Lime Ears Model X Custom Earphone Review – Composure and Complexity

Sound –                             

Tonality –

The Model X utilises a switch system to deliver two distinct signatures. Lime Ears reason that this was necessary in order to satisfy the Fletcher Munson curve that outlines how the human ear hears differently at varying volumes; specifically being less sensitive to low-frequencies at low volumes. In turn, the Model X implements an 8dB bass-boost stretching up to 200Hz before tapering smoothly into a mostly similar sound at and above 1KHz. The result is a high clarity sound that is slightly bright to my ear or a well-balanced sound with a slightly warm, organic midrange and crisp treble.

In its default form, the Model X definitely pursues a brighter and more typical diffuse-field neutral sound. However, it has a few key tuning choices that provide some colour and excitement to its sound. Most notably, the earphone features a gentle upper-midrange emphasis producing slightly forward vocals with excellent clarity. Moreover, a 5KHz lower-treble peak ensures a crisp yet well-bodied presentation of treble instruments and copious foreground detail.


With bass boost enabled, the Model X effectively targets what I would consider to be a free-field neutral sound with light warmth that permeates into the vocal range, more upfront male vocals and increased body throughout. Bass becomes fuller and more prominent within the mix. It’s subjectively a more natural sound at the cost of separation. It also tones down the upper-midrange a touch.

The result is two quite substantially differing tonalities, one clean, clear and aggressive, one warm, balanced and natural. Though there has been some contention regarding the use of switches, Lime Ears do effectively provide two very approachable sound signatures in one IEM and with some impressive technical traits on top.

Bass –

The Model X features a fairly neutral bass presentation with a hint of additional mid-bass warmth to create a sound that remains inviting. A modest sub-bass emphasis reaffirms respectable bass extension while smooth ascending and descending slopes into its mid-bass hump and slightly recessed lower midrange create a rather natural bass note reconstruction. Quality is also what one would expect from a high-end multi-BA earphone.

Control is very high and decay is swift. In culmination with its clean tuning, the Model X delivers superb definition and detail retrieval in addition to very textured notes that avoid becoming overly aggressive or forward. Even with the bass-boost enabled, the Model X is hardly a bassy earphone but it does alternate between being reserved and neutral to being balanced and slightly warm and full.

Mids –

Coming from the dense, smooth beasts I’ve become accustomed to seeing around this price point, the energetic and immaculately extended vocals of the Model X were a breath of fresh air. I do personally prefer a natural, resolving midrange, and though the Model X is not perfectly linear, it is well-tuned within the lower-treble to avoid sibilance and similarly within the bass and lower-midrange so as to permit adequate separation of the bass from midrange notes while still imbuing some warmth and body into the midrange to enable natural vocals.

With the bass switched enabled, vocals satiate with a light warmth while the off position permits a slightly cooler sound, both being clean, clear and extended. At lower volumes with the bass switch on, the Model X impresses with its well-resolved notes and accurate body. The earphones provide a delicate balance between vocals and instruments, and male and female vocals, offering a superbly balanced listen overall. It is, overall, clean and very revealing without sacrificing naturalness with regards to vocal smoothness or exacerbation of sibilance.

Highs –

With dual treble peaks at 5KHz and 8KHz, the Model X combines a crisp, organic foreground with an open yet not excessively bright background. Strangely, when measured, the Model X appears to be a very bright monitor, however, in listening, it offers a very balanced sound and high-frequencies that aren’t piercing in the slightest. In particular, the lack of middle-treble glare is exceptional, the Model X produces crisp yet well-bodied treble instrumentation with ample texture and excellent detail retrieval. As the 6KHz region has been finely tempered, it isn’t sharp or metallic. The middle treble, by all accounts, should not sound as refined as it does.


This ability of the Model X to craft such an open soundscape while maintaining absolute composure during even the busiest of passages is a prime asset. Indeed, extension and resolution are outstanding even at its price point. The Model X elucidates fine background details and again, impresses with its multi-faceted balance, here, with regards to the background and foreground. Upper-treble has a subtle lift as is characteristic of high-end IEMs, producing that slightly sparklier character to its sound and drawing attention to micro-detail. However, this is a subtle enhancement and one that doesn’t overly skew its timbre. The Model X is ultimately a precise, focussed and effortless performer; this is one for the detail lover.

