however get them with a bite block in my mouth.
The impressions, regardless of form, are then sent to their headquarters in Irvine, California where the building process commence. Physical impressions require some carving and polishing work from highly trained specialist before being scanned into a digital print where as digital impressions are immediately skipped into the next step of the process: SLA-3D printing of the shells. This has significantly reduced the build time for each monitor according to the folks from UE, but has currently limit the shells to be only of the clear variant as coloured once has previously brought upon certain build quality issues that did not comply to UE’s high standards. Folks who order their UE CIEMs should have their units built within 7-10 days after UE receives their impressions, and even shorter if the rush option was included.
EJ:          Personally I would have loved for coloured shells, as one of my dreams is to have a custom IEM from UE to be customized to the colour of my old UE900, my first ever higher end IEM. I received my UERRs in the UK about a week after my order was made, with the rush option and the fastest delivery option with UPS included in the package. Talk about fast. I have readily made headphones arrive much later than that upon order.
AM:        While I do love having colour shells like with my Noble 5C, I do understand some of the reasoning for not being available. The UERR is a very good looking IEM. I live in SoCal where UE is based and I ordered it on a Wednesday. It was shipping on Friday the very same week, which is insanely fast. Most high end companies have a couple of months lead time before you get your unit. UE gets them out fast and this is all thanks to the 3D printed shells. Another reason that they do clear shells is so you can tell if the IEM is actually broken or just had a bunch of wax build up when you are having problems with your IEMs.
EJ:          The shells of my UERRs are so impeccably crafted that I have difficulty finding words to describe certain aspects of it. It is first and foremost, bubble-less, which is to be expected but not always received from all CIEM manufacturers. These shells however had a different feel than most of the other CIEMs that I had the opportunity of inspecting, where it is much smoother than I have expected, perhaps due to the stream-lining of the manufacturing process that reduces potential of human error.
The fit of the UERR is probably the best of any gear I have owned till date. I don’t think I have anything related to audio that fits more comfortably on me than the UERR, and this is a major selling point for many. However, it does break the seal a little when excessive movements are made with your mouth. This is probably because my impressions were made with my mouth closed, as instructed by most operators if you are not a professional musician, but I think it should be made standard that the impressions should be open-mouthed to allow for better comfort when talking with the IEMs on. Not that I would really talk with the UERRs on but it’s a nice option to have.
AM:        The UERR and the UE18 fight for the best fit for CIEM gear that I have. As for the problem Eu Jin has, I don't have that issue because as mentioned before I took my impressions with a bite block which I thought was always the normal way to do it, as I had to do it that way with Noble as well. So I actually can use the mic cable on mine without the seal breaking and I can eat while wearing them. However, when I got the UERR, there was a chip on the right monitor. I ended up sending them back and got them fixed ASAP and free of charge. The chip wasn't too bad though as I was able to wear them without noticing, I only felt it when I would be putting them in.
A wide array of options is available for the faceplates, with UE intending on including more faceplate options according to the seasonality. Hence you should expect a collection that is different to one another when it changes from one season to the other. Whether a particular faceplate would be available at a different season was not explicitly announced, so do ask if you are interested. The faceplate that would probably be the selection of most is the standard faceplate with UE’s logo on the left and Capitol Studios on the right with a white background instead of the black found on the UERM’s standard faceplate, which only available if you order the UERR.
EJ:          Personally I went for the stock white faceplate as I prefer my CIEM designs to be clean and simple, or as ‘stock’ as possible, which is hard to come by with CIEMs. It is also nice that I could showcase the two companies involved in my CIEMs in honour of their collaboration and efforts that brought forth the product.
            AM:        I felt the same, plus I have a set of UEs that have custom arts on them already so I didn't need this one to be all flashy and what not. I think the “normal” look is good the way it is.
Evaluation Process
EJ:          As a standard for most of the gear I review (unless under a time-limited review tour), the UERR were burned-in for about 200 hours before critically listening sessions were made. Yes, they are equipped with balanced armatures but I would like to start my reviews with a level playing field. The sessions were conducted with files that are either FLAC/ALAC from a wide variety of genres, with metal a notable exception. Not my cup of tea. The source gears that I used during the evaluation period are as follows:
  1. Chord Mojo
  2. iBasso DX90
  3. Questyle QP1R
  4. Calyx M player
AM:          I did my listening sessions with FLAC/ALAC as well as Tidal for some albums. I listened to a wide variety of genres including the genre that Eu Jin doesn’t like – Metal. The gear I used:
  1. Apple iPhone 6S Plus
  2. Cavalli Audio Liquid Carbon 2.0
Initial Impressions
EJ:          I would honestly admit that I was less than impressed with the UERR at first listen. For everyone’s information, the UERR I first listened to was connected to UE’s demo listening system, which although provides a unique demoing experience has led to a decrease in sound quality for most if not all of UE’s products. It sounded muddy, slightly veiled, with most of the instruments being placed in a congested area.  The mids were the only saving grace of demo unit, as vocals are present and clear, but the overall picture was a mess as the instruments would just be on top of one another and not presented in clear layers. Save to say I was more than a little disappointed, but remained hopeful that the custom unit would perform differently with a different source system and a better fit.
To my delight, my hopes were merited. The custom unit when compared with the demo unit was night and day, with it being clearer and now having its separation as one of its greatest strengths as appose to one of its greatest weakness. The overall sound was more balanced, and definitely more neutral, which was the intended sound signature.
AM:        Admittedly when I signed up for the review I was a bit wary because I haven't heard the UERR beforehand but I have heard the UERM and I wasn’t the biggest fan. The UERM for me was very tame sounding and at the time I was more into fun sounding headphones like the UE18. So upon getting the UERR I was kind of happy and disappointed. While I did like it better than the UERM, the kind of music I listened to didn't sound amazing, or so I thought. For me, my biggest problem was the way the drums sounded on the unit. They sounded very hollow and at the time I was so used to the way the 18s and my Hifiman HE500s sounded. I thought they sounded wrong but then after listening more and more I realized they just sounded more as if it was live. The longer I listened to the UERR the more I appreciated it.
