The MEMS Microphone. The Biggest Selling Microphone Ever!

History lesson

If we go back 100 years or more, every telephone on the planet transmitted speech via a carbon microphone. This was a small container of carbon granules polarised by a low voltage and having a diaphragm at the front. As the diaphragm vibrated, the granules were subjected to varying pressure causing small changes in the voltage. This signal passed through a transformer and went off down the telephone line to be picked up by the receiving phone. Carbon microphones continued to be used in telephones all way up to the 1980s. Millions upon millions of carbon microphones were in daily use right across the world! The audio quality was a bit shit to say the least, with plenty of crackling and unwanted noise, BUT……. speech was intelligible, they were dirt cheap to manufacture AND they were utterly reliable over many years of use.                                                                             

End of history lesson.

Scroll forward to the present day.

Exit the carbon mic, enter the MEMS mic. Today, mobile phones, laptops, tablets and other portable communication devices are everywhere. Most of these devices contain at least one MEMS microphone. Recent sales figures from US manufacturer Knowles Acoustics show sales for their SiSonic silicon based MEMS microphones in excess of 1 billion units!! 1 Billion units!! That is a lot of undercover microphones.

So What Is a MEMS microphone?

Knowles SiSonic MEMS microphone SPU0410LR5H-QB

A MEMS microphone is manufactured using micro-electromechanical systems processing techniques. These microphones are etched into a semi-conductive silicon wafer. A pressure-sensitive moveable membrane (diaphragm) is etched behind a stationary perforated backplate. The perforated stationary plate and the diaphragm act together to form a capacitor (similar in design to a condenser microphone). The MEMS mic is designed to be mounted on a circuit board along with preamp and other application specific components.

MEMS microphone motor

Sketch of a MEMS microphone motor (not to scale). The diaphragm has a thickness of 1 µm, the gap between the backplate and the diaphragm is 4 µm, the diameter of the perforations in the backplate is 10 µm, and the thickness of the backplate is 2 µm. The distance across the motor from support post to support post is 590 µm. Sketch courtesy of Knowles Electronics.

Just like the carbon mics of the last century these MEMS microphones are extremely cheap to produce and are highly reliable. However, what is very different is the audio quality. The Knowles SiSonic MEMS microphone pictured above has a near flat frequency response from 100Hz to 10kHz which is pretty good for such a tiny, inexpensive, microphone. (<£1)

Knowles SPU0410LR5H-QB MEMS mic frequency response 100-10kHz

But what is really mind blowing is the Ultrasonic response!

The graph continues on up to 80kHz !!! (and beyond)

Knowles SPU0410LR5H-QB MEMS mic frequency response 10kHz-80kHz

This brings me to my current project Ultrasonic Recording,

This MEMS microphone is perfect for recording the activity of bats, amphibians, crickets and other wildlife whose calls are in the ultrasonic range high above our rather limited human hearing.

AudioMoth https://www.openacousticdevices.info/ is a miniature recording device currently being developed to record and collect data on the activities of a variety of wildlife. The latest version of AudioMoth uses the Knowles SPU0410LR5H-QB MEMS microphone featured above. 

Open Acoustic Devices AudioMoth

So what does it sound like?

CLICK HERE to hear ‘BATS with Guitar’ (Yes, you heard right! )

N.B. The BATS have been slowed down to bring them within the range of human hearing

Conclusion

Hidden away out of sight on a circuit board inside a mobile phone or a laptop or some other electronic device the MEMS microphone is never going to gain any awards for stylish good looks. Even though its audio quality is amazing (considering its price) it isn’t about to replace the Neumann U87 in the recording studio! Nevertheless it is an extremely versatile tool that will be with us for many years to come and is without doubt the biggest selling microphone ever.

Sennheiser MD408 N Super-Cardioid Dynamic Gooseneck Microphone. 1960’s/70’s

Sennheiser MD408N
Sennheiser MD408N

Originally designed for speech and vocals the Sennheiser MD408 N is a solid, reliable, workhorse microphone which is useful for many tasks. It performs well on guitar cabs, delivering a rich beefy sound with plenty of midrange punch. The flexible gooseneck makes it particularly easy to position. It is also useful on snare and a variety of percussion. Once again the gooseneck is very handy for manoeuvring in awkward spaces. Being a super-cardioid it also has excellent feedback rejection.

