Fit and Comfort

Such is the nature of the shell design and size that Audeze has created a short video to demonstrate how to fit the Audeze Euclid in your ears. I highly recommend following those instructions since it removes a lot of potential seal issues as well as ambiguity on whether you have it inserted properly even if it may feel like it. Seen above are two images using the provided size M Audeze silicone and Comply foam tips on the right ear bud inserted into an artificial ear mold. I have average-sized ears, and the ear mold seen above usually represents my own experiences well, although I will say I could have probably inserted the ear buds further in here since the gold trim is supposed to be inside the concha when done correctly. Also, this is probably the first time the foam tips were better for fit and comfort. Part of this has to do with the inclusion of some of the best foam tips on the market, if not the best subjectively, and I do wonder again about the lack of SpinFits in the current packaging.

As it stands, I recommend using the foam tips even if you will have to replace them sooner than the silicone ones. Compress the foam into a thin cylinder and insert the tip into your ear canal. Then hold the ear bud in place for 20–30 seconds while the foam expands to naturally fit the cavity, creating a good seal. The size of the ear buds is above average, but the shape is such that it was one of the more comfortable fits for me to date, especially when following the video to get it done properly. The use of the aluminium also keeps things light for the size, with each ear bud weighing around 7.5 g to where a good fit will allow you to wear these for a long period of time. I bet this is the first time someone has said an Audeze product is lightweight for the size! These are closed-based IEMs with no vents, so there is a good deal of passive isolation already, and the ventilation, or lack thereof, is the reason I found myself taking these out every hour or so, and I gave the tips a clean as well before re-inserting them.

Audio Performance

Audio Hardware

I recommend reading the equivalent section in the review of the LCD-2 Classic that goes over planar magnetic drivers in more detail. It is a fascinating piece of engineering which merits a deeper dive in itself, but this is not the right place or time for it even though the driver system employed here is arguably more complex than on the LCD-2C. You still have an ultra-thin diaphragm with thickness measured in the single micron range, and a single-sided set of Audeze's patented Fluxor magnets generating a high density magnetic field strong enough to resonate the diaphragm uniformly far more efficiently than, say, a typical dynamic driver in a cone speaker configuration. The so-called Uniforce voice coil is also placed directly on the diaphragm, thus resulting in a fully resistive load, which helps with the flat impedance curve that makes these so easy to drive without a dedicated DAC/amp. Unlike the LCD-2C, however, we do get Audeze Fazor waveguides that aim to eliminate the phasing and distortion typically associated with closed-back headphones/earphones, including the Euclid. Also, as with every other Audeze product, the Euclids are individually tested, and the drivers undergo a mandatory burn-in period before they ship to you ready to go out of the box.

Driving the hardware thus actually ends up sipping less power than your average IEMs since the rated impedance is just 12 Ω! But then I will note that the rated sensitivity is 105 dB/mW, measured at the drum reference point, which I will thank Audeze for mentioning since no one really does and the numbers by themselves don't mean much without said information. Sensitivity isn't quite as high as a few other IEMs I have tested to date, but coupled with the lower impedance mean you should carefully pick your high-res source and files to avoid clipping and make the most of the Euclid. A portable DAC/amp or even DAP might be nice to have on the go, especially with the lack of a 3.5 mm jack on most phones today. I am going through a few such options separately too, and the Qudelix 5K (review coming soon) pairs really well with the Euclid even in wireless mode. The FiiO BTR5 adds some warmth, so perhaps read on and see if you prefer that instead. Both also offer 10-band EQ for further tuning. If not on the go, space is less of an issue, but the 1.2 m cable might be a potential handicap if connecting to a PC as the source.

Frequency 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.


Our current testing methodology begins with a calibrated IEC711 audio coupler/artificial ear that ear buds can feed into to where you have decent isolation similar to real ears. 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 pinna mold that fits to the audio coupler for a separate test to compare how the IEMs fare when installed in an ear and cheek geometry and not just the audio coupler by itself. 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, just within our own library of measurements. 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 Audeze Euclid, or at least the useful part of it. The left earbud 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 pretty much spot on most of the way. There is a slight difference in the sub-bass, and you might as well toss a coin to identify the two throughout the mid-bass, all the way to the upper mids following which there is about a ~1 dB differential between them. This is of course considering that the IEC711 isn't all that reliable at higher frequencies. I will also mention that there was no discernible break-in period or effect, so there is overall good reproducibility and consistency since the average response for each channel is also basically the same across the three repeated tests.

See that region of uncertainty marked in the graph, as with the Audeze LCD-2C before? The latter was because I did not feel the testing setup was best representing over-ear headphones, and some of that applies to the largest IEMs tested to date. The IEC711 standard microphone used is an IEC 60318-4 occluded-ear simulator, and my unit was individually calibrated to be within the standard all the way. However, the standard itself is not too reliable past ~8–9 kHz. Smaller audio solutions, including IEMs, also have the fit factor strongly influencing results whether or not you are using the coupler as-is or with the artificial ear and cheek simulator. The larger Euclid exaggerated the situation to where I had to mark said region again, but this time from 9 kHz. I will also mention that Audeze had provided a copy of the factory frequency response measurement for my specific sample done on their professional HATS (head and torso simulator) setup, and the results above are quite similar across the board except for a peak shift or two slightly into the treble region, which is as expected. I have procured a new testing setup which will be implemented once ready to help address such issues, especially for headphones.