Sound Signature
EJ:          The UERR is the most neutral audio listening equipment I have heard in my entire journey as a Head-Fier, though I have to remind that I have never heard the UERMs. Many CIEMs are claimed by their manufacturers to be reference in sound signature which I agree to in the overall picture but would always tilt to either end of the spectrum ever so slightly. Not this. In fact, the UERR should be a reference standard to judge all other gear, then you will truly know where your gear lies on the spectrum.
The music is presented in a smooth and effortless manner, hence making the sound of the UERR very organic. The overall sound is that of a balanced reference monitor, where no particular aspect of the sonic spectrum is emphasized over the other. It does remain highly musical, never sounding boring or sterile even across a long listening session, which is really hard to do. It sounds very clear and transparent to my ears, neither forward nor laid-back in its overall presentation, making it feel like you’re listening to the artist in the middle of a medium sized room.
The sub-bass is controlled but may prove to be subdued for many people, especially those who mainly listen to modern music, so bass-heads should look elsewhere. I do appreciate the sub-bass of the UERR as my taste tilts towards gear with less emphasized sub-bass but sometimes I do wish for a little more rumble down the spectrum, especially with my dance and electronica orientated tunes. The bass above the sub-bass spectrum is equally controlled, full but not warm, hence making it play rather well with music focussing on male vocals.
The mids are slightly more pronounced when fully dissected, but only relative to the other ends of the spectrum of the UERR. The smoothness of the UERRs mids should not be underestimated, and I found few others that can match it on smoothness even when compared to its bigger size competitors. It is decently punchy, and made a highly satisfying experience of listening to instruments like pianos and guitars.
The highs are airy, with no sibilance or rolling off found, at least to my experience. It probably lacks the crispness found in other IEMs that claim to be of the reference sound signature, but is nicely extended in its own right. There is certainly no veil on the UERR, and I found the cymbals in my music to be well-presented, a huge requirement for me to properly appreciate most of my music.
The UERR is well-detailed but never reaching the point of being analytical, to continue with its intention of producing a smooth image of your music. Perhaps its second biggest strength in its sound, after its neutrality, is the separation and layering that I found in the piece. I highly appreciated the ability of the UERR to place the instruments in my music at just the right level, making it easy to differentiate each instrument from one another, something I found particularly present when I try to picture the layers of the kicks, snares and cymbals in my music. The soundstage is not the widest nor the deepest I’ve experienced from an IEM, but it is of good depth and width.
A particular pairing that I enjoyed for my UERRs is when I used it with my Chord Mojo. As the Chord Mojo is also highly detailed, smooth but musical source equipment albeit being a touch warmer than neutral, it helped to keep the music engaging at all points while being easy to listen to. It helps me learn that the UERRs are never intended to be fatiguing, and will always play to its source equipment. The QP1R plays well with the UERR as well, just not to the synergy that I found with the Mojo.
AM:        The unit for me is the best mastering IEM I have ever heard, and it’s the most neutral/ balanced IEM as well. With the UERR, I could place myself in the seat of the person in charge of mastering the music. I could imagine the potential lack of balance found in the headphones/earphones used by said person based off listening to the track with the UERR, which gives off a flat frequency response. This led me to believe that the usage of unbalanced equipment by the producer would force him/her to tune his/her music in a way that allow him/her to listen to the track with a better balance coming out, but would end up being presented as unbalanced when listened through something as flat as the UERR.
I agree with Eu Jin here about the sub bass, there will be some people that don't like it that much. I do enjoy it however because it reminds me of the AKG K701 style of sub bass that is very deep sounding and extends for what seems like a limitless amount. It’s very controlled and to me somewhat fun sounding and it did put a smile on my face once my ears finally adjusted to the sound of it.
The mids are very satisfying on the UERR, very smooth especially on acoustic guitars and female singers. Very detailed and textured sounding, the UERR has one of the best sounding mids I have heard on an IEM probably, only rivalled by the Noble Katana.
The highs on the UERR are very crisp sounding, and very transparent. I think it was the one part of the IEM where when I first put them on I said ‘Wow that is really good sounding.’ I agree with Eu Jin that there is no sibilance or rolling off in the highs, which probably comes from the frequency response extending to 18 kHz and it gives the UERR a feeling of endless highs.
The UERR is the most detailed IEM/headphone I own period. I actually think the UERR is pretty analytical but that might just be because I don’t normally use very detailed headphones. I tend to drift more towards fun sounding headphones that aren’t always very revealing except maybe the Hifiman HE-500. THE UERR has a way of making me think about how the music is produced and why they did certain things on tracks or why something sounds a certain way, unlike anything I have heard before. It has a really good sense of layering and instrument separation that make listening to metal and rock very enjoyable, because there is so much separation the sounds never get too clogged up and distorted which is a common occurrence on metal music and most headphones. I do agree with Eu Jin on the sound staging while it is not the widest or deep it does have some depth and width to it.
Comparisons (Eu Jin)
EJ:          The IEMs I used for the comparison part of this review, clockwise starting from top left: Noble Audio Katana (Custom), Empire Ear Zeus-R (Custom), JH Audio Roxanne Universal (Generation 1) and the UERR.
EJ:          I used my custom Empire Ears Zeus-R, custom Noble Katana as well as my JH Audio Roxanne Universal (Generation 1) for the comparisons. Yes the price point is rather far apart, but I felt the UERRs deserved to be compared with the best of the best within the market. I do emphasize that these are comparisons and do not paint the overall standalone sound signature of those compared.
UERR vs. Empire Ears Zeus-R
Compared to the Zeus-R, I found the R’s to be just a touch wider in soundstage but significantly deeper. The R’s satisfies me more with just a touch more rumble down low and its seductive mids. The highs of the R’s are crisp, much more so than the UERR. The R’s sounded much more resolving that the UERRs, bordering analytical. However, the UERRs make the R’s sound less smooth in comparison, which is a difficult feat in itself. The R’s are also significantly more sensitive than the UERR’s, and most importantly, is twice the price of the UERR’s, more so when the ADEL version is officially launched. I would recommend the R’s regardless of price, but the UERR’s prove themselves to be no slouch even compared to its more expensive competitors.

