Sennheiser HD 540 reference headphones are professional, high-quality around-the-ear headphones. They feature plush padding, DuoFol transducer, internal sound reflector and E.A.R. channels. The headphones were manufactured by German-based Sennheiser, which has a subsidiary in Connecticut that handles its product line in the U.S. Sennheiser no longer makes the HD 540, but they sold for more than £130 when they were first introduced.
Internal Sound Reflector
The internal sound reflector generates a surround-sound experience. The sound seems three-dimensional and moves around the listener as it does in a surround-sound theatre. This is achieved by the large reflector surface in the headphone that bounces certain sound waves off the reflectors, creating the illusion of surround sound.
E.A.R., or Eargonomic Acoustic Refinement, technology helps make accurate channelling of sound possible. The headphones are capable of reading many channels and producing them for the listener, with the same expansive feeling as speakers. The E.A.R. technology controls and adjusts channel levels to ensure a high-quality listening experience.
Duofol diaphragms restrict undesired resonances. The ear pads, headband and cushion are made from soft velour which makes the headphones barely noticeable to the wearer. The headphones are lightweight, with aluminium voice coils.
The Sennheiser HD 540 reference headphones have a gold-plated 1/4-inch plug and an 1/8-inch (or 3.5mm) adaptor. They weigh approximately 0.644 Kilogram and are 8 inches by 4 inches by 9 1/2 inches. The total SPL is 112 dB. The cable length is 10 feet. The impedance is 50 ohms and the frequency response is 15 to 28,000 Hz.