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REVIEW: Unique Melody Merlin - hybrid dynamic/balanced armature custom IEM

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  1. project86 Contributor
    In November of last year, I did a review of the Unique Melody Miracle custom in ear monitors. They set a new benchmark for me, surpassing my prior favorites of Westone ES3X and JH13pro. I was intent on making them my next purchase until I learned of a new project UM had in the works. That project would eventually be named Merlin and it is the subject of this review.
    Stephen Guo from www.custom-iem.com informed me that UM was working on a hybrid custom. It was to be 3-way configuration, with quad balanced armatures covering highs and mids and a dynamic driver handling low frequencies. This sounded very intriguing to me, so I decided to hold off on my purchase of the Miracle to see how this new project panned out. A few weeks later Stephen advised me that the new model would be called Merlin and they expected a January release.
    Obviously January has come and gone by now but the Merlin is finally here. It seems that there were some difficulties in development, and I suspect a big part of it had to do with deciding on what the final sound signature should be like. Even without that aspect it’s easy to understand the delay: hybrid BA/dynamic designs have only been attempted a few times, and never in such a complex configuration. This product really puts the “unique” in Unique Melody and I applaud them for making the effort.
    Since I had proven myself by borrowing the UM Aero and Miracle demo models for review (and not disappearing with them), UM was willing to make me an actual custom molded demo this time around. It helped that I intended to purchase either the Merlin or the Miracle – if I decided on the Merlin then I could just pay for them and keep the pair I already had. So in April of this month I received the Merlin. I was immediately impressed by the sound but found that it was more balanced than I had anticipated. I was under the impression that the Merlin would be more of a bass heavy option, but to me it sounded fairly similar to the Miracle. After making some inquiries with the head office, Stephen informed me that UM Lab had made some last minute adjustments to the Merlin tuning. This effectively made my pair a prototype model since it didn’t reflect the final sound of the actual product. For that reason I decided to wait on doing a review until I could get my hands on the final version.
    Stephen and UM graciously set things up for me to receive another custom molded Merlin, this time with the final tuning. I received it in June. Any customer ordering a Merlin will get the same product (obviously they are customs so they will be different but you get the idea). Over the course of this review I’ll refer to this product simply as the Merlin, or sometimes as “final Merlin” when discussing the differences between the two versions. The prototype, while interesting in its own right, is not really the topic of this review, so I’m not going to spend much time on it. When I do it will be called “proto Merlin”.
    You may be wondering what the last minute change in tuning is all about. I wondered the same thing. I am still not 100% clear on the story, but I suspect there might have been a difference of opinion within UM about what the target sound should be. I imagine an engineer designing the proto Merlin and thinking it sounded great. Then I imagine someone in charge of marketing listening to it and saying “This sounds too similar to Miracle. Give it more bass!” I have no idea what really happened by my theory seems plausible enough. UM seems to have a very clear delineation between each of their models, and to undercut their flagship Miracle by $150 with a product that sounds relatively similar just doesn’t make much sense.
    As I mentioned before, the Merlin is a 3-way design. It sells for $779 from www.custom-iem.com. It uses dual balanced armature drivers for highs, dual BA drivers for mids, and a single dynamic driver for lows. They have a very small vent which sits at the intertragic incisure, which is the space between the tragus and antitragus. Since the vent is small and out of the way, UM is still able to do custom artwork just like they would with their other models.
    Aside from the hybrid aspect and vent, the Merlin is the same as any other UM custom. Buyers can choose from a large selection of faceplate and shell colors in either translucent or opaque. A small “uniquemelody” text or a larger “UM” text can be added to the faceplates at no charge. Titanium-look faceplates are available for $45 extra, and custom artwork can be added for $50. UM apparently upgraded their artwork capabilities recently, so they now offer detailed multicolor graphics rather than simple engraving.
    Sockets come standard as recessed but can be flush if desired, and the appropriate matching cable is provided.
