Regarding the units assessed in this comparative feature, the UERM was provided to me free of charge by Ultimate Ears as part of their showing me what the Ultimate Ears experience was all about, vis-à-vis my visit (as managing editor of CYMBACAVUM) to Ultimate Ears' lab in Irvine, CA in August of 2013. The Noble Audio 4C is also a review unit, provided by Noble Audio. My belief is that both companies are truly exemplary markers of the custom in-ear monitor industry respective to their individual strengths, and I have no incentive to prefer one brand over the other. Individual reviews (rather than comparative) of each monitor will also be released on CYMBACAVUM in the near future.
Notice on Photography and Media:
"Part of the human condition is that we sense care."
--- Sir Jonathan Ive, Apple Inc.
Care. Attention to detail. Hallmarks of excellence. For those of us looking for a custom in-ear monitor, it is these variables that draw us to any one company. The level of care applied to a product is instinctively perceived by each and every one of us, and it is this instinct to which Jony Ive, Apple's maven of design, speaks in his quote.
Both Ultimate Ears and Noble Audio craft custom in-ear monitors --- with care. The former hangs its hat on a constant reexamination of the user experience and a methodical readjustment of its product parameters. The latter manifests its care most illustriously on the surface, concocting visual masterpieces that only true artists could muster.
But enough fluff. This is more of a utility-based comparison; for the most part, I try to differentiate between the needs of a hobbyist listener and a professional user. This distinction is necessary because of the shifting nature of the custom in-ear monitor. Prior to just a few years ago, the clear majority of clients purchasing custom in-ear monitors was from the professional music industry. As the popularity of IEMs has grown, however, a new generation of CIEM companies has sprung up, servicing primarily personal audio listeners and/or amateur musicians. UE is part of the established school of companies, while Noble Audio represents the cream of the crop of of new companies that have managed to garner the interest of a lot of audio enthusiasts, but have yet to groom a regular stable of performing musicians in the customer base.
Why compare these those models in particular? Currently, they represent the two most neutral-oriented offerings from their respective companies. It's true --- not everyone prefers a neutral sound, but "neutral" is a signature that most corresponds most to reference levels of sound balance and detail. "Neutral" tends not to attract the deepest pockets either, and perhaps that's why neither product is considered a "flagship" model. There are offerings from both companies with (much) higher price tags and far higher driver count; those are the offerings that dominate the collective attention and imagination of the public hype machine, but perhaps, if we remove all the extra emotional trimmings that colored sound signatures bring to the sonic landscape, what we're left with is a bare look at what the music itself offers, and that's what the Ultimate Ears In-Ear Reference Monitors and the Noble Audio 4C help bring to the table.
That is why I'm attracted to neutrally-tuned earpieces, and what my particular senses are accustomed to --- they help me identify individual elements of music and understand the direction of both the artist and the production. It is also for these very reasons that I encourage any and all head-fi hobbyists to have at least one very neutral-sounding monitor in their collection, regardless of individual preferences. The old adage, "We all hear differently" still applies, but only up to a certain point. No person will experience an absolutely flat sound with a neutral monitor, but a neutral monitor gets them pretty darn close to resolving everything under the sun. Attention to detail is the name of the game here, and when both the sound and the service are on the same page, the results are spectacular.
Build Quality and Aesthetics (Noble > UE)
Perhaps the place to start with when examining these two monitors is in their build quality.
Functionally, there really isn't a workable difference in build quality, but aesthetically, the two monitors run on very different tracks. Perhaps it's that I gave no indication of what I wanted aesthetically in the UERM; in fact, I only knew I was receiving a unit about a week prior to receiving it. Thus, the UERM was finished with its default look: a black faceplate, clear shell body design. I've got to say, it's an extremely utilitarian look. The shells aren't the most transparent looking, and there are functional scratches (they don't look accidental, as they're deep and deliberate looking) on the surface of the shell that allow for extra friction fitting inside the ear (my right ear canals have a tendency to allow custom in-ear monitors to slide in and out, and the extra scratches really help secure the UERM in my ears).
While simple in appearance, there's an understated sense of handsome, hardhat appeal to the UERM.
Thus, it's a good thing there's no such thing as a beauty pageant for CIEMs, as I'd have trouble imagining the UERM to win much of anything, even Miss Congeniality. Luckily, Ultimate Ears does give customers the choice to customize faceplate colors (per the new SLA production process, all shell bodies are clear by default) and actually have special Designer Editions available from up-and-coming artists.
