Hi @Fosi Audio Team and Fosi Fans,
My first review so let me know what you think and if you agree in the comments.
Fosi Audio enters the headphone arena ready to fight!
1. Overview
Brand & Model:
Fosi Audio’s new i5 headphones Fosi audio see themselves as pioneers in accessible HiFi excellence, targeting premium audio experiences for their customers at aAordable prices. They began in 2017 and predominantly produce amplifiers and more recently speakers. However they are beginning to expand their portfolio of audio equipment and entering the arena of headphones, aiming high with their first product, the i5 open back, planar magnetic headphones and in recent weeks a brand new IM4 IEM (In Ear Monitor).
Type & Specification:
The Fosi Audio i5 are open-back planar magnetic headphones featuring a 97mm nanodiaphragm driver with a 28 Ω impedance and 98 dB sensitivity, a frequency response of 1050,000 Hz, and a weight of approximately 550g. They include a 97mm driver, metal yokes, walnut accents, and plush earpads, with recommended power input of at least 500mW for optimal performance.
Price Range: $549.99 USD (approx. $845 AUD)
Release Date:
Fosi i5 is now available for purchase from various online retailers. Originally it was launched as part of a Kickstarter campaign that started on April 22nd, 2025.
2. Design & Build Quality:
Overall my first impressions when seeing the Fosi i5 headphones in person, and especially picking them up for the first time, was a feeling of high quality. After weeks of use now, the same impression is still there every time I pick up my i5’s. They have a great overall design and build quality.
Aesthetics & Materials Used:
The sleek matt-black aluminium outer ear-cup grills and metal frames, compliment the natural earthy elements in the light-brown leather suspension head-strap, as well as the polished (real) wood ear-cup housings. The ear cushions are made from a thick, plush responsive memory foam and wrapped in a perforated pleather on the sides, and a soft breathable fabric on the front surface. This makes for a smooth gentle contact with the skin, allowing them to stay cool over extended periods. The material choices are not only visually appealing, but are of high quality, and compliment the overall comfort and premium feel. Even though the size is large, the i5’s still look well proportioned and are aesthetically pleasing to look at.
Comfort:
The Fosi i5 headphones are the largest and heaviest headphones that I own, however from watching and reading previous reviews, I was expecting them to still be comfortable, and yes they most definitely are. The ear-cushions are extremely soft with a yolk that allows for minor ear-cup adjustments in all directions, so that they sit perfectly on the side of my head, with a clamping force that is just right. They maintain a stable position on my head, even when moving around slowly, but never a feeling of over-pressure. The suspension strap can also be adjusted to the correct height and works well and appears to be distributing the weight evenly across the head.
However, despite the high level of comfort and overall positive first experience, after approximately one hour of continuous use, I did start to notice a slight pain in the centre top of my head. This is quite common for any headphone, but less so with a suspension strap, or ones that have a designated cutout to avoid this issue. I was a little surprised by this, given the initial high level of comfort, but had seen another reviewer raise this as an issue for them. Therefore, although every design element leads towards a comfortable fit (as I imagine would be the case for most people), inevitably I’m guessing due to the weight or for larger heads like mine, at some point you may experience a pain point on the top of your head. Simply moving the suspension strap backwards a little bit fixed the problem for me, but at some point the issue will likely return.
Having a closer look in the mirror, it does appear that the strap is fully taught when at the optimal height for me, so potentially for larger heads, the strap length may be the issue. i.e. a slightly longer leather strap may help, or potentially an adjustment somehow on that too.
Therefore, although I like the premium look (and feel) of the wood element, I imagine this partially contributing to the excess weight, and by forgoing the wood for a lighter material may have been a better overall design choice if long session comfort is of high priority. I do like the look of carbon fibre, which is obviously light, but not as easy to work with and may be cost prohibitive. Plastics are another option, but then lose the premium aesthetic. Or potentially they could explore a slightly diAerent suspension strap positioning, as although I expected it to distribute the weight well, and even though it was super comfortable, it did create a hot spot earlier than expected right on the centre top of my head.
Durability:
The overall build quality is high and the premium materials mean the headphones should last a long time with careful use. The weakest link is likely the suspension strap adjustment, or the edges of the head-strap that may fray over time and use. However, unlike some studio headphone that appear bullet proof, you do need to handle these headphones with care and you wouldn’t want to drop them, as they will likely scratch, or potentially dent/bend the metal, mainly due to the momentum that would build up due to their weight. The cable and connections feel robust and secure, with a nice click sound when you connect the cables (which are also of a high build quality and should handle the test of time).
