64 Audio A4S Custom In-ear Monitors

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64 Audio is proud to introduce our newest four driver custom in-ear monitor, A4s. This complete redesign of our four driver platform is elevated by the Dynamic low frequency driver, making this 64 Audio’s second hybrid custom IEM. Along with that major update, inside A4s is our Tia technology, LID and our patented Apex and 3Dfit tech. While this is targeted at musicians looking for a rich enveloping monitoring experience, the frequency response, detail, and soundstage capabilities of A4s exceed other audiophile products at almost any price point.


Exclusive technologies that challenge traditional in-ear monitor designs to give you the absolute best listening experience

A4s features the following unique technology:

A tubeless design that reduces resonance for a transparent and lifelike sound signature.

This pneumatically interactive vent relieves air pressure in a sealed ear canal, alleviating listener fatigue and opening the soundstage.

LID is a correctional circuit that presents a flat impedance to the amplifier, resulting in a sound devoid of artificial coloration.

A new way of manufacturing custom in-ear monitors preserves the details of your ear impressions for the most comfortable-fitting IEMs possible.


Transducer Type

Dynamic & Balanced Armature

Transducer Configuration

1 dynamic low, 1 BA low-mid, 1 BA high-mid, 1 tia highText

Bore Configuration


Frequency Response

10Hz – 20kHz


107 dB/mW (94mV) @ 1kHz


11Ω @ 1kHz


Integrated 4-way passive crossover


20dB w/ m20 module, -15dB w/ m15 module.

Ships with M20 Module standard


  • A4s Custom In-Ear Monitors
  • 64 Audio Personalized Protective Case
  • Dehumidifier
  • Cleaning Tool
  • Shirt Clip
  • 48" or 64" Detachable Professional Cable
  • m20 apex Modules
  • Round Sticker
  • Product Manual