Some microphones were destined to appear with the stars, glittering centre stage with Elvis or Tina Turner or David Bowie. Others however, never quite made it to the limelight. Back in the 60’s and 70’s the MD408 N was often used as a humble studio talkback mic. Even so, when it comes to dull publicity photos the shot below takes a lot of beating!

Sennheiser Advert 1969 for MD408N
Sennheiser MD408N  Klien Tuchel Connector and standard 3/8 inch stand adapter.
Sennheiser MD408N Klien Tuchel Connector and standard 3/8 inch stand adapter.
Sennheiser MD408N On/Off switch

The MD408 also has a silent on/off switch which is very handy if it is used for talkback or as a lectern mic. The neat square plastic actuator has sadly gone missing on mine but you can see it in the publicity photo.

CLICK HERE to listen to the MD408 on rock’n’roll Guitar at a live show.

Conclusion

Whilst it may not have the kudos and charisma of the more famous Sennheiser Models such as the MD421 and MD441 it is nevertheless a recommended addition to any collection.

The Valan Atlas PMS3. The Best Microphone Stand Ever?

Valan Atlas PMS3 Microphone Stand with AKG D202E

The Valan Atlas PMS3 was originally manufactured in the late 1960’s by Valan Electrics, Birmingham, England. It is the only microphone stand that I can think of that has appeared regularly as a ‘must have’ on the Technical Riders of many well-known performers. A quick glance around the internet reveals pictures of famous users including Jimi Hendrix, Van Morrison, Helen Reddy, Ozzy Osborne, Led Zeppelin, Status Quo, Deep Purple, The Slits, The Clash and Bono (U2)

Bono of U2 with Valan Atlas Microphone Stand

 It has also been a firm favourite with comedians. Here below is British comedian and national treasure Ken Dodd. On stage at the Theatre Royal Norwich.

Ken Dodd with Valan Atlas Microphone Stand

So what is it about the Valan Atlas that makes it so different to other mic stands.

1. Thanks to its unusual woven wire clutch mechanism the height is instantly adjustable. It goes up and down with a single movement of the hand and stops wherever you let go. So no faffing around slackening or tightening anything.  

2. It has a very heavy cast iron base with a small footprint. This makes it extremely stable but also very easy to tilt in any direction. You can even lean it right over like Bono in the picture above. It is perfect for the theatrical showman/woman.

3. The small footprint of the base also means that the performer is unlikely to trip over it!  From the sound engineer’s point of view it also means that singers and guitarists who tap their feet are less likely to hit it!

Base of Valan Atlas PMS3 Microphone stand

 4. The solid construction of the stand and its clutch mechanism also acts as an excellent shock absorber. This helps protect the microphone against unwanted handling noise.

5. The middle section covering the clutch mechanism also forms a very comfortable hand grip at waist height.

6. The chrome finish is superb and always looks fabulous under a centre spot.

Valan Atlas PMS3 Microphone Stand

The Bad News and the Good News.

Very sadly Valan Electrics went out of business in the early 1980’s. The last mention of them I can find is in a Studio Sound survey in July 1981. However, these iconic stands have remained popular and the good news is that they are once again being made by US company RCI    http://www.rcistarlite.com/micstand1.htm 

Conclusion.

We all know that cut-price microphone stands are never worth it. They will always let you down (usually in the middle of the gig)! Valan Atlas PMS 3 microphone stands have never been cheap. However, they are beautifully made, a joy to use, and will last for years. I bought mine in the 70’s. It has been centre stage on thousands of shows and still looks as good as the day it left the factory. Worth every penny!

Status Quo with Valan Atlas PMS3 Microphone Stands

LABOR W MD7 Omnidirectional Dynamic Microphone Circa 1950.

A Short History Lesson.

In 1945, just a few weeks after the end of World War 2 Fritz Sennheiser and 7 fellow engineers from the University of Hanover set up a business designing and producing a range of electrical equipment in a laboratory called Laboratorium Wennebostel (“LABOR W” for short). The laboratory was named after the village of Wennebostel in the municipality of Wedemark, where it had been relocated during the war. LABOR W began building microphones in 1946 and by 1953 (see catalogue below) they had developed a whole range of microphones, including the legendary MD 21 which is still in production today. By 1955 the company had expanded to 250 employees and in 1958 changed its name to Sennheiser.  

These days microphones from the early LABOR W period are becoming increasingly rare, so when this unusual looking MD7H turned up on eBay, ‘untested’ but very cheap, I immediately clicked ‘Buy Now’.