3. Sound Quality
Bass:
Starting with the bass response, the Fosi i5 headphones have great extension and the bass is well presented in a true, tight and controlled fashion. It is very clean and overall to my liking. There is definitely no over emphasis on the bass, which some may find lacking, but for most instrumental music and live bands, the i5 captures the bass well.
Mids:
Similar to the bass, the mid range is well controlled, and presents all the music I listened to in a slightly warm, clean manner. Vocals were realistic and instruments had good separation.
However, the main exception to this may be due to my relatively good musically trained ear (that can also be a bit sensitive), was that I noticed a few particular frequencies that seemed to stand out above others when watching some music video clips. At first I thought maybe the volume was too high, but on one hand I felt I wanted to turn it up higher to really hear and enjoy the great music tracks, but I kept hearing particular voice frequencies that stood out with a sharp tone, and not in a good way.
They were slightly piercing frequencies from the female vocalist, somewhere in the upper midrange, so I decided to analyse this further with my Nord Grand piano. I started by working through some scales across the entire keyboard, and similar to the slightly harsh notes of the mid-range vocals, I also noticed that particular notes stood out as unnaturally louder, when I was trying to play at a consistent volume.
I quickly switched to my AKG Q701’s (still to this date, my favourite headphones to match my Nord Grand), and they did not have this issue, but rather a consistent volume across the entire keyboard.
I had watched quite a few of the online reviews whilst awaiting delivery of my i5’s, so I was interested to see if what I was experiencing aligned with any of the accentuated frequencies that were created as part of the v2 sealing “fix”, and I believe this to be the case. i.e. the bass response may have been improved (I can’t tell as I don’t have the original unit (pre-fit) to test), however I believe the slightly piercing frequencies aligned with the peaks in the frequency response chart below, as per Fosi Audio Kickstarter Campaign Update #5:
The 3 peaks within the red circle are around: - 659 Hz, 1.1kHz & 1.6kHz
Before I knew the above frequencies, I took photos of the few notes that stood out more than others, and looked up their corresponding frequencies (see images below). I don’t think there is a co-incidence that they align with the above peak frequencies, and this explains (to me anyway) why they sound harsh and unnaturally louder than the other notes.
Unfortunately this characteristic forces me to choose my AKG Q701’s when playing my Nord specifically, but for general music listening I still enjoy picking up my i5’s, as otherwise they are still a great headphone.
Highs:
Unlike the mid-range issue explained above, the high frequencies are once again clean and clear. I haven’t noticed any obvious sibilance or distracting coloration, so overall they perform well in the highs, if anything maybe on the lean side, especially when playing my piano. I think it is a fine balance as getting too much more body behind the highs, can very quickly turn to fatiguing territory.
Therefore, just like the bass, the highs are well balanced.
Soundstage & Imaging:
The i5 has a clean, open sound stage across the entire frequency range, with quite a wide presence and a slightly warm texture. When comparing to my AKG Q701’s, they are not quite as airy and open but provide a good overall balance.
The i5’s imaging is very precise, probably by nature of the magnetic drivers, as I could clearly differentiate between instruments in any song I listened to.
Noise Isolation: None, due to open-back design.
Summary of Sound Quality:
Overall I am quite impressed and enjoy listening to all types of music using the Fosi i5’s. It is definitely up there as one of the better headphones that I own. It has a very clean sound across the entire frequency spectrum and there is an overall sense of warmth. This feeling of warmth is emphasised by the physical form factor, given the extra weight and super plush ear-cushions that make the i5’s sit comfortably on your head.
4. Features & Functionality
Connectivity (wired headphone):
The Fosi i5’s are an audiophile style, wired connection headphone, that comes with a very high quality, soft to feel, 3.5mm cable. The supplied cable is a comfortable length for most applications, but in a studio or for larger setups, the cable may be on the shorter side. The choice of 3.5mm cable entries in each ear cup makes it more universal, meaning after-market cables are an easy option if you need something longer.
There is also an optional 4.4mm balanced cable on offer from Fosi Audio which I didn’t have to test.
Additional Features:
As this is an audiophile style wired headphone, there are no additional features like microphones, wireless connectivity etc that you may find on consumer type headphones.
Although, as part of my submission to the Fosi co-creation challenge last month, I’ve suggested they explore making a high audio quality wireless transmitter / receiver, as with my cheap units I had (see image below), it works surprisingly well.
