Earlier this week, I awarded The Verge’s highest ever score, 9.4, to the extraordinary Focal Utopia headphones. Inhabiting the space between those cans was a rare (and terribly expensive) privilege, but it wasn’t something I could ever take on the move with me. So today I want to talk to you about the absolute best way to enjoy your music on the go: custom in-ear monitors (CIEMs). Think of them as the supercars parked outside the Utopia luxury condo.

Custom earphones have been around for a long while, and their premise couldn’t be simpler. Instead of throwing a dozen different types and sizes of tips your way, customs are designed for the specific shape of your ear canal — they’re like a tailor-made audio suit, basically. What’s held them back from mass popularity is the steep price, bulkier size, and the extra effort of having ear impressions done. I’ve been testing two models over the past few months — the $1,650 Noble Audio K10 and the $1,350 Ultimate Ears 18 Pro — and they do little, by themselves, to address those barriers to entry; though I’ve also learned a lot that gives me hope that custom IEMs are growing more accessible to us mere mortals. And, okay, I’ve enjoyed the hell out of the experience because they sound absolutely superb.

You've never heard silence like this

The first thing you’ll hear when you put on a pair of custom-designed IEMs is nothing. It’s like stacking multiple sets of noise-canceling headphones on your head: there’s just pure silence, thanks to the personalized fit of the hardware. I want you to consider how different a starting point this is to any other type of headphone. Customs provide a blank canvas on which to paint musical soundscapes, whereas everything else is in some way compromised, either by external noise or artificial noise suppression. Both the Noble K10s and UE18s nullify the incessant drone of busy London streets with ease (UE advertises a -26dB passive noise suppression), and once I’m playing music, they create a completely isolated bubble of my own. There are circumstances where that’s not a desirable thing, of course, but I doubt I’ll need to argue the benefits of being able to detach from the world occasionally.

With such a perfect seal as customs provide, I never have to turn the volume up to high levels. A few notches above the middle on an iPhone or Android device’s volume control is all the loudness I need inside the sanctum of silence provided by a custom monitor’s design. And yes, unlike the Focal Utopia, which would be blasphemously wasted without the help of a good DAC and amplifier, CIEMs can be driven by and sound beautiful with just a phone as the music source.

Another benefit that many might not consider: custom IEMs basically never fall out of your ears, and I’ve found them super comfortable for running. Neither company would probably endorse sweating profusely over their sophisticated engineering, but they do a damn fine job in the gym all the same. I’d recommend the lighter 18 Pros over the more complex and bulky K10s for this purpose. Is this the most expensive fitness headphone recommendation? Probably, but that’s why I call these things supercars.

It takes passion, patience, and purchasing power to reach the peaks of great audio

Beside their literal cost, the price you pay for customs comes in the form of daily practicality and initial setup. First, you have to find an audiologist to fill your ears with gooey silicone in order to create earmolds from which your customs can be built. I’ve done it twice and actually enjoyed the process, but it takes time and is costly. Ultimate Ears is now working on improving this process by using a digital scanner, but when I tried that it didn’t work at all and I ended up with more silicone in my ears. The other problem is you have to store these in a hard case when you’re not wearing them, and it takes a solid minute to put them on correctly. These things go deep inside your ear, so taking them off is also not a trivial matter. Some people also report pressure buildup inside the ear canal owing to an overly tight fit, though I’ve not had that issue.

One tiny bit of discomfort I have experienced is a slight soreness after listening to either the Noble K10s or UE18s for hours at a time. My ears never hurt, but they feel more sensitive the next time I insert the custom IEMs. I haven’t used either set quite so regularly as to be able to tell whether that would be problematic on a daily basis or whether my body would grow accustomed to it. Like I say, supercar stuff.

So I’ve enumerated a number of inconveniences and I’m sure many of you started reading diagonally once you saw the prices, which invites the question of why people do it. Why do audiophiles go to such lengths when a pair of $30 Xiaomi Pistons sounds pretty good already? The answer is because there’s nothing else like it. Because custom IEMs truly are the best.