    Early speculation was that the Merlin would be the same as the Miracle with the exception of the single dynamic driver in place of Miracle’s dual BA drivers for bass. That turned out to not be the case. The Merlin uses two sets of Knowles Acoustic TWFK drivers, which are themselves dual driver units, for a total of four drivers. One set is assigned high frequency duties and the other mid range. This is in contrast to the Miracle which uses the same TWFK for highs but swaps a pair of larger drivers for the mids. I don’t know the specific part number they use. So in reality the Merlin and Miracle have only their high frequency drivers in common. A closer match to the Merlin would actually be the ES5, which is the recently released flagship from Westone. That model uses the same configuration of 5 drivers including dual TWFKs on mids and highs, but substitutes a large BA driver on low frequency duty instead of the Merlin’s dynamic driver. Specs on the Merlin are as follows:
    Sensitivity (at 1kHz): 108dB spl (1mW)
    Frequency response:  10Hz - 19000Hz
    Impedance: 12ohm
    Noise isolation: -26dB
    Let’s break those numbers down individually. The sensitivity rating of 108dB is fairly reasonable. It’s higher than the Head Direct RE series models, Jays Q-Jays, and Etymotic ER4S, but lower than JH13pro, all of the Westones, Sennheiser IE8, and many others. The 12ohm impedance is very much on the low side though. The only earphones I recall with such low impedance are the low priced SoundMagic models and Phillips SHE9850. The result of those two numbers combined - I’m still trying out different sources, but so far it seems that the Merlin is a bit more difficult to drive than most IEMs. It still sounds reasonable on a basic iPod or other portable, but to really get the most out of your investment you are going to want some type of amplification. I did run into a mild issue with my Matrix M-Stage and Quattro amps – they both exhibit some background hum, independent of the source. This only happens with the Merlin, as those amps are generally quiet with all other IEMs. Aside from that the Merlin works well with the amps I’ve tried.
    The frequency response numbers given are impressive, although we routinely see inaccurate numbers listed from various companies so it is hard to compare directly. Each Merlin comes with a frequency response chart to refer to. My prototype did but unfortunately my final version didn’t. UM shipped it without the usual accessories since I already had those, so maybe that’s why they left out the chart. I will include a few pictures of other Merlin FR charts for comparison.
    Isolation is an interesting subject. Since the Merlin has a vented design, it does not provide as much isolation as an average custom IEM. It also leaks a little bit of sound, which is not the case with most IEMs. I don’t think that the -26 dB rating is accurate in this case; I suspect UM just used the same number from their other models. Many people have asked me about this issue, so I’ll do my best to describe it.
    I don’t want to overstate the issue of sound leakage: it is minimal but it does exist. The determining factor will have to do with what you listen to and how loud. If I listen at moderate levels to classical, my wife doesn't complain when she is sitting next to me reading in a quiet room - she can hardly hear a thing. But if I play some Metallica or something like that, at loud levels, she can tell what I'm listening to. It doesn't really bother her, but she can tell. If it was a noisier environment like a car ride, the average busy office setting, etc, then it would probably not even be noticed. The leakage is no worse than a Yuin PK1 or any other earbud design would be at that volume level, probably less than that actually. But it is there. This is not exactly new for a portable though - earbuds, Koss KSC75 style clip-ons, and Sennheiser PX100 types all suffer from this same issue.
    Another way to explain it is this little experiment: Take an in ear monitor of any type. Listen to it and find a good volume level that represents something you would normally listen to. Now remove it from your ears and see how loud it is from a few feet away. That sound level will be significantly louder than the sound leaking from the Merlin when it is in your ears. So if you find that tolerable, then you are good to go.
    The flip side of leakage is always isolation. The Merlin is not the best if heavy isolation is required. It does block some noise but certain things like wind seem to get through. Think of an IEM you've tried that doesn't insert super deep or isolate a lot, but is still better than an earbud - the Merlin is like that. Running or bicycling gives you the worst of that wind type sound, although once the music plays it is still very usable. There is some good attenuation of other sounds though. I was out for a walk the other day and was waiting for the traffic light to cycle so I could cross the street, when a very loud Harley Davidson motorcycle pulled up next to me with the typical loud rumble. As usual the rider was revving the engine a bit so it was louder than just an idle. I was within arms reach of the thing, but surprisingly it wasn’t bothering me. I turned off my music to double check and sure enough, the Merlin was making an obnoxious, almost painfully loud sound into something easily tolerable. So as far as IEMs go the Merlin is on the lower side of the scale with regards to isolation, but not at the bottom.
    The standard warranty on UM customs is 1 year, with free refits offered within the first 30 days. But Merlin gets the same special treatment as the flagship Miracle: warranty is doubled to 2 years, and the customer has 60 days in which to decide if a refit is required. This 2 year/60 day refit policy is among the best in the business.
    UM has become well known for their exceedingly high build quality. They certainly met my expectations with the Merlin. Both the prototype and the final version Merlin I received were very well done – not a single bubble, smudge, or other issue in sight. Their flawless finish is among the best I’ve ever seen from any custom IEM company. I was unsure how the dynamic driver would affect things but it doesn’t seem to have been a challenge for UM.
