Massimo
Member
As already described in other reviews of mine, I am a music enthusiast. I do not chase detail at all costs, but I attach great importance to sound quality without going to extremes. I am not interested in the obsessive search for micro‑details, often imperceptible, and this is why I do not consider it necessary to invest exorbitant amounts of money to obtain a satisfying listening experience. However, I expect coherent, balanced sound reproduction that is faithful to the original recording.
What follows represents the result of my impressions after receiving and testing the Fosi Audio IM4 during dedicated listening sessions.
I must say that I was impressed not only by the cleanliness of the sound that emerges considering the price range, but above all by their versatility in daily use and by the possibility of “shaping” the sound character according to one’s tastes thanks to the included accessories.
As is my habit, I leave aside the description of the technical features, which are detailed by the manufacturer on its official website
https://fosiaudio.com/products/fosi-audio-im4 and I immediately move on to describing my audio impressions, wearing the earphones carefully and using their included accessories.
The earphones come in an essential yet professional‑looking package, inside which you find the earphones made of precisely machined aluminum, lightweight but structurally solid, with beautiful and light aluminum that is very pleasant to the touch, along with a complete set of accessories including an excellent replaceable cable, a comfortable and functional carrying case, and three sets of ear tips in various sizes that not only ensure comfort according to the ergonomics of your ear canal but also refine the sound.
In fact, one set is oriented toward obtaining a “balanced” sound, one toward emphasizing the “bass,” and one dedicated to “deep bass,” with perceptible variations.
What follows represents the result of my impressions after receiving and testing the Fosi Audio IM4 during dedicated listening sessions.
I must say that I was impressed not only by the cleanliness of the sound that emerges considering the price range, but above all by their versatility in daily use and by the possibility of “shaping” the sound character according to one’s tastes thanks to the included accessories.
As is my habit, I leave aside the description of the technical features, which are detailed by the manufacturer on its official website
https://fosiaudio.com/products/fosi-audio-im4 and I immediately move on to describing my audio impressions, wearing the earphones carefully and using their included accessories.
The earphones come in an essential yet professional‑looking package, inside which you find the earphones made of precisely machined aluminum, lightweight but structurally solid, with beautiful and light aluminum that is very pleasant to the touch, along with a complete set of accessories including an excellent replaceable cable, a comfortable and functional carrying case, and three sets of ear tips in various sizes that not only ensure comfort according to the ergonomics of your ear canal but also refine the sound.
In fact, one set is oriented toward obtaining a “balanced” sound, one toward emphasizing the “bass,” and one dedicated to “deep bass,” with perceptible variations.
The package also includes two pairs of interchangeable metal nozzles, one in aluminum and one in brass, equipped with acoustically transparent protective meshes.
The aluminum nozzle introduces a slight increase in the low range, giving more warmth and roundness to the timbre; the brass one, instead, presents a more linear response, highlighting mids and highs.
It may seem like a marginal detail, but the ability to easily replace the nozzles solves one of the most annoying problems found in other earphones: the loss or deterioration of the internal mesh. This is exactly what happened to me with other, despite a rather limited use over the course of a year, and considering their cost, it was not pleasant.
The cable is replaceable and uses detachable connectors, a solution that allows for easy upgrades or replacements without affecting the integrity of the IEMs. This design choice ensures greater durability and makes it possible to adapt the earphones to different setups depending on listening needs
The cable is replaceable and uses detachable connectors, a solution that allows for easy upgrades or replacements without affecting the integrity of the IEMs. This design choice ensures greater durability and makes it possible to adapt the earphones to different setups depending on listening needs
For the evaluation of the Fosi Audio IM4, I carried out dedicated listening sessions, including a direct comparison with my professional Ultimate Ears earphones. I also checked the behavior of the IM4 against consumer models not directly comparable in design philosophy, such as the Beats Studio Buds+ and the Samsung Buds+, to better contextualize the overall performance.
I did not include mid‑range earphones, as during testing they could not hold up to the comparison and were therefore set aside immediately.
I immediately set aside the Bluetooth models as well, since despite their higher price they were not comparable in terms of quality.
After several hours of use, what emerges most clearly is the way the IM4 can be listened to without ever becoming intrusive. The sensation is that of a sound that breathes, that never pushes artificially in a precise direction but develops with a certain spontaneity. The open tuning plays its part: the soundstage does not remain confined inside the head but extends in a credible way, giving space to the instruments and making the listening experience more relaxed, especially with well‑produced recordings.
Naturally, and this is very important, you must pay attention to choosing the correct size of ear tips based on the ergonomics of your ear canal; otherwise, for example, if you choose small balanced tips that do not fit well with a brass nozzle, you risk perceiving an excessive presence of mids and highs, with a consequent loss of body in the low frequencies and an overall imbalance in the sound.
