Klipsch Reference R-40M Bookshelf Speakers (Pair) The Klipsch Reference R-40M bookshelf speakers are compact, passive speakers designed to deliver surprisingly big sound from a small footprint, making them ideal for music or home theater in smaller to medium rooms. Featuring a 1" aluminum LTS tweeter with a Tractrix horn and a 4" spun-copper woofer in a rear-ported MDF cabinet, they provide clear highs, punchy mids, and respectable bass with high efficiency, so they're easy to drive with most entry- to mid-level receivers or amplifiers. Product Highlights: 1" LTS (Linear Travel Suspension) aluminum diaphragm tweeter with Tractrix® horn 4" spun-copper TCP (thermoformed crystalline polymer) woofers Frequency response: 71-21,000 Hz (± 3dB) Power handling: up to 50 watts RMS Sensitivity: 91 dB Impedance: 8 ohms Bass-reflex design with rear-firing port Magnetic grille protects drivers and looks stylish Scratch-resistant textured wood grain vinyl finish Single gold-plated binding post speake