    I ordered the Merlin with clear shells and translucent blue faceplates. I opted for the free “uniquemelody” text which I think looks very nice. It was hard to capture in the pictures but it is very small text, yet is still precise and well done. They use a kind of silver font that is still understated. I personally prefer that to the larger “UM” text option. I also went with recessed sockets which is the new standard offering from UM (flush fit is available as a free option).
    One question I had, that I’m still unsure of, is about the vent. How will it stand up to long term use? Could dust or other foreign substances get inside and cause problems? Obviously those are questions that can’t be answered until Merlin owners start accumulating experience with the product. I can say that after several months of having the prototype, I don’t see or hear anything unusual. My only main concern is moisture – wearing these in the rain is probably fine due to the size and placement of the vent, but I do wonder how that would contribute to long term wear on the drivers. I appreciate the fact that UM gives a 2 year warranty, so it then becomes less of a concern. I’m sure if there was a problem several years down the line UM would be able to repair it for a low price anyway.
    Here is the FR chart for my prototype Merlins. It shows the relatively mild bass boost.
    My final Merlin didn't include an FR chart, but this is an example from someone else. Notice how much more boosted the lows are compared to the proto. Now go find an FR chart for the Sennheiser IE8 to put this into perspective.  
    The Merlin comes with the same packaging as the Miracle did: large red (faux?) leather storage box, 50” cable, cleaning tool, warranty card, and a printout of the frequency response chart for your particular Merlins.
    The large storage box is very nice for home storage but is absolutely not suited for portable use. The user might want to pick up a more useful portable storage solution from Pelican or Otterbox. Luckily those can easily be had for under $20.
    Pictured with the Beat Audio Cronus cable, which is not included stock
    Merlin and Audeze both offer nice looking storage solutions that are not so good for travel
    This is the associated equipment I used to evaluate the Merlin:
    Source: custom server fronted by a Squeezebox Touch, Lexicon RT-20 universal disc player (as transport)
    DAC: Anedio D1, Resonessence Labs Invicta, Audio GD Reference 7, Matrix Quattro DAC
    Amplification: Violectric V200, Matrix Quattro amp, Analog Design Labs Svetlana 2, Lead Audio LA200
    Portable: used directly with a Sansa Suze, Sansa Clip+, or QLS QA350, or sometimes amplified by a TCG T-Box or Audinst AMP-HP
    Matrix Quattro system with three low frequency champions: Merlin, LCD-2, and LA7000
    Since the Merlin is positioned as a “bass-heavy” alternative to the usual balanced UM sound, I expected it to have fairly large bass. The prototype version I first received did have very high quality, deep, and substantial bass impact, but surprisingly it was only mildly boosted compared to what I remember the Miracle sounding like. I greatly enjoyed the prototype sound but I can see why UM decided to tweak it for more low-end volume.
    By the time I received the final version, I had been using the prototype exclusively for a while. It took a bit of adjustment for me to come to terms with the extra bass. I find that I can switch full sized headphones and adjust to the new sound fairly quickly, but with custom IEMs I have a harder time. I’m not sure why that would be. In any case, once I got used to the “real” Merlin sound I was very pleased with it.
    I’ll start by describing the lows since that aspect could be considered the focus of the sound signature. Bass on the Merlin goes incredibly deep. It is fast and clean sounding, with no bloat or overhang, and sounds very convincing. But so far that describes both the proto and the final version. The difference is that bass on the final Merlin is louder; it takes the slight boost of the proto and bumps it up by a significant amount. Now bass becomes the driving force in many songs – anything with a kick drum, double bass, or other low frequency instruments will really stand out. This makes electronic music, metal, hip-hop, and many rock songs have immense drive and energy. Other music remains largely unaffected since the boost mostly takes place way down low. Every once in a while you do hear it creep in as a bit of unwelcome midbass thickness; usually this was present in lesser recordings that were prone to that behavior from the start. But in most cases it stays put where it should.
    I found classical music to be an enjoyable experience with the Merlin. But I recognize that not everyone will. Purists who demand a totally neutral response should look into the Miracle or even the Mage which is positioned just below the Merlin. Some people listen to classical with a Denon D7000 or a Lawton modified version and totally enjoy it. Others think those are a bad match for that application. Merlin falls into the same category. What makes it very enjoyable for me is the huge soundstage, smooth presentation, and startling dynamics. But I admit that the low frequencies can at times be slightly distracting if we are looking for a lifelike balance of sound. That’s the price we have to pay for making all those other genres sound so good. Honestly though, UM is positioning this as a bass heavy custom – potential buyers should think about their listening preferences and adjust their expectations accordingly.