UERR vs. Noble Audio Katana
Compared to the Katana, I found myself caught in a war between two smooth criminals (see what I did there). Both share a similar aim in achieving a more neutral but highly smooth sound in their design to my ears, with the Katana perhaps having a slight tilt towards the highs compared to the UERR. I still find the Katana more resolving than the UERR, but perhaps due to the Katana’s smooth signature, smoother than the UERR at times for me, the gap does not feel as big as the one when compared with the Zeus-R. The Katana is a little easier to drive compared to the UERR, and in comparison has a wider and deeper soundstage than the UERR. Then again, the Katana is easily double the price, so the UERR once again has proven its worth to be in the pen with the big boys, and might even be the better choice in terms of value for money.

UERR vs. JH Audio Roxanne Universal (Generation 1)
Compared to the Roxannes, with the bass selector at minimum bass which is my default configuration, I found myself to actually prefer the UERRs slightly. The Roxannes are more detailed, and have a wider soundstage than the UERRs, but I found the separation ability of the UERRs to be hard to ignore. The Roxannes are also just a little less balanced when compared to the UERRs, with a slight emphasis placed on the lower end, which is less suited to my current taste of more reference, perhaps slightly brighter sound signature. I do prefer listening to live music and recorded concerts through the Roxannes, but I would rather listen to my UERRs for studio recorded sessions.
One thing I can vouch for is that the UERR’s is easily the most comfortable piece of equipment I have in my arsenal currently, and triumph against everyone else in this department. I could easily wear them for hours and hours on end, not that I couldn’t with the others, but this is just a step above.
Comparisons (Andre)
             AM:          For comparisons I used my UE18 and my Noble Audio Katana Universals.
So when comparing the UERR and the UE18, one of the first things you notice is how much cleaner sounding the UERR is compared to the 18s. The 18 is a more fun sounding IEM compared to the reference UERR. While I do enjoy both IEMs, I think the UERR is superior to the UE18 in not only being more neutral but by having a wider and deeper sound staging. The 18 is by no means a balanced IEM. It has strong low end which sometimes bleed into the mids while the UERR has an overall balance sound to it. One of the biggest differences in the UE18s and the UERR is the highs. The UERR has some of the most crisp sounding highs I have ever heard in a IEM, rivalled only by the Katana, while the UE18 has very textured highs (in a good way) but they do roll off more than I would like. If I had to choose to listen to either IEM, I would use the UERR for rock and metal over the 18s because they are cleaner sounding and most heavy metal sounds distort on the UE18s and cymbals just sound amazing on the UERR. However I would use the 18s for more pop music or hip-hop as it has the more fun sound.
So with the Katana, I would have to say that these IEMs are so similar sounding, much to what Eu Jin said above, the Katana has the UERR beat in how good the highs are. For me the Katana is much like the UERR but with a bit more edge, which isn’t always a good thing. The Katana to me has some bite to it, while the UERR is always very smooth and never really fatiguing while with the Katana on some songs I get sibilant highs. As Eu Jin has mentioned above the Katana is about 2 times the price of the UERR and I have to agree with him the UERR does hold its own against the Katana. They both set out to achieve similar things In the IEM world and I think they both have their respective uses, as I would use the UERR over the Katana for mixing or recording as it is more detailed and neutral sounding overall. Katana has a little spike in the highs. I would however use the Katana for listening sessions as I do enjoy the spike in the highs; I know I am odd compared to most of the people in the Hi-Fi world.
EJ:          How do you appreciate your music? Do you like it if your music is conveyed with that extra thump in the bass? Do you prefer it with a lift in the treble so that all your string instruments are more pronounced? Maybe you like a very forward and aggressive midrange so that all your vocals sound just sound more euphonic? Or, you simply wanted to listen to your music like how your favourite artist had intended to? If the latter is your choice, then the UERR is definitely the best IEM for you. To me, it succeeded in its goal of trying to achieve a neutral but not boring, detailed but not analytical and most of all balanced sound. If that wasn’t sweet enough, UE makes probably the comfiest pair of CIEM I have yet owned, packaged with the best carrying case I’ve seen so far and a plethora of accessories to go from.
Some may find the UERR too flat for their taste, especially if they crave that extra lift on the bass region. Some may find the UERR too be a little too smooth, making sound more laid back than they perhaps prefer. Due to every person’s different perspective on how music should sound like, the UERR may not be for all of us. However, these people would be missing out on what is perhaps the best separation and layering I found on an IEM, which is a key tool in music mastering.
UE’s great work on the UERR has made me very excited to listen to their new flagship, the UE18+, something that I hope I could have a listen to in the near future. Until then, I am highly satisfied with my UERRs, and it would probably be in most comparison I make in regards for IEMs as it is easily the best one to act as my measuring stick for the rest of the stable.
AM:          The UERR has become one of my staple IEM, hell one of my staple headphones to listen to and to use as a reference of what neutral should sound like in my opinion. The UERR has given me a new appreciation for the neutral sound as before the UERR I enjoyed a more warm sounding signature and I never really enjoyed anything too neutral sounding.
So does the UERR do what it sets out to do? Yes, I think it does, the UERR is definitely a studio monitor. The RR was designed for studio engineers by studio engineers, and we audiophiles get to reap all the spoils of this collaboration between UE and Capitol Studios.  The RR has a solid flat frequency response that doesn’t seem to roll of in the highs and extends into the low end in ways that most in-ears don’t. But there are some flaws with the unit as nothing is perfect. The flat response can sometimes make some music very non-engaging and the micro details can bring out the worst in your music which can be a bad thing but is a good thing about the UERR.
I remember hating the UERM so whole heartedly when I had heard it back at CanJam 2014, but the UERR just seems to have a dynamic that I was not prepared for, I fell in love with it. This might be due to the new proprietary drivers that UE is using, and if that is so I can't wait to hear the new UE18+ in the future as I think the 18 would benefit a lot much like the UERR has over the UERM. Would I recommend the UERR to anyone, the answer is yes, the UERR is a very beautiful sounding IEM and its comfortable which is a very important thing for a CIEM.
Excellent review, guys! I found it interesting that you guys had contrasting views on the Katana. I listened to a universal Katana and found it pin sharp, so when I heard that the custom was smooth it made me go Wut?
I think the Katana, in itself, might be a little pin sharp for people, but I feel that it still sound smooth in my books. Its probably the smoothest one of the more 'reference', treble heavy sound. Then again, I prefer the reference sound pieces usually so yeah YMMV.
How about we find out again sometime?
The funny thing is my Katana is Universal and his is Custom.
Pros: Airy big soundstage, lovely treble and bass, precision and speed, noise isolation, neutral tonality, excellent tool for reviewing, look awesome
Cons: Can’t share how wonderful they sound with friends, can be a touch thick on some vocals

Thanks Mike Diaz at Ultimate Ears for supplying these as a review sample, with special thanks to David Guitierrez for his excellent customer service. These are going to kick butt and take names in lots of upcoming reviews. They already have in a few. This review was originally posted here.


Ultimate Ears and Capitol Studios strike gold again! I’ve never heard the original Ultimate Ears Reference Monitor, but I hear tell that it was a beauty. I’d never had an experience with custom in ears, so when my buddy ejong7 on HeadFi asked me if I’d like to participate in reviewing the UERR my response was immediate and decisive. You kidding me? Of course I’ll review that monster of audiophile goodness. Now, off to get some impressions. Lets get this thing on!


There’s nothing wrong with ears

Full of goop, ah ah no no

And putting these in your ears can never be wrong

If the music’s true

Yes, verily let us get this thing on.

I don’t think that Ultimate Ears or Capitol Studios need any introduction, but here’s some stuff to satisfy those who disagree:

Ultimate Ears (stolen from Wikipedia)

  1. Ultimate Ears was started up by Jerry Harvey in 1995. Jerry Harvey started making designs for in-ear monitors using balanced armatures so that Alex Van Halen could hear what was going on when performing. Westone manufactured Jerry Harvey’s designs. Westone owned all the patents and trademarks. Eventually that relationship went sour. This led to Ultimate Ears bringing a new designer to run their manufacturing and Ultimate Ears breaking up with Westone. Jerry Harvey eventually left in 2007, claiming he was forced out. All three companies are doing just fine now. Drama, drama, but all in the past.
  2. Holy crap, 31 years and counting making custom monitors. Ultimate Ears are truly some of the grand-pappies of the industry.

Capitol Studios

  1. Capitol studios was founded in 1956, and recorded titans like Frank Sinatra, Nat King Cole and the Beach Boys. They also were the studio setting for Elliott Smith’s Figure 8, probably his best album; and Green Day’s American Idiot, probably their best album (in my opinion, but I’m a political junkie, so pay no mind).
  2. In 2010 they first collaborated with Ultimate Ears on the Reference Monitor
  3. In 2014, they upgraded their studios to become completely state of the art.
  4. Soon to follow they partnered again with Ultimate Ears to develop the Reference Remastered (released December 2015)
  5. Unless you’ve been under a rock for your whole existence, you’ve heard some Capitol Studios productions.


If you want to know more about me, you can take a look here. Each reviewer has their own set of biases, preferences and beliefs, so it is often worthwhile to know these before you commit yourself to following the opinion of a reviewer.

Form & Function


Lets have a start at this with the unboxing. The UERR comes in a nice magnetic close presentation box with print materials that welcome you to the group like you’ve just joined a really friggin’ exclusive club. You better have your belt match your boots, or you might be out on the street. Inside the box is a velveteen fabric gently crumpled into a circular indent wherein lies all the fun—a personalised metal case that has totally turned me around on the idea of metal cases. This little puck is perfect for storing 2 Ultimate ears cables (2.5mm balanced and plain Jane 3.5mm), the buffer jack, a cleaning tool and the UERR themselves.


When the UERR arrived, I had some touch and go moments when trying to put a cheapie aftermarket cable on. The cable that the UERR comes with is jammed on there like it is trying to keep the weight of the sea from flooding the undersea laboratory. It’s tight. Damn tight. So tight that I had to email David at UE to make sure I wasn’t going to break the headphones minutes after I got them. When you go to try different cables, use pliers to get the stock cables off. They have a little lip on them that helps with using the pliers. I never would have thought of using pliers. I went at the cables for a long time wiggling and jerking on them, and I’m sure that was the reason that my initial 3.5mm cable had cut-outs on the right channel. UE took care of me and replaced the cable quickly. It’s a good warning to have though, use pliers to get the cables off for at least the first time. With repeated cable switches the fit gets a bit more fluid, still firm, but fluid. I have no problems switching between the SE and balanced cables now. Don’t do what I did, I hurt myself and the cable getting it off.

