Alan Blumlein
Alan Dower Blumlein | |
---|---|
H2S radar | |
Significant design | Ultra–Linear amplifier |
Significant advance | Stereophonic sound television |
Alan Dower Blumlein (29 June 1903 – 7 June 1942) was an English
He died during
Early life
Alan Dower Blumlein was born on 29 June 1903 in
Alan Blumlein's future career seemed to have been determined by the age of seven, when he presented his father with an invoice for repairing the doorbell, signed "Alan Blumlein, Electrical Engineer" (with "paid" scrawled in pencil). His sister claimed that he could not read proficiently until he was 12. He replied "no, but I knew a lot of quadratic equations!"
After leaving Highgate School in 1921, he studied at City and Guilds College (part of Imperial College). He won a Governors' scholarship and joined the second year of the course. He graduated with a First-Class Honours BSc two years later.
In mid-1930, Blumlein met Doreen Lane, a preparatory school teacher five years his junior. After two-and-a-half years of courtship the two were married in 1933. Lane was warned by acquaintances before the wedding that, "There was a joke amongst some of his friends, they used to call it 'Blumlein-itis' or 'First Class Mind'. It seems that he didn't want to know anyone who didn't have a first class mind." Recording engineer Joseph B. Kaye, known as J. B. Kaye, who was Blumlein's closest friend and best man at the wedding, thought the couple were well matched.[5][6]
Career and inventions
Telecommunications
In 1924 Blumlein started his first job at
During his time there, he measured the amplitude/frequency response of human ears, and used the results to design the first weighting networks.
In 1924 he published (with Professor Edward Mallett) the first of his only two
In 1925 and 1926, Blumlein and John Percy Johns designed an improved form of
His inventions while working at STC resulted in another five patents, which were not awarded until after he left the company in 1929.
Sound recording
In 1929 Blumlein resigned from STC and joined the Columbia Graphophone Company, where he reported directly to general manager Isaac Shoenberg.
His first project was to find a method of
Early in 1931, the Columbia Graphophone Company and the Gramophone Company merged and became EMI. New joint research laboratories were set up at Hayes and Blumlein was officially transferred there on 1 November the same year.
During the early 1930s Blumlein and Herbert Holman developed a series of moving-coil microphones, which were used in EMI recording studios and by the BBC at Alexandra Palace.
Ultra-linear amplifier
In June 1937, Blumlein patented what is now known as the
Long-tailed pair
Blumlein may or may not have invented the
Stereophonic sound
In 1931, Blumlein invented what he called "binaural sound", now known as
Blumlein explained his ideas to Isaac Shoenberg in the late summer of 1931. His earliest notes on the subject are dated 25 September 1931, and his patent had the title "Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems". The application was dated 14 December 1931, and was accepted on 14 June 1933 as UK patent number 394,325.[7]
The patent covered numerous ideas in stereo, some of which are used today. Some 70 claims include:
- A "shuffling" circuit, which aimed to preserve the directional effect when sound from a spaced pair of microphones was reproduced via stereo loudspeakers instead of a pair of headphones
- The use of a coincident pair of velocity microphones with their axes at right angles to each other, which is still known as a "Blumlein Pair"
- Recording two channels in the single groove of a record using the two groove walls at right angles to each other and 45 degrees to the vertical
- A stereo disc-cutting head
- Using hybrid transformers to matrix between left and right signals and sum and difference signals
Blumlein's binaural experiments began in early 1933, and the first stereo discs were cut later the same year. Much of the development work on this system for cinematic use was completed by 1935. In Blumlein's short test films (most notably, "Trains at Hayes Station", which lasts 5 minutes 11 seconds, and, "The Walking & Talking Film"), his original intent of having the sound follow the actor was fully realised.[8]
In 1934, Blumlein recorded
Television
Television was developed by many individuals and companies throughout the 1920s and 1930s. Blumlein's contributions, as a member of the EMI team, started in earnest in 1933 when his boss, Isaac Shoenberg, assigned him full-time to TV research.
His ideas included:
- Resonant flyback scanning (the use of a tuned circuit in the creation of a sawtooth deflection waveform). (British Patent No. 400976, application filed April 1932.)
