How It's Made - ribbon microphone

the ribbon microphone was invented in the 1920s and first commercially produced in 1931 it's called ribbon microphone because inside a thin aluminum ribbon positioned between two magnets converts sound waves into electrical signals introduced in 1931 ribbon microphones revolutionized the broadcasting and audio recording industries with unprecedented sound quality this company manufactures a modern version of the RCA 44 one of the first ribbon microphones this manufacturer handcrafts the microphone starting with the frame which holds all the components after cutting a flat piece of brass the machinist makes two bends with a press then drills threaded holes for the fasteners that will connect the frame to the rest of the microphone then he puts the bar into another press that bends the two ends upward to form a u-shape the frame goes off to another department to be chrome-plated and polished meanwhile another machinist takes a sheet of perforated brass to begin forming the microphone signature grille he secures it to a die with two mounting plates the die is the shape of one half of the multi-sided grille he mounts it onto a fly press a press operated by rotating a heavy counterweight as that counterweight spins the die descends into a forming bowl that's also in the shape of half of the grille a high-speed automated cutter trims the perimeter to make a neat even edge all around then the grille halves are sent off to be chrome-plated and polished next a technician assembles the motor the heart of the microphone first he snaps on two strong magnets the gap between them is where he'll later insert the key component the thin aluminum ribbon which gives this type of microphone its name after aligning the top of the motor with the bottom he attaches the frame which has since acquired a custom-made transformer electrical terminals and side brackets now for the all-important ribbon a technician crafts it from a hair thin sheet of pure aluminum it's so fragile he has to handle it with tweezers first using the edge of a razor blade he closed down the edges to a thin sheet of paper set on a glass cutting surface then he places a second sheet of paper on top and with a razor blade slices lengthwise dividing it into four ribbons each 2/10 of an inch wide when sound waves pass through the microphone they cause minut differences in air pressure between the front and back of the ribbon inside this causes the ribbon to move in response to the peaks and valleys of the sound wave the technician Cora gates the ribbon so that it responds to these minut air pressure changes more accurately he removes the protective papers and installs the ribbon in the motor between the two magnets in this position the moving ribbon is a conductor in a magnetic field generating a tiny current an electrical replica of the sound wave that can be recorded amplified or broadcasted a technician tests the ribbons tension to ensure it's neither too tight nor too loose he hooks up the terminals to an audio signal generator and measures a wood frequency the ribbon resonates if necessary he Tunes the ribbon by adjusting its tension he installs what's called a puff shield it prevents puffs of air from stretching or tearing the delicate ribbon a two-part metal housing will encase the lower part of the motor however before assembling it a technician glues on an embossed metal medallion bearing the company's logo then he takes the motor which by now has acquired an output cable stands it upside down and assembles the housing around it then he turns it right-side up and assembles the two halves of the grill a sleek-looking chrome-plated band hides the joint he fastens the microphone to a u-shaped stand called a yoke on each side there's a thumb nut which you loosen to tilt the mic then tighten to lock the position although newer technologies have emerged since the classic ribbon microphone still remains a favorite of sound engineers around the world

Channel: morrisonAV

Views: 173,219

Keywords: AEA, ribbon microphone, How It's Made, audio, microphone

Id: SHkOkqnJjy0

Length: 5min 0sec (300 seconds)

Published: Sun Oct 28 2012