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Stax Ltd. (有限会社スタックス Yugen-gaisha Sutakkusu ) is a Japanese company that makes High-end audio equipment. Stax is best known for their electrostatic and electret headphones, called "earspeakers". Electrostatic headphones work just like electrostatic loudspeakers on a smaller scale.
Stax Ltd. was founded in 1938. Twenty-two years later in 1960, Stax released their first electrostatic earspeaker, the Stax SR-1. Over the following thirty-six years Stax produced a variety of amplification, earspeaker, tonearm, CD player, DAC, phono cartridge and loudspeaker products. In 1995, fifty-five years after the company's foundation, it became insolvent. The company was revived in 1996 as the new STAX company. In December 2011 Edifier announced the acquisition of 100% equity in Stax.
As of June 2009 the current Stax product lineup consists of eight electrostatic earspeakers, seven electrostatic amplifiers and accessories for these products including extension cords and a headphone stand.
Four models of earspeaker are based upon Stax' classic "Lambda" design. These are the SR-202, SR-303, SR-404 and SR-404 Limited.
Two models are of small sized in-the-ear earspeaker. The SR-003 is terminated with a standard Pro-Bias plug and is designed for use with a standalone electrostatic amplifier. The S-001 MK2 is terminated with a proprietary plug and is designed for use with its matching battery powered electrostatic amplifier for use as part of a high end portable audio system.
One model, the 4070, is a closed back electrostatic earspeaker, primarily targeted at studio and broadcast application.
Stax' flagship earspeakers are the SR-007Mk2 on the export market, and the SR-007A on the Japanese market. They are identical, apart from the housing color. The SR-007Mk2 has an MSRP of $2,200 in the United States. Their predecessors are the SR-007 and SR-007BL.
In Autumn of 2007 Stax released the SR-007Mk2 earspeaker, the design of which changes the finish of the materials, such as the earpads. A couple months later they released the SR-007A on the Japanese market.
There are two different bias voltages for Stax earspeakers. The first earspeakers have a 230 volt bias, referred to as Normal bias. While the later earspeakers have a 580 volt bias, referred to as Pro bias. The Normal bias earspeakers use a 6 pin plug, while the Pro bias ones use a 5 pin plug. Pro bias (5 pin) earspeakers plug into a Normal bias (6 pin) socket, but for obvious reasons not the other way around. All current Stax earspeakers are Pro bias, as the last Normal bias earspeaker went out of production around 1992.