LABOR W MD7H   front view
LABOR W MD7H  front view 2
LABOR W MD7H rear view
The ‘H’ indicates that this is the High impedance version.

The photograph on eBay however, gave no sense of scale and it wasn’t until the microphone arrived that I realised just how small it is! I was reminded of the anecdote of the person who buys a gorgeous sofa online at a bargain price and when it arrives it turns out to be for a dolls house! Had I seen the LABOR W advert below that might have given me a clue.

LABOR W MD7 Advert early 1950's
‘Our most powerful moving coil microphone
MD7 for speech’

Below are the microphones featured in the 1953 LABOR W Catalogue.

Microphones featured in the 1953 LABOR W Catalogue. Page 1
Microphones featured in the 1953 LABOR W Catalogue. Page 2

(Translation of catalogue description above)

‘MD7 Speech microphone

Particularly good speech intelligibility due to emphasis on high frequencies. Therefore recommended for announcement and dictation systems. The soft rubber housing makes the MD7 insensitive to rough handling. Available in low and high impedance versions.

Dimensions: 76 x 48 x 48mm.’

For a sense of scale here below is the baby MD7 along with its Senneiser cousins the MD21 , MD421 and the mighty MD441.

LABOR W MD7 along with its Senneiser cousins the MD21 , MD421 and the mighty MD441.

Innovative design

In the early 50’s the soft rubber housing of the MD7 was an innovative design feature, and indeed made it very robust and resistant to rough handling. I haven’t tried it, but I think it would probably bounce if dropped from a height! It therefore came as no surprise once I had soldered a jack plug on to the cable it burst into life working perfectly.

So what does it sound like? CLICK HERE

LABOR W production came to an end in 1958 and the name changed to SENNHEISER. The rest is history!

The Capac BIN-AURAL (1936- c1960) ‘The accurate and simple equipment for testing the internal condition of mechanism “by sound” .

Although we are all familiar with the medical stethoscope used by doctors to listen to the internal condition of the patient’s heart and lungs etc., few will be familiar with the use of stethoscopes in other industries.

In 1936 British engineer Charles Edward Noel-Storr, Managing Director at Capac Co. Ltd in London, came up with an interesting variation on the stethoscopes that were available at the time.                                            

 The Capac BIN-AURAL 

Capac BIN-AURAL oak case
Who can resist a gorgeous oak case?
Capac BIN-AURAL in its oak case
WOW!
Capac BIN-AURAL in oak case with tray removed.

Capac Company’s BIN-AURAL was somewhat similar in appearance to a medical stethoscope and was used to detect faults and assess the condition of a variety of mechanical devices and structures.

Capac BIN-AURAL with single tectoscope.

The long probe called a tectoscope can be put in contact with the outside part of a machine/engine/structure and the sound from inside is transmitted back to the earpieces via a metal diaphragm. In this way the skilled mechanic can identify specific problems. Virtually no sound is picked up from outside, making it perfect for isolating faults in noisy environments such as factories and machine shops.

The Author. Listening to car engine using Capac BIN-AURAL with single tectoscope.

So what made the Capac BIN-AURAL different to its competitors?

Apart from the single tectoscope illustrated above the user could also employ a second tectoscope. This enables the operator to listen to the mechanism from 2 different points simultaneously.

Capac BIN-AURAL with two tectoscopes.

A further option is also available in the form of the Tectophone.

The tectophone (illustrated below) is a small exponential horn which is screwed on to the diaphragm. This can be used to listen in close proximity to the outside of a mechanism in the particular location where faults are suspected. It can also be used in conjunction with a tectoscope to listen to the outside and inside simultaneously or to compare.

Capac BIN-AURAL with tectophone and tectoscope.

For a detailed explanation of the uses of the Capac BIN-AURAL I have reproduced below the original manual that came in the box.

01 CAPAC BIN-AURAL Manual Cover
02 CAPAC BIN-AURAL Manual Page 1
03 CAPAC BIN-AURAL Manual Page 2
04 CAPAC BIN-AURAL Manual Page 3
04 CAPAC BIN-AURAL Manual Back Page

CONCLUSION

In the build up to World War 2 aero engine makers such as Armstrong Siddeley Motor Limited, Bristol Aeroplane Company Limited, D. Napier & Son Limited and many other British engineering companies adopted the Capac BIN-AURAL as an effective diagnostic tool. With the aid of the BIN-AURAL, a mechanic could pinpoint the source of a sound, or listen to that sound from 2 different perspectives.

