Sennheiser electronic GmbH & Co. KG is a German manufacturer of equipment for recording, broadcasting and playback of sound. The interesting life of engineer and scientist Fritz Sennheiser was not always easy. Looking ahead a little, I note that the creation of the company by chance was predetermined by the defeat of Germany in World War II. The engineer’s ingenuity and fertility laid the basis for long and successful work. Today, the company he created produces world-famous headphones, microphones, communication systems, radio systems, aviation equipment and much more.


The influence of the company created by Fritz Sennheiser on the global audio market is evidenced by the following facts: more than 100 types of products, average annual sales income of about 400,000,000 Euros, 2,100 employees, every tenth headphone, and every 15th microphone in the world are produced by this company . Fritz Sennheiser was born on May 9, 1912 in Berlin. Where he spent almost all of his childhood and adolescence. Sennheiser attended the Karlhorst district gymnasium, from which he successfully graduated in 1932. The future inventor developed an interest in electronics during his school years.

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Fritz Sennheiser 

Despite his successful amateur radio experience, Fritz did not dream of a career as an engineer or inventor. The young Sennheiser’s real passion was landscape design. However, the harsh reality made its own adjustments to the young man’s life. The global financial crisis of 1929 changed Fritz’s views on the future; the plight of Germany in the early 30s deprived landscape design of commercial and career attractiveness. And instead of his favorite occupation, Fritz, assuming that the engineering profession is in demand, enters the Berlin Technical University. After graduating from university, Sennheiser gets a job at the real “Mecca” of European telecommunications research, the Hertz Institute, where he writes his first dissertation under the guidance of Dr. Oscar Wierling.

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Sennheiser MD 2 (1947) 

Interestingly, by 1936, under the leadership of Sennheiser, a group of engineers from the Hertz Institute developed an original reverb, which was first used to change the sound of the piano at the opening of the Olympic Games in Berlin. According to reviews of those who heard the instrument, a modified piano with a Sennheiser reverb made it possible to achieve an effect that is today called Large or big Hall (simulating the sound of an instrument in a large cathedral), the sound being reminiscent of an organ. Having completed work on the “Olympic” reverb and other projects, he took the position of chief engineer of the Hertz Institute in Hanover, and a little later (in 1938), on his initiative, the Institute of Radio Frequency Engineering and Electroacoustics was created. The scientist will remain in the position of director of this research institute until May 1945.  In 1940, Fritz Sennheiser defended his doctoral (in the Bolognese system, an analogue of a candidate’s) (PhD) dissertation. Due to the bombing of 1943, the building of the scientific institution in Hanover became unsuitable for continued research, after which Sennheiser’s group moved to another premises in Wenebostel, where Sennheiser’s laboratory was based until the end of hostilities.

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Sennheiser MD 421 (1960) 

Ironically, the day of victory over Germany – May 9th – is the birthday of Fritz Sennheiser. It should be noted that Fritz did not worry for long about the defeat and cessation of the institute’s work. As a seasoned pragmatist, he quickly realized that engineering and scientific expertise could be a source of income. Already in June 1945, a team of seven engineers under the leadership of Sennheiser created a small manufacturing company. It is symbolic that the office and production were based in one of the surviving buildings of the Hannover Technical University. At that time the company was called Laboratorium Wennebostel (abbr. “Labor W”), after the village to which Sennheiser’s group moved after the bombing of Hanover. The first products were voltmeters. Labor W began making microphones in 1946 and renamed Sennheiser electronic in 1958. In 1947, specialists at the then “Labor W” created their first original microphone, MD 2, and due to its qualitative superiority over competitors, it became very popular in radio broadcasting. In 1949, the company developed and produced power amplifiers for some time. These were the first devices to meet the hi-fi standard, and a few years later it would be adopted by all manufacturers of home audio equipment. In 1952, Labor W added miniature magnetic headphones (HM 11, HM 21) to its portfolio. Miniaturization is becoming key in all areas. 1954 – Labor W introduces the first shotgun microphone, the MD 81, for film and television. The next model, MD 82, gained success in 1956. 10 years after its founding, in 1955, the company already employs 250 employees. The foundation of a new large company building has been laid. In 1956, the company introduced the MD 93 reversible transducer microphone, which works as both a microphone and a loudspeaker. Could be used, for example, in voice recorders. In 1957, Labor W introduced a wireless radio system for professional use on stage and television, developed jointly with specialists from the radio company NDR. Since 1958, it has been marketed jointly with Telefunken under the brand name “Mikroport”. In 1958, Labor W was renamed Sennheiser electronic. In 1959, the MDS 1 stereo microphone was developed. In 1960, the classic Sennheiser MD 421 microphone was released. In 1961, Sennheiser created the first telephone answering machine for Telefunken. In the same year, at an industrial fair in Germany, Sennheiser demonstrates the first samples of RF-Condenser condenser microphones, which laid the foundation for the famous MKN series. In 1962, Sennheiser produces the first microphone for audio monitoring of children, the so-called “babysitter”.

