Realistic Deep Bass and Mid-to-High Range Clarity Bring Out the Original Sound Quality in Every Detail
SZ Series – the Breakthrough in Headphone Architecture

Immerse yourself in the raw presence of a live stage performance. JVC’s passionate pursuit of original sound quality has written another new page in the history of headphones. Responding to the challenge of creating headphones that can deliver both realistic and impressive bass and high resolution mids and highs, JVC developed the industry’s first* Real Sound System. JVC has taken another step closer to reproducing the inimitable quality of the original sound source.

* Launched on May 21, 2013 as dynamic headband-type headphones according to JVC Kenwood research.

Application of audio speaker acoustic theory and the Kelton speaker design method to headphones

In the case of inner ear or around ear headphones, it is virtually impossible for a single driver unit to simultaneously reproduce both the delicate nuances in the mid-to-high range and the powerful presence of deep bass sound. Multiple units separately driving the mid-to-high range and bass acoustic range is a solution, but requires measures to prevent frequency bands of these driver units from interfering with each other. One way is integrate network circuitry to electronically cutoff unwanted band frequency, but overreliance on electronic solutions can result in a less realistic “live” quality. That’s why JVC looked at the Kelton speaker design method. This approach consists of sealing one side of the speaker unit, installing an air chamber on the other side, channeling the bass sound through a resonance duct and taking advantage of the Helmholtz resonance of the duct.

Speaker design based on the Kelton Method

SZ series also features a Double Bass Reflex design

The SZ series of around ear headphones introduces the Stream Woofer DB – an evolved version of original JVC technology, which not only applies the Kelton method, but also adopts the double bass reflex method - an acoustic design theory for enhanced speaker system performance. The double bass reflex method is a speaker design approach that “filters out” the mid-to-high frequency range from the bass unit output by natural decay as it passes through the two chambers.

Double bass reflex speaker

Stream Woofer DB (SZ series) frequency characteristics

“Industry First”* Stream Woofer DB (Double Bass Reflex) Architecture

Deep bass range is reproduced by a large 55mm carbon diaphragm secured in a highly rigid unit base with superior vibration damping performance. Bass ports measuring 8mm in diameter and 8mm in length are positioned at three locations in the first chamber of the housing. The second chamber surrounds the outer circumference of the first chamber like a donut, and is equipped with a “Dual Stream Duct” (6mm in diameter and 70mm in length) that serves as the second stage bass ports. In the case of the HA-FXZ inner ear headphones, the Stream Duct is a needle-like duct with an internal diameter measuring only 0.4 mm and is designed to deliver rich bass to the 2cm3 space inside the ear. However, in the case of the SZ series headphones, a duct with an internal diameter of 6 to 8 mm has been adopted to fill the relatively large 40cm3 space within the ear cup with pure bass. Undesirable mid-to-high frequencies completely decay as the bass unit output passes through the two chambers and bass ports that comprise the bass reflex system, resulting in the reproduction of only the bass frequency range.

Deep bass driver unit incorporating a newly developed large carbon diaphragm (55mm in diameter)

Stream Woofer DB Structure

Comparison of frequency characteristics (single bass reflex vs. double bass reflex system)

Dual Stream Duct in the SZ Series Delivers Impressive Bass Depth and Presence

While the unprecedented deep bass performance of the HA-FXZ series of inner ear headphones is produced by a stream duct that is as thin as a needle, the SZ series of around ear headphones uses two dual stream ducts connected to the double reflex structure to deliver rich deep bass. In both cases, the innovative design and shape are the product of extensive trial and error in pursuit of a solution that both aspires to “original sound” quality and fit in very limited available space.

Stream duct
(HA-FXZ series)

Dual stream duct
(SZ series)

Specially Tuned Mid-to-high Driver Unit for Ideal Balance with the Stream Woofer DB Output

The mid-to-high range driver unit features a lightweight and highly rigid carbon nanotube diaphragm (30mm in diameter) for reproduction of mids and highs with extreme clarity. The unit is specially tuned for optimum balance with the rich deep bass output of the Stream Woofer DB.

Mid-to-high range driver unit (30mm in diameter)

Carbon nanotube (Image figure)

Ideal frequency characteristics achieved by special tuning of the mid-to-high range driver unit to balance the bass unit

Highly Rigid Vibration Damping Cylinder Eliminates Undesirable Vibrations

The Stream Woofer DB is secured in a highly rigid vibration damping cylinder to suppress undesirable vibrations. The premium HA-SZ2000 model adopts a cylinder made of brass, which has a higher specific gravity and enhanced vibration damping performance. The HA-SZ1000 headphones incorporate a cylinder that combines the highly rigid unit base and vibration damping material to achieve crisp deep bass.

Brass “vibration damping” cylinder

Quality in Every Detail: OFC Cables and Other Features

Oxygen-Free Copper (OFC) means an extremely high copper purity of 99.95% with virtually no oxygen content. The lower the degree of impurities in the cable, the higher the electrical conductivity, which means less signal loss and crisper sound with high resolution. The premium HZ-SZ2000 headphones come with silver-coated OFC cables for even greater electrical conductivity, contributing to vivid resolution throughout the entire sound range from the deepest bass to the mid-to-high range.
In addition, the steel commonly used in the magnetic circuitry of the HA-SZ2000 series driver units has been heat treated to reduce internal deformation. Powerful neodymium magnets with a magnetic strength of 360kJ/m3 are used in both the bass and mid-to-high driver units of the SZ series. Reproduction frequency bandwidth and output levels are 4 to 35,000 Hz. Maximum allowable input of 1,500mW has been achieved. Each detailed enhancement brings audio reproduction ever closer to the original sound.

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