It is VERY liberating walking around the house listening to a great pair of headphones, as opposed to being stuck a meter or so away from your desk. Or having to carry your source and have a cable hanging down to your pocket. Let’s see what Fosi thinks!
5. Performance in Use
Daily Use Experience:
Primarily for listening to music, ideally with a decent amplifier (although not that diAicult to drive). Or they are a relatively good option for musicians wanting a good set of headphones for their digital piano, unless you are overly sensitive to upper mid-range frequencies as explained above.
I’m not a gamer myself, so can’t really comment on that as a use case, but it would probably perform fairly well in terms of realism and nature scenes. However, probably not enough punch and excitement for most action style games.
I would definitely not recommend the Fosi i5’s for any travel, commuting or work-out/ active use, simply due to their open-back nature and also their size and weight. These are for home listening.
6. Pros & Cons
Pros:
7. Comparison
Compared to my main Beyerdynamic DT770 Pro X headphones, the Fosi i5’s provide a slightly more detailed, neutral and obviously open response given their “open back” design.
The i5’s aren’t quite as wide and airy as my AKG Q701’s, which I slightly prefer when playing my Nord Grand piano.
They don’t have the impact when playing my Aerodrums 2 virtual drums, where I find my older MSR7’s or Shure840’s provide the best drumming feedback, so for drums accompanying a good acoustic track they are great, but for live drum specific feedback they didn’t perform that well.
Regardless of the minor areas where some of my other headphones suit better, the Fosi i5’s are generally good across all applications, best for casual music listening, especially ballads, strings, acoustic music.
One thing I will say though in comparison to all my other headphones is that the i5’s feel like the most premium and “audiophile style”, which is a fairly new area for me. I think I may have the bug now though, and can’t wait to see what Fosi brings out next in their over ear headphone range. It certainly is a great overall result for their first headphones.
8. Verdict
My first review so let me know what you think and if you agree in the comments.
Fosi Audio enters the headphone arena ready to fight!
1. Overview
Brand & Model:
Fosi Audio’s new i5 headphones Fosi audio see themselves as pioneers in accessible HiFi excellence, targeting premium audio experiences for their customers at aAordable prices. They began in 2017 and predominantly produce amplifiers and more recently speakers. However they are beginning to expand their portfolio of audio equipment and entering the arena of headphones, aiming high with their first product, the i5 open back, planar magnetic headphones and in recent weeks a brand new IM4 IEM (In Ear Monitor).
Type & Specification:
The Fosi Audio i5 are open-back planar magnetic headphones featuring a 97mm nanodiaphragm driver with a 28 Ω impedance and 98 dB sensitivity, a frequency response of 1050,000 Hz, and a weight of approximately 550g. They include a 97mm driver, metal yokes, walnut accents, and plush earpads, with recommended power input of at least 500mW for optimal performance.
Price Range: $549.99 USD (approx. $845 AUD)
Release Date:
Fosi i5 is now available for purchase from various online retailers. Originally it was launched as part of a Kickstarter campaign that started on April 22nd, 2025.
2. Design & Build Quality:
Overall my first impressions when seeing the Fosi i5 headphones in person, and especially picking them up for the first time, was a feeling of high quality. After weeks of use now, the same impression is still there every time I pick up my i5’s. They have a great overall design and build quality.
Aesthetics & Materials Used:
The sleek matt-black aluminium outer ear-cup grills and metal frames, compliment the natural earthy elements in the light-brown leather suspension head-strap, as well as the polished (real) wood ear-cup housings. The ear cushions are made from a thick, plush responsive memory foam and wrapped in a perforated pleather on the sides, and a soft breathable fabric on the front surface. This makes for a smooth gentle contact with the skin, allowing them to stay cool over extended periods. The material choices are not only visually appealing, but are of high quality, and compliment the overall comfort and premium feel. Even though the size is large, the i5’s still look well proportioned and are aesthetically pleasing to look at.
Comfort:
The Fosi i5 headphones are the largest and heaviest headphones that I own, however from watching and reading previous reviews, I was expecting them to still be comfortable, and yes they most definitely are. The ear-cushions are extremely soft with a yolk that allows for minor ear-cup adjustments in all directions, so that they sit perfectly on the side of my head, with a clamping force that is just right. They maintain a stable position on my head, even when moving around slowly, but never a feeling of over-pressure. The suspension strap can also be adjusted to the correct height and works well and appears to be distributing the weight evenly across the head.
