Fit and Comfort

Seen above is the right channel of the Lime Ears TERRA placed into an artificial ear mold with the included size M Spinfit W1 silicone ear tip installed. I have average-sized ears, and the ear mold above represents my own experiences well enough as a proxy. Size M silicone tips are my go-to for testing, since foam tips are not included by some brands, and I found these tips to work plenty fine in terms of achieving a consistent seal as well as measuring how I hear the IEMs too. If you find passive isolation to break with a deeper fit, then I recommend looking at aftermarket options that work better for you. The shells themselves are relatively small, and certainly quite light, to where I had no problems fitting them in my ears and using them for longer periods of time without any problem. The gentle curves in the shells provide multiple points of contact in the ears, and the semi-ergonomic shape with the nozzle design should also work well for most people reading this review. It's the 6.25 mm wide nozzle that might pose a challenge for some, and there's also the possibility of the pre-formed ear hooks in the cable not working well for you. For the latter, you can use a hair dryer to gently re-shape the ear hooks to better fit around and over your ears. You can also replace the cable with one that you find is more supple and memory-prone, if you so desire, which might also have an actually functional chin slider too—I can't get over a cable manufacturer greenlighting this aspect of an IEM cable! The shells have no vent from what I can see, so there may be built-up pressure in the ear canals over time. I was fine for 2+ hours, so take that for what you will.

Audio Performance

Audio Hardware

The TERRA is a hybrid driver set of IEMs in that it uses two different driver types. Lime Ears may be shy on sharing the rated impedance and sensitivity of these IEMs—thankfully not a big deal since these are quite easy to drive—but is quite willing to talk about the drivers used here. The sub-bass is handled by a 7 mm dynamic driver using a titanium diaphragm, which is heavier than typical polymer/paper-based diaphragms and is a non-issue weight-wise thanks to the lighter shells used, even assuming the driver size and material amount was large enough to be a big concern here. Two Knowles DTEC series balanced armature drivers are responsible for low-mid range, with another two Knowles DWFK series BA drivers catering to the mid-high frequencies. A newish (2023) Knowles RAU super tweeter BA driver, which Lime Ears says has been customized by it for use in the TERRA, is placed by the tip of the nozzle itself and handles the ultra-high frequencies. This makes for a 6-driver, 4-way crossover design that you can use with a decent portable DAC/amp and not worry about being held back in any way.

Frequency Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature with a slightly elevated bass, smooth treble range, detailed mids, and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear that IEMs can feed into enough for decent isolation. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through a capable and transparent DAC/amp—I used the Questyle M15 here. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the appropriate ear mold fitted to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry instead of just the audio coupler. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the Lime Ears TERRA. The left channel was separately tested from the right one, and colored differently for contrast. I did my best to ensure an identical fit for both inside the IEC711 orifice, so note how the two channels are within 1-2 dB throughout the frequency range, differing past the resonance peak matched at 8 kHz where the coupler is not the most reliable anyway. The sub-bass exhibits a tiny difference too, albeit I'd be lying if I said I noticed this before I even measured the set, and even then I struggled to pick up any imbalance thereafter. I've seen better channel matching from other products of course, yet there was nothing here to merit a complaint beyond simply pointing it out. Measurements taken after 75 hours of testing, which included these playing a mix of various songs as well as white or pink noise and sine sweeps, showed no difference. There was no perceived burn-in effect thus, and none was measurable, either. The response with the anthropomorphic pinna in place matched the ideal scenario in the coupler exceptionally well, and this is more an indicator of how well the IEMs can fit in a human-shaped ear, or at least one that doesn't complain about discomfort.




Here is the average frequency response for both channels of the Lime Ears TERRA plotted against my personal target taken from VSG.squig.link, which also gives you an idea of my personal preferences to better correlate any possible biases. The tuning of a set of headphones or earphones does not have to match my target as long as it is tuned with some direction, makes sense, and is executed well. After all, no one set will appeal to everyone, and having different options is what makes this hobby so interesting and hard to quantify. This is in addition to a second graph comparing it to the Harman 2019 in-ear target as well as a third graph using a newer target that's based on a more scientific methodology involving a -10 dB tilt (-1 dB/octave) applied to the diffuse field target for the newer, more reliable B&K 5128 but then compensated for my exact 711 coupler instead. Do scroll down to the targets in my database linked above and see the new 5128 section to the left where you can click on the yellow question mark for a brief primer. The bottom line is this target is closer to what many people are likely to prefer out of IEMs and headphones alike. I have chosen to plot this graph with the frequency response normalized/compensated to the target to make it easier to see how the TERRA is tuned—U-shaped, plenty of bass, some treble excitement, and good extension on both ends.