    Moving to the mid-range, I feel that the Merlin is a little bit of a departure from the typical UM sound. The Aero and Miracle both have slightly more forward mids that are very fast and clean. They have extreme detail (obviously the Miracle more so than the Aero) and can really grab your attention. The Merlin has a somewhat more laid back presentation. It is not recessed by any means, just a little bit relaxed in comparison. This could be due to the different choice in drivers, or it could simply be an artifact of the larger bass drawing our attention away. In any case, don’t mistake my “relaxed” comment as being negative; I absolutely love the presentation here. It seems to fit better with the overall feel of the Merlin. If I imagine the overall Miracle sound but with Merlin-sized bass, the result seems likely to overwhelm with too many things grabbing for your attention. The Merlin still offers incredible insight into your music; it just does so with a more casual attitude.
    Highs on the Merlin bring us back to the classic UM house sound. They are very extended yet still smooth, resulting in a realistic sound that doesn’t fatigue the listener. Spatial cues abound, the energy of cymbals is reproduced clearly, and micro-details ooze with clarity. All of this occurs without a trace of harshness. Overall the highs remind me very much of the Miracle which can only be a good thing.
    Soundstage on the Merlin is another very strong point. This may very well be the largest soundstage I’ve yet heard in an IEM. The Miracle was astounding in this department and the Merlin is at least as good, but in a somewhat different way. The Miracle sets up a very large stage and then renders each performer on that stage with pinpoint accuracy. The Merlin starts with an even larger stage, making for more space in between each respective performer. Because of the large size there is more overall distance involved from left to right and front to back. There is still a very high degree of accuracy but ultimately it seems slightly less defined than the Miracle. So it ends up being a bit of a tradeoff – a little more space for a little less definition of placement. Both models are still excellent in each category though, and the presentation of each seems to fit their overall nature.
    Instead of just trying to describe the sound in general, I feel that it might be illuminating to include some of my listening notes. These are mostly taken directly from my listening journal, although I did a little reorganizing to make it more intelligible. These are not meant to be definitive for each song but collectively they do tell a story. These were all done in a quiet room at home using reference grade equipment.
    Angelique Kidjo – Voodoo Child (Slight Return)
    *Extremely smooth vocals, very believable
    *Deep, powerful bass – just on the edge of being overwhelming but not quite over the line for me, it might be for some people though
    *Great layering of guitar and percussion
    Apocalyptica – Nothing Else Matters
    *Rich tone to the strings
    *Palpable “plucking” sound
    *Great timbre – very believable
    *Extremely dynamic
    *Busy solo at roughly 3:19, Merlin gives plenty of control, sounds better than ES3X in this area
    Something Corporate – She Paints Me Blue
    *High hat is well controlled – it sounds a bit bright at times on LiveWires and especially UE4pro
    *Overall thickness of the sound seems fitting
    Elektric Music – Overdrive
    *Good soundstage, nice and airy
    *Extra thump in the bass is very welcome, as the recording is a little thin for this type of music
    Crystal Castles – Celestica
    *Very open, almost ethereal sound
    *Bass drum hits very hard but not too accented to distract
    *NO sibilance at all
    *At 2:05, a sort of background bass drum sound appears, sounds like the envelope has been tweaked, also seems like it has been low pass filtered at a very low frequency – only the Lawton LA7000 can compete with the quality of the Merlin here
    Salvatore Accardo - Concerto for Violin and Strings in F minor, Op. 8 No. 4, R.297 (from “Vivaldi - The Four Seasons” XRCD release)
    *Very fast transients
    *No blurring due to bass overhang
    *Lows ARE emphasized
    *Very enjoyable presentation for me but maybe not so much for some purists
    The Weepies – Little Bird
    *Simply too much bass for my taste, it feels a little thick and distracts me from the vocals
    The Weepies – Riga Girls
    *Much better…. Extra thump is welcome in this scenario and vocals remain clean
    Nancy Wilson – You’d Be So Nice To Come Home To
    *Clear, smooth vocals
    *Sense of scale with the entire presentation, especially the band
    *Bass is big, very clean, massive depth