1965 – the Sennheiser M 101 mixing console was created. In the same year, production of the audiophile acoustic system “Philharmonic” began – the first active Hi-Fi system. In 1966, to demonstrate the superior directionality of the new MD 411 supercardioid microphone, it was placed in a reverberation chamber along with a cardioid and an omnidirectional microphone. The echo in the chamber was so strong that it was difficult to make out the words. However, the MD 411 demonstrated clear sound even in these extreme conditions. In 1968, the company released the world’s first open-back headphones, the Sennheiser HD 414, the introduction of which revolutionized the headphone industry. Sennheiser HD 414 sold more than 10,000,000 units. In addition, the first professional lavalier microphone, the MK 12, was released in 1968 for use in the broadcast industry. The classic MD 441 microphone was released in 1971. In 1975, Sennheiser pioneered the use of IR (infrared) technology to transmit sound over a distance. In 1977, Sennheiser introduced the world’s first open-back electret headphones, the Unipolar 2000. In 1977, Sennheiser released the electronic vocoder instrument VSM 201. Following the success of electronic instruments, the VCM 2001 turns the human voice into an electronic sound effect. With the launch of the first professional multi-channel rack-mount receiver in 1977, the clarity of audio signal transmission over the radio channel was significantly improved. In 1982, the classic radio microphone SKM 4031-TV launched the further success of Sennheiser radio systems. In 1982, Prof. Dr. Fritz Sennheiser hands over the management of the company to his son, Prof. Dr. Jörg Sennheiser. In 1983, the first directional (cardioid) lavalier microphone, the MKE 40, was developed. In the same year, the smallest studio lavalier microphone at the time, the MKE 2, was developed. In 1987, at the 59th Academy Awards ceremony, Professor Dr. Fritz Sennheiser awarded for the development of the MKH 816 shotgun microphone. In 1987, Sennheiser develops the active noise compensation system “NoiseGard” for Lufthansa. In 1989, the first wireless mixing console WM 1 was developed for field broadcasting. In 1990, a third factory was opened in Tullamore, Ireland. In 1991, several subsidiaries were opened at once: Sennheiser Electronic Corporation (USA), Sennheiser Belux (Benelux), Sennheiser Canada (Canada). In 1993, the world’s first digital IR (infrared) headphones, the IS 850, were released. In the same year, the classic wireless microphone SKM 5000 was released. In 1995, Sennheiser presented to the public its first wireless RF headphones, the RS 5.

In 1995, subsidiaries were registered in the following countries: Mexico and the Netherlands. In 1996, Sennheiser was transformed into a private limited liability company (GmbH & Co. KG). In 1997, a second research and development unit was opened in Burbank, near Los Angeles, California, USA. In 1998, Sennheiser became the first company in the world to market RF headphones in the form of a stethoscope (RS 2400). In the same year, the evolution microphone series was launched, revolutionizing the music industry market. In 1999, wireless systems of the evolution wireless series were launched. In 2000, a fourth factory was opened in Albuquerque, New Mexico, USA. In the same year, the MKH 800 was released – the world’s first studio condenser microphone, providing a reproducible frequency range of 20 Hz – 50 kHz, corresponding to new digital audio formats. The company’s founder, Professor Dr. Fritz Sennheiser, died in 2010 at the age of 98. In 2015, Sennheiser celebrates its 70th anniversary. Over the years, the company has made a significant contribution to the development of the audio technology industry, and the list of innovative products it has created includes dozens of legendary models. Opening a series of publications related to Sennheiser’s anniversary, we will talk about one of these developments that brought the company well-deserved fame. In 1968, the company made a landmark invention, which led to the creation of a product that turned out to be even more successful than the most popular Sennheiser microphones. We are talking about the legendary HD 414 – the world’s first open-back headphones, which created the very market for such devices. At the time, Sennheiser engineer Erhard Michaelis was developing microphones for voice recorders and once placed two microphones on one holder for testing purposes. By feeding them a signal and putting them to his ears, he discovered that dynamic capsules, not enclosed in housings, sounded much better than conventional headphones of the time. Back in the shop, he made a headband for the two microphone capsules and added a layer of foam to the plastic bases to relieve pressure on the ears. To his surprise, the sound became even better. A real revolution took place in the audio industry: open headphones were created!