- Use of constant-impedance network in power supplies to obtain voltage regulation independent of load frequency, extending down to DC (421546, filed 16 June 1933).
- Black-level clamping (422914, filed 11 July 1933 by Blumlein, Browne and Hardwick). This is an improved form of DC restoration, compared to the simple DC restorer (consisting of a capacitor, diode and resistor) which had been patented by Peter Willans three months earlier.
- The slot antenna. (515684, filed 7 March 1939.)
Blumlein was also largely responsible for the development of the waveform structure used in the
H2S radar
Blumlein was so central to the development of the H2S airborne radar system (to aid bomb targeting), that after his death in June 1942, many believed that the project would fail. However it survived and was a factor in shortening the
His invention of the line type pulse modulator (ref vol 5 of MIT Radiation Laboratory series) was a major contribution to high-powered pulse radars, not just the H2S's system, and continues to be used today.
Death and investigation
Blumlein was killed in the crash of an H2S-equipped Handley Page Halifax test aircraft while making a test flight for the Telecommunications Research Establishment (TRE) on 7 June 1942. During the flight from RAF Defford, whilst at an altitude of 500 ft (150 meters) the Halifax developed an engine fire which rapidly grew out of control.[9] The aircraft was seen to lose altitude, then rolled inverted and struck the ground.[9] The crash occurred near the village of Welsh Bicknor in Herefordshire.[10] Two of Blumlein's colleagues, Cecil Oswald Browne and Frank Blythen, also died in the crash.
The Halifax was carrying a highly-secret cavity magnetron as part of the H2S test system, and the immediate recovery of the device was essential. A team led by Bernard Lovell arrived at the crash scene the same night, and took the magnetron.[11]
"Then reports of a crash in south Wales began to come in and the rest of that night was just a nightmare. I was driven by the C-in-C of the aerodrome [Defford], a man called King,[12] and winding through these lanes near Ross-on-Wye searching for this wreckage, and then the field with the burnt-out Halifax, and of course it was wartime, there was no time for emotions, our first duties were to search for the precious highly-secret equipment, and collect the bits-and-pieces of it." – Bernard Lovell. [13]
After the RAF investigative board completed its report on the Halifax crash on 1 July 1942, it was distributed to a restricted list of approved recipients, but not publicly divulged.[9] In the interests of wartime secrecy, the announcement of Blumlein's death was not made for another three years.[14] The investigative board, headed by AIB Chief Inspector Vernon Brown – who later also investigated the post-war Star Tiger and Star Ariel disappearances – and assisted by Rolls-Royce, who had made the Halifax's Merlin engines, found that the crash was caused by engine fire, attributed to the unscrewing of a tappet nut on the starboard outer engine, which had been improperly tightened by an RAF engine fitter while inspecting the engine three hours prior to the crash.[9]
During the flight the loosened nut caused increasingly excessive valve clearance eventually allowing collision of the valve head with the rising piston fracturing the valve stem, which then allowed the inlet valve to drop open, resulting in the ignition by the spark plug of the pressurised fuel/air mixture within the inlet manifold and, eventually, the pumping of the ignited fuel outboard of the rocker cover and along the outside of the engine, leading to an extensive fire in the engine nacelle.[9] Due to the fire originating in the induction system, where the supercharged fuel/air mixture was at higher pressure than atmospheric, the heart of the fire was much hotter burning and intense than would be the case in a simple fuel fire.
Constantly fuelled by the broken intake, the fire burned rapidly along the wing and fuselage, eventually causing the outboard section of the starboard wing to separate from the centre section at approximately 350 feet (100 meters) of altitude.[9] With the loss of a substantial part of the starboard wing, all control over level flight was lost, and the plane rolled inverted and struck the ground at approximately 150 mph (240 kph).[9]
The board found that the crew and passengers had not jumped immediately from the aircraft owing to several factors, including a loss of altitude while attempting to find an emergency field, the rapidly spreading fire, which blocked or impeded egress from the plane, and the fact that a sufficient number of parachutes were either not on board or were not being worn.[9] Almost immediately following the crash, Prime Minister Winston Churchill issued a directive requiring any test flights with civilians or scientific personnel to carry a sufficient number of parachutes for all individuals involved.[9]
After the RAF investigative board completed its report on the Halifax crash, it was ordered to be kept secret by Prime Minister Churchill, and the cause of the crash was not revealed publicly, even to the relatives of the deceased.[9] As a result, numerous unfounded rumours of German sabotage as the cause of the crash would circulate for many years afterwards.[9]
Personal life
Alan Blumlein had two sons, Simon Blumlein and David Blumlein.
