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Custom IEM Review: Ultimate Ears Personal Reference Monitor – Your Sound

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Custom IEM Review: Ultimate Ears Personal Reference Monitor – Your Sound







Ultimate Ears (UE) pioneered custom in-ear monitors (CIEMs), plugging musician’s ears with ear speakers made uniquely for their ears.  CIEMs can help musicians achieve the same sound regardless of the venue they perform at and due to the noise isolation, they can reduce the outside noise levels allowing quieter listening that will help protect against noise induced hearing loss (NIHL).  In 2008 Logitech bough UE (and is now officially called Logitech Ultimate Ears), keeping the existing UE CIEM lineup and just adding to it.  Most of UE’s pro product line was designed for stage use, but the post Logitech acquisition models, the In-Ear Reference Monitor (IERM) that I reviewed and now the Personal Reference Monitor (PRM). The IERM was made for sound/recording engineers and designed in conjunction with Capitol Records.  I found the IERM to sound neutral and perform well, but the analytical and neutral sound won’t fit everyone’s preference for personal listening.


UE is once again a pioneer in that the customer gets to tune the sound of their PRM before UE makes it, resulting in a monitor that sounds the way the customer wants!  How about that for personal!  If you want more bass, tune it that way, if you have high frequency hearing loss, crank up the treble, and if your ears aren’t balanced, adjust the PRM setting accordingly.  The goal is to find the sweet spot for your listening, not the sound the company thinks is right.


How to Order, Warranty, & Options

The Logitech Ultimate Ears PRM is available from the Logitech Ultimate Ears website for $1999.00.


The PRM is unique in that you tune the sound before you buy, so you had to go to where the tuning boxes were located to tune your monitor.  There were select locations throughout the US, but that was limiting.  UE has come up with a better solution, a smaller box that can be sent to the customer, allowing people to tune the PRM in the comfort of their own home.


Warranty: 2-year limited hardware warranty


Options: cable length: 48” or 64”; cable color: black or clear; artwork - fine wood veneers: Cherry, Walnut Burl, Carpathian Elm Burl or Purple heart, a finish exclusive to the PRM



Input Sensitivity: 110.6 dB @ 1 kHz, 50mV

Efficiency: 115.6 dB @ 1mW

Frequency Response: 20 Hz to 18,000 Hz

Impedance: 21 ohms @ 1kHz

Internal Speaker Configuration: 5 proprietary precision balanced armatures

Noise Isolation: 26 dB

Input Connector: 1/8" (3.5 mm) gold plated


My Tuning Session

When I had the chance to tune my PRM, I spent a good deal of time tuning the sound and playing around with the limits of the box.  During my tuning sessions I used the Spiral Ear SE 5-way Reference as a reference point, and also had my IERM for comparison.  An iPod Touch was provided as a source for tuning purposes, however I used my iBasso DX100 with songs I am familiar with.  One of the first things I noticed about the PRM was the spacious sound that was as impressive as that of the IERM, and the note thickness and tonal balance sounded more organic than the IERM.  Note that the PRM demo is just that, a demo unit, so you will have to rely on ear tips to get a good seal.  They provided the standard single flange UE tips and Comply foam tips, however you may want to bring your own if you have other ear tips that work well for you.


I started my testing with the knobs all six of the knobs at 50, which is neutral.  There are three knobs for each channel representing bass, midrange, and treble.  Turning a dial to a lower number will increase the amplitude of that part of the frequency response with a maximum of 0, which is around 7 dB change.  While 100 represents an approximate 7 dB decrease, slight changes can still take place above 100.  There are buttons for each channel that will reset the settings to neutral which will give perspective on how your settings sound compared to the “neutral” of all 50s on the knobs.


As I adjusted the knobs, I listened for the best sound for me, compared with the 5-way, and IERM, and listened for technical changes within the sound.  The small incremental changes sneak up on you as revealed by pressing the “neutral” button.  The largest technical change I noted was with the midrange adjustments, as the imaging and depth of the presentation were slightly reduced as the knob was changed between the extremes.  This may or may not occur with the customized PRM as the treble of the real thing is better than the demo.  When changing the bass knob, most of the bass spectrum changed adding warmth to the sound which was already warmer than the IERM with a setting of 50.  However, deep bass didn’t change which could have been because I was listening to a demo.  When the magnitude of the treble was increased I had a similar feel to that of the IERM, however with more smoothness.  But, it still wasn’t the highest quality treble I have heard.  I ended up with the following tunings:

Treble: 54 (slight decrease)

Midrange: 50

Bass: 45 (slight increase)


I chose the slight boost to the bass because I figured the bass between the demo and real thing would be a bit off.  The treble decrease was chosen because I find the IERM bright, and I have experience where some of my customized CIEMs are brighter than the demo units.  As it turns out, the PRM was more spot on with the demo, except in the deep bass, and I could have gone with all 50s.


So, how much can the PRM change with tuning?  While 7 dB is a good amount of change, it won’t change the note PRAT, and the bass driver won’t allow it to compete in the bass department with a CIEM that has 4 dedicated bass drivers.  You can make the PRM a warm and bassy CIEM, a more mid-forward CIEM, although it will never be intimate, and a much brighter CIEM.  The changes can make the PRM sound like something quite different than the neutral tuning, the ultimate “how much” question will depend on perspective.








