Fosi i5 Review by iiWi Reviews: Incredible Soundstage, Lush Tuning, and Killer Value

Introduction: Fosi’s First Headphones and a Bold Statement

From the start, iiWi made it clear: these aren’t just another pair of mid-tier planars. They’ve got big, bold sound, premium build quality, and surprising musicality that could easily fool you into thinking they belong in the $1,000 category.

In his own words:

“Around their price point, they’re the best headphones I personally ever tested. Even if I lift that price point up to $1,000, I encountered only one set—the Meze 109 Pro—that I actually slightly preferred.”

That’s a bold statement for Fosi’s first headphone release. So let’s break it down.

Design & Comfort: Premium Looks, Premium Feel

The Fosi i5 looks and feels far more premium than its price suggests. iiWi walked through the details:

• Metal overhead railings for sturdiness.

• Sheepskin leather headband that feels luxurious.

• Walnut wooden accents on the earcups.

• Metal grills in the back for the open design.

• Huge oval earpads that swivel and rotate with your head.

What really stood out to him was the size and comfort. These earpads are massive, easily surrounding his ears without clamping down. And he has large ears himself, so if they fit him comfortably, most listeners are covered.

“For all of you big ear dudes out there that always feel discomfort from headphones clamping on your lobes, these will definitely not do that. They’re just huge and go all over around your ears.”

Despite their size, they’re not overly heavy. The weight is balanced, making them easy to wear for long sessions. And the continuous sliding headband adjustment? Smooth, firm, and reliable.

iiWi didn’t hesitate: “Looks, feel, comfort, ergonomics—10 out of 10.”

Specs: What’s Under the Hood

The Fosi i5 are open-back planar magnetic headphones with some impressive numbers:

• Driver type: Large planar magnetic driver (one of the biggest iiWi has seen)

• Impedance: 28 ohms

• Sensitivity: 98 dB

• Cable: Detachable, thick, and sturdy (though a little rigid for portable use)

Now, what does this mean in practice? These are not the easiest to drive. A decent modern desktop headphone amplifier will have no problem powering them, but dongle DACs and ultra-portable devices won’t do them justice.

If you want them to sound alive, dynamic, and punchy, give them proper power.

Sound: Big, Rich, and Natural

The First Impression

The moment iiWi pressed play, he knew he was dealing with something special:

“As soon as I started listening to the Fosi i5, what I noticed immediately is how rich—totally rich—they sound.”

And that richness isn’t about bloated bass or boosted treble. It’s a natural richness, where tones feel full, real, and musical.

Tonality: Balanced but Musical

The i5 delivers a neutral tonality with a natural twist. The midrange is super open and revealing but never harsh. Vocals and instruments carry harmonic depth without sounding edgy.

This is where iiWi drew an interesting comparison:

“The sound of the Fosi i5 reminds me a lot of the sound of a good R2R DAC. Bigger, richer, more spacious, more airy, lusher, but even more natural.”

For those familiar with older HiFiMan models, he likened the jump to upgrading your DAC from a budget chip-based design to a high-end R2R ladder DAC like Denafrips or Holo Audio. It’s that sense of tonal fullness and realism.

Soundstage & Imaging

Here’s where the i5 really shines:

• Wide, spacious soundstage—among the biggest iiWi has heard under $1,000.

• Excellent tone separation—instruments have their own clear place.

• 3D-like immersion—you feel surrounded by the music.

But it’s not just about space. The tones themselves are big, bold, and dense. Nothing sounds thin or analytical.

Midrange & Upper Harmonics

The midrange is rich and natural. String instruments sound like strings—vibrating, resonating, real. Brass and wind instruments have husky, dusty tones that feel alive. Vocals, both male and female, are simply a joy.

As iiWi put it:

“There’s just that emphasized naturalness of the sound that I can notice.”

Bass Response: From Roll-Off to Fix

Early units of the i5 had a problem: sub-bass roll-off below 50 Hz due to a seal issue. For jazz, vocals, and acoustic, you might not even notice. But electronic tracks revealed the lack of pressurized sub-bass notes.

Fosi quickly fixed it with a redesigned ring around the driver. The current version goes straight down into the sub-bass region.

So if you buy the i5 today, you’re getting the fixed version with full, punchy, extended bass.

Dynamics & Punch

Planar headphones have sometimes been accused of sounding flat compared to dynamic drivers. Not here. The i5 is alive, punchy, and dynamic. Drums hit with authority, bass notes have grip, and music feels energetic.

“Tonally bold, but also dynamically bold and alive sound.”

Comparisons: How Does It Stack Up?

iiWi didn’t stop at describing the i5 in isolation. He compared it against several well-known headphones.

Fosi i5 vs. Meze 105 AR ($400)

• Meze 105 AR: Smaller, lighter, easier to drive from portable devices.

• Fosi i5: Bigger soundstage, richer tonality, better dynamics—if you use a desktop amp.

Verdict: For portable use, Meze 105 AR wins. For home use, the i5 pulls ahead.

Fosi i5 vs. Verum 2 ($500)

• Verum 2: Leaner, sharper, more analytical.

• Fosi i5: Bolder, warmer, harmonically richer.

Verdict: Analytical listeners might prefer Verum 2, but iiWi’s taste leaned toward the lush i5.

Fosi i5 vs. Aune SR7000 (Closed-Back)

• Aune SR7000: Closed-back, offering isolation and a dark, clean background. Treble has a precise, glossy character.

• Fosi i5: Bigger soundstage, warmer highs, more natural presentation of wood, leather, and wind instruments.

Verdict: The SR7000 is practical for isolation and portability. The i5 is better when you want that lush, open experience.

Fosi i5 vs. Meze 109 Pro ($800)

This was the most telling comparison. The 109 Pro is a beloved headphone in the $800 range.

• Meze 109 Pro: Slightly deeper sub-bass, a touch more treble precision.

• Fosi i5: Almost identical tonality, equally wide soundstage, equally rich mids—at $250 less.

iiWi admitted:

“For realistic, practical purposes, you could say that these two have equally big sound stages.”

That’s remarkable praise for Fosi’s debut headphone.

Market Context: A Time Machine Moment

At one point, iiWi reflected on the headphone market:

Back in the early 2000s, flagship headphones from brands like Sennheiser and AKG cost $400–$500. But they were mostly plasticky builds, nowhere near the metal, wood, and leather of the Fosi i5.

And sound-wise? They couldn’t match this combination of richness, dynamics, and spaciousness.

“If you take this one, put them into a time machine, and bring them back to early 2000s, people would think it’s a $2,000 flagship. Then they’d listen, and they’d be blown away.”

That’s how far headphone technology has come—and how much value Fosi packed into the i5.

Verdict: One Mighty Good Sounding Set of Headphones

By the end of the review, iiWi didn’t hold back:

“One mighty good sounding set of headphones.”
“Around their price point, they’re the best headphones I’ve personally ever tested.”

Even compared to models up to $1,000, only the Meze 109 Pro stood out slightly above the i5. That puts the Fosi i5 in incredible company.

FAQs

Q1: Do they need an amp?
Yes. They can play on a dongle, but they truly shine with a desktop headphone amplifier.

Q2: Warm or analytical?
Definitely on the warm, lush, musical side. Still balanced, but never clinical.

Q3: Which genres suit them best?
Jazz, classical, vocals, acoustic, country—anything that benefits from tonal richness and soundstage.

Q4: Is $550 justified?
More than justified. They rival $800–$1,000 models in sound and build.