Soundstage –

Excellent treble extension grants a sizeable soundstage, reaching just beyond the head in width while delivering a slightly more intimate depth with upfront vocals. As the background is on the slightly brighter side, the Model X doesn’t have the distinct layers of darker earphones nor the same sense of grand scale with details stretching into the blackness of an attenuated middle treble. Instead, this is an earphone focusing on sharp, precise imaging, with smooth gradation of instruments across its stage and a strong centre image. Its tuning and composure ensure that a hyper-defined background and foreground are not necessary in order to pinpoint small details, they remain abundant and fulfilling. Separation is a strength, even with bass-boost activated, and though the Model X isn’t the grandest earphone, it is natural and thoroughly enveloping. Enabling bass boost creates a stronger centre image and greater depth while turning it off grants slightly greater width with airier vocals.

Driveability –

Lime Ears don’t provide a sensitivity or impedance though from subjective testing and volume matching with an SPL meter, it appears to have a higher impedance and an above average sensitivity. This was reaffirmed by various pairings with higher output impedance sources such as the Hiby R6 where the Model X did not see as large a tonal change as my lower-impedance multi-drivers. The result is an earphone that requires a little more volume than most high-end IEMs but rewards by being more source agnostic with higher hiss resistance. Nonetheless, the resolving Model X benefits greatly from a resolving source with slightly more current such as the DX200, even cheaper sources such as Shanling’s M2X serve the Model X very well. From a high-impedance source, bass roll-off was evident, however, this could be counteracted to some extent with the bass switch. A lower-impedance source with a high current output is advised to maximise the potential of the Model X.

Comparisons –

The comparisons below will be conducted with the bass-boost activated as this produced a more balanced sound to my ear.

Hyla CE-5 ($940): The CE-5 is a substantially more V-shaped earphone. Its greater bass extension is immediately evident as is its more prominent sub and mid-bass emphasis producing a much warmer tone. The CE-5 has thicker notes and a smoother texture, its decay is slower than the Model X and it isn’t quite as defined as a result. Into the midrange, the CE-5 employs a large lower-midrange dip to counteract its lower warmth and produce a more transparent midrange. However, as a result, it can sound inconsistently voiced between tracks. The Model X is more linear, it is more transparent due to its more neutral low-end and its midrange notes are more wholly resolved. The Model X has substantially greater vocal presence though both have excellent clarity. Both employ 5KHz emphasis, the CE-5 comes across as brighter, with treble standing out more by comparison to its more recessed midrange. On the contrary, the Model X’s upper-midrange progressively feeds into its emphasized lower-treble and it more integrated as a result.

Thus, the CE-5 comes across as crisper and more aggressive, it has thinner instrument body but also more attack and clarity, both are very well detailed earphones. With regards to the background, the earphones are once again divided, the CE-5 pursuing a blacker background with more distinct layers, the Model X a brighter but airer one. And up top, both extend terrifically well for their price bracket, the CE-5 has a more prominent sparkle though it also has a somewhat unique voicing due to its adoption of a ceramic super-tweeter. The Model X sounds more natural here, though it also doesn’t have the same energy. Both have excellent micro detail retrieval, the CE-5 being more upfront in its presentation, the Model X being cleaner but also more composed. The CE-5 offers a larger soundstage which is exacerbated by its recessed vocals and darker background that create the impression of greater separation and depth. On the contrary, the Model X provides more coherent and natural imaging, its separation is superior which makes background details easier to pinpoint.