The Personal Reference Monitor utilizes 5 balanced armature drivers per ear in a 3-way configuration (two crossover points).  There is a single bass driver, dual midrange, and treble drivers.  The shell is acrylic with dual sound tubes and protruding sockets for the cable.  One of the sound tubes is larger than the other and both dual element BAs have their own short sound tube within the larger sound tube.  The canal portion of the shells is backfilled with acrylic.  Custom wood artwork comes standard, however other options are available.  The ground channel is the upper socket and the positive channel is the lower socket.



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The unboxing experience for the PRM is very nice.  The outer box is a nice looking black and contains an envelope with instructions and warranty information.  Within that box, there is a metal case that holds the PRM, a cleaning tool, an airplane adapter, and a 1/4” male stereo plug to 1/8” female stereo jack.  The PRM also comes with RewardTag, which is a system designed to get your monitors back in your hand if you lose them.  There is a sticker on the inside of the carrying case, and if someone returns your CIEM to UE, they will get a reward.  Great concept, and one that I can see giving a big sigh of relief for some people, but I am NOT going to lose my PRM!!!



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UE changed the sockets on their CIEMs, so it is not strange that they changed the cable as well.  And all of the changes are positive ones!  First, the cable itself is thicker with a very tight braid, minimalist Y-split made from heat shrink, tightly twisted cables above the Y-split, and a heat shrink cable cinch.  Ergonomically the UE cable performs as well as a stock cable, yet it seems more robust.  The shell connectors are made specifically for the protruding sockets which provide a very secure and stable connection as well as a design that will keep moisture away from the sockets and CIEM internals.  The memory wire is shaped to work with the setup and comes out of an angled over-molded plug. Available in either clear or black, I choose black due to the oxidization that the clear cables experience over time.  The overall feel of the cable and the connection to the CIEM are very professional. 



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The isolation of the PRM is a 6/10 on my scale, which puts it ahead of hollow shelled CIEMs, but below solid acrylic and silicone shells.  The increased isolation is due to the acrylic fill of the canals.



Disclaimer: My review is a comparative review, and since I have many similarly priced CIEMs, my perspective is based on equal competition.  My goal is not to tell you how great the item being reviews is, but to explain the sound signature and characteristics as well as bring you a balanced account of the strengths and weaknesses to help you decide if this particular CIEM is for you.  When I listen to CIEMs without any comparison after some time away, I am continually impressed with the sound and it is the contrast that enables my perspective.  So take the review as a critical look at the CIEM and realize there will be positive and negative aspects of every product I review and product selection should be based off what sound signature you want or the purpose of your purchase instead of looking for technical top performance.

Quick reference: My review technique, Thoughts on reading a review, CIEM information


The PRM received 100+ hours of burn in as is customary before I do my serious listening.  The following CIEMs were used for comparison: Ultimate Ears In-Ear Reference Monitor, Hidition NT-6, Spiral Ear SE 5-way Reference, M-Fidelity (formerly Starkey) SA-43, Heir Audio 8.A, ACS T1 Live!, JH Audio JH16, Earsonics EM4, and Rooth LS8.


Review Note: Since the PRM is tunable, the quantity of the bass, midrange, and treble are not as important as the quality.  My tuning notes discuss some of my findings about how far things can be tuned and changes to the sound.


Bass: The bass is reminiscent of the UE IERM, but with better extension and more warmth.  Of course, the bass quantity can be tuned to your preference, but the overall bass has more warmth at the 50 position than the IERM and is smoother with a bit more detail as well as the ability to sustain deep bass rumble better.  The deep bass note sustainment, while adequate, is less than the competition save the ACS T1 Live!, which also uses a single BA driver for the bass, but can a CIEM that cost close to half be considered competition?  Technically, other than the capability, the bass is excellent with nice levels of detail and impressive layering and texturing in the bass.  In bass heavy music, the PRM makes many other bass enhanced CIEMs sound loose in the bass region.


The PRM shines with natural instruments, due to the detail, texturing, and natural tone, but move to bass heavy pop or electronic music and the PRM can’t output the same level as the multi-driver and dynamic counterparts.  Even with the bass tuned up, the rumble doesn’t improve as the bass is limited due to the single driver, but the quality of what is present is top notch.  You can tune the bass up or down from my settings, however the quality will remain.


Midrange: Spacious and detailed, the midrange is balanced with the rest of the spectrum. The excellent imaging, focus, resolution, instrument placement, and instrument separation along with the large and 3D space result in a very convincing and immersive experience that is focused on the overall presentation.  Instruments have high levels of detail, higher than the IERM and on par with others such as the LS8 and JH16, but falling a bit short of the Hidition NT-6 and NT-6 pro as well as the SE 5-way, but resolution is similar to the 5-way and Hidition products.  The midrange is very reminiscent of the 5-way, but the upper midrange is more forward and the tonality is different with both sounding “right” in their own way.  Overall, the PRM midrange is one of the best out there.  With tuning you can pull the midrange closer or push it back, however when those changes are made the depth of the presentation is reduced.