Leon Nguyen Designer Edition UERM (NOT my picture; sourced from an external source, via a former head-fier.)
On the flipside, there's a keen sense of artisan craftsmanship to the Noble Audio 4C that really doesn't exist with the UERM --- or any other custom in-ear monitor I've come across, for that matter.
The painstakingly-layered polymerization of the textured shell, the fineness of the lacquer finish, and all-around specularity of the colors all point to a savant-like obsession with aesthetic finish. My first custom in-ear monitor was a 4.A, and two years ago Dr. Moulton also put his finishing touches on it. I thought it was stunning. This time, I once again made the simple statement, "I like the color blue", but the results were even more astonishing with the 4C.
The photography really doesn't do it proper justice --- it's very difficult to show off the kind of depth presentation the 4C possesses, but just about everything about the Noble 4C is a step up over my old 4.A.
Tiny details, like the ends of the bores, kept clear for just the last three millimeters to allow for better visual inspection of tube cleanliness, point to the obsessive mentality with which this pair of CIEMs was made. It's not just the finishing; even the two-pin sockets are tighter and keep the cables tightly interfaced with the monitors themselves. To top things off, the sumi-e style inlays look effusively elegant against a cerulean (yes, that's the word --- not merely blue) finish.
The Heir Audio 4.A (left) circa 2012, and Noble Audio 4C (right), are both finished in beautiful blue, but the craftsmanship is even better two years later.
This is one area where Logitech's extensive experience in consumer electronics has helped Ultimate Ears succeed, and succeed in spectacular fashion it has. From the redesign of its cables to the design of its carrying cases, UE has managed to trailblaze and rethink how the whole battery of accessories enhances and defines a product in portable audio, whether it is for the professional or consumer sector. The success of UE's alterations has directly led to a change in the supply chain of cables and cases for the rest of the custom in-ear industry, as well as copycat designs that have gone on to achieve a measure of success on their own.
Few companies in the CIEM space have paid as much attention to the unboxing experience as has UE. The first thing you see in its manual is a big 'Thank you.'
Storage/Carrying Case (UE >> Noble)
The Noble version of a carrying case is an Otterbox-like solution. It's crushproof, waterproof, and all that jazz. However, to be honest, while it does appear quite sturdy, it really isn't the most handsome case in the world, and thus there seems to be a bit of an aesthetic disconnect between the case and its beautiful contents.
Historically, the Otterbox/Pelican case axis in the CIEM industry came about because of custom in-ear monitors' professional roots. Musicians and their handlers need devices that can withstand the rigors of being trucked around in 18-wheelers, thrown (literally) into the luggage compartments of tour buses, shoved into luggage bins of cargo planes, and more. Professionals do have a necessity for ruggedized protection.
The consumer, however, does not, and while an indestructible case may give the first-time customer peace of mind, it's ultimately unfit for the typical road warrior whose accoutrements entail mostly nylon backpacks and messenger bags. Thus, for normal transport inside a backpack or briefcase, the Otterbox really is a little too large and heavy to be practical. I personally use another case for normal transport purposes; the protective hard case sits idly inside the crate it was first shipped in. There's also not enough padding, in my opinion. The monitors are prone to shifting around with only a thin few layers of (albeit high-density) foam.
I can only imagine that Noble Audio, with its penchant for impeccable aesthetic presentation, is currently looking for a better-looking and more utilitarian solution. It's possible they just haven't found the right case yet.
The issue is finding a case that has both the aesthetic panache of a Noble Audio product and utilitarian safeguards. Noble could do a custom solution, to the beat of a significant sunken investment, or it could look to a ready-made solution but risk being labeled a "follower". In a convergent industry where JH Audio has switched its cases from Otterbox to a circular screw-top aluminum tin, Unique Melody and Rooth have also done the same. Rumor has it that UE is also considering a similar solution, though I can't imagine why they would, as their current compact case is absolutely excellent. Westone has its own plastic Monitor Vault, and still others have their own solutions, but really, nothing stands out as truly compelling.
Nevertheless, I hold out hope that Noble will continue to march to the beat of its own drum and implement a unique solution. The current one is simply too clunky to be practical, especially when the majority of Noble's customers are from the consumer sector, rather than the pro audio world.
For all of the Noble 4C's beauty, the ho-hum case contrasts starkly. Frankly, it feels a bit prosaic.
