Description
Universal Fit, Tailored Comfort
Most universal-fit earphones on the market share a standard formula — reusing existing shell designs, combining them with new driver configurations and decorative faceplates, adding foam or silicone eartips and packaging, and they’re ready for sale.
However, the majority of these designs fail to take into account the individual differences in each person’s ear shape, canal angle, or depth.
Even if a listener finds a sound signature they love, a poor fit often forces them to look for another pair of earphones that actually fit their ears.
As a result, generic universal IEMs often suffer from:
– Ear pressure or pain after just one to two hours of wear (“about an hour in my ear holes … begin to hurt” — Reddit /r/inearfidelity)
– Loose seal or shifting shells, some users report that “the edges of the shell become uncomfortable after a few hours” (HiFiGuides Forum)
– Sound leakage leading to bass loss, causing the music to lose body and impact (“a poor seal will result in significant loss of bass response” — Sensaphonics)
Multi-Adaptive Wear Design MAWD™
When designing this new generation of universal in-ear monitors, our goal went beyond achieving perfect sound — we wanted every listener to truly experience and enjoy the sound we created.
Drawing on nearly 30 years of experience and data from crafting custom in-ear monitors, ACS developed the Multi-Adaptive Wear Design (MAWD™) — a system built to solve the long-standing fit issues of universal earphones.
MAWD is based on close to a million ear impressions collected from custom earphones and earplugs.
This data enabled us to create a uniquely contoured shell cavity, paired with a compound-angled sound port that adapts precisely to different ear shapes and canal orientations.
It also includes three interchangeable sound-tube lengths (4.1 / 4.75 / 5.45 mm) and seven sizes of memory-foam and silicone eartips, offering 21 fitting combinations.
MAWD accommodates the vast variety of ear shapes, canal angles, and depths — ensuring a secure, comfortable fit while preserving accurate sound delivery.MAWD also features the “JANUS Dual-Mode Transform System”—allowing you to switch from Universal-Fit to Custom-Fit within 20 seconds.
This allows one earphone to deliver two distinct fit experiences: the everyday convenience of a universal design and the precise seal of a custom fit.
See below for detailed images and the introduction.UNA — The Entry Model of the ACS JANUS Series
UNA embodies minimalist sophistication with its matte black aluminum alloy shell and detachable matte-black faceplates.
It is paired with the ACS Vintage Series cable, featuring four strands of 4N OFC silver-plated Litz wire in a refined braid, and uses a 0.78 mm 2-pin connector for durability and stable signal transmission.LiveSound — Hear the Music, Stay Connected to Life
UNA’s LiveSound acoustic structure originates from stage-monitoring technology, but in daily use it offers remarkable benefits: greater sonic layering, improved safety, and superior comfort — all in one design.
Equipped with a custom 10 mm dynamic driver, an ACS LiveSound filter, and a precision-tuned vented resonance chamber, the system finely controls frequency response through acoustic engineering rather than digital tuning.
LiveSound reduces listening fatigue during long sessions and alleviates the pressure and heat caused by fully sealed designs. Tuned for modern pop music, UNA delivers powerful and responsive bass, smooth vocals, natural instruments, and detailed, airy highs. Compared with the previous EVOKE model, UNA offers a wider and more open soundstage, aligning with the deep, punchy style of today’s music — making it ideal for music, gaming, and movies alike.Five Everyday Advantages of UNA
✅ Open Soundstage, Airy and Relaxed
Greater spatial depth and breathing room than traditional earphones — natural and fatigue-free listening.
✅ Hear Your Surroundings, Stay Safe
Stay aware of traffic or alerts without pausing your music — perfect for outdoor running.
✅ Ambient Awareness, Stay Connected
Easily hear phone calls or people calling your name — ideal for commuting and work.
✅ No Voice Occlusion, No Echo
A patented vented filter design eliminates echo and “blocked-ear” sensation while talking.
✅ Reduced Ear Pressure, All-Day Comfort
Listen through an entire album — or marathon your playlist — without fatigue.
JANUS Dual-Mode Transform System
Can a single pair of earphones offer two distinct listening experiences?
Previously, you had to choose between the convenience of universal eartips and the isolation of custom sleeves.
Now, with the ACS JANUS Dual-Mode Transform System, you can switch UNA from a universal-fit earphone to a tightly sealed custom-fit monitor in just 30 seconds.
4 Key reasons for UNA + JANUS Custom Sleeves:
✅ DualFit Transform – One earphone, two ways to wear: universal or custom
✅ Consistent Sound – Signature tuning preserved across both fits
✅ Immersive Upgrade – Switch from casual listening to closed-back depth
✅ Freedom to Choose – No pressure to go custom on day one—upgrade when you're ready
