St Giles Norwich - Royal Wedding 1934

MARCONI 1923

MOVING IRON see Marconi

CRYSTAL
Similar principle to, but an advanced style of carbon mic. In this case the diaphragm is attached to a piece of quartz crystal, which again when the diaphragm is vibrated by air waves, sets up an electric current in the crystal, which is then transferred to the amplifier. This works on the same principal as a crystal pickup cartridge, except that in this case, the crystal is vibrated by the movements of the stylus attached to it. Crystal microphones are of high impedance, better quality than carbon and quite sensitive, but also again poor "back to front" ratio

CARBON
The oldest type, and very rarely used today, and as was used in the earlier types of telephones. The diaphragm of these, is set on a container of carbon granules. When the diaphragm is vibrated by air waves, this creates a disturbance in the carbon .granules which produces an electrical current, which passes down the line to the amplifier. These microphones are generally very sensitive, but poor quality especially on music and are very subject to "feed back" because of the poor "back to front" ratio. They are of very high impedance.

1932

DYNAMIC or MOVING COIL
The most commonly used type today. Can be of high or low impedance dependant on whether a transformer is fitted into the microphone or not. This type of mic works on the same principle as a moving coil loudspeaker, only in reverse, Again the diaphragm is vibrated by the air waves which moves it backwards and forwards, therefore moving the voice coil, up and down the central magnet pole. This in turn (because the coil is in a magnetic field) produces the electric current. The frequency of this backwards and forwards movements produces the various "frequencies). Slow moving for Bass notes, fast moving for Treble. The polar diagram of this type of mic depends chiefly on the quality and design of the microphone, and therefore you can have either good or bad, "back to front" ratio. For indoor use where the microphone is within hearing range of the loudspeakers, the best type is one with a very good Cardioid pattern, produced by, rear and side rejection of the low frequencies.

RIBBON
Were used very extensively a few years back, not quite so popular now. They are not really robust enough, especially for P.A. work, but are ideally suited for Studio use, where they are placed on a desk and not handled or held up to the mouth (as for group work) where spittle from the artist very soon destroys the ribbon. The diaphragm of this type of mic, is actually in the form of a ribbon of silver paper then metal (hence the name) suspended rigidly in a magnetic field created by magnets. This ribbon again vibrated by the air waves in the magnetic field creates a small electric current which is then transferred to the amplifier. Ribbon mics are quite sensitive, but also highly directional at back and front, there is virtually no pickup at either side. They can be of high or low impedance, with the use of an internal transformer.

CONDENSER
The diaphragm in this case is attached to a capacitor, which has a small current fed to it (usually from a small internal battery). Again dependant on the quality and design of manufacture, they can be very good for both music and speech, and have good directional polar diagram. Again this type is more useful for Studio work, than for P.A

For the Student
The frequency response of any microphone, denotes the highest and lowest frequencies, that it can accept and reproduce. Low impedance mics are generally of much better quality than high and further the most important advantage of this they can used at the end of a very long mic line. Generally up to 200 metres, as opposed to a high impedance mic with a maximum, of 4 or 5 metres.
Balanced line is when the microphone has a 2 core cable connected to the voice coil, and a separate screen to the transformer.
Unbalanced line is when there is only a single conductor and the screen is used as the other.
Unidirectional Mic picks up in one direction only.
Omnidirectional Mic picks up in all directions.

Many kinds of microphones have been used by the BBC in its 7O years of history and here, (the late Pat Leggatt traces their development).

THE FIRST MICROPHONES
The first really striking British broadcast took place on June 15 th 1920 when Dame Nellie Melba gave a song recital from the Marconi Company's experimental station MZX at the Chelmsford works: this of course pre-dated the more famous 2MT station at Writtle. Melba's microphone was a GEC-Peel-Conner solid back carbon granule type, similar to that in a telephone handset, with the addition of a short horn hastily knocked-up by Captain Round home-made from wood from a cigar box.