P.S. Whilst the Capac BIN-AURAL is not itself a microphone, a microphone can be easily attached, making it a great tool for gathering unusual sounds from inside engines and machines and other structures.

Capac BIN-AURAL with Sennheiser MKE2. Insert into tubing.
Capac BIN-AURAL with Sennheiser MKE2. Insert into tubing. Closeup.

The following ‘collage’ recording of bits of my car engine has been made with a Sennheiser MKE2 inserted into the rubber tubing which connects to the tectoscopes.

CLICK HERE to listen

RSA Selmer RL1 Ribbon Microphone 1947-1958

Wireless world Advert October 1946

Looking back from the 21st century it is hard to picture a ‘dream’ PA system as being 2 x 8” speakers attached to a 12 WATT amplifier with 2 mic inputs!! However, in the UK this marks the beginning of the age of amplified, modern popular music. Within a few years the wattage and power output of PA systems would be rising rapidly, trying to keep pace with bigger and louder guitar amps!

In 1947 R.S. Amplifiers Ltd was bought by H. Selmer & Co Ltd who were at that time the largest musical instrument manufacturer in England. RSA’s newly launched Truevoice U12 PA system (described in detail below) continued in production until 1958 and formed the starting point for the Selmer Truevoice range of amplifiers. Selmer amps soon became a firm favourite for a whole generation of guitarists and bands.

R.S.A Selmer U12 PA system
Photographs of U12 PA Courtesy of Mario Martins.
R.S.A Selmer U12 PA Amplifier
R.S.A Selmer U12 PA Speaker with Mic compartment.

The handy compartment lined with green baize is where the microphone would be stored in transit.

The RSA Selmer RL1 Microphone

R.S.A. Selmer RL1 Ribbon Microphone.

Designed as a gigging PA microphone the body of the R.L.1. is very solidly cast in aluminium. The styling is distinctive and unusual. Somewhere between Art Deco and Mock-Tudor!  I can’t think of another microphone like it. The design of the grill is also peculiar to this model (and the later RL2) with baffled slots cleverly contrived to prevent the direct implosion of breath on the ribbon.

Inside the R.L.1. the ribbon motor is also further protected by a cotton bag.

R.S.A. Selmer RL1 Ribbon Microphone Interior.
R.S.A. Selmer RL1 Ribbon Microphone Interior case.
R.S.A. Selmer RL1 Ribbon Microphone Grill Interior.
R.S.A. Selmer RL1 Ribbon Microphone Rear View..

Optional step-up transformer 15 Ohms – 50k Ohms (below)

 This enabled the mic to be plugged into a high impedance PA input or even a guitar amp.

R.S.A. Step-up Transformer 15 Ohms- 50k Ohms.

Performance.

In terms of performance the R.S.A. Selmer RL1 is pretty much what you would expect from a ribbon microphone designed to go with the U12 PA system. Although it is somewhat lacking in high end response this would not have been a problem when delivering through 2 x 8 inch speakers! However, it has a pleasing, warm midrange which is flattering for most vocalists.

I had been intending to record a vocal clip to illustrate the qualities of this microphone but current COVID-19 restrictions here in the UK still make it difficult to meet up with performers. Hopefully in the next few months this situation will improve and I will be able to add a suitable recording to complete this post. 

P.S.

Here are a couple of likely lads from Liverpool (circa 1960) with the Selmer RL2. The grill is identical to the RL1 but the bodywork is somewhat different. I wonder what ever happened to these fresh-faced youths?

Tannoy Microphone Circa 1950.

Background.

The Tulsemere Manufacturing Company was founded in London in 1926 by Guy R. Fountain. In 1928 the name was changed to Tannoy. Rectifiers used in the company’s amplifiers utilised an alloy made from lead and tantalum. The name is simply a contraction of TANtalum/allOY.

 In the UK throughout the 1930’s Tannoy built up a considerable reputation for the design, manufacture and installation of industrial public address systems. Tannoy systems appeared in department stores, factories, offices, public buildings, academic institutions and sports grounds. In fact, just about anywhere that public announcements needed to be made- indoors or outdoors. There were even mobile systems fitted to vans!  

During World War 2, Tannoy manufactured installations for the British Army, Navy and Royal Air Force. Orders and day to day communications would be announced over ‘the Tannoy’.