Treble: The treble is well integrated with the rest of the spectrum and reminiscent of the IERM treble, but better in many ways.  The IERM treble is analytical and very revealing of any issues, but the PRM treble is a good deal less analytical and not as sharp.  I wouldn’t say the PRM treble is smooth and detailed like that of the LS8, 5-way, or even the NT-6 Pro as it is still on the analytical side of the spectrum, but the quality is very good.  My tuning is not bright and more in line with the LCD-2 and 5-way.  Detail levels are good, but the instrument details aren’t pronounced like in the brighter CIEMs such as the JH16, LS8, NT-6, and NT-6 Pro; however the note decay is natural.  While the treble isn’t quite up to the quality of the midrange, it is still is near the top in quality.


Presentation: Let the music flow to you!  The PRM doesn’t focus on individual instruments, but has a relaxed presentation that lets you become immersed in the overall presentation of your music.  High levels of detail are present but don’t dominate the picture the PRM paints.  The PRM gets out of the way of the instruments, not giving you cues to the location of the drivers.  Coherence between the drivers is excellent. The ability of the PRM to keep up with fast music when necessary and reproduce the proper warmth when called for is due to the excellent note attack and decay capability.  Notes are organic in general, but more analytical than the 5-way, 8.A, and SA-43.  Dynamic range is very good as is clarity given the way the music is presented.  Listening to the PRM with a good source and well recorded tracks can be a real immersive and engaging experience due to the excellent presentation, which is one of the best out there.




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IERM: While these two share many characteristics, they are indeed different in many ways.  The IERM has a similar presentation and soundstage space of the PRM, but the IERM midrange is a bit more forward and not quite as spacious or 3D.  With more upper midrange emphasis, the IERM pulls vocals forward in comparison with the PRM, but this could change with different PRM tuning.  Both image very well, but the PRM is superior as well as having a cleaner and clearer presentation and sharper focus.  Detail levels are higher on the PRM with better instrument detail as well as recreation of black space.  Clarity is similar between the two even though the IERM is more emphasized in the “clarity” part of the spectrum, which is a result of the better focus and higher resolution.  Note attack and decay is a bit slower and therefore more natural on the PRM, especially in the treble where the IERM can be a bit too quick on the attack and decay taking away from the smoothness of the presentation.  While I have issues with the IERM treble and less than perfect tracks, the PRM is much more forgiving.  When you combine improvement of the PRM over the IERM the result is a more realistic, natural, and organic sound.  While the IERM is purpose built for recording engineers, the PRM should please those that want a top notch personal listening experience. 


NT-6 with Whiplash Hybrid V3: This comparison was performed using the NT-6 with the Whiplash Hybrid V3 cable to close the gap in price.  The V3 cable changes the note decay resulting in a more organic and natural sound while taming the upper end.  Even with the cable the NT-6 V3 is brighter and more mid-forward than the PRM with less warmth.  The NT-6 V3 presents a clearer, slightly more detail, but the detail presented has better focus and the details are in higher definition.  Treble notes are more prominent on the NT-6 V3, closer to the IERM in quantity, but sound more natural due to a longer decay and overall smoothness.  The NT-6 V3 can sound a bit hot in the upper vocal range in comparison with some sources and tracks.  Bass quantity with my PRM tuning is similar but warmer, however the NT-6 bass has more emphasis down low that can sustain sub-bass rumbles longer as well as additional headroom.  The NT-6 V3 is more dynamic and in comparison with the more relaxed and forgiving PRM.  With a slightly larger, more 3D soundstage, the PRM gives a better sense of space.  Images of the PRM is superior and layering is similar, but the NT-6 presents more detail within the layers. 


Both perform at very high levels and the differences come down to your listening preferences and usage.  The PRM is easy going with its more laid back, forgiving presentation while the NT-6 V3 is more aggressive and revealing.  With the PRM you give up a slight bit of clarity and resolution for a more organic sound while the NT-6 V3 gives you the details in stunning clarity.  Essentially, the PRM is more focused on the overall presentation while the NT-6 V3 presents the instrument details with more of a focus.  Both are musical in different ways and perform at high levels, but the PRM is a better all-around daily listening CIEM while the NT-6 would excel as a tool for dissecting music or those that don’t want to miss a thing.


SE 5-way: Considering I used the 5-way for comparison during my tuning session, the PRM sound signature is close.  Both have a spacious, layered presentation, excellent imaging, and an overall organic sound with a very natural tone.  The 5-way presentation changes quite a bit with each track while the PRM is more consistent with a larger space on many tracks.  Note decay is very similar, although the 5-way can sustain notes better, but the attack of the 5-way is slightly more aggressive resulting in a more dynamic and punchy sound.  Detail levels and resolution are higher on the 5-way, however the PRM is very close.  Tonality is a bit different as the PRM upper midrange in general sounds a bit more natural, however the changes of the 5-way seem to change due to the tracks themselves, so the issue is most likely due to the recordings and not the 5-way.  Transparency is quite similar, however due to the ability to change more with tracks and superior dynamics, the 5-way edges out the PRM.  Coherence of both is top notch.


The bass capability is greater with the 5-way as is quantity making the PRM sound more neutral and “reference” than the 5-way.  The mid-bass region isn’t too far off, but the 5-way is warmer.  The midrange is quite similar, although the 5-way has better layering and the size of the presentation changes more with each track.  As stated, the upper midrange of the 5-way changes quite a bit making comparison difficult.  Sometimes the 5-way sounds off in this region vs. the PRM and other times it sounds better, it just depends on the track.  By themselves, both are excellent.  The treble of the 5-way extends further and has a bit more air and has a very nice PRAT, although the PRM is no slouch.


