The Fosi Audio IM4 is a wired open-back dynamic IEM, an unusual pairing in a category dominated by sealed shells. It trades isolation for a more relaxed, less pressurized presentation, making it a home and desk listener's change of pace from sealed daily drivers rather than a commuting set.
Who the Fosi Audio IM4 is for
Home and desk listening: In a quiet room the missing isolation costs nothing, and the open-back shell gives a more relaxed, less pressurized sound.
Owners of sealed IEMs: It works as a change of pace next to your sealed daily drivers rather than a replacement for them.
Dongle and desktop amp users: Being wired, it runs from the dongle DAC or desktop amp you already have.
Skip it if: you need isolation for a noisy commute; the open-back design gives it up.
Fosi Audio IM4 key specs
Driver type: dynamic
Design: open-back shell
Connection: wired
Colors: Gray, Black
Genuine Fosi Audio stock. Free shipping on every order and 45-day returns.
Fosi Audio IM4 vs similar options
vs TANCHJIM NORA: Also a dynamic-driver IEM, using TANCHJIM's DMT5 unit, and it ships with interchangeable 3.5 mm and 4.4 mm plugs; the IM4's draw is its open-back shell.
vs SIMGOT EA500 LM: SIMGOT's EA500 LM uses a 10 mm 2nd-gen DMDC dynamic driver with a lithium-magnesium dome and three interchangeable tuning nozzles; pick it to tweak tuning, the IM4 for a relaxed open-back presentation.
vs EPZ K5: A 1 dynamic + 4 balanced armature hybrid aimed at critical listening; the IM4 sticks to dynamic drivers in an open-back shell for a relaxed home presentation.
Yes. Every unit we sell is genuine and brand-new, shipped in its original packaging, and backed by our 1-year TonePier warranty and 45-day returns.
Where does my order ship from, and how long does it take?
Every order ships from our warehouse in China, with full tracking, and most orders ship within 3 business days. Shipping is free on every order; most US orders arrive within 7–15 business days and most orders to other countries within 7–20 business days — see our shipping policy for details.
What if it isn't for me?
You get 45 days to decide. Keep the packaging, keep it in like-new condition, and send it back for a refund. Ear tips unsealed for hygiene reasons are fine — we expect you to actually listen.
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