Sennheiser HD 414 (1968) 

The headphones were quickly patented and received the name HD 414. They were a system of two miniature speakers located directly opposite the ears – the sound propagated simultaneously into the ears and into the surrounding space, and was perceived by the human ear as it happens without the use of headphones – freely and openly. The use of porous foam for the comfortable ear pads further protected against unwanted resonances, and the high impedance of the HD 414 headphones meant they could be connected to most sound sources without issue. In addition, the headphones’ superior efficiency allowed them to reproduce sound at maximum volume levels, and their frequency response was unrivaled. However, at first, experts were skeptical: in the spring of 1968, the new product was confidentially presented to a select group of specialists and did not impress them: the HD 414 headphones were very different from all the others and seemed to lack pretentiousness. Experts estimate their annual sales at 500 units. at best. How wrong they were! The HD 414 opened up an entirely new market and sparked an unprecedented boom in the company’s sales. In fact, Sennheiser has managed to reinvent headphones! The HD 414 model has become an absolute bestseller: since the start of production, more than 10 million of these headphones of various modifications have been sold, and this is an absolute record in the field of electroacoustic equipment. To mark the 25th anniversary of the start of their production, the company even released a small anniversary series of such headphones.

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Sennheiser HD 414 (1968) 

The unprecedented success of the HD 414 provided a powerful impetus for further growth in Sennheiser’s sales and workforce. In 1969, sales growth for Sennheiser branded products was almost equal to the overall industry dynamics, which guaranteed a more independent position for the company in the market. In 1970, when the company celebrated its 25th anniversary, it employed over 750 people. A spacious new office building has been opened at the headquarters in Vennebostel, where the new development department, the design department and the preparatory work department have moved. To meet the growing demand for headphones, additional production capacity was rented in Burgdorf, and if all three factories – in Vennebostel, Soltau and Burgdorf – could not cope with the volume of orders, home workers were brought in. In 1982, Prof. Dr. Fritz Sennheiser hands over the management of the company to his son, Prof. Dr. Jörg Sennheiser. One of the primary tasks that he had to solve in his new position was to unite all the scattered industries, especially the numerous homeworkers, on a single central platform.

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Sennheiser MD 409 (1970) 

Production at the new factory began the same year. The main focus was on the production of headphones, which were in constant demand and were handmade in large quantities. The first HD 414 model was soon followed by others. “In the beginning it was a production of only one model,” recalls Jörg Sennheiser, “and it was simply vital for us to expand the model range in order to secure our position in the market. If for some reason the market crashed, it would drag the entire company down with it. Therefore, we began to successfully expand our range, releasing other models and products for various consumer groups.”

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Sennheiser MKH 800 (2000)  

The headphones also became the company’s most successful export product. In 1978, 45% of sales were exported: a quarter of this amount to the United States, where by that time the company had become the second largest headphone manufacturer. Headphones accounted for more than half of total sales, which amounted to 55 million marks. Sennheiser invested 11% of its turnover in development and development, which was double the industry average. And the number of employees by this time had increased to 980. The HD 414 model took an honorable permanent place in the Headphone Hall of Fame, but in 1973 it surpassed its own outstanding achievement. The American space agency NASA chose HD 414 as on-board headphones for the Skylab orbital station, which gave them every right to say: these headphones have been tested in space.

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Sennheiser Digital 9000 (2012) 

Moreover, the HD 414 headphones were a resounding commercial success: the patent for open-back headphones, which expired in 1983, opened up an additional source of income for the company, as other manufacturers showed keen interest in the design. “At one of the trade shows, a representative from Sony approached us with an offer to sell a license for the production of open-back headphones,” recalls Fritz Sennheiser. “We knew that Sony does not produce headphones, and after considering the offer, we decided to sign a contract. Two or three years later, Sony released its Walkman – and this player required open-back headphones. So, in order to make sure everything went smoothly, Sony management chose to make licensing payments for several years without taking on the risk of in-house production. I must say that this is a very impressive example of planning.”