These two are close in many ways and could be considered competitors.  Both have strong points.



Consistent sound across a wide range of tracks

Changes with each track, which is both good and bad

More neutral sounding

Amazing bass capability

Ability to tune the sound to your preference

The changes with each track give you what is in the original recording

On average, more spacious presentation

More accurate recreation of the soundstage in the recording

Artwork available

No artwork

Slightly better than average isolation

Silicone shell isolates quite well

Widely available as you can have a tuning box sent to you

Limited availability as Spiral Ear will only ship within Europe

The last comparison in the above table will be one of the biggest determining factors in the purchase of either.  If I had both to choose from and listened non-professionally, the decision is a difficult one.  A case can be made either way for professional use: consistent sound (PRM) or a CIEM that will reveal the true nature of the track (5-way).


 8.A: The 8.A has a much more intimate and mid-forward presentation along with much more bass that gives the presentations a greater sense of power and dynamics compared with the more laid-back and neutral PRM. Overall soundstage size is larger with the PRM and while the 8.A has a good amount of ultimate width (headstage), the PRM is a good deal more spacious.  Depth and height of the presentation is superior with the PRM and in direct comparison recreates a more accurate sounding space.  With better imaging and a sharper focus of instruments within the soundstage, the PRM presents has better instrument separation as well as a clearer and more coherent presentation. 


As mentioned, the 8.A is more dynamic and punchy and a good deal more capable in the bass region with a much stronger emphasis, even if the bass was tuned all the way up on the PRM.  The bass region is controlled better on the PRM resulting in better texturing, if only by a bit.  Midrange quality is close between the two, but the PRM has a bit better layering with a smoother note.  The upper midrange through the treble of the PRM sounds flatter and more balanced than the 8.A, which has an upper midrange/lower treble bump and then decays in quantity.  While the 8.A treble quality is nice, the PRM treble decay is more natural but the more aggressive leading edge can result in a less forgiving treble, although the PRM has sharper S’s.  Bass and midrange note attack is close, however the 8.A has a bit quicker leading edge while the PRM decay is a bit shorter than the 8.A, which to my ears sounds more true to life. 


Overall, the presentations are quite different and the choice between the two comes down primarily a decision between a neutral, laid back and spacious sound vs. an upfront, punchy, and bass enhanced performance, not to mention the price difference.  Also, while the PRM fit, finish, and artwork is good, the 8.A is spectacular.


EM4: The PRM is more laid back and open sounding than the more mid-forward, punchy, and bass heavy EM4.  Spatially, both are enveloping, although the PRM has a larger space with better imaging.  The PRM has a cleaner presentation that is more forgiving across the spectrum, which is readily apparent playing well recorded music in the upper midrange and treble region. Coherence is better with the PRM, and note attack and decay are more natural with the PRM leading to a more believable presentation.


The EM4 has more bass quantity from deep bass through mid-bass, however the PRM bass quality is superior. While the PRM can be tuned for a sound that is quite close to that of the EM4, I don’t think the bass of the PRM can have the same impact of the EM4.  Midrange presentation is quite different with the EM4 placing vocals up-front and center while the PRM is more laid back.  The EM4 is brighter than the tuning of my PRM, but both have nice treble decay.   The treble area of the EM4 is less sensitive to sources/amps than the PRM, but with the right combination, the PRM outperforms the EM4 with a more natural presentation and more true-to-life note decay.


The PRM provides a cleaner and more balanced sound with a laid back presentation in comparison with the more up-close and personal EM4 that offers more bass and punch. 


SA-43: With a similar sound, the SA-43 is a bit more laid back and sounds overall smoother than the PRM.  With the presence switch off, the usually laid back PRM sounds forward in comparison while the presentation is similar with the SA-43 presence switch on.  However, with the switch on, the tone of the SA-43 changes and the PRM sounds slightly more natural.  While the PRM is spacious, the SA-43 is more so with as good of a 3D presentation, however the PRM images a bit better.  Clarity is in favor of the PRM in part due to a bit more analytical sounding note.  The PRM technically beats the SA-43 in speed, detail, and overall resolution within the soundstage as well as having slightly better dynamics.  Both are very transparent and coherent.


Bass quantity of the SA-43 with the bass switch off is at about the same level as the PRM, except the PRM extends deeper and has slightly better layering.  When the SA-43 bass switch is on, there is a tradeoff of quantity for control, however extension improves, equaling the PRM.   The PRM is a bit warmer than the SA-43 with the switch off, and vice versa with it on.  With a comparatively more forward midrange, the PRM has more of a focus on vocals with easier to hear details.  The upper mids of the PRM are also more forward, giving a brighter and more lively presentation while the SA-43 has a better balance from the midrange through the treble.  In the treble region both present similarly, although the SA-43 treble is slightly smoother, if just by a bit.


