64 Audio Duo 2 Universal IEM

Technical Specification

Drivers : Dual Driver - 1 tia High Driver – 1 Dynamic Low Driver
Crossover : Integrated 2-way passive crossover
Input Sensitivity : 98 dB/mW Sensitivity
Frequency Response : 20Hz – 20kHz
Impedance : 9Ω Impedance
Noise Isolation : -12dB isolation apex core technology
Input Connector : Stereo 3.5mm Minijack
Ambient Feature : No
Custom Fit : No
Duo is a two driver hybrid universal in-ear monitor (UIEM). Following Trió and Fourté, Duo is another fully tubeless design in our product range, with the added benefit of being one of the worlds only semi-open back UIEMs. 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.
  • Music
  • TV & Film


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.

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.


  • Rather than constricting the sound of the drivers by fitting a tube onto them, Duo’s complete Tia System reduces unwanted resonance and distortion by allowing the 9mm Dynamic Driver + Tia High Driver to radiate freely into the single large Tia bore with no obstructions to the front of the drivers.
  • Apex Core is 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.
  • 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.

    Black Premium Cable
    0.23 Ohms Total Impedance
    7 x 7 x 4 Multi-Twist
    Silver Plated OCC Copper Wire
    26 AWG
    Terminated in 3.5mm
Whats Included
Duo Universal in-Ear Monitors
64 Audio Premium Leather Case
TrueFidelity Foam Eartips (S,M,L)
SpinFit Silicone Eartips (S,M,L)
Silicone Eartips (S,M,L)
Black Premium Cable
Round Sticker


Looking for other amazing in-ear monitors? Check out 64 Audio A18s Custom IEM & 64 Audio A2e Custom IEM.

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