A one-piece headphone design

The goal was straightforward: create a headphone with no resonance and a sound as dynamic and clean as possible. That pursuit pushed SJY toward a simple yet radical solution: remove all non-essentials. The Zeph’s driver, chassis, and ear cup form a single precision-machined structure, reducing variables and minimizing vibration. This approach enabled the thinnest chassis SJY could physically build—just 7mm—resulting in a fast, low-resonance open-back headphone with nothing standing between you and the music.

Low distortion & minimal energy loss

The Zeph’s goal is Immediate response, low distortion, and minimal energy loss. Traditional headphones place a driver inside a cup, leaving multiple surfaces and interfaces that can vibrate. The Zeph eliminates those surfaces entirely. With the driver itself being a single machined aluminum body, the entire assembly behaves as one piece: stable, rigid, and sonically quiet. This tighter control over motion enhances magnetic force efficiency, lowers distortion, and gives the Zeph its energetic, highly detailed character.

The thinnest chassis possible

SJY made the chassis as thin as physics allowed, stopping only when they reached the minimum depth required for a 3.5mm connector. The internal driver assembly totals just 4mm in thickness—2mm magnet, 1.5mm diaphragm structure, and a 0.5mm grille—stacked inside a CNC aluminum frame that keeps the driver perfectly rigid and stable. 

Magnetic ear pads with dual tuning modes

The Zeph’s ear pads attach magnetically, making them simple to remove and fast to swap. Each pad uses velour on the exterior and suede on the inner surfaces for a gentle seal and controlled treble response. Flip the pads to switch between two voicings:

• Perforated side forward — more open, more spacious, laid-back vocals, enhanced instrument presence.
  
• Non-perforated side forward — warmer, more focused mids with forward vocals and increased texture.

Lightweight CNC aluminum construction

All structural components, from the chassis to the headband frame, are CNC-machined aluminum engineered for rigidity and low mass. This keeps the Zeph stable on the head, eliminates unwanted vibrations, and complements the minimalist design philosophy that defines the headphone.

Two-layer full-grain leather headband

A soft full-grain leather top strap provides natural comfort, while a heavier full-grain leather underside offers long-term resilience. Stainless steel reinforcement maintains a low profile while matching natural head geometry for an easy, even fit.

How we’re listening to it

Tom at Apos here. I first heard the SJY Zeph at CanJam SoCal 2025, exactly one year after I’d been bowled over by Jeffrey’s Horizon Closed Carbon. As I was sitting at the table listening to the Zeph, I couldn’t believe that he’d created not only another headphone that amazed me, but one that I liked just as much, if not more, than the Horizon Closed Carbon. As an open-back, it didn’t have quite the low-end as the Closed Carbon (no surprise there), but it provided a lushness and immediacy to vocals and mid-range instruments that I typically only find in dynamic drivers. There was all the speed, imaging, and detail of a planar, but with the natural midrange timbre and tonality of a dynamic. As a photographer (I took the photos to the left!), I’m naturally a visual thinker, and when I’m listening to a product that I want to champion on Apos, I immediately start visualizing how I’m going to photograph it. For the Zeph, that visual direction was color. Not coloration, per se, but color. Like seeing all the colors of the wind. Like Remy from Ratatouille visualizing ingredients. With the Zeph, music comes alive. Oh, and before I forget, I prefer the ear pads perforated side forward. Let us know your preference in your review.

Product highlights

• One-piece CNC aluminum chassis with integrated planar magnetic driver
  
• 7mm ultra-thin ear cup design
  
• Full-grain two-layer leather headband
  
• Magnetic ear pads with dual tuning profiles
  
• Carbon fiber + stainless steel aesthetic grille
  
• Lightweight, rigid aluminum structural components
  
• 3.5mm connector with custom ABS driver-mounted socket
  
• Low-resonance construction with reduced part count

Specs

• Driver: 96 × 73mm proprietary planar magnetic
  
• Impedance: 22 Ω
  
• Sensitivity: 89dB/mV
  
• Driver assembly thickness: 4mm
  
• Chassis thickness: 7mm
  
• Magnet thickness: 2mm
  
• Diaphragm structure: 1.5mm
  
• Outer grille: 0.5mm stainless steel
  
• Connector: 3.5mm

What’s included

• SJY Zeph Open-Back Planar Magnetic Headphones
  
• Magnetic dual-tuning ear pads (installed)
  
• Detachable 3.5mm headphone cable
  
• Protective storage case
  
• Note: Pencil for demonstration purposes only, not included