A Rare Siemens (?)/ Telefunken (?)/ Klangfilm (?) Ribbon Microphone. (circa 1931)

The Facts

  1. It is a cardioid ribbon microphone.
  2.  Weighs over 10lbs.
  3. The microphone was aquired many years ago in America by the previous owner, the film editor David Hawkins (known for his work on the films of Jean Renoir and also The Collector.)
  4. It carries no manufacturer’s identification marks……….. however
  5. The lower half of the microphone is identical to the Siemens SM3, (aka Telefunken  ELA M25b and ELA M201 and as Klangfilm ELM24) as specified in Siemens (UK Reg) Ribbon Patent 1931
  6. On the front there is a simple brass plate declaring it to be a ‘Microphone Type R’ and a ‘Serial No 1028’

An Interesting Comparison

1930’s Siemens SM3 technical illustration

Same view of lower half of my Siemens (?) Appears to be identical, even down to the painted letter N indicating the polarity of the magnet.

My Theory

In the history of microphone technology Harry Olson of RCA is often credited with having invented the ribbon microphone and developed the first directional microphone. However, whilst it is important to recognise Olson’s major contributions to microphone technology, the accolade for inventing the ribbon microphone clearly belongs to Erwin Gerlagh and Walter H  Schottky, working for the German company Siemens in the mid1920’s. It was also the case that the early Siemens models such as the SM3 were well known for their directional properties. The back of the ribbon is enclosed by a huge ring magnet, and an ingenious arrangement of acoustic chambers,  thereby producing a cardioid polar pattern. Although the lower half of my huge microphone, including the magnet and ribbon assembly, is identical to the standard SM3, the upper half appears to be an additional acoustic chamber of some sort, packed with wadding (perhaps to provide additional damping to the ribbon and influence the HF reproduction?)

In the early days of Talking Pictures in America the microphones available were omnidirectional and thus it was difficult to balance the level of one actor’s voice against another especially if the one was more powerful than the other. Omnis also tended to pick up camera noise and anything else in the way of unwanted sounds on the set, considerably degrading the quality of the finished product.

Technical competition within the industry was fierce and American film studios of the period had strong commercial ties with the major players in the development of cinematic technology such as Western Electric and RCA.  In Europe competition came from the Tobis-Klangfilm cartel, and Siemens was pumping large sums of money, and expertise, into developing the technical prowess of its Klangfilm system.

However, there is a small body of evidence that would suggest that a number of American studios, realising the advantages of a directional microphone, bought in the Siemens microphone. It is well documented that MGM used one on the voice of Jeanette MacDonald in their 1935 film of the operetta ‘Naughty Marietta’. It is interesting to note that Douglas Shearer (head of MGM’s technical department) won an Oscar for the sound on that film! The Siemens mic was subsequently used on several other films featuring Jeanette McDonald and Nelson Eddy in order to even up the level difference between their voices ( Eddy being much more powerful.)

My suspicion is that the use of the Siemens microphone in American studios before the arrival of Olson’s superior RCA models was perhaps more wide spread than has been previously admitted! Could this be a possible reason why this Siemens(?) mic in my collection bares no German markings…… could it be that they have been carefully removed for reasons of commercial sensitivity? …… and is the plate on the front in English simply an attempt to make it appear to be of American origin?

As the decade progressed the Siemens was largely superseded by the, lighter and more sophisticated RCA models developed by Harry Olson. Also the dual element Western Electric 639-A.


In Germany the Siemens microphone was popular throughout the 1930’s appearing regularly on stage and on screen with that rising star of news reel cinema, Adolf Hitler! During the 1930’s Siemens formed close ties with the Nazi party and helped substantially to finance Hitler’s war machine. During WWII Siemens went on to employ thousands of slave labourers in their factories……….. All of which makes me wonder……  Could it also be a possibility that uncomfortable associations with Germany and Nazism lead to the de-badging of my Siemens microphone?


I think that there is no doubt that the lower half of this microphone, including the huge magnet, cased in shiny black leather, and the ribbon motor assembly were manufactured by Siemens. Whether the upper chamber was a later modification by a third party or whether the whole thing is a very rare model or even a prototype we may never know. Seimens own records for this period are somewhat incomplete and I have found no documentation or pictures (anywhere) relating to this exact model.

If anyone reading this has any more information or other theories relating to this post I would be very interested to hear from you. Meanwhile here are a few more pics of this extraordinary piece of hardware.

Wadding in top chamber.

Empty top chamber. Screws on inside left indicate possible position of missing transformer.

Ribbon assembly removed, awaiting a new ribbon.

Ribbon, cut, crimped and ready to tension

Ribbon in place ready to slot into gap.

Siemens SM3 Magnet gap into which ribbon assembly slots.

Upside down. (though I think it is designed to work either way up.)

Finished at last!! Fully restored and working…… so pleased!!

So what does it sound like?  Here is my first test recording on acoustic guitar.  (many thanks to Den and Adrian for a fun afternoon experimenting!)

Guitarist Den Parratt with the author setting up the mic for our first recording!

Following in the footsteps of mad dictators and MGM film stars of the 1930s here is a vocal clip from talented young singer Joe Martin.

Here also is a fabulous album of gypsy jazz recorded by Echoes of France on this extraordinary microphone. https://echoesoffrance.bandcamp.com/

Joe Stalin. Another satisfied customer!

11 responses to “A Rare Siemens (?)/ Telefunken (?)/ Klangfilm (?) Ribbon Microphone. (circa 1931)

  1. Fascinating story about your Siemens(?) mic. Before you get too involved in its restoration, however, I think you should give your garden table a coat of Danish Oil!


  2. Hi Martin. Really interesting to read about your mic and hear the nice guitar playing. I have just finished repairing a Tele M201 for a customer which has an impedance around 250 ohms and an output comparable to a Beta57! I wondered if you managed to measure the impedance on your mic? Could it be 50 ohm model, which is why you needed 60dB gain?

    The one I saw does not have the top box – I think yours looks better! Not sure it is an acoustic trap for the pattern, as I can’t see how it is linked to the main chamber. Is there an air vent in the top of the main part of your mic? Cheers. Stewart


  3. OK, I can see how it vents from the top, above the ribbon… you could be right!

    I can’t see how the cable exits your mic. Does it pass through this additional top box? The holes in the back are interesting – space for a matching transformer and output connector? Perhaps you really do have an international ‘export’ model? Fascinating stuff.


    • Ever since I bought this mic a few years ago it has provided a fascinating area of research and speculation! The holes in the back are interesting, and as you suggest must have been where the original connector went. At present I have made a simple metal plate mounted using the original screw holes and the cable simply passes through a rubber grommet in the centre. To begin with I have used a fairly cheap matching transformer which is simply packed in with the wadding in that top chamber. I just wanted to establish that it worked before spending money on an expensive transformer! To be honest, as this is my first ribbon ‘project’ I was amazed when I plugged it in and sound emerged from it!!! As far as impedance goes I assume it probably is 50ohm but I haven’t measured it.
      It is, I think, still a ‘work in progress’ and I would welcome any suggestions about a better transformer and speculations about what the original connector might have been. Meanwhile if you ever come across a similar version let me know.


  4. Here are my observations on the Tele M201/1


    Also, I would be happy to send you a matching transformer to try out. Feel free to drop me a line.


    • Interesting post on the tele. As you say lining up the ribbon to insert into the gap is tricky. I had about five goes!
      If it is not too much trouble to send, I would be really interested to try out your suggested matching transformer.


  5. Pingback: How to get that Vintage Mono Sound. A 1930’s Microphone Shoot-out! | Martin Mitchell's Microphones

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