After a long absence from the bleeding edge of the high-end earphone market, Shure has just debuted a four-driver canalphone model: the SE846 Quad Driver Earphones ($1000). Using 10 laser-cut, laser-welded stainless steel plates, Shure boasts that the SE846 earphones offer a true subwoofer experience through a revolutionary low-pass filter. The earphones feature two low-frequency drivers, one mid-frequency driver, and one high-frequency driver. Users…