The workmanship is generally good. I have a clear shell, so you can see all the gubbins pretty good. My wife thinks they’re pretty, and so do I. I don’t think most people in public even have a clue that the weird things in my ears are headphones. The people who do notice think they look stunning though. Make yours awesome too. They’ve got some really great designs.


With regards to fit, I find that my ears aren’t always exactly the same shape depending on weather factors, so I sometimes my ears get a bit of fatigue, primarily in my right ear. This may just mean that my digital impressions weren’t perfect. I also had to learn early on that being gentle with the CIEMs was the way to put them in. Initially I tried to push them in a bit. Just rotating them and leaving them be is the way to go. It takes a bit to get used to having hard plastic way inside your ear. I may just never really get used to the sensation. When my ears are right, these are seamless, and do an incredible job isolating noise.

The case is solid metal make. When I reviewed the Fidue Sirius, I was pretty hard on their case, noting that it was heavy and pretty good for smashing stuff in your bag. Now that I’ve had a ton of time with a metal case, it doesn’t really smash things all over, but it will find the bottom of your bag and it will scratch other metals found therein—don’t put your phone in your bag with this, that’s just asking for trouble. The metal puck is easier to put in my backback than a Pelican case. It is just the right size for transporting the IEMs and the circular shape minimizes memory effects on cables. There is also some foam rubber inside the case, so it may have some modicum of weather resistance when the lid is pressed all the way down. After having this I’m now seeing the light on metal cases, but softened edges would be a boon, though less aesthetically striking.


For this review, I had both the stock cable and the stock 2.5mm balanced cable. These cables are the same cable, with a different termination. Each cable consists of two twisted pairs. These cables are not braided, and after seeing a friend braid some adaptors for me, I totally understand why. A machine can twist cables really tight, braiding is time consuming and it is harder to see which lines are ground and live, hot and cold. So all you folks and manufacturers calling twisted cables braiding, please stop. It is not the same. Both cables are good quality lightweight cables. Nothing really to see and nothing to complain about. You can get the cables in silver or black. I’ve got black.

Audio quality

The UERR have astonishingly good sound quality. Many folks hear reference and think library books, musty tomes with mustier librariens, boring intonality, a lack of life, a place for analysis. The UERR are none of these library analogues. These are not reference like a library, these are reference as in authoritative representations of a state of the world; these are a neutral reference, a tool made for analysing music, but these manage to do so without sounding detached, etched or boring. These have good transients with accurate attack and decay across all frequencies which gives a great sense of realism.

The UERR have natural sounding bass with good texture and accurate timbre. They aren’t high on bass, but I don’t feel that these are bass light. These have good bass with all the things I’m looking for: some violence when called for, dynamic texture, speed and accurate timbre. The bass is only as warm as bass instruments themselves, no colouration here, and I like that.

The mids are flat, in the right way, no peaks and valleys giving fake dynamics or messing with instrument presentation, for the most part. I say for the most part because I have noticed these to have a little thickness in the vocals from time to time. This observation is quite possible the source being revealed a bit. I think many some sources push mids forward a little, so when that happens with the UERR, it can sound a bit thick. These excelled with any kind of instrument thrown at them, and any kind of vocalist.

The treble is special on these. Sparkle is there when called for, for instance on the delicate tings of the xylophone in Time, but the sound isn’t piercing or overly bright. The presentation is natural and fulfilling. It has excellent extension and realism with stellar instrument placement and impressive stage height, depth and width. For me, the most impressive element of the stage presentation is the height. Very few IEMs I have listened to have achieved out of your head height, these do. Similarly, the stage width is beyond the ears by a good margin. Instruments are well layered with excellent ability to pick out detailed location information.

What really sets apart top level headphones from midfi headphones is resolution. By resolution I mean the ability to reveal small details, subtle notes below the noise floor of many headphones, minor inflections, room reflections, instrument placement, correct leading and trailing edges of notes. Whilst the UERR aren’t the top I’ve heard in resolution (Noble K10E for that), they are damn impressive. Damn damn, but not in a bad way like Doc Brown below. In a good way, like a punch in the face making the future all roses, McFly.

Rebecca Pidgeon’s Spanish Harlem (24/96) is dripping with reverb on the vocal, but also has precisely placed instruments and interaction with the studio environment apparent on the recording. The placement of the stand-up bass, the violin, percussion and piano fan beautifully around her. The sound is beautiful and infectious.

When listening to Daft Punk’s Fragments of Time (24/88), the depth of the sound is not as great as the Chesky Recording of Rebecca Pidgeon, which is expected, as the dynamic range is much lower on the Daft Punk recording, but separation between the funky bass and the steady snare drum rhythm is good and all the elements in the stage are easily picked out in space with a natural coherent presentation. The image is never jumbled, just precision rendered.

The UERR will not forgive poor mastering. I love Wolf Parade, but the mastering on Apologies to the Queen Mary is craptastic. The low level hiss from the heightened noise floor, the compressed soundstage, the aggressive sharp treble mastering on cymbals, and boosted distorting guitars are all apparent. When listening to badly mastered music, a warm headphone like the Fidue Sirius will be more forgiving. I can listen to Wolf Parade with the UERR, but it’s a much more pleasant experience with the Meze 99 Classics.

Also playing well in the UERRs favour, it isn’t hard to drive, and doesn’t pair badly with anything reasonable. If you’ve got a nasty shade of colour on your equipment, the UERR won’t lie about what you are doing to the audio. You may or may not like the truth.


For this review I made all comparisons using the Aune M1S in single-ended mode with stock cables, except for the RHA CL1 which used an adaptor from the stock silver cable. I’ve noted that the UERR sound louder than comparable headphones at the same volume. I believe that this is due to the deeper insertion they offer. To adjust for this I play the UERR 2dB lower (76 db) in comparisons. This makes the volume levels sound more matched, but this may introduce imprecision and bias as I have depended on my ears to come up with this reduction. The table below contains the volume match settings.

HeadphoneGain setting1Volume  

DAP number (~dB)
UERRMiddle78 (76.2)
Noble K10ELow78 (78.2)
RHA CL1High74 (78.1)
Meze 99 ClassicsMiddle79 (78.3)
UERR Ultimate Ears Reference Remastered, Noble K10E Noble Kaiser 10 Encore  

1All comparisons were made using the Aune M1S in singled ended with stock cables


Listening to Charles Mingus Fables of Faubus (24/88 SACD rip), there is hissing in quiet passages. The soundstage has good width. The mids are a bit recessed which leads to a slightly off-kilter presentation. Cymbals are lively with excellent shimmer but are thrown too far forward in the stage. On the UERR the stage is set back further from you, and instruments have more natural placement with cymbals and the rest of the drum kit being in the same plane. Instrument heights are also better matched in the stage. The UERR has a more coherent representation. Notes sound much more natural for instruments playing in the mids and lower mids. The stand-up bass especially benefits from the switch to the UERR with more correct placement in the stage and more full, organic sounding notes. The UERR doesn’t have a hissing noise like the CL1.

Damien Rice – The Animals are Gone. The hissing is heard on this track too. This song has a mid-forward presentation, which is partly what gives it such heavy emotional weight. The CL1 has an airy delicacy on this track. Damien is certainly not robbed of emotional weight, and the violins are beautifully rendered. At about 2:30 soft swept and tapped percussion comes in. The soft cymbal drags are forward on the CL1. Violins really soar on the CL1 but have more emphasis on the upper reaches of the violin notes. The UERR gives a little richer intonation to Damien’s voice. Violins have a fuller sound with more representation of the lower elements of their notes. The cymbals are placed further back in the stage, with more emphasis on the mids. This isn’t surprising, as the CL1 is a v-shaped IEM, whilst the UERR is neutral. I will note that the volume levels sound very well matched, the 2dB measured difference isn’t perceptibly different on volume.