With this accounted for, allow me to talk about how the measured frequency response of the Audeze Euclid came across and compare and contrast it with my own listening experiences. As I write this, I have listened to the Audeze Euclid for over 60 hours, excluding another 30 hours to check for any burn-in effects. It is also only my second Audeze product, and I can already discern a pattern. I talked more about the various LCD lines for the Audeze over-ear headphones in the other review, including the LCD Reference line meant for audio mixing and monitoring courtesy a flat, neutral response. The Audeze Euclid might as well fit into this line given its neutral and accurate tuning. At first glance, the frequency response also suggests a totally flat profile that might be too dry for many, but such is the nature of planar magnetic drivers that this is not wholly indicative of the story in your ears. This is all the more relevant here since (a) the frequency response curve above is with the audio coupler as-is, and (b) I want to re-test this with the upcoming setup to be more confident about the effect of the pinna, which means I am not going to show that measurement here, which currently looks different enough from the one above.

Imagine a gentle stream of water flowing by without much of a change in incline, and you as an observer on the bank. When further away, this stream of water looks to be a cohesive body moving in a near-laminar pattern without any disruptions to its flow. Getting closer, you start noticing some irregular, localized patterns, be it Eddy currents or otherwise, to where there are regions of higher entropy rather than an overall body. Where I am going with this weird analogy is that the mostly flat response from 20 Hz to 20 kHz ends up being closer to the Harmon curve target when listened to in the ear, which is lightly V-shaped. There are regions of entropy as well, which you might as well divide into the lows, mids, and highs to talk further about.

There is indeed a sub-bass elevation that might catch some folks unaware. To be fair, the elevation is slight where I would describe it to be less than on the Etymotic Evo, but slightly more than on the Campfire Audio Satsuma, both of which are among the more neutral IEMs I have here in the lows. Mid-bass is more subdued to where I would personally bump it up about 4–5 dB with EQ, and I will take this opportunity to say that the Euclid scales magnificently with EQ to where you can likely bump regions up by 5–10 dB without really noticing any loss in details. This is where the strength of the Euclid lies—there is so much detail preservation in the lows that it easily provides the best pure listening experience I have had with IEMs when it comes to funk music in particular. I adore jazz and Latin music as well, and the bass notes here struck so many chords I could finally actually consider these to be bassy genres. Lovers of heavy metal/death metal, house music, and the like with more bass-heavy tones might want to EQ the Euclid as well, but I would also say there are other options more fitting for those genres.

The mids are the closest to the frequency response itself, with a smooth transition from the lows leading to extremely relaxed mids with an obviously wide range, too. There were occasions where I felt things were a touch recessed, but it was once again more because I had EQed the lows, which artificially caused the dip elsewhere. Going back to the default tuning showcases the same strength in details and tonal separation here. This especially helps with male vocals, with pop and country music again quite strong. Female vocals are not as strong, however. There is some loss in naturality, at least relative to male vocals, and I am not sure I could fix this with EQ to be honest. In fact, there is even the occasional tinniness with female vocals, but perhaps the closed-back nature of the shells is to blame here. There is nothing else I have here in this price range, so I do have higher standards because of the cost factor too, but would probably take the ThieAudio Monarch over the Euclid for the overall performance in the mids even so, especially in the upper mids.

On the flip side, I had an audible "what!" moment when it came to the soundstage and imaging with the Audeze Euclid. These are closed-back IEMs that outperform several of my open-back over-ear headphones in this regard. I have no idea how Audeze managed to get this magical width inside; making the inside seem larger than the outside is clearly a Time Lord trick! It's certainly not going to have a wider/deeper/taller stage than some of the airy open-back headphones, such as the Sennheiser HD800S or even Audeze LCD-X, but I had to go back and forth with the LCD-2C to confirm the latter was actually besting the Euclids in this regard after all. I observed more details with some songs than before, including David Bowie's The Man Who Sold The World, but clearly identifying the source of the drums and percussions relative to the guitars and vocals was quite an experience.

Remember those female vocals and upper mids that were a slight letdown relative to the new standard set thus far elsewhere? Some of that bleeds into the highs, unfortunately. I have no qualms about stating that the treble region tends to be where I distinguish headphones and IEMs the most. I am that guy who has to cover his ears when an elevator goes too fast, and am often pulled in to see whether I can hear something being "off" somewhere. The treble frequencies are where so many try and fail with the tuning, especially as it pertains to meeting set marketing goals, lofty as they tend to be. I will give Audeze props in that there are no unnatural decays at any frequency I could hear, with a fairly consistent offering all the way to 10 kHz. Then comes an appreciable dip soon after that is barely going to be felt by 95% of people if I had to guesstimate, but I did. This extension into the highs, or lack thereof, is the culprit that takes away from an otherwise well-presented base here. There is the expected hump at 2 kHz to account for inner-ear resonances, followed by a relatively consistent signal that gets darker than I'd like. What I mean is that I'd have preferred the boost to continue slightly further down to compensate for the IEMs being shoved inside the ear canal, but everyone has a different geometry. Instead, we see the response roll-off commencing from here and continuing onward. So while piano keys will resonate very well with just the right amount of hang time, cymbals and triangles can feel depressed in both senses of the word. Once again, this dip is not something EQ can magically fix to where this is another case of an Audeze product in 2021 for which EQ is absolutely not mandatory overall.