Fit and Comfort

Seen above are the two included ear tip types in size M, installed on the right ear bud and inserted into an artificial ear mold. 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, and as mentioned before, the Symbio foam tips aren't truly that anyway. Indeed, even though it may look similar in the second case, the fit with the Symbio tips is not very secure and does not seal as well. My fears about the foam being too dense turned out to be valid, with these tips highly pressure sensitive and not easily conforming to the ear canal, which almost has them work the opposite as, say, Comply foam tips that squish easily and then expand to fill in the surroundings. I don't know why Lime Ears went this route, at least for the foam density. The concept itself is worth exploring again, but this particular combination wasn't a success in my books. The silicone tips are much better, one of the better tips I have used to date. Do try out other tips if you have them on hand, but I leave content knowing that at least one provided type works well enough here.

The ear tips are more important than you may think given the larger physical form factor of the Lime Ears Pneuma. It may well be too large for many with smaller conchas and ear canals, so keep that in mind when considering the universal fit version. Some tips, such as the final Type-E ones, may help by positioning the shells slightly further out without affecting the seal too much, and I will give credit to Lime Ears for designing a nozzle that isn't too wide but long enough to extend in without cramming the large shells into the ears. These weigh ~8 g each, and the cables add a further point of contact on top of the general ergonomic design for the shells. Passive isolation is fairly decent depending on the fit since the IEMs will aim to take up more room in the concha than most. They will be an attention grabber, especially with the vivid colors and striking pattern, so don't expect this to be a stealthy set of IEMs.

Audio Performance

Audio Hardware

If the image above confuses, I don't blame you. You see, the Lime Ears Pneuma is a hybrid set of IEMs with two types of drivers. Lime Ears informed me that the drivers were chosen based on a lot of testing, and I do find the implementation of the 1 DD + 4 BA driver configuration per IEM quite novel. Indeed, the 7 mm titanium diaphragm—probably coated, not pure titanium—dynamic driver is not catering to the bass as you might expect; instead, it just handles the sub-bass. In that sense, the smaller size of the driver makes complete sense, and its role explains why there is no bass vent port here, which helps with isolation. This also happens to be my first such experience with a sub-bass DD handling 100 Hz and under only. This is part of the technology Lime Ears calls "BAM," or Backfiring Acoustically Damped Membrane. I'll let Emil from Lime Ears explain more:

BAM is a special way of implementing Dynamic Driver for the low end. I have used the back vent of the DD driver to get the signal from. So It's naturally low-pass filtered and phase inverted (which has been corrected) and seems to have slightly different impulse response due to initial backward diaphragm movement. Plus we added open-cell foam to the front to additionally damp the driver in higher frequencies and emulate padding inside the speaker enclosure. Anyways the "subsonic rumble" that I got from "fairly" small transducer (7 mm is much smaller than 10 or 12 mm used in some other designs) resembles the one that is received from bass-reflex enclosures which further led me to indicate the origins of the idea in technology description.

When asked why BA drivers were chosen to cater to the mid-bass and on, with the Pneuma employing two BA drivers for the bass, one BA for the mids, and one BA for the highs, he mentioned that most DDs tested don't sound as good as BA drivers for the mid-bass owing to bloat from the otherwise heavy, slow response, which BA drivers with a much lighter diaphragm can get around with higher accuracy. There's also VariBore here, which is a technology where different sound-bore diameters are used by Lime Ears for different types of transducers. The sound-bore diameter and length seemingly add a specific acoustic impedance to the signal, significantly changing frequency and impulse responses. As per Lime Ears, the higher the frequencies moving through, the bigger the diameter for them to travel through unharmed. This explains the use of larger bores on the nozzle, especially for higher frequencies to, in their own words, "maintain their clarity and space."

The switch is where that graph above comes in, where it toggles between an elevated bass response for tweaking the listening level based on the Fletcher-Munsun to add some listening volume or trade it for further clarity in the mids if you are in a noisy environment and need to use these IEMs as actual monitors. All of these implementations ultimately make for a 1+2+1+1 driver configuration for a 4-way passive crossover in the Lime Ears Pneuma, and these come together to make for a very easily driven set with an impedance of just 7 or 9 Ω at 500 Hz depending on the switch position and, presumably, a high sensitivity of 115 dB/mW since Lime Ears to my displeasure omitted the full units. The Pneuma is just fine with mobile devices thus, and a portable DAC/amp will suit your needs perfectly for when you find yourself without an available 3.5 mm audio jack on the go. If not, the shorter cable included with IEMs might be a potential handicap if connecting to a PC as the audio source.

Frequency Response Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature emphasizing a slightly elevated bass and smooth treble range with 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 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 the sound card. 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 1/6th 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 Pneuma, or at least the useful part. 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 there is unfortunately some channel imbalance. To confirm further, the relative differences were the same across both channels irrespective of whether the switch was in or out, and the slight difference in the sub-bass is of no significance since I did not perceive it whatsoever. It's more the gap from ~400 Hz to 1.8 kHz that got me, at least to where I noticed it during my initial listening, which had me generate a measurement right away to ensure it was real. This is unfortunate, but could well be a one-off for all I know. Still, I have to base my findings on this sample, especially as I did not receive a response from Lime Ears on this. Things are quite consistent again in the upper mids and onward, so no complaints there. I would not say there's a strong burn-in effect, but I did get to appreciate the sub-woofer implementation of the dynamic driver better after ~5–6 hours of playtime. The measurements above were taken after 50 hours of testing, and I even took another measurement after ~100 hours we will see on the next page, and it was within error margin of this one. The response with the artificial pinna in place is incredibly impressive for its similarity to the coupler itself, with a slightly darker roll-off in the upper treble there.


