Fosi Audio Debuts IM4 In-Ear Monitors

Only days after announcing the ZH3 desktop DAC/amp aimed at making hi-fi separates more accessible, Fosi is now turning its attention to the portable market. The IM4 represents the brand’s first step into the in-ear monitor category, underscoring its strategy to offer budget-conscious listeners genuine hi-fi performance across multiple listening formats.

Ryan Huang, Founder and CEO of Fosi Audio, described the IM4 as:  

a milestone in our journey of earphone development, our first step in this category made with sincerity and care. With its natural, open sound and lightweight comfort, the IM4 is ideal for everyday listening, whether you are unwinding at home or discovering detail on the go.

At the heart of the design is a 10mm beryllium-coated diaphragm driver, working in conjunction with an N52 dual-magnet system and a dual-chamber acoustic housing. The open-back construction significantly broadens the soundstage, extending it well beyond the typical range of in-ear monitors. This produces a presentation more akin to that of full-size headphones, while remaining lightweight and portable. Each earpiece tips the scales at only 7 grams and is machined from aluminium, with an ergonomic, breathable fit designed to support extended listening sessions.

Fosi has also built in flexibility to cater to different tastes. The IM4 ships with three sets of ear tips — balanced, bass, and deep bass — while interchangeable aluminium and brass nozzles allow users to fine-tune the tonal balance, from smoother highs to more energetic treble and low-end weight. Detachable cables are supplied in both 3.5mm and 4.4mm terminations, offering broad device compatibility.

The IM4 is available starting September 30, 2025, in black and silver finishes, priced at US $99. Additional regional pricing for the UK and Europe will be confirmed shortly.

For more information visit Fosi Audio