Naturally, and this is very important, you must pay attention to choosing the correct size of ear tips based on the ergonomics of your ear canal; otherwise, for example, if you choose small balanced tips that do not fit well with a brass nozzle, you risk perceiving an excessive presence of mids and highs, with a consequent loss of body in the low frequencies and an overall imbalance in the sound.
I tried listening with some tracks chosen by me for their characteristics, but this is purely a matter of personal taste:
With Hotel Lalo by Harry Edvino, the behavior of the IM4 in the bass range is immediately clear. The bass line is present from beginning to end and always remains firm, without smearing. There is no “bloated” or unnecessarily boosted bass.
Following the track over time, the bass never gets lost even when other elements enter. It remains readable, with distinguishable notes and a natural decay, without annoying tails. This greatly helps maintain the groove and gives solidity to the arrangement without taking space away from the rest.
With a track like Bubbles by Yosi Horikawa, the IM4 clearly show their sonic character, especially regarding spatiality and precision. From the very first sounds, you can perceive how each sonic event is placed coherently in space, without overlaps or confusion. Small noises, sharp impulses, and intensity variations emerge naturally, giving the sensation of an open and well‑organized sound field.
The IM4 manage to follow very well the fast transients typical of Horikawa’s productions: the hits are sharp but never harsh, and the decay of the sounds occurs in a believable way. This contributes to a rendering that does not appear artificially hyper‑detailed but rather fluid and realistic. Even at moderate volumes, micro‑details remain perceptible, a sign of good overall transparency.
In the context of listening with the IM4, a track like Algo Contigo by Inés Gaviria and Samper becomes particularly indicative for understanding the type of performance these IEMs are capable of offering. From the very first passages, you can perceive how the reproduction favors fine detail readability and proper stereo organization rather than immediate impact.
The egg shakers positioned on the left side of the panorama remain clearly distinguishable, with a sharp contour and well‑defined texture, while maintaining a deliberately low level in the mix. Even when the bass and cajón enter, their contribution is not masked: the IM4 manage to preserve transient articulation and rhythmic continuity, delivering that sense of micro‑dynamics that is difficult to find in IEMs of the same price range.
Overall, you can notice the ability to deliver transparency and order even in more layered mixes, a quality that, considering the price, places them at a level of sonic maturity rare compared to many direct alternatives, often more showy but less faithful in reproducing subtle details.
I would like to thank Fosi Audio for giving me the opportunity to try their IM4 earphones. I specify that my evaluation has been totally transparent and independent: every consideration expressed was based exclusively on my listening experience and on the comparison with the other models I regularly use.
Following the track over time, the bass never gets lost even when other elements enter. It remains readable, with distinguishable notes and a natural decay, without annoying tails. This greatly helps maintain the groove and gives solidity to the arrangement without taking space away from the rest.
With a track like Bubbles by Yosi Horikawa, the IM4 clearly show their sonic character, especially regarding spatiality and precision. From the very first sounds, you can perceive how each sonic event is placed coherently in space, without overlaps or confusion. Small noises, sharp impulses, and intensity variations emerge naturally, giving the sensation of an open and well‑organized sound field.
The IM4 manage to follow very well the fast transients typical of Horikawa’s productions: the hits are sharp but never harsh, and the decay of the sounds occurs in a believable way. This contributes to a rendering that does not appear artificially hyper‑detailed but rather fluid and realistic. Even at moderate volumes, micro‑details remain perceptible, a sign of good overall transparency.
In the context of listening with the IM4, a track like Algo Contigo by Inés Gaviria and Samper becomes particularly indicative for understanding the type of performance these IEMs are capable of offering. From the very first passages, you can perceive how the reproduction favors fine detail readability and proper stereo organization rather than immediate impact.
The egg shakers positioned on the left side of the panorama remain clearly distinguishable, with a sharp contour and well‑defined texture, while maintaining a deliberately low level in the mix. Even when the bass and cajón enter, their contribution is not masked: the IM4 manage to preserve transient articulation and rhythmic continuity, delivering that sense of micro‑dynamics that is difficult to find in IEMs of the same price range.
Overall, you can notice the ability to deliver transparency and order even in more layered mixes, a quality that, considering the price, places them at a level of sonic maturity rare compared to many direct alternatives, often more showy but less faithful in reproducing subtle details.
I would like to thank Fosi Audio for giving me the opportunity to try their IM4 earphones. I specify that my evaluation has been totally transparent and independent: every consideration expressed was based exclusively on my listening experience and on the comparison with the other models I regularly use.
IN CONCLUSION
For my part, in my opinion, considering the price, it is difficult to find the same combination of transparency, micro‑detail, and tonal coherence in this price range. With the IM4, Fosi Audio has begun its approach directly with substance: the earphones maintain a clean, open, and coherent listening experience that is not at all guaranteed in this price range. A product that will certainly be appreciated more with use, as you move from one genre to another without feeling the need for corrections or obvious compromises.