However, despite the high level of comfort and overall positive first experience, after approximately one hour of continuous use, I did start to notice a slight pain in the centre top of my head. This is quite common for any headphone, but less so with a suspension strap, or ones that have a designated cutout to avoid this issue. I was a little surprised by this, given the initial high level of comfort, but had seen another reviewer raise this as an issue for them. Therefore, although every design element leads towards a comfortable fit (as I imagine would be the case for most people), inevitably I’m guessing due to the weight or for larger heads like mine, at some point you may experience a pain point on the top of your head. Simply moving the suspension strap backwards a little bit fixed the problem for me, but at some point the issue will likely return.
Having a closer look in the mirror, it does appear that the strap is fully taught when at the optimal height for me, so potentially for larger heads, the strap length may be the issue. i.e. a slightly longer leather strap may help, or potentially an adjustment somehow on that too.
Therefore, although I like the premium look (and feel) of the wood element, I imagine this partially contributing to the excess weight, and by forgoing the wood for a lighter material may have been a better overall design choice if long session comfort is of high priority. I do like the look of carbon fibre, which is obviously light, but not as easy to work with and may be cost prohibitive. Plastics are another option, but then lose the premium aesthetic. Or potentially they could explore a slightly diAerent suspension strap positioning, as although I expected it to distribute the weight well, and even though it was super comfortable, it did create a hot spot earlier than expected right on the centre top of my head.
Durability:
The overall build quality is high and the premium materials mean the headphones should last a long time with careful use. The weakest link is likely the suspension strap adjustment, or the edges of the head-strap that may fray over time and use. However, unlike some studio headphone that appear bullet proof, you do need to handle these headphones with care and you wouldn’t want to drop them, as they will likely scratch, or potentially dent/bend the metal, mainly due to the momentum that would build up due to their weight. The cable and connections feel robust and secure, with a nice click sound when you connect the cables (which are also of a high build quality and should handle the test of time).
3. Sound Quality
Bass:
Starting with the bass response, the Fosi i5 headphones have great extension and the bass is well presented in a true, tight and controlled fashion. It is very clean and overall to my liking. There is definitely no over emphasis on the bass, which some may find lacking, but for most instrumental music and live bands, the i5 captures the bass well.
Mids:
Similar to the bass, the mid range is well controlled, and presents all the music I listened to in a slightly warm, clean manner. Vocals were realistic and instruments had good separation.
However, the main exception to this may be due to my relatively good musically trained ear (that can also be a bit sensitive), was that I noticed a few particular frequencies that seemed to stand out above others when watching some music video clips. At first I thought maybe the volume was too high, but on one hand I felt I wanted to turn it up higher to really hear and enjoy the great music tracks, but I kept hearing particular voice frequencies that stood out with a sharp tone, and not in a good way.
They were slightly piercing frequencies from the female vocalist, somewhere in the upper midrange, so I decided to analyse this further with my Nord Grand piano. I started by working through some scales across the entire keyboard, and similar to the slightly harsh notes of the mid-range vocals, I also noticed that particular notes stood out as unnaturally louder, when I was trying to play at a consistent volume.
I quickly switched to my AKG Q701’s (still to this date, my favourite headphones to match my Nord Grand), and they did not have this issue, but rather a consistent volume across the entire keyboard.
I had watched quite a few of the online reviews whilst awaiting delivery of my i5’s, so I was interested to see if what I was experiencing aligned with any of the accentuated frequencies that were created as part of the v2 sealing “fix”, and I believe this to be the case. i.e. the bass response may have been improved (I can’t tell as I don’t have the original unit (pre-fit) to test), however I believe the slightly piercing frequencies aligned with the peaks in the frequency response chart below, as per Fosi Audio Kickstarter Campaign Update #5:
The 3 peaks within the red circle are around: - 659 Hz, 1.1kHz & 1.6kHz
Before I knew the above frequencies, I took photos of the few notes that stood out more than others, and looked up their corresponding frequencies (see images below). I don’t think there is a co-incidence that they align with the above peak frequencies, and this explains (to me anyway) why they sound harsh and unnaturally louder than the other notes.
Unfortunately this characteristic forces me to choose my AKG Q701’s when playing my Nord specifically, but for general music listening I still enjoy picking up my i5’s, as otherwise they are still a great headphone.
Highs:
Unlike the mid-range issue explained above, the high frequencies are once again clean and clear. I haven’t noticed any obvious sibilance or distracting coloration, so overall they perform well in the highs, if anything maybe on the lean side, especially when playing my piano. I think it is a fine balance as getting too much more body behind the highs, can very quickly turn to fatiguing territory.
