"Scott Dorsey" wrote in message
...
Richard Knoppow wrote:
My one and only Turner mic is a 999, a low impedance
dynamic. I came into a windfall of good impedance matching
transformers (UTC 01 Ouncers) so matching is no problem.
Its
a decent mic but may not be representative since I had to
remove a dent from the diaphragm. This can be done with
sticky tape and great care. The mic sounds good, less rise
in the high end than my Electro-Voice 635. I think this is
probably the original sound.

The 252 definitely has a serious rise on-axis and it's
kind of
grating-sounding. That comes across nicely in a pileup.

Turner seems to be the only one of the original big
four makers of PA mics that did not survive. Astatic,
Electro-Voice, and Shure Brothers all managed to navigate
the vicissitudes of life.
American Microphone was another company who did not
survive. Their last line of mics was a valiant attempt to
break into the high quality broadcast and recording market
but their technology left a lot to be desired. I have a
couple of their high-end cardioid mics.

Are they any good? I remember American Microphone trying
really hard
to sell into the broadcast market with really cool-looking
handheld omni
mikes. The chief engineer of the radio station I worked
for dismissed
them all as "crap that's designed to look nice on TV."

A friend had a recording made on his Ampex part of
which was done with an experimental American pressure mic
intended for high quality recording and another section
with
a "Telefunken" mic, actually a Scheops 201-M. No
comparison,
the American mic made all the instruments sound like they
were made of paper boxes. The Schoeps mic is the one that
actually established Telefunken's reputation and is the
mic
used for the Mercury Records "Living Presence" series.
The cardioid used a ribbon element with a dynamic
just
under it. It has decent patterns in one plane going
horizontally around the mic but, of course, there is no
match whatsoever in the vertical plane and very poor
directivity. Actually, Brush made a similar microphone in
the mid or late 1930s, essentially an RCA Junior Velocity
mic with a Brush crystal element fixed to the top of the
ribbon and facing up. I suspect it had much the same
problems. Brush used a rather complicated network to match
the two sections. I don't think they made these for long.

Actually, the WE 639 (later the Altec 639) used the same
arrangement.
It could be a figure-8, an omni, or a cardioid, but it
only sounded
even remotely decent as a figure-8 because the dynamic was
just so awful.

I thought all the Living Presence recordings were done
with Telefunken
condenser mikes?
--scott

It seems that many microphones designed for
communication purposes had/have a haystack in the
articulation range, i.e., rising above about 500 hz and
peaking around 3 to 5 K. As you probably know most of the
energy in the human voice is below about 500hz but the
frequencies that contribute to articulation are around 1k to
3k. Good articulation can be had even if no frequencies
below about 1500hz are included but naturalness requires
some of the lower frequencies.
The 639 dynamic element is the same as used in the 630A
"Eight-Ball" and 633A/B "Saltshaker". The diaphragms were
hard to make. They were annealed to get the hard spots out.
John Frayne told me that there was more than a 50% rejection
rate. Good ones sound decent many were not so good. Altec
was not as careful as WE even though they had to meet WE
specs. Doc Frayne told me that WE lost money on every 639
they made. It was a prestige item.
The 639 was arranged with the moving coil element facing
front where the American Mic had the element under the
ribbon facing up. This makes sense if one thinks about the
pattern in the horizontal plane only. The problem is that
the moving coil mic is not truely omnidirectional due to the
diffraction effects of the microphone case so there is no
match or a very poor match in the vertical plane. The 639
actually has reasonably good discrimination in both planes
because the directionality at high frequencies depends on
diffraction effects rather than the phasing of the two
elements, the ribbon is rolled off above about 3Khz. The 639
is a bit of a kluge but a very cleverly worked out one. BTW,
the Marshall and Harry patent shows the moving coil element
mounted _on top) of the ribbon, but facing forward. I think
the revesed arrangement on the production mics was done for
appearance. The case was a Raymond Lowey design and I think
the mounting was compromised for appearance.
The 630A was also expensive to make because it was
complex. The case has two parts with a baffle and acoustical
resistance between them. The 633 was an attempt to make a
cheaper version.
Altec made some plastic diaphragm versions of the same
capsule which were also used for small tweeters. I don't
know how they sounded in comparison to the metal diaphragm
version.
In general, I don't like moving coil microphones for
high fidelity applications. They alsways sound mushy to me.
They are eminently suitable for communications purposes
because they are extremely rugged and can be made to have
high output. Most moving coil mics rely on some sort of
resonator at the high end to keep the response up. The 630A,
which was thoroughly described in a paper in the Bell System
Technical Journal, has a cavity resonator plus a capacitive
resonator below the diaphragm. All these resonators combine
to produce a very sharp cut-off at the high end and
typically result in poor transient responce.
The American mics do not sound very good because the
moving coil elements are not very good. Again, metal
diaphragms and rather poor transient response. The
omnidirectional mic showed up on some of the local TV
station, I remember seeing them on KTTV, but were no
competition to Elecro-Voice who used molded plastic
diaphragms and had pretty smooth response. I think American
tried hard but simply did not have the technology to
compete. The cardioid mics are also adjustable pattern, they
have a board with jumpers under the label. I don't know a
lot about the history of the company. I think I did read
something or hear somethign about them long ago but its
faded away.
There were two other small microphone manufacturers in
the Los Angeles area in the 1930s and 1940s, they were
Universal Microphone Co, in Culver City and Carrier
Microphone Co. I beleive Carrier was the superintendent of
Universal. I am not sure of American Microphone personel had
any relation to these companies but think they might have.
American was in East LA at first but moved to Pasadena.
Telefunken never built any microphones but acted as the
marketing agency for both Neumann and Schoeps. I think they
even marketed some AKG mics at one time. While Neumann mics,
particularly the U-47 became famous under the Telefunken
name the Mercury Living Presence series was apparently made
using the Schoeps 201-M, a dual capsule cardioid/variable
pattern mic. They are shown in some publicity photos of the
sessions. Mercury used a single-mic pickup, somewhat unusual
for American recording at the time. They also used modified
Fairchild cutterheads. Mercury was one of the first
recording companies to adopt hot stylus (orinated at
Columbia) and variable pitch. The pitch variation was done
by hand by the recording engineer following a marked up
score. Not sure when the first automatic groove pitch
machines came out but it must not have been much later.
Meissner (SP ?) wrote a letter to Audio Engineering
magazine after an article describing the Columbia Hot Stylus
technique was published claiming he had developed a similar
system in the late 1920s or early 1930s which he attempted
to use at Brunswick. The management thought the resulting
records looked funny and did not ever use it in practice.
Hot stylus makes a lot of difference in both noise and in
high frequency response where the original is made on
laquer, perhaps less on wax but I am not certain of that.

--
Richard Knoppow
Los Angeles
WB6KBL