Disclaimer
Hello everyone! Before we start, I want you to know that Fosi Audio sent me the i5 so I could test it, give it a proper listen, and share my thoughts. I’m not being paid for this, and Fosi Audio hasn’t told me what to say, asked to see my draft, or set any publishing schedule.
Everything you will read here is 100% based on my own time with the i5. I always try to be as fair and objective as I can, but in the end this is just my opinion, and our points of view and preferences aren’t the same, and that search for the best lifelike sound experience is part of what makes this hobby great.
Huge thanks to Fosi Audio for trusting me with the i5, and big thanks to you for taking the time to read. Your support really means a lot to me!
Introduction
I remember a couple of months ago that I saw a Fosi post about one of their products, and in the background there was a pair of headphones, and it got me very excited as I realized that Fosi is working on their very first pair of headphones. I’ve always loved their gear because they are always bringing amazing value for money. I mean, these guys just know how to hit the sweet spot between price and performance. But moving into making headphones? That is super exciting for me.
Fosi really did aim high with this one, as it is priced at 550$, and it can be clearly seen that they have put extra effort into both the build quality and sound quality. They also have gotten some feedback from other reviewers regarding the bass roll off below 80Hz, and they have made a change to the design in order to fix it. This isn’t just another product launch from them, and I think that it’s a big step forward for the company. They have made their name by creating affordable yet great gear, and now they are stepping into a new territory.
Holding their very first pair of headphones in my hands felt special. I felt like Fosi was really trying to prove that they can make high quality headphones, and in some ways, I think they have already succeeded in that. But I’ll leave the specifics for later.
Today, I’m finally reviewing the i5, and I’m excited to find out if these headphones truly live up to what we have come to expect from Fosi Audio. So now I think it’s time to get started.
Unboxing
The i5 comes in a big box, which makes sense because these headphones are huge. Inside, everything sits in a thick foam so nothing moves around. The headphones sit in the middle in a foam cutout. Under each cup there is a velvet bag. Inside each bag there is a thick, nice feeling cable. One cable ends in a 3.5 mm plug, and the other is a 4.4 mm balanced cable. You also get a 6.35 to 3.5 mm adapter and a user manual.
The presentation is simple but quite fine. The foam protects everything, the bags are soft and useful for storing the cables, and the cables look well made but a bit too stiff in my opinion. I like that they included two cables out of the box, as this is what I want to see at this price, but on tier website it shows to include only the 3.5mm cable, and I think its best to include both. Also another replacement pair of earpads would have been nice too.
I am, though, disappointed that there is no carrying case, or better, I say, suitcase, because the i5s are humongous. I really believe that every headphone or IEM should come with at least a basic case or bag, and even more so for a 550$ pair. Other than that, the unboxing is fine and gets the job done.
Technical specifications
Specs
- Transducer Type: 97mm Planar Magnetic Transducer
- Maximum SPL: ≥ 120 dBSPL
- Frequency Response: 10 – 50,000 Hz; THD: < 1% @100dBSPL
- Sensitivity: 98 dB/mW @1kHz; Nominal Impedance: 28 Ω
- Recommended Power: ≥ 500 mW
- Weight: About 550g
Build and design
These are big and pretty heavy headphones. The cups are huge. Each cup has a walnut wood ring that looks really nice, and the faceplate is metal with an open design, and overall, I really like the classic design of the i5. The headband strap is made out of genuine sheepskin leather. The earpads are made out of breathable protein leather, and at this price I would have expected genuine leather for the earpads too, especially since the headband is sheepskin. The yoke and headpiece are metal with a cup rotating design, and the slider is stiff but smooth. I hope it stays firm over time.
One thing I do not like is the rubber rings used where the headband connects to the cups. In my past experience those rings can dry out and tear after a while, so I hope these hold up. The earcup connectors are standard 3.5mm. The earpads are semi pleather, with fabric on the part that touches the head, and they attach to the cups with Velcro, so you can replace them in the future.