On the other hand, UE does have its own custom solution --- a product of iterative improvement over the years. If you're familiar with the near-ubiquitous (and now discontinued) Triple.Fi 10, then you'll know that it came with a nifty metal carry case. The current compact case is an evolution of that very case, going from that design to one that has a stiffer design that doesn't flex with pressure and one that possesses scratch-resistant anodize in order to allow for a rough and tumble lifestyle.
To me, this type of carry case outstrips the usefulness of the plastic Monitor Vault by Westone, as it's made out of a more confidence inspiring material (metal vs. plastic), and is larger (but not too large), thereby more versatile. Westone's Monitor Vault has the added benefit of being waterproof, but seriously, how many of you are taking your custom in-ear monitors to a pool or into the great outdoors?
Currently, it is UE's storage solutions that, in my mind, come closest to "perfection" in the industry. They are convenient to use and allow for integrated storage of all important accessories. The only detracting aspect I can think of for the UE case is that it doesn't accommodate dessicant pods. While it's arguable that dessicants are not too important for or effective in maintaining your monitors' shelf life (consistent cleaning of your monitors is), it'd be nice to have the option, especially for individuals that reside in very humid, tropical and sub-tropical climate zones. Current hot markets for CIEMs, such as Singapore, Malaysia, Indonesia, Taiwan, and China all fall into climes that are often (or always) very humid. The UE case is also (as mentioned already) not quite waterproof, unlike many a Pelican Case, Otter Box, etc.
The UE small carrying case has been optimized for size and durability. The matte finish does not scrape easily.
The cleaning loop neatly tucks into a specially-designed crevice within the small case, allowing the user to have the cleaning loop around at any moment. Everything else just sits in the semi-hard rubber tub, which isn't perfect for shock protection, but is at least convenient. Apparently, UE found that many performing musicians just didn't have the time to be coiling their cables according to intricate cable guides and then laboriously putting their earpieces into perfectly-cut negative molds.
My version of the UERM didn't come with the larger engraved carrying case, as I told the folks at UE that I probably would not be using it anyway, but that one does provide a snugger fit and more shock protection than the small one, having gone through multiple iterative revisions itself. However, the same detraction holds for the larger case --- there's no dedicated area for a dessicant pod, but does seem a little more water resistant (though I'm not sure whether it really is or not). Again, it's also the little touches that matter --- the RewardTag embedded into every single case gives customers peace of mind, even when they might not ever need to use it.
The recess for the cleaning loop and RewardTag show off UE's attention to detail.
Cable (UE >= Noble)
In 2011, Ultimate Ears was the very first company to come out with a two-pin connector that integrated an overmolded right-angle bend to its monitor cables in an effort to decrease external strain to wires that would otherwise have risked cable breakage. While the majority of CIEM cables are still fitted with the straight angle connectors (like those on the 4C), this paradigm shift has spawned a slew of copycat aftermarket connectors (here), as well as a nearly identical offering from Unique Melody. ALO Audio (here) and Firestone Audio (here) have subsequently come out with similar overmolded connectors as well. Perhaps UE should take it as a compliment to be so closely imitated.
Cables for both the UERM and the Noble 4C utilize the "twisted-twisted pair" four-core braid. This type of braid has begun to replace the old "triple twist" design found on most CIEMs for the past decade (as popularized by the Westone EPIC cable found in most of Westone's universal products as well) as it allows for the limiting of interchannel crosstalk as well as allowing for fully balanced configurations, all without losing flexibility.
Contrast this with most aftermarket specialty cables made with the Miliot "litz" braid --- the Litz braid enables intrinsic cancellation of EM radiation, but significantly gives up flexibility and wasted space to the "twisted-twisted" pair braid. The "triple twist" cable configuration, of course, has the disadvantage of an extra solder joint at the Y-split, as well as the risk of increased interchannel crosstalk.
The most interesting tidbit was that, during my interview with Philippe Depallens of UE, he mentioned that they spent much time changing the various textures of the insulation to make sure the cable was not only comfortable against the skin, but also sufficiently sweat proof. "We even imported buckets of sweat and have one [unfortunate] guy dedicated to testing it out on our cables," he said. As incredible as it sounds, I believe him.
This is the cable that has inspired similar designs from other companies.
Interestingly, the Noble cable is slightly thicker than the UE cable, but is actually softer and more flexible. However, I have a feeling that if I'd received the Noble 4C at the same time as the UERM, the cables would be of similar stiffness, as these cables tend to harden over time, and the added flexibility would ultimately amount to be negligible.
