In reflection of the recent increasing popularity of 4.4mm output compatible digital audio players (such as SONY's NW-ZX300), Ocharaku is widening their lineup to fulfill such needs.

"Ocharaku x 4.4mm balanced plug." It had been eagerly desired by fans of Ocharaku, and must be a great approach for audiophiles all over the world who pursuit the most immersive listening experience.

Same as the previous Flat4 SAKURA/AKAZAKURA model, of course, it features highly acclaimed Ocharaku original technologies. The quantity is strictly limited for only 100 pieces worldwide as some materials used are rare. Don't miss out before they run out.


Made with Japanese Wooden Craftsmanship

The center cabinet is made of solid Sakura - a wooden material having unique sounding in its category. Coated with a layer of natural raw lacquer, which is a key element contributing to the impressive aesthetics and the most crystal clear sound.

Each piece is specially selected and handcrafted by master craftsmen from OAK VILLAGE, a woodcrafts company established in 1974 in the forest of Hida-Takayama.

Features of Flat4 SAKURA/AKAZAKURA Balance

A phase correction tube, a key technology of Ocharaku detailed later, applies vibration-resistant coating to suppress the howling noise. It realizes minimizing sound deterioration and warmer and softer high-tone range.

Applies a 4.4mm 5-pole gold plated non-oxidized copper balanced plug, which is made by NIPPON DICS. It highly enhances the unique sound the Sakura material has.

Differences Between SAKURA and AKAZAKURA

Flat4 SAKURA/AKAZAKURA can be divided into two types, depending on the color of the phase correction tube:
Black is for SAKURA while Red is for AKAZAKURA.

It also can be divided into two types, depending on effective length of the ear canal: SAKURA is set for 28mm while AKAZAKURA is set for 30mm.

The length of the ear canal is generally referred to as 25 to 30mm as shown below, and the length set for Flat4-SAKURA is relatively appropriate for more people than that of Flat4-AKAZAKURA. Sound quality will be better if the effective length gets closer to your ear canal length.

References on the ear canal length 

The Human Ear Canal – V (
Ear canal (Wikipedia)


"FLAT4" Describes How Ocharaku Technology Works

FLAT4 is an abbreviation of "Full range 2-element 4-way effect," and it shows how Twin Equalized Element System, one of their patented technologies, works. It realizes the wide frequency range, especially delivering the bass deeper than conventional closed dynamic headphones, as well as the spread of sound just like open-air ones.

Along with that, it dramatically proves two problems conventional canal headphones have: characteristically high-intensity noisy sound and masking effect in certain specific high-tone range both mainly caused by the closed tube resonance of the ear canal.

Followings are the details of how "4-way effect" works.  

1st effect

Placement of two elements ("2-element") opposed to each other cancels mechanical vibration due to reaction of vibration system. It realizes deeper bass tones than that of conventional closed types.

2nd effect

In low and mid range tones, parallel drive of the twin elements enhances sound pressure sensitivity.

3rd effect

The phase correction tube suppresses the closed-ear canal resonance and eliminates the masking effects, dramatically improving sounding in mid- and high-tone range.

4th effect

By eliminating acoustic resistors and applying small elements, it dramatically improves ultra-high-tone range. Also it realizes the spread of sound like open-air types.



Cabinet Front & Rear: Liquid crystal polymer / Center: Solid Sakura with "Fuki Urushi" (wiped lacquer) finishing
Element 010e002 Φ10mm Dynamic Type x 2
Acoustic System Twin-Equalized-Element System
Sound Pressure Level 104 dBSPL/mW
Frequency 3.5Hz to 45kHz (High-resolution compatible)
Maximum Input 400mW
Impedance 18 Ohms
Weight 21g (approx.)
Cable 1.2m (Y type) Quadruple Conductor Cable
Plug 4.4mm 5-pole Gold Plated Non-oxidized Copper Balanced Plug (Pentaconn / Made by NIPPON DICS)


  • Comply T-200 Ear Tip x 2 (Size: M, L / M is attached to the main unit)
  • Silicone Ear Tip (final, E type) x 5 (Size: SS, M, L, LL)
  • Cleaning Cloth
  • Wooden Casing (Sakura & Paulownia Solid Wood)
  • Instruction Manual / Warranty Card

Other Features

  • Applies tangential-less vibration plates, reducing the distortion on mid- and high-tone range.
  • Strong magnetic circuit with neodymium magnet, pure iron, and yoke improves sensitivity and sound quality.
  • Applies specific CCAW voice coil, greatly improving input resistance.
  • Applies liquid crystal polymer on the cabinet, enhancing slightest lingering sound and beautiful resonance.

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