Bass Gear Magazine has previously brought you reviews of the Ultimate Ears 11 Pro in-ear monitors and the UE PRO Reference Remastered in-ears (designed in conjunction with Capitol Studios). Both of these models are in the UE PRO range of custom in-ear monitors for professional and stage use. The process for ordering a set of custom UE PRO in-ears begins with getting your ear canals scanned. Ultimate Ears has refined this process over the years, and getting your canals scanned is fast, easy and no longer involves holding your mouth open with a spacer (yea!). The UE PRO in-ears are referred to as “pro-fit for active use,” and these types of in-ear monitors do extend fairly deep into your ear canal for a tight, secure fit. For most performers on stage, this range of products are what you are after.

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However, the kind folks at Ultimate Ears also wanted to offer up high-quality custom earphones for everyday listening, and this is where the UE CSX line comes into play. These earphones are referred to as “lifestyle-fit for extended wear,” and these models are aimed at the different use scenario of listening to music, as opposed to monitoring your performance on-stage. With (presumably) less jumping/moving around, the earphones don’t need to extend as deep into your ear canal to stay put, and this does make for a slightly more comfortable fit (though to be honest, I have done a good bit of casual listening with my UE PRO Reference Remastered in-ears, and they never caused me any discomfort).

DIY Custom Ear Molds

As previously mentioned, in order to get properly fitted for the UE PRO line of in-ear monitors, you can either order your in-ears through one of Ultimate Ears’ global dealers (who will directly scan your ear canals and build a digital image), or you can to have molds made of your ear canals by a qualified audiologist and ship the molds/measurements to Ultimate Ears in Irvine, CA. While this process is far from onerous, with the UE CSX line, you can do all of the measurements by yourself in the privacy of your own home.

Ultimate Ears

The new Ultimate Ears Fitkit option includes molding tips (in two sizes), a fitting device, a mirror, a power adapter, and a return shipping label. Once you download the UE Fitkit app to your phone, step-by-step instructions guide you through the process of selecting the right molding tip size, using the fitting device, connecting your phone, inserting the tips in your ears, and initiating the impression process. When the process begins, the molds begin to warm up – which is a unique sensation – though they do not get uncomfortably hot. The heat allows the molds to adapt to the shape of your ear canals; after doing so, they begin to harden. The app prompts you to remove the molding tips after 60 seconds, and your impressions are complete! After you return the molds (using the prepaid shipping label), Ultimate Ears gets to work and promises to deliver your new custom earphones in 10 business days.

First Steps

In my zeal to tell you about the new at-home Fitkit option, I skipped the first step: choosing your UE CSX earphones model and features. The UE CSX line includes four models: the 2-speaker UE 5 CSX ($499), the 3-speaker UE 7 CSX ($899), the 4-speaker UE 11 CSX ($1,199), and the 6-speaker UE 18+ CSX ($1,499), reviewed herein. The differences between these four models goes beyond merely slotting into different price ranges, as each model offers unique characteristics and benefits. For instance, the UE 7 CSX have a focus on the midrange, making them great for vocals, classical and jazz. Much like the UE 11 PRO in-ears we previously reviewed, the UE 11 CSX are exceptionally robust in the lower frequencies, making them great for drummers, bass players and fans of “big music.” The UE 18+ CSX are very balanced across the lows, mids and highs, with exceptional detail. All models offer excellent noise isolation (26 dB reduction).

Once you’ve selected the model you want, you can choose from eight different pre-defined color options: Jet Black, Clear, Translucent Jet Black, Translucent Lucky Red, Translucent King Blue, Carbon Fiber, Mother of Pearl, or Wood (the last three options do involve an upcharge), or you can design your own custom look. If you go the custom route, you have a choice of eight colors, five wood choices, or six different materials. You can then choose to add a silver halo, a gold halo (both options add $200 to the bill), or opt for no halo. Next up, you can choose between silver or gold “UE” logo, no logo, or custom initials (two characters, max). The UE CSX earphones come with a traditional braided cable as well as a Bluetooth cable (more on that in a minute), and are packaged in a quality metal case (which can be engraved for free). For the review unit, I chose Translucent King Blue, no halo, silver UE logo, and my name engraved on the case. Man, they look great!

