Yamaha NS-333 - EF Series - Bookshelf Speakers (Pair)2 Way Acoustic Suspension Speaker System. The EF (Elliptical Form) Series feature Waveguide horns, PMD (Polymer injected Mica Diaphragm) woofers and highest quality internal Monster Cable wiring for total enjoyment of digital movie sound and music sources, plus elegant Yamaha traditional piano finish cabinets. High sensitivity and wide dynamic range for contemporary digital sources Waveguide horn allows the sound field to be shaped and controlled for