Driver
The i5 uses a 97 mm planar magnetic driver with a very thin 2 micron diaphragm with N50 neodymium magnets. Fosi also mentions magnetron-sputtered silver alloy coating. I mean, I know that silver is the best conductor, but other than that, I don’t know what further benefit it brings. The rated specs are 28 ohms and 98 dB/mW, so on paper it is not so hard to drive, but in practice it does need some good amount of power to shine.
New tuning ring
As I have mentioned earlier, Fosi made a change to improve the bass. There is a silicone ring around the driver that helps to seal it better between the earpads and the driver. This gives a more extended bass performance and overall cleaner lows. The ring is not glued in. It just sits in place and can be removed if needed.
Cables
The included cables are pretty thick and feel durable. They keep the curve from how they were packed, but I can change it, and they will mostly keep the new form, which is nice, but they are a bit too stiff in my opinion. The outer layer is a fabric sleeve that feels quite nice to the touch. My unit came with both a 3.5 mm single ended cable and a 4.4 mm balanced cable, plus a 6.35 to 3.5 mm adapter, but I can see on their website that it comes only with a 3.5mm one, and I think they should include both. Overall the cables look and feel solid.
Sound Performance
Bass
With the rings installed, the bass goes deep and stays well controlled and extended. Without the rings it is almost nonexistent for me, so the rings make a big difference for sure. This is not a bass cannon, and I do wish for a bit more slam sometimes, but the upside is speed, texture, and precision. I like checking bass speed with “The Stage” by Avenged Sevenfold. Those quick double kicks at the start sound tight, distinct, and just good on the i5. For sub bass, I like testing it with “ENTROPYYY” by Lorn and “Consumed” by The Haxan Cloak, and both dig very low. The i5 handles the bass cleanly and without any bloat. I still want a touch more power, but overall the bass is deep, fast, and very well behaved.
Mids
This is where I have some mixed feelings. Up to about 1 kHz, the mids are shown to have some bumpiness, but to be honest, they sound mostly fine to me, though they can feel a little uneven sometimes. The pinna gain region around 2 to 4 kHz seems slightly recessed to my ears, which can make vocals and some instruments sound a bit veiled. On “Grieve No More” by Patty Gurdy, when she sings in a lower voice, it can feel a bit hidden, while when she gets into higher notes, they pop forward and shine. It is not extreme, and I am really listening for it, but it is there. If you are a casual listener, you might not notice it, or it may not bother you that much.
Treble
The treble is nicely done. Extension feels good, there is sparkle, and it never feels harsh or fatiguing for me. Details in the highs are a strong point on the i5, which is what I expect from a planar at this price. When female vocals climb higher, the i5 sounds clean and full. But still, the slight dip in the pinna gain region can sometimes give me the sense of a veil on some voices and make them sound a bit unnatural, even if the treble itself is clear and airy.
Technicalities
Technical performance is where the i5 really flexes. The stage sounds spacious, probably because of the large cups and the driver sitting a bit farther from my ears. There is a real sense of space. Detail retrieval is excellent, and I keep noticing small background details in familiar tracks. Imaging and layering are also strong. Thanks to the driver’s quick response, the i5 never, ever sounds congested on busy tracks, like “Retreat and Reveille” by Hans Zimmer, and all of the instruments stay very separated and in their place.
Comparisons
I am putting the Fosi i5 up against two FiiO planars I know well, the FT1 Pro at 200$ and the FT7 at 700$. This way we can see where the i5 really sits in the market at 550$.
