In a simple sense, sound is a series of pressure waves sent through a medium like air or water. Think of standing in front of a speaker when loud music is playing — you can feel the sound vibrations travelling through your body from the soles of your feet. With his understanding of how sound waves behave, Thomas Edison developed the phonograph, the grandfather of modern record players, in 1877.
The phonograph could record sound and play it back. The receiver consisted of a tin foil wrapped cylinder and a very thin membrane, called a diaphragm, attached to a needle. Sound waves were directed into the diaphragm, making it vibrate. A hand crank turned the cylinder to rotate the tinfoil cylinder while the needle cut a groove into it to record the sound vibrations from the diaphragm.
The output side of the machine played the sound through a needle and an amplifier. The needle was set in the groove and the cylinder set to the beginning. The amplified vibrations played back the recorded sounds.
The recording medium used in the original phonograph was awkward to use and broke easily. In 1887, Emile Berliner, a German living in America, developed a hand-cranked machine that turned a hard rubber disc on a flat plate (instead of a cylinder) which became known as the gramophone. Unlike Edison's phonograph, it could only play back recordings, but this format gave the public access to music they would not have heard, and sparked the start of the recording industry.
Modern record players
While the technology used in recording and playback devices improved steadily, record players are still based on the needle in groove concept. One of Berliner's breakthroughs, the turntable, has been improved and mechanized to spin the record with the aid of a belt or a direct drive system. As the record turns, a stylus 'reads' the grooves. This cone shaped needle hangs from an elastic band of metal and is made from a hard material, usually diamond.
The stylus is set at one end of the tone arm, which is set at the side of the turntable, parallel to the record, and moves across the record while the stylus follows the spiral groove. The stylus picks up vibrations as it moves through the grooves of recorded sound, and those vibrations travel along the metal band at the end of the tone arm, to wires in a cartridge at the end of the arm. A coil in a magnetic field turns the vibrations into electrical signals, which are carried along wires to the amplifier. These boosted signals are finally turned back into sound through the speakers, producing the sounds and music recorded on vinyl records. [Reviews: The Best Speakers]
The development of vinyl records
Vinyl records have replaced Berliner's rubber discs. Easy to mass produce, master recordings are copied by placing a lacquer on a record-cutting machine. The master copy sends electrical signals to the turning record-cutting machine through a cutting head, which holds a stylus and cuts a groove in the lacquer that coils to the middle of the round disc. The cut lacquer is sent to a production company where it is covered in metal to make a metal master copy. This disc is a negative imprint of the lacquer and is ridged, not grooved. The metal master is used to make a metal record to be used to make the stamper, a negative of the end product. The stamper is put on a hydraulic press with vinyl between the plates. The vinyl is softened with steam, stamped and cooled off with water to create a finished vinyl record.