    *Nancy sounds suitably embedded in the presentation, not too close or too distant
    Hiromi – Joy
    *Great details: snare rattling in the background for example
    *Drums very crisp, can clearly hear impact of sticks on cymbals
    *Toms have thicker textures than usual
    *Bass guitar is very present but still natural
    *Extreme dynamics towards the end of the song, very impressive
    *Makes the 1964-T sound dull and unrefined in comparison
    Electronic Noise Controller – Parallax
    *Eerie, spacious ambiance, utterly convincing
    *Huge bass drop at 0:36 rips you out of your relaxed state and gets your head nodding
    *2:30 or so – bass becomes truncated, possibly another low pass filter trick like Celestica, it barely shows up in the background with most IEMs, Merlin brings it out more and it is very clearly defined
    Pearl Jam – Dissident
    *Very lively and energetic sounding
    *Drums quite realistic, especially snare
    *Eddie Vedder sounds very natural and present
    *LOVE that loose hi-hat sound
    Kent Poon’s Audiophile Jazz Prologue III – Nica’s Dream
    *Great Ambiance, like being there live
    *Bass is tight, prominent
    *I can hear sax valves opening and closing, but it doesn’t seem like a gimmick as it does with some other “detail oriented” IEMs
    *Piano=WOW!!! Very lifelike
    *Sounds like bassist is closer up front on the stage than he probably should be, but despite that it is enjoyable with lots of authority
    *Cymbals very convincing
    Metallica - Harvester of Sorrow
    *Thundering bass drum and toms – closest to Denon sub-bass I’ve heard from an IEM
    *Definitely a thick presentation, not too thick in my opinion
    *I clearly recognize the “Lars” tuning on the drums
    *Hetfield’s voice sounds correct in volume, tone, and distance, not recessed at all
    *Overall presentation not as “crisp” sounding as JH13
    Jimmy Eat World – You and I
    *Good rendition of fairly mediocre (at best) recording, final Merlin sounds the same as prototype Merlin since there is no low frequency information to be boosted
    Further Seems Forever – New Year’s Project
    *Very dry recording; Merlin gives it some life
    *Vocals avoid stridency
    *Most authority I’ve heard from this album aside from my LA7000
    *Decent layering
    *Grain in the track is mildly smoothed over
    Marta Gomez – La Flor
    *30 seconds into the song = chills down the back of my neck as the percussion and bass guitar come in
    *Very rhythmic, in favor of soul over accuracy to some extent
    *Marta’s voice is clear and inviting, one of the best presentations I’ve heard from any headphone
    Living Sacrifice – Local Vengeance Killing
    *Brutal drum intro is very controlled – this track is a great test of speed and the Merlin passes with flying colors
    *Guitars have a very satisfying “crunchy” sound, I prefer this presentation even to my Grado PS1000
    *Lead vocalist Bruce Fitzhugh sounds suitably growly without being too forward in the mix
    *Breakdown at the 2:07 mark sounds very dynamic and again well controlled
    Yo-Yo Ma - Main Theme from Once Upon a Time in the West (Sergio Leone Suite)
    *Beautiful, haunting sound to the cello
    *More dynamic than most IEMs including Monster Turbine Copper and Westone AC2/W3/UM3X/ES3X
    *Lows are weighty but not flabby nor overdone
    Yo-Yo Ma - Cockeye's Song from Once Upon a Time in America (Sergio Leone Suite)
    *Very emotive and raw: sounds like he is beating the cello to death in the intro
    The Merlin is a bit difficult to compare to my other custom IEMs just because the sound signature is so different. I can say from experience that I very much prefer the Merlin over the Ultimate Ears UE11pro, which is another bass heavy custom. UE11 was simply too unbalanced for my tastes, with the lower mids being buried by the boosted bass. Even in the mids and highs, which sound great when not being overwhelmed by bass, the UE11 does not offer much competition for the Merlin. Consider the fact that the UE11 sells for $1150 and the Merlin becomes the clear winner in this comparison.
    My old UE Hybrid customs (which sadly got damaged beyond repair some months ago) were similar to the Merlin from a design aspect – vented shells, dynamic driver for lows, armature driver for highs, large bass response. Those had a fun sound but ultimately did not offer the same level of refinement or coherency as the Merlin. They reminded me of a big JBL or Cerwin Vega speaker setup from back in the day – “full range sound” was really their claim to fame above all else. It could be very enjoyable but the flaws were also easy to hear. Merlin offers a much more mature version of that same sound. The UE-Hybrid has been out of production for a long time so it really isn’t a relevant comparison anyway.