By the end of WW2 the Tannoy brand was pretty much synonymous with any PA system. In 1946 the word ‘Tannoy’ passed into the Oxford English Dictionary as a noun meaning ‘public address system’. This usage is still current in the UK today.

As can be seen on the microphone featured here, Tannoy were not shy when it came to emblazoning the company name on their products. Judging from the tasteful antique bronze and grey paint finish, this gooseneck announcement microphone may well have been mounted on a mahogany desk in a Town Hall or other municipal building.

At first glance I assumed that this specimen, which has no model or serial number on it, was simply a dynamic paging mic in a fancy-looking case. However, when plugged in I was very surprised to hear how good it sounded! I carefully removed the grill and inside this is what I found……………

……. A well-made and neatly constructed, end addressed, ribbon motor. The back of the ribbon is enclosed by the magnet and the rear section of the casing. This produces a pretty much cardioid, directional polar pattern. It is similar in design to the STC4113 featured in a previous post.

So what does it sound like?   Because, here in the UK we continue to be under COVID-19 lockdown restrictions I still can’t get close to any proper musicians. I have therefore put together a slightly eccentric audio ‘collage’ of ‘percussion’ from around my desk to illustrate some of the impressive qualities of this distinctive Tannoy microphone. Marvel at the slightly sinister sound of 2 small terracotta plant pots being rubbed together and check out the creaky floor board! The finest details and complex textures of a variety of sounds are effortlessly reproduced as well as delivering natural speech with a high level of intelligibility.  

 CLICK HERE TO LISTEN.  

Conclusion.

This is definitely a microphone to keep. Apart from vocals and percussion, I have a feeling that it will work well on a whole range of instruments. Ribbons are always great for beefing up guitars! Can’t wait to get back to gigs and try it out!

Tannoy Mic on Rycote shock mount.

P.S.  

Here below are a couple of photos of another Tannoy microphone sent to me by Stewart Tavener at http://xaudia.com/. This mic appears to share the same casing and ribbon motor as mine but has a switch and hinged stand mount.

Image

Season's Greetings 2020

Omnidirectional Dynamic Vocal Microphones

Up until the late 1960’s, cardioid, omnidirectional and figure of eight dynamic microphones were all commonly found in use on public address systems. Singers were able to choose whichever pattern suited their particular style of delivery. Figure of eight ribbon mics, for instance, were enormously popular with the jazz singers and ‘crooners’ of the 40’s and 50’s because of their smooth response and rich proximity effect which enhanced the low end of the voice. Omni was preferred by singers who required a more ‘open’ sound and the ability to move around without altering tone. Unfortunately, with the development of high power PA systems and the introduction of wedge monitoring in the late 60’s, only cardioid microphones had the required rejection characteristics to deliver a suitable amount of gain before feedback. Consequently, within a few years figure of eight and omni all but vanished from the stage and were pretty much banished to the studio!

I recently acquired a number of vintage omnidirectional dynamic mics from the tail end of the last century. Although the primary purpose of these mics was originally news gathering, my attention was drawn to the following excerpt from the AKG Engineering Data sheet for the D130. It perfectly describes the numerous benefits that an omnidirectional microphone offers the vocal performer.

AKG D130 Data Sheet.

A wide-range instrument, the D-130E offers “open”, natural reproduction of speech and music -without harshness, popping or bass emphasis. Moreover, the D-130E ‘s omnidirectional pattern and consequent absence of proximity effect enable the microphone to retain this natural quality -regardless of the relative position or distance of performers working into it. Together with its handling comfort and attractive styling, these same characteristics also lend the D-130E to a variety of hand-held on-camera applications in the studio -especially to pop-free coverage of vocalists who do not desire proximity effect.

Many singers (especially male vocalists) have an uncomfortable relationship with cardioid microphones because of their inclination towards ‘boomy’ bass and unpleasant popping plosives. I have also worked with performers who are in the habit of pulling away from the mic when delivering the loud bits leaving their voices sounding suddenly thin and weedy (N.B. Proximity effect works in both directions i.e. moving away reduces bass). With omni the bass remains constant with the desired reduction in volume.

And another thing………

For performers whose vocal style involves ‘cupping’ the back of a cardioid dynamic, maybe an omni would be a better choice? It comes ready ‘cupped’!