Hotel California is most notable for the first minute of the song for reviewing purposes. It is a good test for instrument separation, tone, and soundstage. After that, the bass drives the sound. On the CL1, the guitar and bass are a bit recessed. The stage has good width, but the airplane is lost in the stage due to the recession of the mids without a full representation of the sound. The mids feel sucked out on this track. It feels lifeless with the CL1. The mids are in their right place with the UERR with good delicacy on elements of the sound. The kick drum at 40 seconds thumps naturally, whilst with the CL1 it lacked presence. Bass grooves are right on the UERR with good thickness.

Verdict: UERR. Not close.

Meze 99 Classics

On Fables of Faubus, the soundstage doesn’t have particularly electric depth, but instruments have a nice full tone. There is some hiss in this track on the Meze, too. The stand-up bass is forward and really winsome. 36-24-36 action on that bass. Soundstage width is average, height is good, depth is not deep but there is good separation. The stage is definitely more cube than traditional theatre stage shape. Mids on the 99 are very present with excellent texture. Piano has a nice feel, too. The UERR is a bit more restrained, mids are more distant, as is bass, but the treble splashes of the cymbals have a bit more voice. The depth of the stage is greater on the UERR, which allows instruments to breathe a bit more and lays out a bit more realistic musical presentation.

When Damien kicks in, his vocals are sweet and syrupy. Rich pancake breakfast coming up. Unfortunately when the bass comes in, it swamps him a bit. The lack of stage depth makes it a competition for space, jumbling the presentation somewhat. The Meze sounds loud, partly due to emphasizing bass and mids. Both Damien’s vocal and the female backing vocal occupy almost the same space, which gives an intimate impression, as if breaking from an embrace. It’s a nice effect. The UERR doesn’t have the immediacy or warmth of the Meze, and due to the forward presentation of the Meze doesn’t sound as loud. There is far more depth in the sound though, and a bit more width. The Meze wins on height. The female vocal is a bit more fragile and breathy on the UERR, which is also a nice effect. She isn’t as forward in the UERR’s representation. Instruments have a lot more separation on the UERR.

The bass is big and bloomy on the Meze 99 in the intro to Hotel California. The airplane flying over head has good presence and is definitely not lost in the mix. The Meze 99 chugs firmly with a bass forward sound, but vocals and other instruments still have good presence. The treble sounds a touch thin compared to the weightiness of the mids and especially the midbass, but the tones are accurately represented. Greater width on the soundstage still goes to the UERR. Don Henley’s vocal tone sounds better on the Meze 99. There is more fullness to the tone on the Meze 99. The UERR is definitely more accurate, but there is something addictive to the sound of the Meze 99. It just has soul.

Verdict: I like both, but the technical capabilities of the UERR put it out in front for me. In practice, this would come down to mood.

Noble Kaiser 10 Encore

Delicate sounds around the bass are nicely revealed on the Noble K10E. The stage height on the K10E is comparable to the Meze 99, but the stage width more closely matches the UERR. Instruments on the periphery of the stage have excellent presence and all instruments have their own little bubble of space. Truly excellent resolution. The bass is a bit forward on the K10E compared to the UERR. The UERR has a bit more stage width. Instruments sound a little less refined on the UERR, and less real and alive. Resolution is excellent, but the Noble K10E is better.

The clarity on The Animals Were Gone is higher on the Noble K10E, there is just more feeling of space around the sonic elements. Vocals sound more natural. It feels like Damien is singing right to me. The bass sounds natural and warm with good delineation from where notes originate. Attack, decay, body, tone—on these the Noble K10E substantially beats the UERR. The female vocal in the refrain is much more emotive and present too with a cozy presentation with Damien’s vocal, whilst maintaining a separation that the Meze 99 couldn’t accomplish. The descriptor for the Noble K10E is natural. It is wondrously natural. This song breaks my cold little heart on a normal headphone, but the emotional content of the K10E just destroys my pitiful little sensibilities.

On Hotel California, the airplane is a bit more distant. Don Henley’s voice is more natural and the thump of the kick drum a bit more present. There are areas of the mids that are more present than the UERR, but nothing is overdone. In fact, I prefer the little boost in musicality. Vocals especially benefit from this. All instruments in the mids have a more organic feel to them. There is just more resolution and instrumental feel on the K10E. The bass notes sound flatter on the UERR, by flatter I mean they have less texture. I prefer the bit of romance and texture on the K10E. The stages are similar, but the K10E sounds airier.

Verdict: Noble Kaiser 10 Encore is the winner. The UERR is not sterile sounding, but it lacks the supreme resolution and emotional content of the K10E, the improved body and airier feel of the K10E set it apart. There is no shame in losing to the K10E, it does cost $850 (£600) more. You can buy an HD800 for the difference in price between these two. You could also just skip the HD800.


Manufacturers have lots to say about their products, and they should! The audiophile market is big, competitive and a lot of what differentiates product success and failure is how well they talk about their products. Here’s what Ultimate Ears had to say about their UERR:


Designed For Producers And Studio Engineers

Record and mix. Anytime, Anywhere.

Mix, Produce, Enjoy

The Ultimate Hi-Res listening experience. Featuring True Tone technology — providing expanded highs and lows, defining our commitment to fidelity.

The Ultimate Sound Remastered

The second collaboration with the engineers from Capitol Studios. Based on the sounds of their state-of-the-art facility.

UE Pro True Tone Drivers

Proprietary True Tone Drivers extend the frequency range and deliver a flat response to 18KHz.

Commitment To Fidelity

Hear the harmonic structure and overtones that are usually missing from most headphones

Not much in that description. Kind of like, hey these sound nice and are excellent tools. Whilst there isn’t much in the description, Jude has some good coverage on HeadFi which shines a little more light. Check it out.


Price$999 (£870)
Drivers3 proprietary balanced armatures with multiple passive crossover points and triple bore sound channels.
Frequency response5 Hz – 25 kHz
Impedance35 Ohms@ 1 kHz
Sensitivity100 dB @ 1 kHz, 1mW
Noise isolation-26 dB
ShellCustom acrylic, I went for legos, as this is a building block piece.
AccessoriesPersonalised metal carrying case, cleaning tool, buffer jack, 3.5mm to 6.3mm adapter (1/8” to 1/4″), display box with velvet insert
Warranty1 year


The Ultimate Ears Reference Remastered gives me about 80% of the sound quality of the Noble Kaiser 10 Encore at 54% of the price. That is excellent value for money. The sound is neutral and revealing, with natural musical tones and an encompassing soundstage. There is now an official universal version of these (UERR To Go, I think), so if you aren’t ready to make the jump to custom and all that entails—including not being able to share how lovely these sound—then Ultimate Ears now has you covered.


Thanks for the review...  you should try to get the linum BaX cable to see them come alive... :)
enjoying the idsd micro black  ??   that should be a very nice pairing...  great with the iphone and Onkyo app in precision playback mode... 
I only had the Micro iDSD Black for the review tour. I've got my fingers crossed that I'll be the UK winner on the tour give-away. That is a really nice piece of kit--undestatement alert.
I haven't yet tried Linum Cables, but I keep hearing good things. I did try a FiiO balanced cable before being sent the stock balanced cable. Balanced operation does open these up, but the FiiO cable is sonically inferior to the Ultimate Ears cables.
Thanks for the review. Very much looking forward to buying a pair.