Both of these CIEMs can be tuned in various ways, one before customization, and one after.  The tuning of the SA-43 is done by switches giving you 4 sound options while the PRM has a much larger range for the tuning, but once you pick your tuning, that’s it.  Technically, the PRM equals or outperforms the SA-43 in most every technical characteristic except soundstage size and space.  Here is a summary of how they compare:



Pre-customization tuning

Four sound tuning levels with switches

Laid back, spacious presentation

Even more laid back and spacious presentation

Bass is tight and neutral, but on the warmer side

Bass can be fairly neutral or enhanced, but enhancement reduces control

More forward and detailed midrange

Midrange presentation puts you further in the audience

Artwork options

No artwork

Hollow acrylic shell with special shell connectors and excellent cable

Silicone filled acrylic shell with standard cable and replaceable filters


Half the price of the PRM



JH16: With an enhanced deep bass and bright sound, the JH16 is more analytical sounding than the PRM, which is organic and natural.  While the tuning of the PRM can result in a closer match, the JH16 sound can’t be replicated by the PRM.  The JH16 is more forward than the PRM and the overall soundstage isn’t as 3D, although width is similar.  Imaging, coherence, and transparency are better on the PRM, speed and clarity are about the same, and the JH16 is faster, has more bass rumble and dynamics.  Instrument detail levels are similar but the PRM conveys more information within the soundstage.  The PRM is more forgiving.


The bass of the JH16 is a good deal more enhanced and forward with a faster note, but can also reverberate more than the PRM.  In comparison, the JH16 has pounding bass compared with the fairly neutral and not as warm PRM.  The more mid-forward JH16’s analytical note gives a sense of more detail within the midrange, however the detail levels are similar.  While the JH16 has a liquid midrange, the PRM sounds more organic.  The treble of the PRM is much smoother than that of the JH16, as the treble could be somewhat harsh in direct comparison with the PRM.


If you are looking for a more analytical sound with enhanced bass, or you listen to pop music, the JH16 is for you.  If you want to tune the bass, midrange, and treble of your monitor and are looking for an organic sound with a more 3D presentation, the PRM is it!


LS8: The LS8 is more mid-forward with enhancements in both extremes of the frequency spectrum giving a more exciting and intimate presentation in comparison with the organic, natural, and laid back PRM.  Imaging is better with the PRM, which also has a larger and more 3D soundstage.  Dynamics, instrument detail, and clarity are superior on the LS8, if just by a bit, while the PRM bests the LS8 in transparency, coherence, resolution within the soundstage, and note decay.  Speed is about the same between the two and the PRM is more forgiving due to the 6K peak of the LS8, but the LS8 is more forgiving of rough and grainy mids.


Bass of the LS8 is more forward, punchier, enhanced, and warmer than that of the PRM but does give up some in control for the enhancement, resulting in a higher quality presentation from the PRM.  Continuing from the bass, the midrange is also more forward and liquid with more instrument detail while the PRM is analytical and laid back in comparison.  In the upper midrange and lower treble region the LS8 is more enhanced with a smooth and liquid treble above that while the PRM has a different upper midrange/treble balance.  While the PRM is more analytical, imperfections can hide in the comparatively laid back treble presentation.


If you want a natural and organic sound, the PRM is the way to go while the LS8 provides a dynamic and exciting presentation with enhancements on both ends of the spectrum.  The LS8 gives a more immediate presentation that focuses more on individual instruments with a very good presentation, and conversely the PRM has more of a focus on the entire presentation, although the individual instruments are still very high in quality. Technically these two are fairly close, but the PRM does pull ahead, as it should for the price. 


T1 Live!: The T1 Live! has a similar sound signature to my PRM tuning, but with some minor differences.  The T1 Live! is a bit more forward and brighter, but they share a similar tone and organic presentation.  Technically the PRM outperforms the T1 Live! in every technical category, however, the differences are not huge.  The T1 Live! is a slightly underperforming, more forward PRM, at least with the tuning I chose.  You could tune the PRM to sound just like the T1 Live! if you wanted.  Bass is similar in quantity and the ability to rumble, but the PRM is slightly superior in the midrange and treble as the PRM has better clarity, especially with complex tracks.


The decision comes down to how price, availability, how important tuning is to you, and if you are willing to pay for better technical ability of the PRM.  Not to mention the silicone shell of the T1 Live! that provides better noise isolation.


NT-6 Pro: The NT-6 Pro presents an exciting, amped up performance with its enhanced deep bass and treble while the PRM presents a relaxed and organic performance.  One of the first things I noticed comparing the two was the NT-6 Pro has a slightly faster note that, when combined with the upper region really pulls all the details out to the forefront in contrast to the organic, laid back presentation of the PRM.  Detail, resolution, speed, and dynamics are higher on the NT-6 Pro while coherence and transparency are similar and both exceptional.  The soundstages are quite similar in size and shape even though the presentation is different, with an ever so slight edge in imaging going to the PRM.  Both have a liquid presentation and PRAT is good, however they are both different as due to the note speed difference.  The PRM is more forgiving of poorly mastered tracks and is easier to find a good source.


Bass of the NT-6 Pro is enhanced in the lower registers, rumbling quite a bit more than the PRM with deep bass, and while the PRM isn’t bad in the bass region, the NT-6 Pro can output more bass with similar quality.  Warmth goes to the PRM, although the NT-6 Pro isn’t too far behind.  The midrange of the NT-6 Pro is more forward than the PRM with a more intimate sound that picks apart the presentation, delivering plenty of easy to hear detail vs. the presentation focus of the PRM.  The upper midrange of the PRM is excellently balanced with the rest of the spectrum, and while the NT-6 Pro has a boost in the region, it still manages to sound tonally right.  There is a good deal more treble presence with the NT-6 Pro, and detail levels are higher.