    Compared to my JH13pro, the Merlin is a very different animal. Bass obviously takes the spotlight in the presentation, making the JH13 seem almost flat in comparison. Mids seem smoother and more natural, with the JH13 seeming a little more forward and aggressive in comparison, especially in the upper mids. This comes down to preference or even mood – some would call the JH13 a bit too aggressive, others love the clear presence it has. Some would call the Merlin a bit boring in the mids, while others would love the smooth analog feel it gives. This is just a worst case argument, as I suspect most people would really enjoy both presentations. Highs are fairly close but again Merlin seems a tad more smooth, having a similar amount of sparkle but drawing less attention to itself. Ultimately I’d describe the JH13 as having a more “crisp” presentation with a relatively intimate feel while the Merlin is warmer and more relaxed with a more open feel. The JH13 gives me an experience that brings to mind a high-end studio monitor used in a near field configuration. In comparison, the Merlin feels more like a large audiophile-oriented speaker; specifically one that utilizes a dipole design such as the Jamo R909. It is not unusual to find speakers using an open baffle design for their midrange drivers and/or tweeters, but they usually have a sealed enclosure for their low frequency driver. The R909 is an exception to that rule, as are some others like the Linkwitz Orion, Legacy Whisper HD, and the various Emerald Physics models. Where this analogy fails is that the Merlin has significantly more bass by quantity, although by quality it is fairly comparable. The bass produced by these open baffle designs always sounds a bit different to my ears than that of standard enclosures, and the Merlin seems to echo that by having a slightly different character compared to balanced armature designs. It might be the vented dynamic driver actually moving a quantity of air that gives it this somewhat unique attribute (armature drivers don’t exactly move air in the same way), it might be the specific tuning that gives it this feel, or it might even be just be my imagination.
    I have heard people complain about BA designs not being able to “do bass” to their satisfaction, and I never really understood what was meant by that. In my opinion the JH13 has fantastic low frequency response, as do several of my other customs using BA drivers. So I’ve never felt that I was missing anything from using armatures. The Merlin sounds slightly different to the point where I can say I somewhat understand where people are coming from, but the difference is fairly subtle. This isn’t some revolutionary increase in bass quality… that would be unrealistic to expect considering the great performance given by the JH13. But what the Merlin does, it does very well, and it is very possible that a BA based design would not be capable of replicating it. Either way, both the Merlin and the JH13 should be considered top level customs, and they both easily carve out their own specific audience that they will appeal to.
    Comparisons to the Miracle are a bit tough simply because I don’t have the Miracle here any longer for direct comparison. What I do have is my memory along with extensive listening notes. My impressions of the Miracle (see my profile for the review link) were extremely positive, to the point where I was sure I’d buy them in the near future. Then I heard about the Merlin being in production so I decided to wait. I was hoping that the Merlin would be very similar to the Miracle but with elevated bass levels for a more “fun” type of sound signature. The prototype Merlin did precisely that, to the point where it didn’t really make sense to sell it for $150 less than Miracle…. but more on that shortly. The Final Merlin has a different enough sound to where it really doesn’t compete with the Miracle; like the JH13, they go after different audiences. Miracle seems more focused on accuracy. It has a more immediate attack, and the overall presentation is more high energy. The Merlin is more focused on musicality, with a more relaxed pace. Of course, the Miracle is still very musical and the Merlin is still very accurate – they just excel slightly differently. But the real deciding factor remains the bass presentation. Those desiring a neutral, transparent sound should look to the Miracle instead of the Merlin.
    Now for an arguably worthless comparison: the proto Merlin compared with the final Merlin. I don’t know what exactly was changed with this revision. Drivers all seem the same so it must just be the crossover that is tweaked. Either way, the result is different enough to comment on. The final tuning is closer to a Denon D7000 while the prototype is more like the Lawton LA7000. The D7000 mids are a little more distant, likely due to the huge bass volume. The LA7000 is more even but does dial the bass down by a noticeable margin. This analogy is flawed because I feel that the Merlin has better mids than the D7000, but it does capture the similar-yet-different nature of these two versions.
    One last comparison: I was sent a universal demo of the Merlin to compare to my molded version. The person who had the universal demo wanted to see how close they sounded to the real thing, because he found them a little disappointing. I was shocked to hear the demo because it was substantially different. Bass was similarly large but not even close with respect to clarity and control. Highs had an edginess to them that became fatiguing after a short while. Mids were more distant. And the soundstage was all wrong in comparison. I can only speculate that the smaller size of the universal demo makes it impossible to get the same results. Whatever the cause, it seems that a user will not be able to properly experience the full potential of the Merlin unless they actually buy it. For that reason, I’ve tried my best to make this review as accurate and descriptive as possible.
    A quick note about powering the Merlin – although they sound pretty good straight out of a DAP, I feel that they truly shine when given a solid source and some good amplification. I don’t always use a portable amp with most customs but I found that the improvement in the Merlin made it worth the effort of lugging a bigger system around. That’s not to say you need to spend a ton of money; my $99 TCG T-Box and $160 Audinst AMP-HP both matched very well without costing an arm and a leg. Using the Merlin in a home setting was even better though, as it seemed to scale well with a high end DAC in the chain. I found its deep insight into the music very useful when evaluating the high end Resonessence Labs Invicta DAC.