Grand Master Moe "G"….Don't crossface me, bro!
Ping Pong Champ: SF Meet (2016,2017), CanJams (London 2016, RMAF 2016, NYC 2017, SoCal 2017, RMAF 2017)
Pros: Beautiful reference sound, great customer service, 3D scan leads to a better custom fit
Cons: Shells only available in clear, relatively proprietary connectors
Review: Ultimate Ears Reference Remastered
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Before I start the review, I would like to thank Ultimate Ears for the complimentary IEM.
You've heard about Ultimate Ears - they are a custom in-ear and lifestyle company that caters to musicians and audiophiles alike.  If you haven't heard about them, it's all good, you'll learn a bit about them today.  
This review will be a bit different from my others, as this will be more of an experience with pictures review than an uber detailed impressions with comparisons review.
Pictures speak at least a thousand words, so we are going to focus on that today...let's go!
First is a trip to the Ultimate Ears headquarters in Irvine, CA.  I had experience with the headquarters as I went on a tour before CanJam SoCal a couple of years ago.  I wanted a reference sounding IEM, and I knew Ultimate Ears has a reputation for creating highly regarded reference-sounding in-ears.  
When I found out Ultimate Ears was updating their UERM, I wanted to give their updated UERM (UEPRR) a listen.  When I did, I was happy with the sound of the UEPRR compared to the UERM, as I thought the UERM was a little too flat sounding for my tastes.  The UEPRR was more visceral in all areas in particularly the midrange and bass frequencies.  Lovely - let's take a look at the 3D scans.
3D scan of my ears - a painless way to obtain ear impressions!
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The 3D scanner
Beautiful packaging
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Personalized case
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Open up!
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UEPRR, buffer jack, brush and pick, 3.5mm to 6.3mm adapter
Gold mirrored faceplates
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Let the light reflect - with the Questyle Audio QP1R
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Great fit
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On the flight to AXPONA
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With the UE 18 Pro
Gold on gold on gold on gold
With some faux flowers
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Lovely reflection
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Earwerkz Omega, UEPRR, Shure SE846, Campfire Audio Andromeda
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The UEPRR is a satisfying custom in-ear that is not only reference sounding in nature, but is delicate with content brilliance. Bass plentiful but not overdone, midrange silky and warm, and treble that is non-fatiguing and brisk.  Customer service is amazing as I received my UEPRR in a few days, and the headquarters are very nice to check out as well.  I recommend not only the UEPRR but any of the lineup to try out via multiple sound-signature kiosk, and choose the one that's best for your ears.
For ordering info:
Ultimate Ears Pro Reference Remastered: Starting at $999
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twice tzuyu
twice tzuyu
Thanks for the great review and nice pictures. I would like to know how did you get the gold mirror faceplates as I couldn't find them on the UE website. By the way, they look amazing on you.
@twice tzuyu - Thanks for the comments.  You can request whatever you'd like to UE, however they may or may not have what you would like available. 
It is amazing review, actually.
Thanks for sharing pics and your experience at Irvine office.
I have been there last week too! They are so nice people =)


twister6 Reviews
Headphoneus Supremus
Pros: neutral accurate tonality, transparency, resolution, soundstage expansion, ready to ship in 5 days.
Cons: not a common 2pin connector, very polite sub-bass with a neutral mid-bass.

The product was provided to me free of charge for the review purpose in exchange for my honest opinion.  The review was originally posted on my blog, and now I would like to share it with all of my readers on Head-fi.
Manufacturer website: UERR.
* click on pictures to expand.