FiiO FT1 Pro vs Fosi i5
Switching between the two, the i5 gives me faster bass, a wider stage, and more detail across the board. It is also much bigger and heavier than the FT1 Pro but has a nicer build that feels more premium, which makes sense at nearly triple the price. The FT1 Pro sounds a bit more natural to me, likely because its pinna gain around 2 to 4 kHz is more pronounced. That lift keeps vocals and instruments more forward. Even so, the i5 is far ahead in speed, separation, texture, and staging, so in terms of technical performance, the i5 is clearly on top. But for the asking price of 200$, the FT1 Pro has a very natural and balanced tuning and is still an amazing value and probably my most recommended sub 200$ headphone.
FiiO FT7 vs Fosi i5
The FT7 is lighter and not as huge, even though it uses a larger driver. Bass on the FT7 has a little more texture and detail to my ears. In my FT7 review I said it had the best planar bass I had heard from my collection at the time, and that still holds. The i5 is excellent in bass quality too, but the FT7 has it a bit better. I still wish both had a little more power there, as they both are not bassheads.
Tonally, the FT7 gives me a bit more natural and balanced sound overall, again because of how its pinna gain region sits more forward. Build wise, the FT7 got carbon with very beautiful wood plates and feels very high quality, and it can be seen that FiiO hadn’t cut in materials here, while the i5 also looks great with its wooden ring and classic overall look.
FiiO also gives better accessories here as well. The stock cable is high quality, although its a very long one, and I wish there was a shorter one in the box as well. You also get a second set of ear pads, a very quality carrying case, and a balanced XLR plug in addition to the 6.5 adapter.
Bottom line on placement
Against the FT1 Pro, the i5 justifies its price with clearly better speed, staging, and detail. Against the FT7, the i5 gets close in technicalities and quality, but the FT7 still sounds more natural to me and has a more premium overall package. That puts the i5 right in the middle of the two. It overall feels like a serious step up from entry level planars.
Conclusion
After spending a good time with the i5, there are few things that are clear to me. Fosi came in strong for a first headphone. The build feels serious (although there are some things that concern me for longevity, like the rubber rings connecting the headband to the cups and the protein leather pads, which tend to not hold for very long), they sound big, with great technicalities, and the driver has that quick, clean planar snap that makes everything more detailed and distinct. The new ring fix gives the bass much better extension, and the overall technical performance is quite impressive.
It is not perfect. The size and weight are serious, so comfort depends on your head size and how comfortable you are with big and heavy cups. The stock cables feel a bit stiff, and I really wish a case was included. Soundwise, I still want a little more bass quantity. The pinna gain region is a bit too recessed for me, which can make it sound slightly veiled sometimes, even though the treble itself is airy and detailed.
Who will love it? If you value detail, layering, a wide stage, and overall great technicalities, the i5 has that. If you want good vocals or you want more bass weight, you might want to EQ the i5 or look at alternatives. A small lift in the sub bass and at the 2 to 4 kHz region can make the sound better.
So, is it worth it?
For me, yes, but even better if you can grab them at a discount. If your priorities are technical performance, you don’t mind or even love the bigger size and want a premium build, then it’s a nice choice. If you want the most natural vocal focus and a lighter fit, and you feel like 550$ is a bit too much, the FT1 Pro remains a killer value. But overall, as the first headphone from Fosi, the i5 is a good release that competes well, and it makes me very curious to see what they do next.
Pros
- Big and spacious stage that feels open and airy.
- Fast planar snap with great technicalities.
- Bass is nicely extended and well controlled with the rings installed.
- Treble is extended, detailed, and not harsh to my ears.
- Premium build with metal and wood that looks and feels classic and premium.
- Fosi listened to feedback and added the tuning ring to improve bass, so that’s a big pro, as it shows that the company cares.
Cons
- Very large and heavy.
- I want more bass quantity and slam.
- Mids can feel a bit uneven, with a slight 2 to 4 kHz recess that makes some songs sound veiled.
- Cables feel too stiff for my taste.
- No carrying case in the box at this price.
- Rubber rings at the headband joints and protein leather earpads may be a long term durability concern.
Where to buy:(Non-affiliated! None of my reviews use affiliated links!)
