On 11/21/2022 12:03 PM, Al Lorona wrote:
Is that really true? If you looked inside all of your local AM broadcast
stations, all you'd see are dynamic microphones.
You're absolutely right, Al. Dynamic mics have long dominated broadcast
announce and DJ studios. EV owned that market until the '90s, when Shure
started making some inroads with their SM7B (which has long been one of
several popular studio narration mics).
I'm not sure why most headsets have electret mics.
Because they are much less expensive to build with very good sound
quality, and because they are MUCH smaller. The electret capsule in the
mics built into headsets and most ham mics probably costs much less than
a buck to manufacture. I suspect that the housings for Heil mics cost a
lot more than the capsules. NY9H, a former broadcast engineer who later
represented a major mic mfr, and who was an early K2 builder, was the
first to observe that the mic Elecraft sold with the K2 was a cheap
capsule crammed into the PTT housing with a bit of foam behind it. If I
remember correctly, was marketed as a Heil product.
Maybe it's because they have a higher output which lessens the need for
a lot of preamplification?
Unbalanced electret mics are built with a FET-follower output stage that
allows them to drive an unbalanced input stage with a reasonably high
input Z, and with bias supplied between the signal pair and return
through a high-value resistor.
When I was a kid, the most widely used mic, by far, was the carbon mic
used in ALL telephones (back when AT&T was a monopoly, and Bell Labs was
the premier engineering research institution on the planet). It was
displaced (maybe in the '80s?) with the invention of the electret.
73, Jim K9YC
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