These two complement each other, with the PRM focusing on an organic and natural presentation while the NT-6 Pro does fun with mind blowing clarity.  The PRM can’t be tuned to the NT-6 Pro levels, and the difference in note separate the two further.  Both are very different and excellent in their own ways.



Volume performance: The PRM performs well with channel balance at lower volumes with most sources due to the lower than typical sensitivity, although it is not on the low side.  With low volume listening from lower end sources the PRM isn’t as immediate, punchy, and accurate sounding as with better sources, and can have a leaner sound.  However, with high end sources such as the 801 or DX100 the PRM dynamics are very good and the sound signature is retained from louder volumes.  At the loudest volumes I can handle for a few seconds (which probably isn’t too loud), the PRM performs quite well in the midrange and treble without any congestion, although there is very slight distortion in tracks with heavy and deep bass.



Sound Summary:  With the ability to tune the sound signature, the PRM offers the ability for people to find their music preference.  Sound is very spacious and laid back with excellent imaging, high detail and resolution levels, excellent transparency, and coherence.  Notes are in a very nice balance between analytical and thick resulting in a very organic and natural sound.  The focus is on the overall presentation vs. the individual instruments, yet the PRM performs very well in that regard also.  The bass will never be dominant, but you do get to tune to your variation of neutral, and the midrange is top notch with an excellent treble.  From a technical performance standpoint, the PRM is one of the top performing CIEMs I own.


Source matching






Portable Sources, DAPs

Clip+: Paired with this high performance CIEM, the Clip+ shows its price by holding the PRM back in dynamics and depth of presentation.  The bass isn’t as impactful and not quite as full as with the iPhone 5, and spatial size of the presentation is constricted.  It isn’t a bad source per se, but you can do a good deal better with an iPhone 5.  3/10

iPhone 4S: The iPhone 4S sounds OK with the PRM with decent soundstage size and good imaging, but the bass is weak and the presentation sounds a bit smeared, lowering the clarity level.  Notes are a bit harsh in comparison with the Clip+.  2.5/10

iPhone 5: The iPhone 5 is a good match for the PRM considering it is a phone.  The bass is ample, the presentation is spacious, and the dynamics are slightly better than Clip+, and about on par with the RoCoo BA.  Detail levels are on par with the Clip+, and both leave the finer details of music out.  There is room for improvement, especially in detail levels, but overall the iPhone 5 is a good choice considering it is a phone.  5/10

RoCoo BA: The RoCoo BA performs close to the iPhone 5, however it has a bit smaller presentation which leads to a little less clarity than the iPhone 5.  Detail levels are higher than the iPhone 5 and the attack is a bit quicker.  The iPhone 5 has a slight bit more upper midrange emphasis while the BA has more treble emphasis, but it is close.  Bass between the two isn’t too far off, but the iPhone 5 extends a bit further.  If you can carry an iPhone 5 around, the RoCoo BA is a device I find hard to recommend unless you want it for the size and storage, or if you want 2 devices.  5/10

801 (with GAME card): The 801 with GAME is a step up from the RoCoo BA and iPhone 5 with better detail, dynamics, a more natural tone, larger space, and better clarity.  Combining the improvement in all the attributes, the 801 with GAME is a nice step up and provides a very natural presentation.  The 801 doesn’t have the same treble issue I had with the IERM.  8.5/10

DX100 (1.2.7 firmware): Fantastic spaciousness along with great clarity and a natural note articulation resulte in a very musical presentation making the DX100 an excellent match.  Compared with the 801 with GAME, the DX100 has a bit more spaciousness, clarity, and resolution.  10/10


Portable Sources, DAPs with Amps

iPhone 4S ->

627: Pairing the 627 with the iPhone 4S does improve the sound with a smoother, larger presentation, however the limitations of the iPhone 4S do inhibit the soundstage.  The presentation is still not the smoothest, and with the lack of depth, the presentation sounds flat in comparison to how the PRM can sound. 3.5/10


iPhone 5 (headphone out) ->


Arrow 4G: Retaining the presentation of the iPhone 5, the Arrow doesn't change much except smoothing notes out, making the iPhone 5 sound a bit grainy in comparison, and adding a bit more depth to the presentation, but not much. 5.5/10

Stepdance: The SD adds a bit of dynamics and more of an upper midrange emphasis to the PRM, but the changes aren't necessarily improvements.  There is hiss that isn't there with the HPO.  The score was reduced by 0.5 for the hiss.  4.5/10


Modded iPod ->

EHP-O2: The O2 sounds good and true to the recording with the PRM.  The soundstage size does constrict the PRM compared with higher end sources and there is a bit of a haze within the soundstage, but there is a naturalness to the sound. 4.5/10

Shonyun-306: With a more mid-forward presentation than the O2, the presentation doesn’t sound quite as natural.  The upper midrange through the treble is not very smooth leading to a fatiguing presentation, even after a short period of time. Not a good match.  1/10

