The IM4 are one of my favorite day-to-day IEMs to wear because they are so comfortable! The semi-custom shell that is all metal sits really solidly in my ears without rubbing up awkwardly against me in any way. Despite being metal, it also isn't heavy, so the weight never bothers me like some other metal IEMs. The sound is laid back, and at least to my ear, I do hear any sharp or shrill parts to the music.
It was an interesting semi-open back vent design, so a little more sound does leak out, but unless you are somewhere completely quiet, I doubt anyone else will hear much of whatever you are listening to.

Everything from the unpacking experience to the sound quality is top notch. Well done Fosi 👍

Som equilibrado e limpo. Simplesmente fantásticos. Muito confortáveis, mesmo para orelhas pequenas. A quantidade e qualidade dos acessórios é excelente. Nada a apontar como pontos negativos.

Muy buenos iems openback, sin duda son los mejores iems por debajo de los 100 dolares

Best monitors i ever used

I was impressed not only by the cleanliness of the sound relative to the price range, but above all by their versatility in daily use and by the ability to “shape” the sonic character according to personal taste thanks to the included accessories. The kit not only ensures comfort through ergonomically designed ear tips tailored to the shape of the ear, but also allows you to refine the sound by adding warmth and depth through two interchangeable nozzle types.
After several hours of listening, what emerges most clearly is how effortlessly the IM4 let themselves be listened to, without ever becoming intrusive. The sensation is that of a sound that breathes—never pushing artificially in a specific direction, but unfolding with a natural sense of ease. The open‑leaning tuning contributes as well: the soundstage does not remain confined inside the head but extends convincingly, giving instruments room to breathe and making the experience more relaxed, especially with well‑recorded material.
In my view, considering the price, it is difficult to find the same combination of transparency, micro‑detail, and tonal coherence within this segment.

These IEMs were my first, when dipping my toes into this massive rabbithole of a hobby. I have definitely heard a difference compared to my wireless earbuds from Jabra. The amount of detail that can be heard and the precision took me by surprise. I am happy with the IM4 and certainly recommend them for the price to performance. 10/10 Fosi!

IEMs made for long listening sessions, and they really don’t fatigue you like closed-back IEMs can. I love the accessories provided and have come to realize how these little things affect the sound; Fosi really encourages you to tweak them. I compared them with the TRI i3, which is good, but harshness comes in during long listening sessions.

Excelente sonido para ser el primer iem, lo probé en el fosi DS3 y suena muy detallado con una escena sonora muy grande y con el questyle m15c lo hace mas musical sin perder detalles, lo probé por la salida 3.5m suena bien pero al conectar a 4.4m el sonido escaló y suena con mas autoridad así que lo recomiendo.

I got these via Kickstarter, a while ago. With the standard package I also got an additional cable with a mic and a USB to 3.5mm adapter cable.
The IM4s came in a very nice looking box, very safely packaged.
Not sure if the included case is true leather or not, but it's quality is great, and it can fit all the included ear tips, the nozzle, and the adapter cable.
It can also fit with a bit of care, the new DS3 DAC, along with the previous items.
The build quality is grate, and the earphones are very comfortable and stable.
The audio quality is fantastic, and the different types of ear tips do actually make a difference and so does the nozzle.
I tried the different combinations of tips & nozzle, ended up using the aluminium nozzle & balanced tips.
Of course, being "open" means that there is little isolation from outside noise. At the same time though, I believe this makes it much easier to use for long periods of time, and personally living on a big city, I do prefer being able to hear what is going on around me.
One thing to note, for people that want to use them as a handsfree set, is that the standard cable does not have a mic on it, so you will need to get another cable.
I have used both cables, I did not notice any difference on audio quality between them.
Overall, a great pair of earphones, well worth the money.

Today 26/12/2025 was my first listening with the open backed in ear monitors and DAC.
I bought these to use with my smartphone, music sourced from my library and Spotify.
Initially I was a little disappointed, the base wasn’t as deep as I wanted, but the clarity and openness were really good.
After trying several different buds the sound had improved significantly.
I’m really pleased with the purchase price and excellent sound quality.

Excellent IEMs brass nozzles with the extra bass tips is the perfect combo powering them with the k7 3.5 cable with mic is great. nice crisp mic used for gaming and when I'm out and about. 4.4 balanced cable for music

Great quality IEM. Very comfortable to wear over long periods of time. The sound quality is fantastic and adjusted with the different nozzle and tips provided. Whether listening to music or playing games, the experience is definitely far better with the IM4s. Very happy with these!

I wanted to try this when I saw open back IEM which is not very common. To my surprise it sounds really great too for the price. Packaging and accessories also great for under $100 category. Though one nitpick would be a modular termination could have been fantastic. I’m using it with my upgrade 4.4mm balanced cable currently. Thanks Fosi Audio

My first pair of IEM and I’m in love. I have full size open back planers and high end closed back. I have been using AirPods when I work the office. Love Fosi products so thought I’d give these a try. Thought I’d step up my office audio game - and wow, did I ever.

I’m already rocking ZP3 preamp and two V3 mono block amps for my vinyl set up (don’t get me started on how fantastic these are) so was already a Fosi fan boy. Once again. I was blown away.

As seems to be the norm…Fosi continues their modus operandi of exceeding all expectations. I need to stop saying “for the money these are fantastic!” when talking about my Fosi purchases. There is no need to qualify my enthusiasm. Fosi audio and specifically the IM4’s are fantastic…regardless of price point.

These are incredible…killer sound and top shelf build. They scream quality. Oh…and they look sexy. Crazy nice. Everyone asks about them. I chose the traditional Fosi black and orange and damn, they look good. top shelf and the fit is very very comfy. So…all good…but how do they sound? Well…is sublime being dramatic? I know I said I need to stop doing this but im back to the cost. How can such great sound cost so little?

I have my IM4s paired with an Onix Alpha Xi1 dongle DAC and purchased the Fosi the 4.4 mm cable (which is also an amazing high quality cable that blew me away) so I can use the balanced connection. The sound is incredible. Beautiful and warm. Bass extension is remarkable. It’s punchy in the mid bass with great texture. Sub bass is quick and tight. No muddiness. Vocals are clean, and neutral sounding. Treble is smooth and controlled.

Where these open back IM4s really shine is with their soundstage which is wide open and airy. Almost holographic. It’s beautiful and is uncommon for IEMs in this price range.

These are amazing IEMs and at this price; they’re a no brainer. The IM4s truly punch well above their price point.

It comes with a USB C DAC, and the quality is excellent. The open-back design provides good resonance, and external noise doesn't get in, so it's best to listen in a quiet place.

Thanks for the overall excellent manufacturing quality.

Fosi Audio IM4 are truly seamless and harmonious dynamic headphones that you enjoy listening to from start to finish. They don't try to impress with sharpness or excessive analysis, but simply deliver music as you want to hear it—live, rich, and comfortable. And I think that within this budget they will be an excellent choice for those who love warm, engaging, and musical delivery that you want to immerse yourself in again and again!

I'm happy it fits my ear perfectly without any pain on the the outer ear above the earlobe. The sound is clear and actually made me lower the volume on my pc because it was so loud which nice. It's also made me aware of what sound I was missing out on

Fosi Audio IM4 Open‑Back Wired Earbuds – All‑Day Comfort for Work, Commute, or Home

Shipping experience was horrid but the headphones are so far great. I ordered them on july 8th and the last update on the fedex website was on the 14th. Delivery was scheduled for the 17th but it arrived on the 22nd with zero updates whatsoever.