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 A12t Custom In-Ears

A12t Story

64 Audio’s A12t is a twelve driver CIEM that builds on the success of its predecessor A12. While the previous iteration of our 12-driver platform was arguably the highest driver count CIEM of its time and became extensively used in the large venue touring industry, the current offering is leagues ahead.

A12t was developed after the successful integration of of our tia™ technology into the custom A18t. In typical 64 Audio fashion, we eventually make the technological innovations of our highest end products available throughout our product range. Our 12 driver CIEM was redesigned from the ground up using 2/3 tia™ pillars, the direct radiating balanced armature driver (tia™ high driver) and the single bore design. Not only did A12t adapt the tia technology from our higher end models, but it was also was designed similarly as a four-way system, as opposed to A12 being a 3-way system. The whole frequency spectrum is now crossed over three times, so separate driver packs were responsible for lows, low-mids, high-mids, and highs. This design methodology became standard throughout the rest of our product range, and now every IEM that has four or more drivers is a four-way system.

A12t didn’t just inherit technology from other innovative models; it introduced the world to our LID™ technology. A12t, U12t, and Trio all released together and came with a solution to a real-world problem that has plagued audio systems for a long time.

LID Technology

Something that is really common among CIEMs is the effect that source and cables have on their sound. This is due to a non-linear impedance curve, which is especially true for balanced armature drivers (BAs) and CIEMs that have combinations of multiple BAs. Electrical impedance refers to the effective resistance of an electric component to current, represented in ohms (Ω). If you have one frequency band with a certain amount of resistance and another band with a different amount of electrical resistance, you’ll find that the current from the source will not be evenly distributed among these bands.

To achieve the intended frequency response from any CIEM you would need to ensure that the total impedance of your signal chain matches that of the manufacturer when originally designed. This can be quite difficult to achieve outside of the R&D departments of these manufacturers who use state of the art equipment.

For example A18t was designed with a headphone amp that introduces less than .075Ω. To achieve the intended frequency response of A18t you’d need to use either the supplied cable or a cable with less than .5Ω and drive them with a headphone amplifier with less than .5Ω. We’re using A18t as a great example because this is our only CIEM built without LID. The sound altering effects that increased resistance has on non-linear impedance CIEMs depends on the shape of the impedance curve; the impedance disparity between frequency bands.

In the real world a non-linear impedance manifests itself in differing frequency responses across devices. You could listen to a track through a wireless IEM pack one day, then listen to that same track on your laptop, phone, or through a quality sound-card and the track could sound different on all of those devices if the output impedance of the headphone amplifier differs in all of those devices. We developed a groundbreaking technology called LID to solve this problem. LID stands for Linear Impedance Design, and a few years after its release we received a patent for it.

LID has proven so effective that we’ve built it into every product release since 2017, following our trend of democratizing our technology within our product range.

A12t Sound

This is one of our three CIEM models that finds itself in use by mixing engineers both live and in the studio, the others being A18t and A18s. It differs from A18t in its softer presentation of a mix. You can think of them similar to how our customer base has naturally segmented between these two. A12t leans more in the direction of a mixing engineer’s monitor while A18t leans more towards mastering.

A12t is balanced, accurate and extremely musical. What do we mean by musical? It’s our best way of articulating an IEM’s ability to present a mix in an engaging yet non-distracting way; getting enveloped into a song or performance while trusting that what you’re hearing is correct.

Lows are punchy, more than enough headroom to satisfy drummers and bass players. The low-end has enough amplitude to spare in case you want to use A12t with one of the other apex™ modules that will slightly reduce it.

Low-mids present just enough “body” without tipping the sound into being “warm,” unlike A18s which is on the slightly warmer end in this regard.

Mids and high-mids are articulate without being too detailed, this is where A12t and A18t differ the most. Highs are beautifully extended and airy because of the tia™ driver that resides in the very tip of the canal.

The sound-stage, which is the perceived width of the stereo field, is in-line with the rest of our reference-grade IEMs. Apex™ and tia™ both contribute to our IEMs’ impressively wide imaging compared to other IEMs and headphones. This distinctive feature surrounds the listener more naturally and improves instrument separation when monitoring live; like your pan nobs are able to rotate further to the left and right.

A12t has also dictated the sonic direction of some of our other models like A6t, A3t, and A3e. Although you’d see a significant reduction in fidelity and instrument separation, they follow a very similar frequency response pattern.


The A12t IEMs are incredibly well balanced, with excellent bass representation, and an ideal solution for those who are concerned about portability.

Ryan McCambridge (Sound on Sound contributor, freelance engineer, producer and sound designer)

The sound across the spectrum (frequency response spec’d at 10 Hz to 20 kHz) is spacious, smooth, and not strident. When a mix is right, I can hear every single detail with the A12t, and all sounds are three-dimensional to my ears. There are elements in songs that I’ve heard all of my life that I was totally unaware of until I tried these IEMs.

Lars Fox (Grammy nominated music editor)

I love the A12t

Michael Brauer (Grammy winning mixing engineer)

Thanks again for the 12T’s.  I absolutely love them.

David Bottrill (Grammy winning record producer)

Gotta say, these are blowing me away. Thanks so much foe making it happen…. The only problem I’ve had is that when I started listening to a record I’m in the middle of, I was hearing all this stuff I had missed…. very humbling. Should have done this a long time ago!

Justin Niebank (Grammy winning mixing engineer)

For me, I really dig them. I did some mixing with them…and I think they are outrageously good.

Billy Bush (Grammy nominated record producer)

Joel, Luke (for KING & COUNTRY) and I were able to stand on common ground sonically checking mixes for this last record (burn the ships) while all being in different parts of the world.  The 12t in ears made that possible.

Tedd Tjornhom (Grammy winning record producer)

Duuuude, they are amazing. The molded units really improve the bass response and imaging. I mastered several songs in them this week without ever checking on our PMC speakers and all were approved with no notes. 

Alex Dobbert (Mastering Engineer)

I have had reason to finish some mixes just on my a12t’s with no access to my normal monitors. I felt really good about the mixes, and became unaware that I was wearing inears, just in the flow of mixing. Hearing everything I needed to hear.

Ainslie Grosser (Grammy winning mixing 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

A12t Specs

  • Transducer Type/Count: Twelve precision balanced armature drivers
  • Transducer Configuration: 1 tia high, 1 high-mid, 6 mid, 4 low
  • Bore Configuration: Single
  • Freq. Response: 10Hz – 20kHz
  • Sensitivity: 108 dB/mW
  • Impedance: 12.6 +1/-2 Ω from 10Hz – 20kHz
  • Crossover: Integrated 4-way passive crossover
  • Isolation: -20dB w/ m20 module, -15dB w/ m15 module

A12t Technology

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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 A12t: mX, m15 and m20.

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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. A12t features two major elements of the tia system: the tia driver and the tia single-bore design.

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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.

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Linear Impedance Design (LID) is a patented circuit that corrects the non-linear electrical resistance of the multiple driver-sets comprising this nine driver IEM. Varying source amplifier output impedance in devices like smartphones, body packs, DAC/amps, and DAPs typically results in varying frequency response across them, depending on the increase in resistance. Restoring proper interaction with the source and preserving the desired sound signature enables a consistent reliable sound.