Custom IEM Model Overview 

64 Audio makes nine custom in-ear monitor (CIEM) models ranging from 2-18 drivers per side which cost between $499-$2,999. Our goal with the whole product range is to offer the best possible sounding monitor at each price point. Regardless of driver-count we aim to get the most out of components for balanced, accurate and musical IEMs. All of our models reflect that signature sound, and with the increase of drivers and cost you get increased fidelity/resolution.

For more IEM info take a look at our Educational Series.

64 Audio A18t custom in-ears on amplifier

A18t Story

The A18t Custom In-Ear Monitor is one of our 18-driver custom fit IEMs, the other being A18s. 64 Audio began pushing the driver-count envelope back in 2014 with the unveiling of our 10 and 12 driver IEMs, A10 and A12. A18t was developed alongside Fourté; one of our universal fitting audiophile IEMs. Fourté and A18t/U18t were released simultaneously to end the so-called “Driver Wars” which describes that era of IEM design. Being able to produce such an incredibly resolving and detailed monitor using 18-drivers while simultaneously offering a similar and unique experience at just four drivers settled the debate.

A18t’s driver count is an integral part of its inception, this was not an arbitrary number we were hoping to reach. One of the most impressive traits A18t has is it’s quick, extremely accurate, yet deep bass. We chose to use modified mid-drivers because of that unique characteristic. This required coupling 8 drivers, in the driver pack responsible for lows, in order to achieve the desired amplitude. Filling out the mid frequency band required another 8-mid drivers.

Because of Fourté’s parallel development, featuring a fully tubeless design, we were able to integrate a couple crucial components in A18t. The proprietary new tia driver was placed in the canal of the custom A18t and the bore redesigned to a large single opening to accommodate it. The single-bore design contrasts the cumbersome multi-bore designs prevalent in most CIEM designs, making it easier to clean and maintain. This direct-radiating driver coupled with it’s un-obstructed placement results in an incredibly smooth and extended high-frequency response. The balanced nature of the HF response allows us to increase the amplitude of the highs without amplifying any narrow fatiguing bands of frequencies.

With A18t you can get the same level of detail, maybe more, as the world’s best mastering monitors within a pocket-sized package at one hundredth the cost. To our surprise, despite its critically flat nature, A18t was quickly adopted by large scale touring professionals and became a staple among live performers. Its popularity in that sphere led us to building A18s on the same platform to eventually address some of the rigorous needs of live performance monitoring.

Eventually the tech developed for A18t trickled down into all of our custom IEM models. The success among audiophiles and audio engineers also led to the development of A12t and A18s, both offering unique reference monitor flavors.

64 Audio A18t custom in-ears on dark foam

Flat Sound

In-ear monitor tuning presents a unique set of challenges that don’t exist in traditional speaker design. The main issue is space. While a speakers can be tested in an anechoic chamber and results can be replicated precisely, a human ear cannot be perfectly modeled and results cannot be replicated across test subjects. While there are testing standards in earphone/headphone design, a lot of our development relies on listening tests. Getting diverse opinions and finding a balance between those opinions is the closest we can get to a bunch of people listening to a speaker in a room together.

Once the issue of space is addressed the shape of the human ear has to be contended with. The audio world has had a pretty good idea of sound preferences in speaker design because of research dating back to the mid 80s. Because headphones isolate the ears and earphones isolate the ear canal, your physical interaction with sound is vastly different than if you were to listen to a speaker. In 2013 researchers at Harman finally presented the audio world with a new “flat” measurement curve that compensates for headphone and earphone placement. While IEM testing is still imperfect in many ways, this gives us a target to compare to based on extensive preference research.

Using state of the art measurement tools, the latest acoustics research, and diverse listening tests A18t is made to be as flat sounding as possible. Just as there are many brands and models of studio monitors, there is still the aspect of preference that should be considered. While we have three reference models to choose from, you also have a suite of apex modules that offer varying degrees of isolation, pressure relief, and low frequency attenuation to help find that sweet spot of accuracy and musicality.


The clarity at low volume is what hooked me about these in-ears for studio use. They’ve become another set of trusted monitors!

Tony Esterly (Writer/Producer/Mixer)

Mixing at the In-Laws couldn’t happen without these In-Ears.

