Fosi Audio IM4 iem earphones personal test and presentation
A big thank you to Fosi Audio for sending me their latest surprise, the im4 earphones. It is important to note that the company are not waiting for me to give good reviews presented products. What you are reading is my own honest opinion about the products.
The box nice. Elegant, stylish.
Further open we see this:
Let's look at the usual ”what's in the box” picture:
We immediately see the earphones and a blue box in which we can store them.
Further full unpacking reveals the complete set:
1.IM4
2. Three sets of ear tips for modifying the sound.
3. Plus 2db brass tube/nose attachment also for modifying the sound.
4. 3.5mm to 2pin cable
5. User manual
6. Quick guide
Available in two colors: “Galaxy” (silver) and like mine: “Obsidian” (black)
When you lift the IM4 out of the foam, you can immediately feel that it is indeed metal. The housing is made of aluminum. This is very encouraging because one of my older earphones recently broke. Well, I don’t think this will break even if you step on it. (Let’s not test this ) There is a single driver inside, made of beryllium-coated PU and 10 mm in diameter.
Looking on the rubber holder cards, you can see that they are marked with what kind of sound we can expect from their use. Deep bass. Bass and Balanced are labeled and there are three sizes.
Since the black alu tube is already factory-wound into the body of the im4, I'll start with that. My ears usually need the largest size of eartips, and that's how it is now. Before starting the sound tests, I usually run the new headphones and earphones for 3 days at a slightly above medium volume in a closed foam box so that the sound doesn't get in the way. That's what I did this time too. I started with first "Balanced " rubber, this promise a balanced sound. I listened to it for a day because I thought I was done because it was almost perfect. Then I screwed in the brass tube. I thought I'd see how the mid and high range would rise and clear up. I won't spoil what I heard here yet. But I can tell you that the sound has changed a lot.
I continued by changing the tubes. I changed the musical styles, packing the black and brass tubes back and forth, and I tried all three types of eartips with each one, and even the ones I found at home. There is also a solid foam material, which I really like on other earphones. But here the foam didn't work. The winning combination came from the IM4's own set. More on that when later write about the sound..
Usage:
The IM4 is an open-back headphone, which consequently does not have the isolation advantage of closed headphones, i.e. closed headphones have no, or extremely low sound leakage to the outside and isolate the sounds of the outside world,. The open back of the im4 lets the sound out to the outside world, even if only relatively quietly. You can also hear the louder ones from external noises. None of this happens at a disturbing level, but those who like to be completely isolated from the outside world cannot do so with these headphones. However, it also has a very good feature precisely because of this openness. The sound field is much wider, larger and airier than closed headphones. This “something for something”
When I took it out of the box and felt that the housing of the IM4 was aluminum, I was happy that it was very solid and strong, but I was also a little worried that it would be cold to the touch in my ears. There is a minimal feeling of cold in any case, but it warms up quickly. I don’t know how this will change when used outdoors in the real winter cold, but now it is very comfortable to wear. The large rubber plug doesn’t press on my ears either. I can listen comfortably and enjoyably for hours. The only strange thing I experienced was that when using the gr70 tube amplifier, I heard a slight noise and the tubes produced a microphone sound at full volume even without connecting to an external input. I haven’t experienced this with any other amplifier, nor did any other earphones make noise at the gr70 output. There was no noise when listen music on phone either. In my opinion, it may be due to the high sensitivity of the IM4. This is just a guess. Since I didn't know the manufacturer from their in-ear and headphones, I was really surprised by the i5 planar and now this iem earphone. They are very, very good!
Let's look at the cable:
We get a 4-strand, 392-core, 5N high-purity, silver-plated braided OFC wire with good quality and color matching silver or black. The cable is not prone to twisting/tangling at all. 2 pins so we can update it at any time depending on our taste and budget. Despite its relative thickness, it is sufficiently soft. The quality of the connectors is impeccable and the material is also metal. The connections are stable. It is easy to assemble out of the box. The tubes are threaded, insulated with rubber rings. These are also easy to replace. Due to the use of materials and the high manufacturing quality (cnc machining for the metal housing and the general good use of materials for all elements), we can count on a long lifespan. Moreover, I did not experience any distortion or unpleasant sound even when listening at very high volumes. So the driver will probably last.
Sound quality:
Immediately audible spacious wide sound field. Loose, light airy and punchy! I varied the included rugger plugs and tubes/noses a lot, listening to many styles. For me, the extra mid and high sound given by the copper tube is too much. Obviously this is a matter of hearing and taste, but with copper my ears reached the level of unpleasant feeling that makes the music shouty after a few minutes and makes me stop listening. In any case, anyone who needs even more clarity and extra mid and high sound will get it with the copper tube, because the change in character is very audible. I also changed the rubber fittings, but in every style I returned to the black aluminum tube and the deep bass fitting. For me, this brought that pleasantly balanced soft and full sound that I listen to for hours with pleasure. This combination winner for me, in every style I listened to. Calm, slightly warm sound. Very clean with very deep bass (using with the deep bass earplug) With sounds rich in bass, e.g. deep house music, we get incredible bass without distortion. Very good detailed mids and highs. The performance is light, loose and airy. The instrument sounds are quite believable despite the small driver. The vocals are very good for both male and female voices, clean and detailed. The placement and body of the instruments is good. Although not as precise as with larger headphones or the much more expensive iem and earphones. But it is very good in its price category! It sets the bar high in terms of price value. Let's add that this is the very first iem device from the company. Still, they managed to make a solid device with good sound and can be listened to for a long time. Absolutely recommended!
Summary: I managed to get to know a very well-built, lightweight and very good-sounding eardphone. I got a pleasant, clear and dynamic sound. With a sufficiently large soundstage and good details. If it is not necessary for it to stand up in noisy places and be completely isolated both in terms of external noise and music filtering out, then with its openness we gain more space and airy sound. I would like to note once again that the listening sound does not full volume come out. But it is audible. I'll be curious to see how the metal house will feel outside in winter cold on my ears., but I will have to wait until it is cold enough outside and try it.
Pros: High-quality construction and use of materials
Very good sound and very good detail, good dynamics.
No distortion even at high volumes
Comfortable even with prolonged listening.
Many accessories for modifying the sound.
Good cable, with good connectors.
Good Price/Value
Storage Box
Cons: Some amplifiers may have background noise due to high sensitivity.