    A tale of three Merlins: prototype, final version, and universal demo
    The three Merlin versions among several of my other other custom IEMs
    The Unique Melody Merlin has had its share of delays and issues on the road to being completed. But now that it is here, I can confidently say that it was worth the wait. Part of the problem was caused by my own expectations: without any word on pricing, I had assumed that the Merlin was to be equal with the Miracle but with different bass tuning. Sort of a JH13/JH16 scenario. That seemed logical, and it probably would have been easier for UM to do in order to get the product pushed out the door faster. But it seems that UM had a different plan, one that called for the Merlin to have its own unique drivers and overall sound signature along with a lower price. In my mind this was the right choice.
    Let’s be clear: the Merlin has a sound that is very bass heavy. This is not an IEM with a mildly enhanced low end, but rather a full blown bass machine. If you are someone who is on the fence about enjoying a larger bass presence, this might not be the best choice for you. That being said, this is some of the most jaw dropping low end performance I’ve ever heard. The last deliberately bass-heavy IEMs I’ve owned were the Sennheiser IE8 and Westone AC2, prior to that was the UE11pro and the UE-Hybrid. All of those are pretty good in their own ways, yet none come anywhere near the Merlin in terms of well controlled yet deep bass extension with no crowding into the mids. When considering other headphones that offer similarly excellent low frequency performance, I keep coming back to the Denon D7000, Lawton LA7000, Audio Technica L3000, and even the Audeze LCD-2. Not much else is able to keep up.
    But the best part of the Merlin is that it is not a one-trick pony – although bass is the star of this show, mids and highs play great supporting roles. Everything is detailed and present enough without being overly forward, and the soundstage is massive. The whole thing seems designed as a cohesive listening experience rather than just taking an existing sound and boosting the bass.
    When we consider all the parts of the Merlin, the total package is very competitive. Excellent sound, typically high UM build quality, great service from Stephen at www.custom-iem.com, a relatively low price (for a top range custom IEM), and a generous extended warranty. There really isn’t much out there as far as competition. As long as potential buyers have realistic expectations about the isolation levels and the large quantity of bass, I don’t anticipate anyone being disappointed with this product.
    I’m keeping this separate from the review portion because it is unique to me and my situation. Feel free to ignore it if you aren’t interested.
    I knew I was going to purchase either the Miracle or the Merlin from UM. Upon hearing the prototype Merlin, I was extremely impressed with it, to the point where I was sure it was the one for me. When I received the final version, it took a bit of adjustment to enjoy it because it was far less neutral than the proto. After lots of listening I started liking it and eventually loving it. The decision became very difficult for me. When I started with the proto and switched to the final, they seemed to unbalanced and unnatural. Then I’d get used to the sound, switch to the proto, and find it somewhat flat and boring. I suspect that some people are better at those types of quick listening switches but I find that I usually need some adjustment time.
    To make a long story short, I ended up purchasing the prototype version. This was mostly based on other factors rather than any deficiencies in the final Merlin. I know myself too well, and I know that if I chose the bass heavy version, I would likely end up buying the Miracle down the road for a more neutral sound. Either that or I would reshell and upgrade my LiveWires Trips to become 6 driver models which should sound similar to the Miracle. By choosing the more neutral prototype version, I’ve somewhat guarded myself against that desire. Another aspect is my usage habits – I found that I used the Merlin more often at home than on the go. Home use means no background noise, so the lack of extreme isolation doesn’t matter. If I was planning on using them on the go more often, I would probably have gone with the final version. The low frequency background hum of the city seems to soak up some bass response (phase cancellation maybe?) so the extra volume on the lows would be welcome. Lastly, I also admit that the exclusivity of the prototype model is appealing; if I missed my chance with it now, I would never be able to go back and purchase it down the road. That’s not the case with the regular version. I know that it sounds silly but there it is. The prototype Merlin has been paid for and the final version sent back to UM. I second guessed my choice a few times in the beginning but at this point I’m very satisfied and no longer looking back.
  2. shamrock134
    Thanks! I've been looking forward to this for a long time.
    Merlin = D7000 in custom IEM form? Yes please!
  3. phntmsmshr
  4. noxa
    great review. looks like i have found my first pair of customs. How does the bass compare to the high end DD universals like the IE8?
  5. shamrock134
    I would also like to hear more about the bass relative to other IEMs. How deep exactly does the Merlin bass reach? Can it reach the 18Hz claimed by the FS Atrio?