Neco V2: Compared with the O2, the V2 is smoother, a slight bit more forward, but more natural sounding with a slight bit larger overall soundstage.  Bass quantity and control is similar between the two.  There is a slight channel imbalance at very low volumes which reduces the score 0.5.  4.5/10

uHA-120: The 120 images quite well in a nice sized, 3D soundstage.  Compared with the V2, the 120 is a slight bit rougher in the treble, however it does image better and provides a larger, more 3D space than the V2.  Bass on the V2 is slightly more powerful with similar control, and the V2 has a bit cleaner and clearer presentation.  The depth of the presentation improve the overall sound, but the V2 is slightly better in instrument detail. 5/10

Pico Slim: The PS is bright by nature which can be heard vs. the uHA-120.  Bass of the PRM is neutral making the other amps I used for comparison testing sound warmer.  While the midrange and treble are good, they aren’t a step up from the uHA-120 and the treble is actually a bit rougher.  Soundstage size isn’t on par with the 120, although imaging is good. 4.5/10

Stepdance: With an excellent presentation of space and a very natural sounding note.  Dynamics are great and the Stepdance gives the PRM nice punch down low while still keeping the quality superb.  The midrange and treble are also excellent and match quite well with the PRM.   There is hiss, which reduced the score by 0.5.  7.5/10

Cruise: The Cruise is a punchy amp that has a fast note, and with the PRM this is no exception.  The presentation is more aggressive than the Stepdance, but the quality is not lacking in any way.  With more upper midrange emphasis, the Cruise sounds brighter than the Stepdance and not as tonally accurate.  The Cruise does allow the PRM to accentuate detail and keep up with the fastest complex tracks with ease.  Another issue with the Cruise is the slight amount of hiss, which does lower the score by 0.5. 6.5/10

627: The 627 takes a step up from the other amps, offering excellent clarity, a large soundstage space, and excellent imaging.  Compared with the Stepdance the entire presentation is cleaner and the bass is controlled better.  Spacious tracks improve in size more than the other amps and the overall presentation is detailed yet smooth with better layering.  9.5/10


801 line out ->

Arrow 12HE 4G: The 4G pairs with the PRM quite well, providing a bit more air and brightness to the HPO of the 801 as well as a more expansive soundstage.  The 801 is more forward with less soundstage depth, so the presentation sounds a bit stuffy and slightly compressed in comparison, however the 801 does have more deep bass than the 4G.  9/10

Stepdance: Pulling the soundstage back a bit compared with the 801 HPO, the brighter SD doesn't add much in the way of quality, and the 801 sounds more weighty.  Tonally, the 801 HPO sounds a bit more accurate, and there is hiss on with the SD, which reduced the score 0.5.  Overall, the SD isn't bad, but if you have the GAME card with an 801 there is no real reason to use a SD.  7.5/10



Desktop Sources

D1: The D1’s direct competition from a sound quality perspective is the DX100, and the D1 is different than the DX100 in that it has a bit thinner note giving it an analytical feel vs. the more organic DX100.  Overall, the quality of the presentation is very  high, however the DX100 images a bit better and had a larger, more 3D space.  9.5/10


Source Summary: Lower end sources and amps restrict the soundstage space and detail of the PRM, typically resulting in less overall clarity within the presentation.  When high quality source components are in the chain, the PRM will come to life with better dynamics, incredible spaciousness, and very high levels of detail.  While the PRM will play nice with some lower end sources, if you are going to spend on the PRM, you should have the source chain to shine.







Does this $2K CIEM live up to its price?  First, being able to tune the sound to your preference solves one of the issues with CIEMs, which is you have to typically buy a non-refundable product to find out the true sound.  If you don’t like it, you are out a good deal of money, which is why the ability to not only tune the sound, but try it before you buy is important and has a high value in my opinion, which people ask me for all the time.  And when people do ask my opinion, I always recommend they buy based on their sound signature preference and usage.  This feature is great.


From a performance perspective, the sound signature of my unit isn’t as important as the sound tendencies and technical performance since you can tune the sound to your liking.  Technically the PRM is one of the top performers I have heard, disappearing and letting the music come through with exceptional transparency and realism.  The sound is spacious and on the organic side of the spectrum, if just by a bit, and it the warmth is north of neutral.  With a laid back presentation, the overall performance is the focus, not the individual instruments, although they are clear and detailed.  The PRM performs at a higher level than the $1K UE IERM and up there with more expensive CIEMs I own.  The Logitech Ultimate Ears Personal Reference Monitor is an exceptional product, even at its price point, due to the sound tuning feature before you buy and the sound quality you get when the customized version is delivered to you.



-       Exceptional imaging and layering within the very large soundstage

-       Note decay is very natural sounding and realistic providing great tonal accuracy

-       Sound tuning allows you to change the quantity/presentation of the three spectrums, providing you with a better fit to your preference



-       Slightly limited deep bass rumble capability

Edited by average_joe - 9/10/13 at 8:03am
post #2 of 61

reserved for a later comment

post #3 of 61

I think I found my true love, the one that can bring me to the end of portable headphone journey.


Excellent imaging, spacious, FORGIVING, laid back, coherent, and tune-able. Can't ask for more! For less price I would tho biggrin.gif


The cons actually hits me a bit because I was a basshead during my earlier era of being audiophile, but not that much nowadays.


Few questions for Joe:

- Artwork options: do you mean by the 4 types of woods? or we can actually requests a custom artwork from our own images? This is one of the turn offs, albeit the woods are quite nice as well

- Smaller tuning box: where do they send these boxes? I am going to USA for tuning next June, but if I can do the tuning earlier, the better. Or maybe someone from UE can answer this question?