Quite often when I'm starting to work on a new product review, I do my homework by reading about the history of the company and the people behind it.  Searching for "Ultimate Ears" brings up a fascinating story how Jerry Harvey, Van Halen's mixing engineer at that time, came up with a dual driver in-ear monitors so that members of the band can focus better on the sound during stage performance.  As the word has spread and the demand skyrocketed, UE was officially born in 1995.  The roots of this company go deep and like a spider web connect many dots between Ultimate Ears, Westone, even Shure, and of course JH.  More than 20 years passed by, industry has expanded, competition is growing, and driver wars are still in effect.  But throughout all this time UE continued to stay true to their original calling by serving musicians and audio enthusiasts and focusing on the sound quality and the customer support.
My previous experience with UE was limited to their trendy portable wireless speakers, where UE Boom still remains one of my top recommendations, and their universal UE600 and UE900s which became my stepping stone into the world of premium in-ear monitors.  I also heard a lot of great things about their first collaboration with sound engineers at Capital Studios and the release of a highly regarded UERM (UE Reference Monitor).  5 years later UE decided to revisit their original design with an updated re-mastered version which received not only the retuning but also an updated UERR name (UE Reference Remastered).
When I was approached with an opportunity to review UERR, I didn't even hesitate for a second.  We are talking about a legendary company and a product that got a stamp of approval from a legendary Capital Studios.  Plus, it gave me a chance to chat with Mike Dias (UE Sales Director), a well known UE "face" on Head-fi.  The only thing that puzzled me about these CIEMs was a lack of attention UERR received in comparison to other flagship monitors discussed on HF.  I really think it deserves more recognition, and I hope this review will shed light on how captivating a neutral resolving tuning could be and what you can accomplish with only 3 BA drivers.  So, let's take a closer look!
Unboxing and Accessories.
I found the unboxing experience of many different IEMs/CIEMs to be either very minimalistic with everything stuffed inside of a Pelican 1010 micro-case or the opposite - an elegant packaging with a gift box presentation.  I have seen plenty of both, and as much as I usually say that only IEM matters, I can't deny that extra attention to packaging details builds the anticipation and also shows the pride company takes in their product.
Arrived in a medium size premium quality cardboard box with a magnetic flip cover, it was dressed in all formal black with a glossy print of UE and Capitol Studios logos on the top.  Once the cover is lifted, you will find a precise foam cutout loosely covered by a satin-like material with a metal round case in the middle of it.  It definitely reminded me of a jewelry box presentation.
The craftsmanship of the aluminum CNC machined anodized round case was impressive, and I like how they customize it with a name I provided when placing order.  Inside the case there was a soft lining to protect the monitors from banging and scratching, and I also found a few included accessories such as 1/4" adapter, cleaning tool, and UE buffer jack.  Considering UE’s emphasis on UERR being intended for mixing and producing, among other applications, here it makes sense to include 1/4" adapter for use with mixing consoles.  Cleaning tool is obviously necessary to scoop out wax build up from the bores of the nozzle.
Buffer Jack, with a solid build and a rubbery coating, functions kind of like an impedance adapter (but not exactly) to lower audio signal level on airplanes and to buffer electrical impedance mismatch.  It's very convenient since you have a right angle male jack and the female part of the connector attached with a short cable for an added flexibility.  It's not a single piece design that will stick out from HO jack of your source.  Also, if your have other IEMs/CIEMs with a noticeable hissing, Buffer Jack can attenuate and reduce the level of background noise, but it will also affect the sound signature since this is not a true buffer and you are introducing a variance in a frequency response, especially with multi-BA drivers.
The only additional accessory I would have loved to see here is a small traveling case since the metal round case is more appropriate for a desktop use and not very practical to carry with you in a pocket.  UE actually offers one as part of accessories you can purchase separately, but I thought it would have been nice to include it with UERR.
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The cable.
UERR comes with a durable stock cable which I suspect has higher purity wires than a basic cheap OFC.  The cable itself has 4 separate conductors, 2 twisted pairs going to each earpiece and then inner-twisted down to a right angle semi-transparent connector with a sturdy rubbery grip and a decent strain relief.  All 4 conductors are kept separate, making sure ground wires are only combined together at the connector.  Y-splitter is your typical heat-shrink transparent tube piece, and the chin slider is a freely moving clear piece with just enough friction.
In case if you need a replacement, UE offers it for purchase under accessories section, and in there you can also find a balanced terminated version which I highly recommend.  That cable is identical, except it's terminated with 2.5mm TRRS balanced plug inside of a nearly transparent right angle housing.  With so many popular DAPs having both HO outputs, in my opinion it makes sense to invest in a balanced cable with 2.5mm TRRS to 3.5mm TRS adapter, or whatever other balanced or single ended termination you prefer.  Just keep in mind, it's not necessary a termination of the cable but the architecture of your source's amp section that will determine improvement in sound quality when going from single ended to balanced.
Also, we are so used to either 2pin or mmcx cables, that many don't realize there is a variation in 2pin connectors, going back to early UE days of Triple Fi and Super Fi with 0.74mm pins vs 0.78mm pins used in majority of today's IEMs, where pins usually have a tolerance of about +/- 0.02mm.  Some might assume that any 2pin cable will fit UERR shell socket, but in reality it's not.  I have a lot of replacement cables, but found many of them not being able to fit or the fit was too tight and I didn't want to risk damaging the connector.  Furthermore, UE cable connector housing is designed to offer an extra level of security with a sleeve that wraps around the shell socket to protect from dust and moisture or the accidental pulling on the cable.  It gives you an extra peace of mind, and at the same time more headaches if you are into cable rolling.
This type of a connector requires more force to unplug it if you want to switch between cables, and majority of your other 2pin cables won't fit.  But it's definitely one of the most secure 2pin connections I have seen since the pin joint is wrapped around with a tight fitted plastic sleeve of the cable connector.  Coincidentally, I have one Pure Silver cable which probably has pins less than 0.78mm in diameter, and I was able to use it with UERR.  In comparison I found a stock OFC cable audio performance to be superior in terms of a deeper bass and more controlled highs.  From my experience of testing other SPC, pure silver, and pure copper cables vs cheap stock OFC wires, I can only assume that UE OFC cable has a higher purity copper.
Bottom line, I found UE stock cable to be of a high quality with a tight and secure connection, and its performance compliments very well UERR sound signature.  Just keep in mind I only compared it to a pure silver cable that happened to fit and also to another basic silver cable (from FLC8x).  The only suggestion for upgrade I have is to invest in UE balanced terminated version which only cost $10 more in comparison to single ended replacement cable.  Otherwise, you will have to buy a new aftermarket cable with a custom 2pin connector.
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The design.
UERR is available in Custom fit which means it requires ear impression from a professional audiologist or UE 3D Ear Scanner.  Customs are great when you are on stage or behind mixing console and want secure fit and maximum isolation.  But when it comes to audiophiles or just audio enthusiast, I noticed that not everybody wants to make a "custom" commitment. 
Some people choose universal fit design because they want an instant gratification without waiting 4-6 weeks to receive their custom model.  But with UERR and their other CIEMs, UE made sure that waiting for your custom earpieces is no longer a painful task.  With their efficient 3D printing of the shells and faster production assembly due to a clever 3-chamber piece which holds together all 3 drivers, the wait now only takes 5-days.  My review pair was delivered within 5 business days, and I also experienced a fast turn around with a prepaid return shipping when I had to send it back for re-fit (my ears anatomy is just not CIEM friendly).
On the other hand, many people who go for Customs are interested in two things: a custom fit and a chance to personalize the shell design.  UE on-line Designer is very straight forward where you choose the color and then the case and the cable.  I didn't find an option to change the color of the shell - it comes only in transparent.  With a faceplate, you have 20 different colors to choose from, including a signature white with Capitol Studios logo.  You also have a choice of 5 wood faceplates, 5 specialty material faceplates, and 9 different patterns.  It's not as exotic as some of the options offered by other manufacturers, but it still offers plenty of choices to add a custom touch to your CIEM.
Of course, it's fascinating to see inner guts of the shell, the arrangement of the drivers, the miscellaneous resistors and capacitors and wires of the crossover, but at the same time clear shell doesn't hide any imperfections of 3D printing.  I don't consider it to be a showstopper, but it was noticeable in a few places when looking closer at the finish of the shell.  Either way, I found UE team to be very flexible when it comes to requests, and I have no doubt they will take under consideration any customization request.
Other than that, when my pair of UERR arrived, the build quality was pretty good, the joint of a faceplate with a shell was smooth, you can see the line where the nozzle was fused to a shell but the seam is unnoticeable to a touch.  Also, each shell had a model marking, my initials, and a serial number printed on the inside in red and blue colors corresponding to Right and Left sides.  The 2pin connector socket was unique, sticking out of the shell to accommodate a sleeve of the cable's connector for extra security and isolation of the pins.
Inside, UERR features 3 proprietary BA drivers, referred to as "UE Pro True Tone".  The design accommodates multiple passive crossover points and triple-bore sound channels with a distinct 2 smaller tubes connecting mids and lows BAs and a larger one for highs - all going up to the nozzle.  Actually, when you look closer at the tip of the nozzle you can clearly see the main wide open bore and 2 smaller ones which could be a challenge to clean even with included tool.  Without a doubt the selection of the sound tube diameter size is not accidental and certainly based on a specific sound tuning, but you have to be aware that smaller tubes are prone to getting clogged faster, thus will need to be checked and cleaned periodically.