As for the Noble cable's improvements, it is definitely a step up over the what has been offered by CIEM companies in the past, though not perfect. The Noble cable now sports large L/R indicators on the overmold and overall it definitely feels more solid, from the braiding to the 45 degree 3.5 mm plug.
Neither the UE cable nor the Noble cable possesses an extra raised portion to its 3.5 mm plug (for increased compatibility with large, bumper-style smartphone cases), so that's a strike to both. It'll be great to see that feature added in the near future, as most consumers are using smartphones as their main portable sources.
I've also heard that both companies are tinkering with special balanced versions of their cables as well, adding support for 2.5 mm TRRS plugs (compatible with Astell&Kern DAPs). If Sony's new proposed 4.4 mm TRRRS unbalanced/balanced portable standard gains any traction, it'd be great to see them follow up with plug support for the new standard just the same.
Both cables also contain relatively stiff strain reliefs. However, I can't imagine cable failures being an issue for either company; for individuals in the US, UE replacement cables are an affordable $40 (compared to >$50 for most other companies). And as for Noble, when I received the 4C, while I noticed that the the left side cable's pins were of unequal length (one pin was especially short), Noble rushed a replacement cable out to me immediately. For matters like these, service from Noble is without reproach.
Of course, cable failures are really a pressing issue only if you're a professional on stage; while both cables are rated for very high pull strengths, the risk of failure still exists, and thus, I'd advise professionals always to have at least one spare cable on hand, regardless of the company or the cable.
Fit/Comfort (UE >= Noble)
The UERM, to date, are the best-fitting monitors I've ever worn, whether they be fabricated in acrylic, silicone, or acrylic w/thermally-active soft tips. I suspect this perfect fitment has something to do with the fact that I got my impressions done with UE's in-house audiologist, who uses an A/B impression material that the lab is used to, as well as a well-practiced pair of hands.
The impressions are then 3D-scanned (using something like a 3Shape H600 scanner), and these days the shells are 3D-printed via one of UE's large industrial stereolithography printers (http://www.head-fi.org/t/734630/ultimate-ears-new-way-of-making-custom-in-ear-monitors-head-fi-tv).
The idea is that UE is now intending on 3D printing all their shells from now on in order to increase fit rates and to minimize repair difficulties. On a case-by-case basis, they will be accommodating special requests for colored shells, likely fabricated with the traditional handmade UV curing process.
The idea for a streamlined digital fabrication process is not new; Ultimate Ears isn't even the first company to formally announce a 3D printing workflow. However, UE has been tweaking that very workflow for many years --- in fact, they've had an in-house 3D scanner since before the Logitech acquisition, have had their SLA printers for several years, and have been testing 3D scanning/processing techniques for that duration. Thus, my money's on UE to get this system right from the get-go.
What's most neat is that their fabrication process also enables them to have the fastest production turnaround (non-rush ordered) in the industry by far, which is a notable feat, considering they were the record holders to begin with. Turnaround times have now shrunken from just over two weeks to just over one week.
Whereas UE is turning to SLA printing, the Noble 4C is still made by hand, and that's no detraction at all. Old school methods still work very well --- the fit is really great, though the glossy smooth surface has a tendency to allow the right ear to be a little more slippery and slide in and out of my canals. In normal use, however, the 4C is as comfortable as can be, without any discomfort at all. There's no real drama to the fit, and perhaps that's why I've merely spent just a couple of lines describing it.
The real key to getting a good fit, though, isn't really about the company, but more about the ear impression process. Good, open mouth (a bite block is recommended) ear impressions taken beyond the 2nd canal bend and covering all the major external landmarks of the pinna up to the scapha, with a high quality A/B silicone curing material, will go a long way in securing a good fit.
Of course, audiologist skill and experience play into the process as well, as injection speed and completeness will impact both curing times and physical material voids. Your own physical state also plays a large role in the process, and if you're tense, you can alter the shape of your ear canals (your body has muscles in the neck that attach from the ear canals to the pharyngeal wall), and inadvertently take poor fitting impressions. Thus, it's best to be relaxed for the entire impression taking process.
Cleaning & Maintenance
When it comes to cleaning, the key is regular maintenance.
After every usage, shells should be wiped down and sound tubes should be scraped for ear wax, or else any CIEM will get very dirty, very quickly and eventually the filth will have a profoundly negative impact on the sound quality --- if you suddenly get a sound imbalance between ears, or if your monitors seem to be getting "darker" by the day, you should definitely check to see whether you have ear wax lodged inside one or more of the acoustic sound tubes.