  6. Stephen Guo
    Here, I show my gratitude to project86 for writing such an extensive and detailed review!~[​IMG]
  7. knubbe
    Nice review. UM customs are always so clean looking
  8. maguire
    Hey, Just want to say how much i enjoyed your review of the Merlins.
    I tried the demo version and albeit brief, I felt the demo's did not really do them any favours.
  9. shotgunshane Contributor
    @project86, The frequency graph of the final Merlin reminds me of the JVC FX700/FX500.  Have you heard those?  I'm interested in the Merlins but I definitely want more forward mids than the JVC's.  Also I was wondering how the coherence is between all the drivers?
  10. Kunlun
    I'm surprised Project86 didn't mention that the Merlin demo has been updated since his audition of them. UM has adjusted the sound to closely match that of the custom fit version.
    Project86 knows this (his feedback was part of the update process)... hmm.
    Well, folks, wait for the reviews coming in from the Merlin demo that's all I have to say.
  11. project86 Contributor

    Thanks for the comments everyone! I'll try to address all the questions that have been asked individually.

    Good question. First, check out the FR chart for the IE8:
    As you can see, the bass boost is rather broad and does somewhat crowd into the mids. This has a sort of "masking" effect where you don't get to fully appreciate the very low frequencies. 
    Notice how the IE8 starts a rather broad spike just below 800Hz or so. By the time you get down to 500Hz they are + 5dB, by 300Hz they are +10dB, and by 100Hz they are roughly +14dB. There is still a lot of musical information in those areas aside from just "bass".
    In contrast, the Merlin is flat at 800Hz. By 500Hz it is roughly +2dB, by 300Hz it is +6dB, and by 100Hz it is +11dB. What this means is that the Merlin has a bigger emphasis on the really low notes. So even though the IE8 has a much bigger boost overall, the Merlin has more perceived impact. 
    Also relevant is the way it peaks at about 60Hz and stays flat all the way down to 20Hz (probably lower but the graph is out of range). The IE8 peaks around 100Hz and by 20Hz is roughly 6dB lower. This also helps explain why the IE8 sounds a little muddy to me, compared to the Merlin sounding more clean.
    That's just bass presentation. Look at the rest of the spectrum and draw your own conclusions....


    I agree, the demo was surprisingly different. I mean, it wasn't terrible in absolute terms, but to me it sounded more like what I'd expect from a $450 custom. 


    I haven't had the pleasure yet. Those JVCs (as well as their big DX1000) have been on my "want to try" list for a while but I never seem to meet anyone who has them. The graphs do look a lot closer to the Merlin than the IE8 does, so that could mean a similar sound. 
    I have not noticed any issues with driver cohesion. I was a bit concerned about the integration of the dynamic driver, but it proved to work just as well as the BA driver(s) used for lows in my other customs. 


    I'm not sure what your angle is here.
    I borrowed the demo from Anaxilus, listened to them for a while, then sent them back to him and described my impressions. I guess that makes me "involved in the process". He did later say that UM swapped it out for another, in case that first demo was defective. I haven't heard the new one so I have no idea how it sounds.
    I don't know where the info came from that it "closely matches that of the custom fit version". I've never heard anyone confirm that. Obviously that would be the goal of any universal demo of a custom IEM but wanting it and achieving it are two separate things. I am scheduled to receive it at some point and I will report back when I do. I do want to hear what other people think about the Merlin, and I do hope that the new demo is an accurate representation of the real sound. As I said in my review, it certainly isn't a sound for everybody. 
    I wish you would just come out and say whatever it is you want to say. No more suspicious sighing or vague, implied accusations.
  12. project86 Contributor


    Sorry, I somehow missed this question. 
    The Merlin bass reaches DEEP. I don't know how well we humans can even hear 20Hz and below - it seems to be mostly felt rather than heard. I suppose something like that would probably even vary based on the size of your ear canals when we are talking about IEMs. But I can say that the Merlin seems to go as low or lower than the IE8, Monster Turbine Copper, and UE11pro, which are the other big bass IEMs I've experienced. And once again, it is not just low but also very clean. 
  13. shamrock134
    I want a Merlin.[​IMG]
  14. shotgunshane Contributor
    Thanks for your replies. Since I've never heard UM customs, I am not familiar with their treble presentation.  Would you say their treble has a sense of "air" or is it more smooth (and laid back like a westone 4) while maintaining clarity and detail?
  15. rawrster
    Excellent review! This sounds like it would be something like an IE8 on steroids? Would that be a fair assessment assuming you have heard the IE8.
    I'm not sure how keen I would be to owning something like this since my preference is more towards the neutral side of things with a hint of warm or something that sounds like the prototype Merlin.
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