SM58 cuppingBeyer M58 2 N (C)

 

 

 

 

 

 

 

So…….. Here’s a thought…….

With the rise of in-ear monitoring many performers and bands are dispensing with their cumbersome (and feedback prone) on-stage wedges. So it would seem to me that for cardioid averse vocalists, perhaps now would be a good time to consider bringing back the considerable benefits of the

Omnidirectional Dynamic Vocal Microphone.

AKG D130

American Microphone Company D9A/ D9AT ‘Skyscraper’ (1938- circa 1958)

American D9AT Where's Wally

Where’s Wally/Waldo?

When the American D9A was launched in 1938 it was notable because of its fashionable Art Deco ‘look’ inspired by the skyscraper skyline of New York and other great American cities. Indeed the side elevation of the mic appears to directly reference Manhattan’s famous Chrysler Building constructed in 1930.

American D9 Side View Chrysler Building

This was the age of Jazz, and Rock’n’Roll was just around the corner. Microphones increasingly appeared centre stage in photographs and on screen as part of the performer’s visual image. Over the following couple of decades the American Microphone Company kept ahead of the game producing a number of stunning designs which appeared in movies and featured in commercials.

Katharine Hepburn, Spencer Tracy, Van Johnson, and Angela Lansbury in State of the Union (1948)Katharine Hepburn, Spencer Tracy, Van Johnson, and Angela Lansbury in State of the Union (1948)

The transducer design of the American D9 is also interesting and unusual.

The D9A /D9AT is often incorrectly identified as a ribbon microphone! This matter can simply be resolved by undoing 4 screws!!American D9AT Interior Front viewAmerican D9AT Rear inside viewAmerican D9AT Interior side view

Does this look like a ribbon motor??!!  In the advertising blurb below it is described as being ‘a pressure-velocity combination microphone’ which may have led some folks to think that the ‘velocity’ element must be a ribbon (like the Western Electric/Altec 639). However, the 2 elements are clearly both dynamic. One pressure element (omni) sealed at the back, and one velocity element (Fig of 8) open at the back. The signals from these 2 elements are combined to produce a cardioid directional response. I can’t off hand think of another microphone that is configured in this way using 2 separate dynamic elements.American Microphone Company D9 Advert

Although I can accept most of the description given above, the notion that the DA9 has ‘qualities of ruggedness’ is somewhat farfetched. Sadly, the bodywork appears to be cast in a cheap zinc alloy which is brittle and easily damaged. The yoke is also made of the same material. These days it is hard to find one without bent, cracked or broken ribs.American D9AT Damage to bodywork

Some years ago I was working on a theatre show in which an over-excited actor, (playing the part of Jerry Lee Lewis) unintentionally launched my treasured Electro-Voice EV664 right across the stage. It landed 30 feet away with a sickening thud. Apart from a slightly damaged switch the mic was unmarked and still worked perfectly! That is rugged! I wouldn’t want to try that with my D9AT. This is definitely not a mic to drop by accident. As well as the fragile body the chrome plating is remarkably thin. Even though my D9AT is from the tail end of production in the mid 50’s much of the chrome has worn away. Nevertheless it is still a stylish looking object.American Microphone Company D9AT

BUT………….. More importantly what does it sound like?  CLICK HERE for Voice Recording

The American Microphone Company D9A / D9AT was not designed as a high quality studio instrument. It was recommended for P.A. and installation use. In 1938 most dynamic P.A. mics were feedback-prone omnis. American’s dual element cardioid with its promise of higher gain before feedback could therefore be seen as an exciting new development. However, the following year Shure launched their game changing Unidyne 55 featuring a single cardioid capsule. The new single capsule design was soon adopted by most manufacturers as it was clearly cheaper to make and capable of producing excellent results. American carried on manufacturing the D9A/ D9AT for another 15-20 years. In 1955 the company was bought by Elgin-Neomatic,Inc. whose main business was watch making. At the time Elgin had the notion that they would develop miniature parts for microphones but this idea soon faded. My D9AT featured here is from the Elgin period.Badge ELGIN American Microphone Company D9AT

Around 1960 American was sold again to General Cement Company Rockford, Il (AKA G.C.Electronics). Several years later the company was finally bought by Electro-Voice who soon retired the brand.

In Conclusion

Although the American Microphone Company D9A/AT may not win any prizes for its audio quality it nevertheless provides an interesting link in the development of directional microphones in the first half of the 20th century.