This time, we review Fosi Audio’s debut headphones, the Fosie Audio i5. They can be bought for as little as $386 USD by backing the Fosi Audio Kickstarter campaign. Note that this is the original i5 before it got the bass upgrade. The i5 Rev2 article can be found here.
Disclaimer: Fosi Audio is not related to Headfonia. They sent me the i5 free of charge to be featured on Headfonia.com.
Fosi Audio
The Shenzhen-based brand Fosi Audio entered the market in 2017 and has since provided the audio market with a steady stream of high-value products, from DACs and headphone amps to dedicated speaker power amplifiers.
The name “Fosi” embodies the four core principles of the company: foresight – thinking further ahead; openness – embracing users’ voices; sincerity – serving you wholeheartedly; and innovation – upholding technical excellence.
So far, Fosi Audio have got a good reputation here with their V3 monoblock class-D power amplifiers impressing Nanotechnos enough to call them “a steal” for the price Fosi are asking. We’ve also reviewed Fosi’s higher-end offshoot Mamoritai Audio’s headphone amp, the Euphony, which, on the other hand, didn’t exactly steal Nanotechno’s heart.
At over $500 USD retail price, the i5 headphone is one of Fosi Audio’s priciest offerings. For now, it’s only available from the company’s Kickstarter campaign. I’m not too enthusiastic about established brands using Kickstarter as a marketing platform, but feel free to disagree with me.
Fosi Audio i5
After researching Fosi products, I wasn’t too surprised that the company went into full-size headphones. Sure, IEMs would have lower startup costs, but there’s an ocean of manufacturers out there already, and good luck differentiating yourself with everyone using the same off-the-shelf drivers and 3D-printing houses. What did surprise me was how Fosi went about doing it.
The $500 – $600 USD range is a bit of no-man’s land in full-size headphones, unless you go hunting for second-hand deals. Sennheiser is trying to sell their HD650 for $500 USD, but everyone knows the real deal is paying less than half that for a DROP HD6XX.
There’s also the French Focal with respectable offerings around that price point, but it’s not immediately clear whether these are worth the price premium over the HD6XX, which can sometimes be had for less than $200 USD.
Overall, the Fosi Audio i5 is a pretty traditional open-back orthodynamic headphone. It employs a 97mm diaphragm with 2 micron thickness. It’s on the larger side, but some are bigger with an extra centimeter in diameter. Looking at the exploded view of the driver, we see that the diaphragm is sandwiched between two magnet arrays.
This makes sure that the flux stays relatively constant throughout the excursion range. Not that you’d need tons of swing with so much effective piston area.
Unlike many Audeze orthos, the i5 doesn’t use fancy magnet shapes to make sure they don’t interfere with the sound wavefronts. Again, Hifiman and others also have chosen not to without incurring audible consequences. In terms of impedance, the i5 is on the lower end with 28 ohms and should be drivable with most amp output stages.
Like most planars, it’s a purely resistive load, so output impedance shouldn’t shift its tonal response.
Features
- Open-back over-ear headphone, infinite baffle acoustics
- 97mm, push-pull planar magnetic driver, 2um diaphragm
- 10 – 50 000Hz advertised frequency response
- 28 ohm purely resistive load
- 98dB/mW or 113.5dB/V
- Weight: 550g without a cable
- Input connectors: 3.5mm TRS
- Cable jack: 4.4mm TRRRS, 3.5mm TRS (6.35mm adaptor included)
- Cable length: 1.5m
Casing
Fosi Audio have chosen to keep it relatively simple and ship the i5 in a hard cardboard box with a magnetic flap cover. Once you swing that flap open, you’re greeted with a deep foam cutout that safely houses the i5 and keeps it from bouncing around.
My version came with two cables – the standard edition single-ended 3.5mm cable, a similar 4.4mm balanced cable, and a 6.35mm adaptor. Apparently there’s also an option for a more premium 4.4mm cable. All cables are 1.5m long, which, in my opinion, is a good length for desktop listening. Buying or crafting custom cords should be painless, as the i5 uses regular 3.5mm TRS jacks on the earcups.
One thing Fosi needs to think about is storing the cables. Mine were stuffed near the earpads and left a nice big indent in one of them. Luckily, once freed, the foam expanded back and all was good. A nice touch would have been some sort of carrying bag for the headphones. The cables are all bagged in nice velour sacks.
Build Quality
Let’s get the obvious out of the way, the Fosi i5 looks like a Hifiman oval earcup planar headphone. Call it inspiration, but there’s no denying that there’s a lot of design influence. Here’s the kicker, though – the Fosi i5 feels better built than even the Susvara. I know that Hifiman has improved immensely when it comes to build quality since their early days, but Fosi somehow still manages to nail the build better.
The basic construction of the i5 is all metal with some wood accents around the outer perimeter of the positively large earcups. I can’t detect any seams in the lacquered wood surface, which makes me think that we’re dealing with real wood and not just a strip of veneer.
On the bottom, there are drill-outs for the 3.5mm jacks, which sit flush with the surface. Of course, time will only tell how well the wood is stabilized and whether users get cracking there. The signal inlet is a weak spot for all wood earcups and is the first place where cracking occurs.
The headband on the i5 employs the hammock design, which usually works wonders for heavy headphones. To adjust the hammock headband, Fosi use two sliders with silicone dampers, so there’s no ratcheting sound.
To couple with the listener’s ear, the i5 uses large hybrid earpads. Both the inner and outer perimeter are made out of finely fenestrated artificial leather, while the surface that faces the side of one’s head is fabric. Hopefully, Fosi will support their headphones well and offer swappable pads when the first pair eventually wears out.
Comfort and Ergonomics
At 550g, the i5 shares the same heavyweight DNA with Audeze, Hifiman, and other full-size planar magnetic headphones. This means that even with masterful weight distribution, your neck might complain after a few hours. Mine did when I was but a wee lad and had my first LCD-2, but now my neck looks like a volcano, and I can keep most planars on for a full day. Thanks for making me a man, Audeze!
The i5 sits on your noggin by a combination of hugging the side of your head and hanging on with the hammock suspension headband. It’s a great design, and I never got any hotspots even after hours of listening. The caliper pressure of the headband spring isn’t too high, and the earpads are supple enough to conform nicely to the architecture of your head.
Of course, the weak hug means that you can shake the i5 off with even moderate headbanging.
Both cables that come with the Fosi i5 are well-made for desktop listening. The 1.5m length works nicely without too much slack, and there are no problems with microphonics. I know that some of you crazies might be interested in using the i5 portably, and the cable is fine for that. It’s not too stiff but not bendy enough to tangle easily.
Isolation
The Fosi i5 is as open as they come. When viewed against a light source, you can clearly see the magnet structure as the diaphragm is translucent. If you’re listening loudly, the headphones will act as speakers and everyone will hear your stuff quite clearly. The magnet structure seems very acoustically transparent, which is good because it doesn’t cause a back wave reflection to muddle up the sound.
The part on sound continues on the second page. Click here or use the jumps below to go there.