Neither monitor is easier to clean than the other. The wider horn bores of the UERM makes it quite easy for pieces of ear wax to drop in, but the debris is simultaneously easier to remove. The regular straight bores of 4C don't allow as much ear wax to enter, but should ear wax enter (it does happen from time to time), it is a bit more difficult to clean.
Should any ear wax enter into the sound tubes of any CIEM and prove difficult to remove, however, I'd advise people to send it back to the lab (or to a third party shell lab) for cleaning. It's not worth accidentally poking open a sound damper and risk voiding the warranty.
While the majority of the shell is mildly opaque, Noble has left a few millimeters of clear space at the exit of the bores to allow for better visual inspection of ear wax and other foreign materials inside the tubes.
The UERM is described by Ultimate Ears to be "perceptually flat", and is Capitol Studios staff-approved as such. It comes quite close to these claims, but the reality is that it's very difficult to get to true perceptual flatness --- there's too much debate as to what that really means, and no amount of reading of the works of Floyd Toole, Hammershøi, Moller (or more recently, Sean Olive and Todd Welti, or just << Insert AES member here >> et. al.) will get you to that description.
However, what the UERM is, is a tool verified and endorsed by very experienced music professionals for use specifically in the studio environment. It isn't merely a claim, as its frequency response possesses many of the hallmarks of an "accurate" monitor, with an applied loudness weighted curve that imparts an ever so slight U-shaped response. For the majority of music listeners, the result should be immense clarity and spaciousness.
The Noble Audio 4C is more of a mellow animal. It has a bit more lower midrange lift (up to the level of its bass shelf), and that particular lift makes the midrange closer, more intimate, and a bit warmer overall. It's also less brightly tilted up top, preferring a more gentle treble response to the take no prisoners approach of the UERM.
Because of the lower midrange lift, however, and because of its treble drivers' particular inherent qualities, the Noble 4C maintains a clarity that cannot be found even in its higher-end brethren, the 8C and Kaiser 10 (at least from brief demo unit listening impressions).
Bass impact is about the same as that of the UERM, with just that tiny bit more midbass impact, and I suspect that the lifted lower midrange shelf has a lot to do with this particular interpretation of sound. When it comes to bass impact, however, both monitors are just about spot on in terms of a reasonable means of accuracy.
To me, that means that you tend to put equal effort into listening to every single section of the spectrum of sound; no one part of the sound "guides" your experience.
Sense of Space (UE > Noble)
Absolute width of the stereo image goes to the UERM, as it sounds as wide open as any IEM that has ever existed. To that effect, the center image of the UERM feels less forward and actually somewhat laid-back, especially if you're used to the in-your-face, in-your-head kind of presentation. It simulates the feeling of being right in front of a pair of precise studio monitors really well.
The 4C is, relative to the UERM, more intimate sounding. The center image is a bit narrower but simultaneously taller and deeper. It's a fitting type of presentation, though, as it really is the more vocal-oriented model of the two, and although its spatial presentation doesn't feel quite as open as that of the UERM, at no point would you ever feel "constricted" by the 4C. I couldn't say the same thing for my 4.A of yesteryear. There were times when the 4.A felt too forward and small, but not so with the 4C --- it merely isn't as open-sounding as the UERM.
It's possible that Noble Audio was reserving the "wide-open" sound for the 8C and K10, as both (especially the Kaiser) sound quite a bit more separated and grand feeling than the 4C.
Neither monitor should be considered "phase-flat", like the JH Audio FreqPhase products, CustomArt Harmony 8/PRO, or even the Nuforce Primo 8. While it's debatable how sensitive humans are to phase distortions in the 3D space when it comes to headphones, I have reason to believe that phase does indeed play a significant role in both the formation of a large center image and the trailing edges of the absolute expanses of the full image (soundstage) --- my thoughts are merely insubstantiable due to lack of measurable correlation.
As headphones and earphones really don't construct a stereo image in the same way a pair of speakers does (there's no diffractive superposition and destruction of waves), our ears can be deluded into strange projections of what the real "soundstage" should be. As mentioned, the 4C possesses a center image taller than it is wide, and deeper than the UERM's, which is shallower and wider than it is tall. "Phase flat" earphones, on the other hand, have a tendency to sound perfectly "round" in the center image.
While absolute size of soundstage, in my opinion, is governed more by frequency extension, phase distortion does seem to play a role in the relative positioning of individual elements in the sound space, and if phase angle in the treble is higher than it is relative to the midrange, it does seem to directly increase the perceived size and separation of instruments.