- less of importance because it's highly dependent on our tuning, but comments on pairing with Headstage Arrow 12HE 4G please? smily_headphones1.gif


Last but not least, I would like to thank Joe for delivering this long awaited review. Thank you for helping this lost soul finding his true destined CIEM

post #4 of 61

finally.a review after a long time ;) good job joe! it keeps getting better. I have to take my time with it;)


But...they send a tuning box to you now?! wow!! that's a very big advantage of the PRM now!!

post #5 of 61

Great review, Joe, thanks for your hard work & dedication in bringing these reviews to the community.

post #6 of 61

I'm wondering if the PRM might be improved to even better performance, in terms of bass rumble, if UE were willing to double-up the bass BA driver.


Yes, I realise there are technical reasons why it's not quite as simple as just putting another BA in there, in terms of matching the tuning of all the drivers, but still, my point stands...popcorn.gif

Edited by Mython - 12/9/12 at 11:43am
post #7 of 61

 Wow, great review average_joe! I can't wait until some UM models are evaluated and after you have demo'd the Tralucent 1plus2, really looking forward to it. Thanks for all the time, money, consideration, and effort you put into this!

post #8 of 61
Thread Starter 
Originally Posted by etherlite View Post

I think I found my true love, the one that can bring me to the end of portable headphone journey.


Excellent imaging, spacious, FORGIVING, laid back, coherent, and tune-able. Can't ask for more! For less price I would tho biggrin.gif


The cons actually hits me a bit because I was a basshead during my earlier era of being audiophile, but not that much nowadays.


Few questions for Joe:

- Artwork options: do you mean by the 4 types of woods? or we can actually requests a custom artwork from our own images? This is one of the turn offs, albeit the woods are quite nice as well

- Smaller tuning box: where do they send these boxes? I am going to USA for tuning next June, but if I can do the tuning earlier, the better. Or maybe someone from UE can answer this question?

- less of importance because it's highly dependent on our tuning, but comments on pairing with Headstage Arrow 12HE 4G please? smily_headphones1.gif


Last but not least, I would like to thank Joe for delivering this long awaited review. Thank you for helping this lost soul finding his true destined CIEM


No shame in finding the one for you, and the PRM makes it easy to verify before you take final delivery!


I actually have yet unanswered questions in to UE, which include the personalized looks and how exactly the loan of the smaller tuning boxes works.  But, since the PRM is personalized in sound, I don't see why they wouldn't customize the look as well.  


Ah, the one amp I didn't test because it was at work.  I will have to test the 4G when I have a chance.


Originally Posted by tupac0306 View Post

finally.a review after a long time ;) good job joe! it keeps getting better. I have to take my time with it;)


But...they send a tuning box to you now?! wow!! that's a very big advantage of the PRM now!!


Thanks!  Yes, the smaller tuning boxes that can be shipped are great.


Originally Posted by Mython View Post

Great review, Joe, thanks for your hard work & dedication in bringing these reviews to the community.


Originally Posted by Mython View Post

I'm wondering if the PRM might be improved to even better performance, in terms of bass rumble, if UE were willing to double-up the bass BA driver.

Yes, I realise there are technical reasons why it's not quite as simple as just putting another BA in there, in terms of matching the tuning of all the drivers, but still, my point stands...popcorn.gif


Yes, that would be great, especially if they could keep the quality as good as it is now.


Originally Posted by RobotsEatCookie View Post

 Wow, great review average_joe! I can't wait until some UM models are evaluated and after you have demo'd the Tralucent 1plus2, really looking forward to it. Thanks for all the time, money, consideration, and effort you put into this!


No problem, glad to do it for the community ;)

post #9 of 61
Originally Posted by Kunlun View Post  reserved for a later comment


"Interesting review" ? tongue.gif


Originally Posted by average_joe View Post

700 700

700 700


Now that's just showing off! wink.gif

post #10 of 61

Noticed you left the Arrow 4G blank. Nevertheless, excellent review. However, for $2k, I won't feel TOO comfortable seeing how it only has a 2 year warranty, if I owned one myself. I wonder how many sales they will achieve

post #11 of 61

Very nice, Joe!  


I appreciate the way you refrain from a single ranking system but compare sonic characteristics and then evaluate them from a particular point of view so that the reader can weight his or her priorities and gather information.


If I ever need to replace my IERM or want to complement them, I'm going to use this review as a reference...PRM SE 5-Way > ES5 would be in the running.


Thanks for your time and effort spent.  Not easy doing something like this...

post #12 of 61

I am crying....

post #13 of 61

First of all, thank you Joe for the great and detailed review!   


Apologies to everyone if this seems like a sales post, but I wanted to let everyone know that we have a much smaller version to "check out" if you cannot find a rep close to you.  Give us a call if you like to play with this.



post #14 of 61
Hi Vincent, can you answer some of my questions?

1. Can we get those smaller boxes in Australia? I plan to go to LA anyway next June, but faster is better
2. Joe mentioned about artwork customization, is that limited to the 4 types of wood you've supplied or can we use our own custom artwork?

Thank you
post #15 of 61

Awesome review and if there was ever a CIEM I wanted it would be these because of the tuning capabilities.  

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