Warren David (Mixer, Engineer, Producer)

I couldn’t imagine working outside of the studio without these.

Steve Vealey (Mixing Engineer)

I need to have a true representation of what I’m hearing at all times… and be very comfortable hearing the entire frequency range top to bottom. Highly recommend them because I just haven’t heard anything like it in the market.

Joe LaPorta (Senior Mastering Engineer at Sterling Sound)

I’m loving having my A18t IEMs for studio work. Absolutely a life-saver having the IEMs and knowing how things should sound on them while needing to adapt to workflow! I’m sure you’re hearing the same from other studio people.

Brandon Bost (Mixer, Producer)

Sounds just really tight, balanced, punchy, clear. More importantly I can work with confidence now, already handed in several jobs 100% v1 approved 🙂

MarcoAntonio Spaventi (Mastering Engineer, Producer)

My A18t are the best headphones / IEMs I’ve ever used, they’re the only thing I trust other than my big PMCs.  It removes the stress when I’m traveling because I can monitor anywhere with total confidence in what I’m hearing.

Nathan Dantzler (Mastering Engineer at The Hit Lab)

Still absolutely loving them… I’m definitely a convert.

Christian Paschall (Record Mixer, Touring Drummer for Maren Morris)

These DESTROY. I pretty much monitor, produce, and mix with these now.

Daniel James (Producer at Dreamlab)

I love the fidelity, I love how accurate they are. It really feels like I’m listening to the record that we made.

John Shanks (Producer, Guitar Player for Bon Jovi)

The 18t’s are possibly the most important piece of gear I own. Being able to make confident decisions on a mix or inside of a production wherever I am! Its invaluable. 

John Rausch (Mixer, Producer, Engineer)

Custom-Fit, Custom-Look, & Custom-Made

Each 64 Audio CIEM is hand built in Vancouver Washington by highly specialized technicians.

Ear impressions are first trimmed and scanned into our 3D detailing software. Our patented 3Dfit technology is used to perfectly recreate the intricacies of your ear shape. We virtually accommodate for all of the internal components before 3D printing with hypoallergenic acrylic material.

Once the shell is printed our assemblers insert the pre-soldered driver packs associated with the model of the IEM.

hands assembling 64 Audio custom in-ears under microscope

The assembled CIEMs are later completed with a faceplate. Along with the 5 shell options, there are dozens of faceplate colors and materials which translates to hundreds of variations. On top of all of those options we’re also able to use custom artwork to make your IEMs truly one-of-a-kind.

earphones aligned on a white background to form a 64 Audio logo

A18t Specs

  • Transducer Type/Count: 18 BA
  • Transducer Configuration: 1 tia high, 1 high-mid, 8 mid, 8 low
  • Bore Configuration: Single
  • Freq. Response: 10Hz – 20kHz
  • Sensitivity: 111 dB/mW @ 1kHz
  • Impedance: 9Ω @ 1kHz
  • Crossover: Integrated 4-way passive crossover
  • Isolation: -20dB w/ m20 module, -15dB w/ m15 module

A18t Technology

Air Pressure Exchange (Apex) is a patented vent that releases air pressure in a sealed ear canal. In addition to relieving air pressure, it also maintains standard IEM levels of noise isolation. The attenuation of ambient noise and pressure relief enables musicians and music enthusiasts to listen more comfortably for longer. This venting alleviates listener fatigue and allows for a much more realistic soundstage. Apex comes in three module variations available for A18t: mX, m15 and m20.

Tubeless In-Ear Audio (tia) is a patented IEM design methodology that aims to reduce unwanted resonance and distortion for a transparent and lifelike sound signature. The tia system is comprised of three major elements: open balanced armature tia drivers, the tia single-bore design, and tia acoustic chambers. A18t features two major elements of the tia system: the tia driver and the tia single-bore design.

3D-Fit preserves the detail of your ear impressions using a new process of digital rendering and 3D-printing. The patented process of incorporating acoustical tuning features within an IEM’s shell allows for designs that would otherwise be impossible to build using traditional methods. We incorporate these advanced and uniquely complex features into the shell in order to manipulate the audio produced by the IEM. This process also reduces distortion in the impression for the most precise and comfortable custom in-ear monitors available.