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Ultimate Earphones case

18 and Older

The UE 18+ CSX earphones feature a 4-way crossover feeding dual high Truetone Plus drivers, a dedicated mid-high balanced armature, a dedicated mid-low balanced armature, and dual low balanced armatures. The UE 5 CSX and UE 7 CSX each feature a 2-way crossover, and the UE 11 CSX has a 3-way crossover. The input sensitivity is 105 dB @ 1kHz, 1mW, which is notably lower than that of the other earphones in the UE CSX line (the UE 7 CSX holds top honors in sensitivity, at 124 dB), though compared to the UE PRO Reference Remastered (100 dB), the UE 18+ CSX are slightly louder, with the same signal. It is also worth noting that the UE 18+ CSX has the highest impedance (least resistance), at 37.5 Ohms @ 1 kHz, while the rest of the CSX line falls between 18 and 21 Ohms. The frequency response for the entire UE CSX line is listed as 5Hz to 22kHz.

It’s Good to be Blue

The included Bluetooth cable really opens up a world of possibilities. The swappable cable option (Ultimate Ears IPX Connection System) gets the initial credit. The IPX connectors make it exceptionally easy to swap between the braided cable and the Bluetooth cable. If you don’t plan on straying very far from your music player, then the braided cable offers the best potential sonic fidelity – particularly if you are also using the excellent UE PRO Sound Guard buffer. But for when you don’t want to be tethered to a device, the Bluetooth option is great. The cable has a dongle housing the controls and a microphone, as well as containing the primary battery for the earphones. A snap-on cradle is used to charge the dongle/battery, but the cradle is not much larger than the dongle and has its own internal battery. Ultimate Ears claims an 8-hour play time when both the dongle and the cradle have a full charge (4-hour play time with the dongle, alone).

I found myself charging the cradle on its own (as it takes up less space on my counter without the cable/dongle attached), and then leaving the cradle attached to the dongle when I was listening to the earphones (to extend battery life). Alternately, you could just throw the cradle in your pocket and break it out when/if you run out of juice on the primary battery, but it’s so small and light, I just left it attached. This also minimizes the chances that I will lose the cradle…

When you power up the Bluetooth dongle, a pleasant voice in your ears tells you that you have successfully turned the “power on” and tells you the current charge level on the battery. It will also tell you when you have successfully connected your headphones to the Bluetooth device. The three buttons on the dongle have different functions when you are using making a phone call, as opposed to listening to music. The Bluetooth function supports Multipoint pairing, so you can be listening to music from one device, and then receive a phone call from another device. The earphones will also pair with most smartwatches, even outside of the Bluetooth range of the phone.

Ultimate Earphones

An Earful of Comparisons

One of the obvious and inevitable comparisons when you are talking about Bluetooth- compatible, wireless earphones is that of the Apple AirPods. Yes, I know that the AirPods are not true earphones, and yes, they cost a fraction of the UE 18+ CSX, but they pretty much kicked off the whole “wireless devices in your ears thing” and I have been using them for a while. Comparing the UE 18+ CSX to my AirPods, I have to say, I was initially surprised at how much bass the AirPods seemed to be putting out. After more critical listening, though, it feels like the AirPods low-end response is artificially hyped – and the same goes for the high end. Listening to Linkin Park, In the End, the snare and cymbals seemed to stand out more with the AirPods, as did the upper range of the guitars. By contrast, the UE 18+ CSX are definitely more smooth and full-sounding. You can hear the “meat” of the rhythm guitar more, and the toms are more in balance with the snare and cymbals. The AirPods sound thin after going back to them following a listening session with the UE 18+ CSX.

In contrast to the AirPods, the UE 18+ CSX feel very neutral and balanced. There is just as much low-end (and high-end) content, but they are presented much more naturally. I’m not sure how they pull this off, but the UE 18+ CSX somehow give an impression of feeling the bass with your body. Impressive! I then fired up Greta Van Fleet, Highway Tune, and on this song, the AirPods had noticeably less bass than the UE’s – which supports the notion that the AirPods are playing with some EQ, while the UE 18+ CSX are producing a full range of music more naturally. On this song, I definitely noticed that the UE 18+ CSX were less fatiguing than the AirPods, and once again, more smooth/full. Moving on to some Chicago, the UE 18+ CSX really let you hear the individual horns as they competed with guitars, bass, keys and drums. The excellent noise isolation from the UE CSX headphones really stands out, as well, and this makes them vastly more desirable in a noisy environment. Man, I wish I would have had these on my last cross-country flight…

For a more vigorous test, I compared the UE 18+ CSX to my UE PRO Capitol Studios Reference Remastered in-ears. For this comparison, I used the braided cable connection for both sets of earphones. As expected this was a much closer comparison. The UE 18+ CSX have a bit more bass, and are slightly louder (due to the slightly higher input sensitivity on the UE 18+ CSX). By comparison, the UE PRO Reference Remastered in-ears have a bit more detail, and are somehow also slightly smoother. True to their design goals, the UE CSX earphones are a bit more comfortable and are easier to put in your ears – though to be fair, after using the UE PRO in-ears for a while, I have no problem putting them in. Both sets of earphones stay in quite well when shaking/moving your head, though the Capitols most definitely extend further into the ear canal and will undoubtedly stand up to more vigorous movement. Still the UE 18+ CSX do an admirable job of staying put.