Ie800S ($999): The ie800S has a markedly more V-shaped sound. It has superior bass extension and is warmer through the mid and upper-bass, granting it fuller bass notes. Its decay is not quite as fast, granting it a smoother texture, however, the ie800S has excellent control so it is almost as defined. Nonetheless, the Model X comes across as more linear, devoid of mid-bass hump and slightly more even into the lower-midrange, where the ie800S has a small dip to counteract its bass warmth. As a result, the Model X is more tonally neutral and its bass, though full, isn’t almost as warm. This is especially noticeable within the midrange, the ie800S is thinner yet its vocals are also more recessed. Nonetheless, it is slightly filled in by its bass warmth, however, the Model X ultimately provides a more even response with more wholly resolved notes. The ie800S offers a slightly smoother upper-midrange, however, on behalf of its 4KHz dip where the Model X offers a more extended vocal reconstruction.

The ie800S is also slightly more prone to sibilance due to its 6KHz emphasis, where the Model X’s lower-treble emphasis sits a little lower down, avoiding exacerbation. Chiefly, the ie800S sounds crisper, with more foreground attack while the Model X sounds slightly thicker. The Model X has a more present middle-treble where the ie800S has a slightly darker background. Both are clean and composed in their presentation of background details though the Model X tends to draw them more to the fore. Both also extend terrifically, the Model X having sligthly superior resolving power of micro-detail where the ie800S overshadows some smaller details with its more emphatic foreground crispness. Both earphones offer similarly sized soundstages, the ie800S is more layered and has more perceived depth, where the Model X is more coherent with greater lateral expansion.

Campfire Audio Andromeda ($1099): The Andro is a staple around this price range, offering a slightly warmer, more U-shaped sound. The Andro offers slightly more bass extension, delivering a plumper sub-bass and more robust mid-bass. Conversely, the Model X offers increased linearity, being more even though its bass and delivering a more neutral tone. Both offer excellent speed and control, the Andro being slightly faster and more aggressive, the Model X being smoother. Into the midrange, the Andro has a slight dip with its vocals and a warmth that permeates from its similarly warmer bass. The Model X is more neutrally toned and transparency is higher as a result. It has greater clarity in return for lower vocal body. However, this changes when the bass switch is activated where the Model X sounds almost as full, just without the warmth due to its lesser mid-bass hump. Both have a very extended upper-midrange delivering clear vocals, and both have ample body from their lower-midrange/bass to permit this.

Up top, the Model X employs a reasonable 5KHz and middle treble emphasis where the Andromeda focuses around a 6KHz peak and a sparkly upper-treble. As a result, the Model X sounds more organic where the Andomeda sounds crisper and more aggressive. Both have adequate body, the Andromeda comes across as slightly more detailed within the foreground, however, as it has a fair dip into its middle-treble, background details are not as apparent as on the Model X. The Andro does have more defined layers and its exceptional sparkle draws attention to its similarly strong extension. The Model X does not offer quite the same upper-octave sparkle, however, its extension and the precision with which it delivers details is similarly fine. The Andromeda has a larger stage and its sharper foreground combined with sparklier background make it sound more holographic. In reality, the Model X is more coherent and it has slightly better separation.

Verdict –

Listening to the Model X, I am quite astounded that Lime Ears hasn’t achieved the same market presence as some others – their second in command may not offer a wholly TOTL sound, however, it gets shockingly close at a more reasonable price. Its signature is meticulously balanced and quality is excellent, with special mention going to the sublime cleanliness of its treble and the coherence of its imaging. Moreover, the ability to adjust the sound to listener choice of volume is marvellous for commuters who can enjoy a neutral/bright orientated sound at home and a fuller sound in the presence of ambient noise.


Staples such as Campfire Audio’s Andromeda have achieved notoriety not for being the best, such a notion is deeply subjective, nigh impossible. Rather, these are earphones offer value and versatility, coming in at barely half the cost of flagships while hardly leaving the listener wanting more. Yes, more can be had, but to clarify, the Model X simply provides an impressively well-rounded experience that is difficult to flaw. Listeners searching for an exceptionally well-balanced earphone with excellent treble detail and clear vocals will love the Model X from Lime Ears.

The Model X can be purchased from Lime Ears for €890. I am not affiliated with Lime Ears and receive no earnings from purchases through this link.



Picture of Ryan Soo

Ryan Soo

Avid writer, passionate photographer and sleep-deprived medical student, Ryan has an ongoing desire to bring quality products to the regular reader.


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