Therefore, just like the bass, the highs are well balanced.
Soundstage & Imaging:
The i5 has a clean, open sound stage across the entire frequency range, with quite a wide presence and a slightly warm texture. When comparing to my AKG Q701’s, they are not quite as airy and open but provide a good overall balance.
The i5’s imaging is very precise, probably by nature of the magnetic drivers, as I could clearly differentiate between instruments in any song I listened to.
Noise Isolation: None, due to open-back design.
Summary of Sound Quality:
Overall I am quite impressed and enjoy listening to all types of music using the Fosi i5’s. It is definitely up there as one of the better headphones that I own. It has a very clean sound across the entire frequency spectrum and there is an overall sense of warmth. This feeling of warmth is emphasised by the physical form factor, given the extra weight and super plush ear-cushions that make the i5’s sit comfortably on your head.
4. Features & Functionality
Connectivity (wired headphone):
The Fosi i5’s are an audiophile style, wired connection headphone, that comes with a very high quality, soft to feel, 3.5mm cable. The supplied cable is a comfortable length for most applications, but in a studio or for larger setups, the cable may be on the shorter side. The choice of 3.5mm cable entries in each ear cup makes it more universal, meaning after-market cables are an easy option if you need something longer.
There is also an optional 4.4mm balanced cable on offer from Fosi Audio which I didn’t have to test.
Additional Features:
As this is an audiophile style wired headphone, there are no additional features like microphones, wireless connectivity etc that you may find on consumer type headphones.
Although, as part of my submission to the Fosi co-creation challenge last month, I’ve suggested they explore making a high audio quality wireless transmitter / receiver, as with my cheap units I had (see image below), it works surprisingly well.
It is VERY liberating walking around the house listening to a great pair of headphones, as opposed to being stuck a meter or so away from your desk. Or having to carry your source and have a cable hanging down to your pocket. Let’s see what Fosi thinks!
5. Performance in Use
Daily Use Experience:
Primarily for listening to music, ideally with a decent amplifier (although not that diAicult to drive). Or they are a relatively good option for musicians wanting a good set of headphones for their digital piano, unless you are overly sensitive to upper mid-range frequencies as explained above.
I’m not a gamer myself, so can’t really comment on that as a use case, but it would probably perform fairly well in terms of realism and nature scenes. However, probably not enough punch and excitement for most action style games.
I would definitely not recommend the Fosi i5’s for any travel, commuting or work-out/ active use, simply due to their open-back nature and also their size and weight. These are for home listening.
6. Pros & Cons
Pros:
- Overall a premium look and feel, with nice material choices and comfortable fit
- Wide Soundstage with an open sound across the range, with clean, precise response.
- Ideal for music listening, especially instrumental and live acoustic genres.
- Large and a little bit heavy, which may lead to fatigue on centre top of head if wearing for longer periods, or potentially a strap length issue for larger heads.
- Although premium materials and well constructed, will still need to handle with care so only suitable for home or studio desk use. Ie not for commuting, travelling etc.
- Upper mid-range peak frequency’s may be noticeable for sensitive ears and distract from an otherwise overall strong frequency response.
7. Comparison
Compared to my main Beyerdynamic DT770 Pro X headphones, the Fosi i5’s provide a slightly more detailed, neutral and obviously open response given their “open back” design.
The i5’s aren’t quite as wide and airy as my AKG Q701’s, which I slightly prefer when playing my Nord Grand piano.
They don’t have the impact when playing my Aerodrums 2 virtual drums, where I find my older MSR7’s or Shure840’s provide the best drumming feedback, so for drums accompanying a good acoustic track they are great, but for live drum specific feedback they didn’t perform that well.
Regardless of the minor areas where some of my other headphones suit better, the Fosi i5’s are generally good across all applications, best for casual music listening, especially ballads, strings, acoustic music.
One thing I will say though in comparison to all my other headphones is that the i5’s feel like the most premium and “audiophile style”, which is a fairly new area for me. I think I may have the bug now though, and can’t wait to see what Fosi brings out next in their over ear headphone range. It certainly is a great overall result for their first headphones.
8. Verdict
- Overall Rating : 8.5/10
- Would You Recommend It: Yes, I would recommend the Fosi i5s. Potentially needs some EQ to clean up the upper-mid region for my taste, but a great overall headphone and excellent entry into the headphone arena by Fosi. Worth the money in my opinion.
- Best For: Audiophiles or musicians that enjoy a detailed sound, especially for stringed instruments, pianos or acoustic music.
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