The UERM sounds as close to a pair of good studio monitors as it gets.
Sound for 'Personal' Use (UE = Noble)
In some ways, when I'm not in my typical "detail monger" mode, I enjoy listening to the 4C just a tad bit more than the UERM. It's just a little smoother, with a bit more delicate and less highly-strung treble timbre. To rehash, the particular coloration of the 4C errs to the "downsloping" side of neutral, while the UERM seems to be on the A-weighted, "Fletcher-Munson U-shaped" side of neutral.
As mentioned, the 4C is also lifted in the lower midrange, and the amount of detail that comes from a heightened presentation of vocal formants and instrumental fundamentals is quite a delight. It plays really well with the area of "intimate, but not too much so", and I really enjoy that kind of presentation.
The less treble-tilted presentation also helps with modern music that makes liberal use of the limiting EQ compressor. Keep in mind that you should still be prepared for numerous facepalm moments if your playlist is composed of Top 40 hits, however. You'll be absolutely perplexed why half of Sia's "Chandelier" is all distortion effects (while the distortion is easily detectable even with laptop speakers, it comes off more as pleasant fuzziness than annoying distortion), and itching to apply a declipper and low-pass filter onto Iggy Azalea's "Black Widow".
At the same time, if you listen to really well-recorded and impeccably-mastered music, you'll see both monitors shine and truly come alive. There's a sense of transformative gestalt to the delivery of all this auditory information --- it won't be merely sounds you're hearing, but music you're listening to.
Sound for 'Professional' Use (UE > Noble)
The UERM manages to go the extra mile in bringing out every bit of midrange and high detail, and is amongst the most revealing monitors available, even compared to flagship-level products. Mixing and mastering engineers will find the UERM as revealing as there possibly is; in fact, the sound signature of the UERM was inspired by the Yamaha NS10 --- the de facto studio reference of any production facility for the past few decades. Perhaps that's why the UERM sport the familiar black and white colorway, as an indirect reference to its sonic lineage. Just like the white-coned NS10, however, the UERM won't pull any punches when it comes to sound, and if your track isn't constructed properly, the warts will show in full detail.
Mastering engineers needn't worry about putting tissue paper over the drivers, though, as aside from a newfangled brightness centered approximately around 9.5 and 12.5 kHz (will vary depending on the individual's particular canal dimensions), the UERM is mostly smooth in frequency response. To me, the brightness translates to a psychoacoustic effect that the entire treble shelf above 10 kHz is lifted, giving life to the airiness of a track. The UERM, luckily, is not bright at all around 7-8.5 kHz, a region I find troublesome for most listeners.
I've found that the optimal sound for the UERM is achieved with a good, tight fit. A loose fit will impart undue, brittle brightness to the UERM, making sound thin and unsubstantial. While the sound will be big and wide, it will feel mostly hollow, as the bass lacks in body and the midrange doesn't feel properly settled. However, with the fit correctly done, all hollowness to the sound disappears and you're left with an incredibly finely-honed listening instrument that presents everything in a precise manner. While to me, the Etymotic ER4S (and B) still possesses the most superior vocal band accuracy of any in-ear around, it does have its shortcomings in bass extension and a love-or-hate fit, and the UERM manages to build on top of those shortcomings.
One of the most remarkable aspects of the UERM is also its consistency of timbre. All balanced armature transducers inject their own timbral characteristics into music; that's why the Knowles TWFK series tends to get a bad rap being "tinny" sounding. Consistency, to me, is the key with balanced armature based IEMs. When the midrange and tweeters sound characteristically different from the bass in terms of speed and texture, the human brain can easily detect the inconsistency, and to me that's a major contributor to what many head-fiers regard as "incoherence" in BA-based IEMs. Thankfully, the manner with which the CI driver in the UERM has been damped makes it sound remarkably similar to the two 2300 (or ED) series midrange and treble transducers.
The UERM was originally designed exclusively for professional use; head-fiers have expropriated it for personal listening. Conversely, the Noble 4C was designed with the personal listener in mind. Does this mean that the 4C shouldn't be used in a professional setting? No. It's perfectly fine as a professional monitor. It's just that the UERM will deliver that little bit of extra ruthless lack of forgiveness crucial for professional mixing and mastering applications.
What role can the 4C play in a professional's workflow, then? It too, is very revealing, but whilst the UERM can be thought of as a "full spectrum" monitor, the 4C is definitely a bit more vocal focused. Thus, if you can afford both, get both. Use the UERM to do the mixing and mastering, and then use the 4C to make sure it all comes out in a way more people are used to.
