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

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.

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.

“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.

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.

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.

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.