Ultimate Ears

During the course of my initial review of the UE PRO Reference Remastered in-ears, my joy of listening to music for the sheer joy of listening was rekindled. The UE 18+ CSX earphones continue to feed this fire, and the Bluetooth compatibility makes it oh so convenient. The detail and texture revealed by either of these earphones is far superior to more casual music playback options. In fact, I was pleasantly surprised to “rediscover” a really cool whispered vocal effect in an original song my band (Gingley JoH) recorded almost twenty years ago. I had totally forgotten about that track – and I apparently couldn’t hear it through my other playback devices…

In addition to comparisons involving the full-on listening experience, I also wanted to see how the UE 18+ CSX performed when making phone calls. To be honest, my expectations were that with the mic located on the Bluetooth dongle hanging behind my ear, the microphone performance would be less than ideal. However, it seems to function just fine, and the parties I spoke to told me that they could hear me even better than when I used the built-in microphone on my iPhone 10XS Max. Switching to the AirPods, the other parties did not discern much difference between the UE 18+ CSX and the AirPods, though both were better than the built-in mic. As far as hearing things on my end, both wireless options were far better than the built-in speaker, but if you really want to hear the person on the other end, the sound isolation and even frequency response of the UE 18+ CSX is fantastic. Phone conversations were much more audible on the UE’s compared to the AirPods, though I will say that if you do need to communicate with someone in the room with you while talking to someone else on the phone, the sound isolation can be an issue, and the AirPods do a better job of letting you hear people around you and hear people on the phone at the same time.

There’s an App for That

Now, if you happen to like a more hyped tone, or if you want to have precise control over the EQ of your listening material, then you will be pleased to learn of the UE Custom app. This free app allows you to choose between one of eight presets (Flat, Bass Boost, Podcast, Tubes Amp, Warm and Clear, Rebalance, Enhanced, Extended Listening) or take full control with the “customize” function. This brings up a 5-band EQ with an intuitive touch-and-drag control for boost/cut and frequency of each band. Once you have dialed in an EQ setting that you like, you can save it as a new preset. Very cool! Please note, this app only functions when you have the UE earphones paired. The app does not function when paired with AirPods or another Bluetooth device. As an added bonus, the UE Custom app also displays the current battery level of your earphones.

Ultimate Ears

The Bottom Line

Ultimate Ears PRO has been an established mainstay in the field of on-stage in-ear monitoring for many years. With the new CSX line, Ultimate Ears brings their know-how and fidelity to the recreational listener. The new Fitkit option allows you to order up a set of custom-molded earphones without leaving your own home. The Bluetooth connection option allows you to break free from the physical tether, and the UE Custom app lets you tweak to your heart’s desire (if need be). With the Bluetooth cable, your UE CSX earphones make cell phone calls much more clear and audible. This is all great news to music lovers, indeed, and the 30-day risk-free trial removes any rationale not to give them a try.


Manufacture:Ultimate Ears
Model:UE 18+ CSX
Input Sensitivity:105 dB @ 1kHz, 1mW
Frequency Response:5Hz – 22kHz
Noise Isolation:-26 decibels of ambient stage noise
Impedance:37.5 Ohms @ 1kHz
Internal Speaker Configuration:6 proprietary balanced armatures with a 4-way crossover
Connection Options:Braided cable with universal 1/8” headphone jack; Bluetooth cable with battery/control dongle
Bluetooth Version:4.1, Multi-point
Profiles:Handsfree, Headset, A2DP, AVCRP, SPP
In-line Mic:MEMS, omni-directional
Battery Life:8 hours (4 hours internal, + 4 more with included charging clip)
Battery Type:60 mAh lithium polymer (in the device)
Battery Voltage:3.7V
Charging Time:2.5 hours
Standby Time:110 hours
Accessories:Road case, cleaning tool, 1/8” buffer jack
Warranty: 1-year