Why do people do it? Because it's the best

I used to ask the same question while attending the Geneva Motor Show. I would sit inside the Ferrari 488 GTB and ponder the cramped interior, hard leather bucket seats, and the horribly inelegant, butt-first method for getting in and out of the car. People pay hundreds of thousands for this degree of discomfort? All of that changed, however, when I took a ride in a McLaren doing supercar things: the Goodwood hill climb this year was the most astonishing, thrilling experience I’ve had... maybe ever. At 200mph, those bucket seats are actually the most comfortable in the world, and all the stuff that people pay extra for makes itself apparent. Supercars don’t exist on the regular cost-to-benefit graph — they have their very own thrill-per-dollar metric by which they are to be judged. And so it is with premium headphones.

To extend my analogy, I would describe the Noble K10s as the Ferraris of the CIEM world. They’re more ostentatious, offering aesthetic panache to go with their exquisite performance, and are designed for pleasure listening with just the slightest touch of extra bass to sweeten their sound. The UE18s, on the other hand, are akin to a McLaren, more of a driver’s car targeting the professionals first, as Ultimate Ears GM Philippe Depallens tells me. Though they approach the challenge of awesome personal audio from opposite directions, both companies eventually arrive at almost the same destination. They’re simply untouchable for sound quality on the move.

Read more: Noble Audio Kaiser 10 review

I loved and lauded the universal-fit Kaiser 10s from Noble a few months ago. Everything I said about them is of course still valid about the custom version, but now it’s all taken up another notch by the perfect seal. I could never make the generic fit earphones actually fit me, so I ended up turning those up quite high to get my bass fix, which in turn led to an overly present treble response. Not so with the custom variant, where every low note booms and bangs with precision and authority. The treble is also perfectly detailed and revealing. In listening to deadmau5’s "Mercedes," I hear the sound of train brakes screeching, and I involuntarily visualize the metal-on-metal grind as my imagined steam locomotive comes to a stop. Then I get dipped in a bass bath that I basically don’t want to leave. The realism of these IEMs is just unrivaled.

The UE18 Pros have a slightly simpler design, using only six balanced armatures per earphone rather than the K10s’ 10 on each side. Despite all that internal complexity, both sets provide a thoroughly coherent presentation of my music, though as I say, I find the Noble Audio is that tiny sliver more articulate and deft in revealing detail. Ultimate Ears does achieve its stated goal of being the best solution for musicians, however, as it has a perfectly balanced frequency response that feels most faithful to the original recording. The UEs are also fantastic in their handling of vocals, and they still carry a hefty bass punch when a song calls for it.

Only open-back headphones like the Utopia can rival custom IEMs

Compared to these custom IEMs, every other portable headphone sounds veiled, as if the sound is seeping through layers of gauze. Other earphones might seem more satisfying at first thanks to their excess bass, but over the long run that can be as fatiguing as excess treble. A bass drop on these premium IEMs sounds truly impactful, punching with the poise and precision of a pro pugilist, without any wasted effort. Sub-bass extension is also sublimely sweet, providing the requisite dynamic contrast to present even challenging music in its truest form.

Only open-back headphones like the Utopia can rival the soundstage of these customs. There's stuff happening on the right side in "Lotus Eater" by Mura Masa that habitually gets congealed into a middle-of-your-head mass of sound on most headphones. The Nobles and UEs present that part of the song in the exact spot where it belongs and with unerring clarity.

So why do people chase custom IEMs? Because they’re the best. But here’s the promising thing about the future: you can buy the 3D-printed version of the K10s for $200 less at $1,450, and Ultimate Ears has the cheapest customs around in its $399 Pro 4 model. As both companies move to use more 3D printing and digital techniques, the time people have to wait to get their custom set is shrinking, and so is the cost.

To get the best sound, I’ve come to find over the past few months, you will always have to pay a premium. I think that’s fair enough, and I like that there’s an actual correlation between how much you spend and how much you get in return. But custom IEMs, as exclusive and luxurious as they are today, have the potential to become a much more mainstream object with the help of better-optimized manufacturing processes. Ultimate Ears tells me that it’s seen a 50 percent drop in returns with its 3D-printed customs relative to the handmade ones. Logically, over the past year, every UE CIEM has been 3D-printed. Once digital scanners live up to their potential, everything can be sped up, automated, and accelerated. Other companies, like Fender, are also jumping aboard the 3D-printing earphone bandwagon.

I recount the tale of custom IEMs today from a knowingly exclusive position. I’m conscious that most of us can’t afford to spend four figures on making our mobile audio experience absolutely batshit crazy awesome, but I’m hopeful that in the near future, we won’t have to.