However, specifically if you're a singer-songwriter and producer all rolled into one, the Noble is the more versatile of the two. It can find use on the stage but also off it. With the UERM, while it is the more finely tuned studio monitor, I don't think many artists would use it on stage (UE has many other options for that purpose).
Listener Fatigue and Reasonable Listening Levels (Noble > UE)
Neutral, analytical headphones and earphones get a bit of a bad rap for being "fatiguing".
While "fatigue" itself is a bit of a vague word, it generally points to a number of things: upper midrange (3-5 kHz) presence and peakiness, treble (6-9 kHz) peakiness, and excessive >10 kHz presence. Consequently, ear fatigue conflates with incidence of noise-induced sensorineural hearing loss (NIHL) at specific frequencies. The most common manifestations of NIHL are a notch at 3 kHz, 4 kHz, 6 kHz, and 8 kHz loci (or at more than one frequency locus). For professionally-oriented stage monitors, it is thereby common practice to "step off the accelerator" in the treble region.
Of the two, the Noble 4C is definitely more easy to listen to, for longer periods of time. While I'd hesitate to call it "relaxed", it is decidedly less bright in the 10 kHz region and is overall tilted downward after the standard 2-3 kHz peak. There is some transient brightness around 7 kHz, but considering the 4C uses the TWFK for treble transduction, that peak is remarkably well-controlled --- better than it was with the 4.A and better than almost all TWFK-based IEMs that I've heard, both universal and custom. I really couldn't call it "sibilant" in any appreciable way.
At the same time, while it is decidedly brighter than the 4C, I don't really find the UERM "fatiguing" either. The mild U-shaped sound signature actually tells you one important thing about how you should be listening to the UERM ---- NOT loudly.
Most mastering engineers usually drive their studio monitors to a maximum dB(A) exposure level of about 70 dB, according to a few engineers that I've spoken to, including Kent Poon of Hong Kong's Design with Sound. Maximum exposure levels over an 8-hour workday point to a maximum of 85 dB(A), according to both OSHA and NIOSH. What the slight U-shaped response does is enhance the sense of sound to hear the "loudness" and detail levels of something driven to 85 dB, while having an exposure value of less than that. That means that as long as you're not pushing the levels on the UERM to loud volumes, it shouldn't sound fatiguing at all, and I trust that Capitol Studios engineers wouldn't have signed off on the UERM's sound signature if they couldn't use the UERM for a full workday.
If you're having trouble determining how loud exactly is "85 dB", install a free sound dosimeter app on your smartphone (there are many, free and paid, in both the Google Play Store and Apple App Store; no guarantees about Windows Phone, but I trust there's at least one, and definitely no guarantees with regard to Tizen or Firefox OS... hah). While they're not perfectly accurate, they can at least give you an approximate gauge of the loudness of your environment.
Even though CIEMs are challenging loads for a source, they're extremely sensitive. Make sure you don't play too loudly.
Source/Amplification Matching & Resistance to Changes in Frequency Response Due to Varying Damping Factor (Noble > UE)
It's fairly common knowledge to most head-fiers that have encountered balanced armature-based IEMs that BA drivers exhibit an exponential curve in its electrical impedance response with respect to frequency. When multiple BA drivers are linked together in a crossover network, that impedance curve becomes even more complex. There may be instances where the electrical impedance rises to over 100 ohms, while dipping down to ~5 ohms in other regions. The addition of even more crossover points makes these variances increasingly unpredictable.
Never mind phase variances (to which human sensitivity is debatable), this widely ranging impedance characteristic is precisely what makes balanced armature-based IEMs a challenging load for a lot of amplifiers. Not only does the output impedance need to be suitably low, current delivery and speed need to be appropriately adaptable, or else the IEM will exhibit clearly discernable variances in frequency response, in addition to heightened intermodulation distortion, not to mention increased overall harmonic distortion.
Is it as simplistic as increasing overall resistance to solve impedance matching woes, though? Not quite. A linear increase in resistance also increases top end impedance, creating a strange interaction between the amplifier and the earphones, and that's why Jerry Harvey opted to go with very low impedance tweeters (part of the Knowles SWFK family) for his Roxanne, in order to obtain a fully-driveable load across the entire listening spectrum. That's why it's fairly important for the crossover design not to introduce undue distortion and for the source not only to provide sufficient voltage, but also current.