Based on what I saw and heard, I am inclined to think the right channel is more representative of the product, and I thus chose to show the frequency response measurements of just the right channel with the switch both in and out as seen above. Feel freeto head over here for other points of comparison, including by normalizing the frequency response measurement as needed. The switch in results in a maximum bass boost of ~3 dB that starts at 500 Hz, meaning it more than just tweaks the dynamic driver and involves the various features mentioned above. It works out quite well in meeting what was promised, and I can certainly get the sense of refinement based on how some frequencies should sound relative to others at equal volume.

In practice, the switch being in makes for a more V-shaped tuning and the switch being out for a more neutral response befitting a monitor, at least relative to other option here. It's of course not a truly neutral tuning as with the likes of some Etymotic gear we have seen in the past, but I will again agree that the switch does what Lime Ears markets it to do. But neither are perfect, both have issue to where this ends up being a case of flipping back and forth to decide if either is to your satisfaction. Let's tackle the bass region first, where I do think the Pneuma shines if you keep the switch in despite the out position seemingly matching my particular preferences better.

This is more to do with the overall tuning since the switch out tuning is more accurate, but falls flat in the upper mids and exaggerates the brighter signature in the treble relative to the rest of the tuning to where it almost comes off sibilant instead of sparkly. The switch being in provides more balance in that there is warmth in the lows to help even out the rest of the frequency response. The dynamic driver dedicated to the sub-woofer functionality opens up more and makes for a funner experience. I am also now convinced by the use of a smaller DD for sub-bass alone since it makes for punch on par with the best IEMs I have listened to, if not better. It is a good example of how the technical performance of a driver configuration can differ from the tonality, whereby it doesn't need massive amounts of bass elevation to achieve the slam and presence that makes for an EDM lover's best friend.

That said, I am not as convinced by the BA implementation for the mid-bass itself, which comes off weaker by comparison and just gets worse with the switch in. The red line with the switch out certainly reduces on any bloat and makes for a clean transition to the mids, which ends up being a compromise, with the effect not as clean with the switch in. So you need to choose between the two depending on what you are listening to and your use case with these IEMs. It's a good thing then that the switch is readily accessible even when the IEMs are installed. For the mids, I'd go with the switch out for more vocal range and better instrument representation. There is still warmth for male vocals to where the likes of country music and rock/heavy metal sound exciting without coming off boomy or even misrepresenting in a mix. If you were wanting to actually mix with these, I'd first ask why and secondly definitely tell you to at least do it with the switch out. Imaging is otherwise very good, and the soundstage felt more expansive with the switch in than out, whether a trick played on my mind or not. It feels somewhat artificially large, however, so once again, my preference with vocals and instruments ends up being better met with the switch out.

The treble response is unfortunately where nothing you do with the switch really helps. The single BA handling the highs is a textbook example of BA timbre and how it is not natural sounding at all, which is not even the worst problem here. I mentioned before how things got overly bright in some cases, but the lack of proper ear gain in the 1–5 kHz region is what got me to pull up Equalizer APO right away. Female vocals in particular felt flat, and this is coming from someone who prefers lower ear gain than most and isn't much of a vocals guy to begin with. The presence at 5 Khz also comes off as deliberate in that Lime Ears targets a "sparkly" treble tuning, but doesn't do much here to add extension and range for string instruments and piano key fundamentals. That said, I can appreciate that the Pneuma is not a fatiguing set to listen to, but the treble response makes me want to see an improvement—be it through another driver configuration, maybe another BA or even EST tweeter, or making the damping filters around less.. convoluted.


I was in two minds about whether to include spectrogram plots or not since I do see the decay shifts there better, but opted for a waterfall decay plot instead since it is more likely to be interpreted correctly. What you see above is the frequency response for the Lime Ears Pneuma in the two switch configurations, with the heat map depicting the relative SPL levels at various frequencies. As such, notice how the sub-bass and bass get hotter in the plot for the Pneuma with the switch in compared to out. The Z-axis is hang time, showcasing note decay in milliseconds. It's mostly in the bass that we feel reverberations here, and this is more tightly controlled with the switch in than out. Definitely make use of the switch accordingly, shifting from in to out depending on music genres, and I never once felt that the switch would break or wear out in the months of testing this inadvertently went through prior to publication.


Comparisons are again weird because the Lime Ears Pneuma is the most expensive set of IEMs discussed thus far. I have a few others that come close, and one that goes even higher, but circumstances surrounding the latter may mean it will never be reviewed. The tuning of the Lime Ears Pneuma is also quite unlike the nearest covered neighbor price-wise, which is the Audeze Euclid. I thus ultimately ended up with three sets here. The first is the DUNU ZEN PRO, which is a $900 set that is closer to the Pneuma with the switch out but showcases better tuning in the upper mids and highs while also having very good punch. I would not upgrade to the Pneuma if I already had the ZEN PRO, and likely would get the ZEN PRO in the first place purely for the fit and functionality, but there's no denying that the aesthetics and custom-fit options with the Pneuma add to it positively in comparison. The second set is the recently released Effect Audio Axiom, which at $1500 makes the Pneuma feel worth the price increase and then some owing to a bizarre collection of features that don't work as intended. Look out for a review of the same in the days to come. The final set is the recently reviewed XENNS UP, which I had mixed feelings about as tribrids, but it is possibly the set I can see owners upgrading to the Lime Ears Pneuma from if they want a similarly tuned set that is in some ways technically more proficient.