The reason I have a graph above compared the frequency response to the Harman target is because Lime Ears had initially marketed the TERRA as being an "invigorating, enhanced take on the beloved Harman curve," although it has since been replaced to say Lime Ears target curve instead—not that we get to know what said target curve is anyway, but calling the Harman curve beloved is something else. I've made my stance on IEMs conforming to the Harman in-ear target well known already, as I believe that results in a poor bass execution giving you both too much bass and also a bass tuck at the same time to hurt timbre and drums/guitar impact, followed by too much ear gain and lower treble causing vocals to come off shouty for many. The TERRA addresses the former by simply being quite generous on the bass side to the point where there is simply no bass tuck at all. The bass shelf starts from ~500 Hz, so the measured 12 dB rise here is better distributed and makes for a warmer sound too. The sub-bass is still clearly more dominant compared to the mid-bass though, and any loss of isolation/seal from the ear tips can make the TERRA sound less punchy than it is capable of. I also feel the DD could have perhaps handled all the bass here, as some snare hits aren't as well textured—perhaps from the BA drivers taking over here? You end up with bass that's quite yet not the most engaging and with slightly less tone weight than I'd like to see for such a bassy tuning.

The good part of using BA drivers for the low-mids means the transition from the bass to the midrange is about as coherent as it gets, and indeed the same could be said when it comes to the treble too. The mids are the star of the TERRA show, managing to combine forwardness with an extremely snappy response too. Vocals in particular shine really well here, and the more forward 1-2 kHz region also helps balance out the pronounced bass to a decent extent. The measurements indicate the mids may be slightly recessed, which I really can't perceive in my ears. Instruments, including piano keys and trumpets, sound correct and with plenty of body. Poorly recorded tracks do not do as well here though, and synth music is also less strong on the TERRA than orchestral recordings. The treble might be divisive in how its elevated, although it's done so in a fairly controlled manner. The mid-treble energy could be sibilant if you are sensitive to this region, whereas others might find female vocals to have a touch of added brilliance instead. This is further emphasized by the part where the TERRA has some sparkle, but less air than I thought from a super tweeter placed in the nozzle tip. This could easily have gone wrong, as we've seen with many other IEMs that have far too much upper treble, and instead the TERRA is able to play triangles, harps, and cymbals without causing undue ringing in the ears or fatigue. I'd say the soundstage is deep enough, albeit it does feel slightly cramped in height. You do get fantastic layering and separation here, with fairly precise imaging too. Overall I'd say the TERRA is competent technically—it's not the most detailed set, yet isn't lacking behind its peers tremendously either.


There is plenty of competition in the price range the Lime Ears TERRA finds itself in, including the versatile 64 Audio U4s with its customizable bass shelf and isolation courtesy the Apex modules included. The U4s is smaller, more comfortable in the ears thanks to the controlled pressure relief, also uses a metal shell, and costs slightly less than the TERRA in the USA. It does sound leaner than the TERRA though, whose strength is adding body and heft to the bass and mids in particular. You will also notice the TERRA and U4s are tuned very differently in the treble, with the former going for mid-treble presence compared to the pronounced Tia air in the U4s. I found the TERRA to fare better with metal and rock music in particular, with female vocals being a wash (and good with both). Fellow Polish-based Custom Art has the FIBAE 5 around the same price too, and this too has a customizable bass shelf courtesy the use of a Knowles damper filter. The FIBAE 5 goes for a more audiophile V-shaped sound, with plenty of bass and treble, albeit hasn't left a strong mark since release due to many people finding the planar magnetic excess treble air too fatiguing. I'd probably take the TERRA over the FIBAE 5 purely from sound, with Lime Ears also winning on the design and build front. Another strong kilobuck contender is the ThieAudio Monarch MKIII, albeit the Prestige LTD is arguably closer in price—I haven't tested that one though. As with the Custom Art FIBAE 5, ThieAudio goes for resin shells with a decorative faceplate—both of which can be customized here for an optional extra. This is also a tribrid set, swapping out the planar magnetic drivers in the FIBAE 5 with Sonion ESTs, albeit again the same concern pops up in terms of excess air which is seemingly a common thread with all three comparison sets here. It's more a showcase of how controlled the TERRA is in this regard than anything else, and I'd say the TERRA comes off more dynamic in the bass and meatier in the mids, with the Monarch MKIII being more resolving and staging better.