When it comes to the fit, it's obviously based on my in-ear impression where I typically struggle due to a sharp turn inside of my wide earcanal.  Usually it's a miracle with any pair of CIEMs to get it right from the first shot, and it wasn't an exception with UERR which I had to send back for a refit.  After that I had no issues, the fit was perfect, the isolation was excellent (UERR is rated at 26dB), and I didn't experience any microphonics.
Overall, I was satisfied with a design (classic default white faceplate with UE and Capitol Studios logos) and a build quality, though the 3D printing finish could be a little better.  But I think some people who got spoiled with exotic finishes offered by other manufacturers might find the available UE customization options to be lacking a bit.  After further discussion with UE team, they explained to me that the benefit in precision when using their 3D process outweigh the losses of the color shell, and that is a reason why UERR shell is offered only in a transparent color.
Also, I heard a great news that UE is starting to roll out Universal version of UERR, and once I have more info about it I will update my review with pictures and comparison.
*** 1/18/17 update: Universal UERR "ToGo" is here! http://www.head-fi.org/t/788168/ultimate-ears-ue-pro-reference-remastered-uerr/375#post_13186494
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The fit.
Sound analysis.
I know that we shouldn't expect too much change in the sound of BA drivers, but I have a habit of putting every new pair of headphones/earphones through 100hrs of burn in.  Maybe it's all in my head, but I believe that solder joints and miscellaneous components of the crossover get conditioned after an extended burn in period.
I find UERR to have a very natural and neutral tonality with a reference signature quality.  This is not your typical flat boring reference quality, but rather a very organic transparent laid back sound with enough energy to get your attention.  The presentation of the sound is so effortless, easily flowing without any overemphasized frequencies, keeping everything in a calm balance.  The retrieval of details is on a high level, not analytical but still very resolving and transparent.  The sound is very clear and detailed, and at the same time smooth and organic.  The most impressive part of it is how natural it sounds.
Low end has an excellent sub-bass extension with a quality textured rumble, but it's very neutral in quantity.  Mid-bass has a nice fast punch and an average speed decay with bass being tight and well controlled without any hint of spillage into lower mids, but at the same tight lacking a bit of a weight due to a neutral sub-bass quantity.  Lower mids are not too thick or too thin, but with enough body to give the sound a natural tonality without any muddiness or congestion.  Upper mids are clear and very detailed, but not harsh or analytical.  What strikes me the most is the natural timbre of the vocals, so organic and so realistic.  Treble is crisp, extended, well defined, absolutely zero sibilance, and with a nice amount of airiness.
It has a great separation of instruments and vocals, everything is very clear and easy to distinguish, the layering effect is good but not on the highest level due to a smother nature of the sound.  And as I mentioned before, there is no hint of muddiness or veil, the sound is very transparent.  The soundstage has a very impressive width and a good depth where you don't feel like being too close to the stage and yet not too far out of your head.  With that in mind, you have a very accurate and realistic placement and positioning of instruments and vocals.  Feels like you are right in the middle of the music, surrounded by a sound.
In this comparison I was using PAW Gold and Opus#2 as my reference sources while volume matching every pair by ear.
UERR vs K10UA - UE soundstage is wider, while depth is the same.  K10 has more sub-bass quantity, mid-bass has a similar impact, and overall both have a tight, punchy, and well controlled bass.  UE has a touch more body in the lower mids, with upper mids being a little smoother and more organic (the timbre of vocals sounds more natural with UE), while K10UA is a little brighter and more revealing.  Treble in both is crisp and very well defined, but K10UA has more airiness and just slightly brighter.
UERR vs Pristine-R - UE stage is wider, while depth is the same.  PR sub-bass has a little more weight, just enough to give bottom end a touch more heft; mid-bass punch is nearly the same, as well as similar control and articulation of the bass.  Lower mids are also very similar, but not the upper mids where tonality of PR feels colder and less natural, while UERR is more organic, smoother, and less aggressive.  UE treble is a little brighter, with more extension and a little more airiness.  The improvement in treble extension also makes UE sound more transparent and with better layering.
UERR vs RE600 - UE stage is wider, while RE has a little more depth.  More sub-bass in RE, but its mid-bass is flatter, slower and overall bass is not as tight or as articulate as in EURR.  RE has is typical dynamic driver performance which can't match BA, including not the same level of control to separate from lower mids.  Lower mids in RE are thicker and upper mids are not as resolving, a little more forward, but do have a similar organic tonality, not exactly the same but close.  UE treble has better extension, more crisp, and with more airiness.  RE600 is a good neutral alternative on a budget, but it can't match retrieval of details and higher resolution of UE.
UERR vs Andromeda - soundstage width is the same, while Andro has more depth.  Andro has a deeper sub-bass extension with more noticeable quantity, stronger mid-bass impact, but UE bass is tighter and faster in comparison, even a little more articulate.  Andro lower mids are a little thicker, but UE upper mids are smoother and more organic, especially with vocals which sound more natural in comparison.  Treble is actually similar.  With more low end impact and extension, Andro is more fun to listen to, while UE is more balanced and more natural in comparison.
UERR vs H8.2 - H82 has a little less width, while more depth in soundstage.  H82 has more sub-bass and more impact in mid-bass with a lot stronger punch.  In comparison, UERR low end is tighter and a little faster.  H82 lower mids have more body and sound a little thicker, but upper mids are very similar in quantity and quality.  They both have a very natural organic tonality with plenty of details.  The only upper mids difference I hear is H82 being a little more forward.  UE has a better treble extension and more airiness.  Here, the bass and a little thicker mids is what separate UE and  H82 the most.
UERR vs Sirius - very similar soundstage width, while Sirius has more depth.  As expected, Sirius has more textured sub-bass extension and a bigger mid-bass impact with a stronger punch.  Lower mids sounds similar, but Sirius upper mids push a little more back and sound a little brighter while UE sounds more natural and smoother while retaining the same level of detail retrieval.  Treble is similar but UE has more sparkle and a little more airiness.
UERR vs ES60 - ES has a touch narrower soundstage, but a similar depth.  ES has more sub-bass and stronger mid-bass punch, very similar lower mids and upper mids, and UE treble is more crisp with a better extension and a little more airiness.
UERR vs Zeus-R - very similar width but ZR has noticeable more depth.  ZR has a little more heft in sub-bass while mid-bass is very similar.  UE has a little more body in lower mids while ZR upper mids are more revealing and detailed in comparison.  ZR treble is crispier, more extended, and with more airiness.  UE sound is smoother and more organic in comparison to a more revealing and resolving ZR.
Pair up.
With a sensitivity of 100dB and impedance of 35 ohm, I didn't expect any problem pairing up UERR with my sources.
LPG - neutral tonality with smooth retrieval of details, deep extended bass but neutral quantity, clear detailed mids, sparkly and extended treble.
AK120ii - neutral tonality, smooth detailed sound, great low end and high end extension, neutral bass quantity, a little less sparkle in treble.
X7 w/AM2 - neutral tonality, a little brighter sound with slightly more forward mids that lost a bit of that organic feeling.  Good sub-bass extension, punchy fast mid-bass, a little thinner lower mids, brighter upper mids, a touch less airiness in treble.
Opus#1 - neutral tonality but with a warmer and a more balanced sound.  The sub-bass gets more weight and I hear a stronger mid-bass punch.  Mids still have plenty of body and excellent retrieval of details, nice organic vocals, crisp well defined treble.  Really enjoyed improvement in bass quantity with this pair up.
X5 2nd gen - neutral tonality yet the sound is more balanced.  Gets more sub-bass and a stronger mid-bass impact.  Nice full lower mids and detailed organic upper mids.  Treble lost some sparkle and not as extended, but still well defined.  Overall sound is not as resolving.
Plenue M2 - a balanced dynamic sound, no longer typical of a neutral tonality.  I hear a deep textured sub-bass with more weight and more punch in mid-bass - definitely more quantity.  Bass really comes to life in here.  Mids are still very resolving, detailed, organic.  Treble is crisp and extended.  Excellent pair up.
Opus#2 - balanced dynamic sound.  Extended sub-bass with a nice deep texture and balanced quantity, nice mid-bass punch, very articulate bass presentation.  Full body detailed mids, very resolving and natural.  Extended crisp treble.  Wide soundstage.  Excellent pair up.
Galaxy Note 4 - the sound is more balanced, though not as transparent or resolving.  I hear more sub-bass and the same amount of mid-bass.  The overall bass is not as tight or articulate.  Mids are smooth and clear but not as detailed, and I hear less sparkle in treble.  This pair up wasn't that great.
In a number of my reviews I often talk about not knowing what to expect prior to receiving a product, but in this case I had some expectations after reading UERM impressions.  I know they are not tuned the same, but still after putting these monitors in my ears I realized that UERR exceeded all of these expectations.  I can't compare UERR to UERM, but did find UERR to give a new definition to a neutral resolving sound.  What impressed me the most was Ultimate Ears being able to accomplish this while utilizing only 3 BA drivers, proving once again that it's not about the number of drivers but how you tune them.
If you crave more impact in the lower frequencies to emphasize the bass or you are into a crisp analytical sound, these will not be your cup of tea and perhaps you can look into other UE Pro models.  Where UERR excels is a neutral transparent expanded sound without overemphasizing any specific frequency bands, giving you a fatigue-free listening experience which is NOT boring!  I know that UE suggests these are intended for mixing and producing because you want to have an accurate flat FR response without applying EQ to compensate for sound signature of your “fun” headphones.  But as a former bedroom producer I found UERR to be equally appropriate for Music Production and Music Listening!
Spec wise, These are like the best iem in existence
akg fanboy
akg fanboy
I really think these should be compared against the fitear togo 334 for the crown of the best iem
Black Phoenix
Black Phoenix
So these are like the HD800 of IEMs