Outside his work, Blumlein was a lover of music and he attempted to learn to play the piano, but gave it up. He enjoyed horse riding and occasionally went cub hunting with his father-in-law.[15]
He was interested in many forms of engineering, including aviation, motor engineering and railway engineering. He obtained a pilot's licence and flew
Tributes
- Alan Blumlein Way is a road on the Tektronix campus in Beaverton, Oregon, in keeping with their policy of naming roads after those who made significant contributions to the knowledge and understanding in the field of electronics.
- There continues to be a meeting room named the Blumlein Room in the Institution of Engineering and Technology (IET) headquarters at Savoy Place, following a major refurbishment in 2015.[18]
- A blue plaque commemorating Blumlein was erected in 1977 by the Greater London Council at his former home in Ealing.[19]
- On 1 April 2015, an IEEE milestone plaque was posthumously presented for the invention of stereo to Alan Dower Blumlein. A ceremony was held at Abbey Road Studios attended by many leading audio experts and recording engineers. The plaque is now located on the right hand side of the front door of Abbey Road Studios.
- In 2017, the Recording Academy posthumously awarded Alan Dower Blumlein with the 2017 Technical Grammy for the invention of stereo and contributions of outstanding technical significance to the recording field.
See also
- Blumlein generator
- Blumlein transmission line, used to create high-voltage pulses with short rise and fall times.
- History of television
Notes
- ^ Semmy Blumlein's father, Joseph B. Blumlein was Jewish, see Burns, p. 2
References
- Citations
- ^ a b c "Early stereo recordings restored". BBC. 2008-08-01. Archived from the original on 2008-08-07. Retrieved 2008-08-07.
- ^ "Alan Blumlein – the man who invented stereo". AbbeyRoad. Retrieved 2009-05-18.
In his short life, Blumlein devised over 120 patents and is considered one of the most significant engineers of his time.
- ^ a b c d Fox, Barry (1990-06-16). "Mystery of the missing biography: A look at the life of Alan Blumlein". No. 1721. New Scientist. Retrieved 2009-06-19.
- ^ Burns (2000), pp. 2 and 4
- ^ Burns (2000), p.49
- ^ Alexander (1999), p. 10 and Chapter 3
- ^ GB patent 394325, Alan Dower Blumlein, "Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems.", issued 14 June 1933, assigned to Alan Dower Blumlein and Musical Industries, Limited
- ^ Robert Alexander (2013). "The Inventor of Stereo: The Life and Works of Alan Dower Blumlein". p. 83. CRC Press,
- ^ a b c d e f g h i j k Alexander (1999), pp.322–339
- ^ "The crash of Halifax V9977". The Official Alan Dower Blumlein website. Archived from the original on 2013-04-08. Retrieved 2012-11-17.
- ^ Burns (2000), p. 461
- ^ Note; Gp. Capt. P J R King.
- ^ The Secret War, Episode 2 - "To See A Hundred Miles", BBC Television, 1977.
- ^ Fox, Barry, The Briton Who Invented Electronics, New Scientist, Vol. 94 No. 1308 (3 June 1982), p. 641
- ^ Burns (2000), p.242
- ^ Burns (2000), p.234
- ^ Burns (2000), p.243
- ^ "New IET London: Savoy Place room names confirmed". IET. Retrieved 2015-07-22.
- ^ "Blumlein, Alan Dower". English Heritage. Retrieved 2015-07-22.
- Bibliography
- Alexander, Robert Charles (1999). The Inventor of Stereo: The Life and Works of Alan Dower Blumlein. ISBN 0-240-51628-1.
- Burns, Russell W (2000). The Life and Times of A. D. Blumlein. IEE History of Technology series. IEE. p. 2. ISBN 0-85296-773-X.