In part 3 of this series we looked at the first practical dynamic microphone…the model 618 by Western Electric which came out in the early 30s. Bell Telephone Labs engineers didn’t rest after obtaining success with their first dynamic…by 1935 they had developed a real leap ahead in microphone design. The new mike was a big improvement over the model 618. This new mike was dubbed the model 630…but everybody called it the “eight-ball”…one look at it and you’ll know why.
Tests made by engineers at Bell Labs on the effects of various shaped objects on sound waves produced conclusive data which resulted in the selection of the spherical-shaped housing as the best suited in reducing directional distortion. The Eight-ball was the first truly non-directional dynamic and was designed to be mounted facing upwards. On top of the sphere were the sound entrance holes and over the top was an acoustic screen, two and a half inches in diameter and surrounded by a protective metal ring. This screen had wire mesh on either side of several layers of treated silk cloth. This screen reflected the sound waves coming from below and above in such a way as to make the pickup very uniform from any direction.
Because of the look of the mike with the flat screen on top of the round body…the British called their version of the Eight-ball…the “Apple and Biscuit”! The British telephone company, Standard Telephone and Cable (STC), had the license from Western Electric to manufacture this mike in England… and I believe it was used by the BBC right up until fairly recent times. This British version had the STC model number of 4021.
The overall quality of the model 630 was much better than the earlier model 618. Response to low and higher frequencies of sound was much smoother. The size of the 630 was much smaller as well and I think it was just a much cooler looking mike than the rather ugly 618. This mike had a special three conductor plug that fit into the bottom of the mike which also incorporated the stand mounting threads. There was also an accessory chrome swivel-joint that could be used to tilt the mike.
The Eight-ball dynamic found it’s way into big and small radio stations all over the country as well as finding uses in motion picture and recording studios. WOR in New York, a big 50,000 watt station, was a big user of the Eight-ball when it first came out. The Oakland Tribune station, KLX, used the model 630 on it’s live morning show back in the 40s and early 50s. I have a big band record album that features the Benny Goodman band with a picture of Benny and the boys in concert in the 1930s with an Eight-ball on a floor stand right in front of the band. I’ve also seen a film of Peggy Lee singing with Benny’s band and using the Model 630 Eight-ball.
Next time we’ll look at the very last dynamic mike designed by Western Electric which became even more popular than the Eight-ball.