In terms of ease of use, the Noble 4C is actually the easier of the two to match for an amplifier. Absolute minimum impedance is about 16 ohms in the bass region, with a local maximum of about 40 ohms around 2 kHz. Further up, a local minimum lies around 7.5 kHz, at around 18 ohms. Thus, between 20 to 22,000 Hz, the Noble 4C's impedance curve lies within a range of 16 to 50 ohms.
As for the UERM, it drops to ~10 ohms in the 10 kHz region, but has a local maximum of over 80 ohms around 500 Hz.
This all means that while the 4C is easier on the demands of the amplifier itself, it's possible that the UERM scales better with a better source (that can deliver ample voltage and current at all load demands). For its midrange driver and tweeter, the UERM is driven "half-coil", meaning that it uses the center tap on its two 2300-sized mid and high drivers, and that it does have a certain value of magnetic bias to it, making it a bit less stable than if it were driven in a "zero-bias" configuration. Why use the center tap? Because it enables the drivers to get that top-end treble extension --- but it definitely has the potential to get uncontrolled with a poor source.
The conclusion is two-pronged: the Noble Audio 4C is an easier load and a better match for a larger variety of sources, but the UERM possesses better input headroom, and given a high quality source that pumps out sufficient current and voltage, it will perhaps outperform the 4C, especially with regard to bass and treble extension and texture.
The 4C really highlights why so many CIEM designers like to double/triple up on the dual FK/WBFK family of Knowles transducers --- it allows them to wire them in parallel, allowing more input headroom (less voltage to each driver, lower output drive distortion) and halved impedance. It's really the most straightforward way to get more treble extension without having to get too picky about quarter-wave resonances inside acoustic tubing and matching acoustic impedance between two environments (e.g. tube to ear canal). The 4C only uses one WBFK (half of the TWFK) for treble, and thus the 8C and K10 will inevitably bring better performance whilst using the same family of drivers, but considering everything, the 4C does a nice job conveying its intended signature. I really couldn't complain at all.
Intangibles and Concluding Remarks
By now, whether it's with the build, the set of accessories, or the sound, it's clear that each product has its own strengths and weaknesses.
The little touches, such as the RewardTag embedded into the carrying case, the big "Thank You" stamped right in front when opening the case for the first time, or the extra inclusion of the impedance adapter (while it is not a sophisticated Boucherot Cell and is merely a voltage-dividing Wheatstone bridge, it does its job relatively well under most circumstances) make UE stand out in the crowd.
On the other hand, Noble's obsessive craftsmanship and fittingly suitable, sumptuous sound signature really show off what a small company can do to define itself in a space that is getting increasingly crowded. In just a short period of time, Noble has managed to launch itself to the forefront of the custom IEM conversation on head-fi and has caught the admiring eyes of many an audiophile. They've been able to do that without the substantial financial backing of a Logitech and that kind of bottom-up effort has to be applauded just as much.
The fact is, both approaches really work. The two companies are very different in structure and ideology, but they both manage to innovate this sub-sector of portable audio. The Noble Audio 4C is a prime example of artisan craftsmanship --- its meticulous, painstakingly built exterior is an indication of the company's care and intensity. The UE Reference Monitors are the product of careful management for the most pain-free experience and consistent available in the industry today --- everything from the 3D scanning/printing, industrial build quality, and 24/7 customer service have professional musicians relying on them for the better part of over a decade.
The UERM is an ideal professional tool, but it's also a remarkably enjoyable listen if openness and detail are what you value (like me). The Noble 4C is a bit more laid-back, a little more intimate sounding, and at times more delicate feeling. It's probably not the very first choice for a professional seeking the same feel of a pair of studio monitor speakers, but it does sound very good and full of detail just as well. It'd be my second line verification to see if things sound right, and for long-term listening, I'd harbor to say that it's even more suitable.
My experience with both monitors has solidified my belief in the approaches of both companies.
I'd like to thank representatives from both UE and Noble for their incredible patience and their trust in my delivering an informative and thoughtful analysis of their products. My life away from audio affords me little time for this kind of stuff, so I consider myself fortunate to have their trust. Specifically, I'd like to thank Mike Dias and Philippe Depallens at UE for their graciousness and accommodation, as well as Miss Gilbert at Finn Partners for her great assistance in facilitation. On the Noble Audio side, my deep gratitude goes out to both Brannan Mason and of course, Dr. John "Wizard" Moulton, with whom I've had many hours of fruitful discussion, both personal and professional.