Introducing Duo


Teased in January 2021

64 Audio’s Duo was a project that was born almost immediately after the release of our three driver tubeless hybrid IEM, Trio.

A two driver UIEM with our full tia system was the plan, during the early R&D phase we discovered that we can go above and beyond with this model and bring a something completely new to the table.

An open-back experience with the intimacy of an in-ear monitor.

Duo Is A Dual Driver Hybrid

64 Audio’s latest UIEM is a dual driver hybrid design. Built with the complete Tia System, Apex Core, Wave Sync, and LID, Duo presents 64 Audio’s signature balanced sound in a whole new way.

The simple audio design captures the listener’s auditory senses while forgetting they’re wearing IEMs in the first place.

The seamless faceplate machining and perforated grill is a departure from traditional IEM aesthetics bearing a welcome resemblance to classic open-back designs.

Duo Wireframe
Apex Core

The constant pursuit of an open, wide, and fatigue free listening experience has led us to develop Apex Core, a deeper understanding of air movement within an earphone system.

Duo’s faceplate features a striking perforated grill that leaves the shell of the IEM open to the outside atmosphere for a less obstructed airflow resulting in an effortless reproduction of music and minimal physical fatigue.


Rather than constricting the sound of the drivers by fitting a tube onto them, Duo’s complete Tia System reduces unwanted resonance and distortion.

Duo accomplishes this by allowing the 9mm Dynamic Driver + Tia High Driver to radiate freely into the single large Tia bore.

Absolutely no obstructions to the front of the drivers!

Wave Sync

Due to the high crossover point between the two drivers, Wave Sync was developed to ensure coherence; another industry first.

By using a type of “all-pass” filter, we’re able to introduce a crossover while correcting for time without having to change the physical distance between the drivers. 

Duo Is An Open-Back Experience


The complex faceplate assembly not only serves an important role in protecting the shell of the IEM while allowing air to flow freely, it is also a major step in 64 Audio’s product design evolution.

Duo is a timeless and elegant design reminiscent of open-back over-ear headphones. 

Sound Signature

Sound Signature

Duo feels light, leaving your ears feeling open and relaxed even for long listening periods. You feel simultaneously connected to your physical surroundings while you’re enveloped by music.

Relaxed tonality lets you put them on and get lost. It’s able to present a non-analytical top-end while retaining air and sizzle.

The vast open air sensation supports an unobstructed soundstage with impactful center imaging (unlike many other open back headphones) as well as no loss of bass.

Duo effortlessly produces deep and rich low frequencies with plenty of sub bass. Find Nio here.

New Premium Cable

Duo Cable

Along with U6t, Duo is also releasing with the same exclusive cable. This new Black Premium Cable offers one of the lowest resistance ratings of any cable available at 0.23 Ohms total impedance.

It’s 7 x 7 x 4 Multi-Twist configuration is made of 26 gauge silver plated OCC Copper wire. Not only is it a superior wire topology, this new thicker cable is softer and more supple which reduces microphonics and makes it less susceptible to tangling.

We also chose to remove the memory wire in the ear loop and replace it with a shrink tubing that comfortably conforms the cable to the back of the ear.

You still get our classic angled 2-pin jacks but the other end of the cable has been replaced with a straight branded 3.5mm jack as well as a metal branded bifurcation.

Duo Unboxing

*Update 11/08/2021* The Black and Pearl versions of this new Premium Cable are now available for purchase on our website. 

The reviews are in:

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