The Peel-Conner was also used at Writtle and at many of the early stations of the BBC in 1922. This microphone was very noisy, insensitive, markedly non-linear, and with a pronounced resonance at 1kHz. It was just acceptable for speech, but not really good enough for music.

WESTERN ELECTRIC double button
Microphone.
Considerably better quality could be had from the American Western Electric type 373, in which two carbon granule buttons were mounted one each side of a stretched steel diaphragm. The buttons were connected to work in push-pull, cancelling most of the non-linear distortion but still noisy and with undesirable diaphragm resonances. This type was used at the Birmingham 51T station from 1922, and later at Cardiff and Manchester for a time in 1923.

METROVICK experiments in
Manchester
Metropolitan-Vickers, original operators of the Manchester station 2ZY, were very concerned at the poor quality of available microphones and carried out experiments on potentially better designs. They rightly blamed diaphragm resonances as a major cause of unsatisfactory performance.

MARCONI-REISZ Carbon 1925

At the end of 1925 the Marconi Company produced a transverse current carbon microphone based on a German design by Reisz. In a hollowed out marble block, fine carbon dust was held between output electrodes and fronted by a mica diaphragm. Sensitivity was good and noise performance acceptable, but there was a pronounced resonance at 5kHz, subsequently cured by substitution of a rice-paper diaphragm. There was a marked non-linear distortion (blasting) at high sound levels which necessitated careful placing of the microphone relative to the artists.

Despite some shortcomings, this microphone gave good overall performance and was much smaller and more portable than the Magneto-phone. By 1927 the Marconi Reisz was in virtually universal use, continuing well into the 1930's

Condenser Microphones

Although much favoured in modern times, only the American Western Electric condenser (electrostatic)
Microphone saw BBC service early on, being used in the Birmingham 51T station from 1923 to 1926. It was not widely popular, exhibiting marked resonance at 3 kHz and very susceptible to damp surroundings which produced disturbing frying noises.

In about 1930, STC produced a compact moving coil
Microphone type 4017. Overall performance was excellent, with coil resonances damped by acoustic filtering incorporated in the mechanical construction. The 4017 remained in widespread use for some twenty years, up to about 1950.

STC Moving coil Type 4021

In 1935, STC developed a variation on their moving coil microphone, designed to be used facing upwards and so giving an omnidirectional response in the horizontal plane. On top of the spherical microphone was mounted a circular disc screen to equalise the response at all angles in the vertical plane to its physical appearance, the 4021 was popularly known as the 'apple and biscuit'.

Being in effect a one-turn moving coil device, a ribbon microphone retains the advantages of the moving coil principle. Furthermore the ribbon can fairly easily be made non resonant and its smaller dimensions ease the problems of achieving constant magnetic flux in the working area.

RCA had, in 1931, produced a ribbon microphone with excellent performance and with the advantage of a figure-of-eight directional response. This was very convenient for interviews and other productions where artists could speak on either side of the microphone; and the zero response on each side of the instrument could advantageously be used to reduce pick-up of unwanted reverberant sound reflected from studio walls etc.

BBC Ribbon Microphones

The RCA ribbon microphone was very expensive at £130 in 1931, unattractive to a broadcaster who might need dozens. Accordingly the BBC undertook its own development, based on the RCA concept, and in 1934 came up with the type A: manufacture of this design was contracted to Marconi's

The Type A incorporated a duralumin ribbon which proved to springy and gave rise to excessive resonances. An improved type AX was therefore evolved, with a pure aluminium ribbon only 30 micro inches thick and corrugated to prevent curling which would have increased the stiffness. The resonant frequency of the ribbon was very low (about 2 Hz) giving no ill effects throughout the audio band.

In 1937, the BBC produced a Type B ribbon microphone design using improved magnets, enabling a much smaller overall size to be achieved, much appreciated for outside broadcast work. The Type B was adapted for use as a close-distance commentator's lip microphone designated L1: an improved version, the L2, was produced in 1951.

A defect of the AX was its susceptibility to interference from studio mains wiring or other current carrying sources. A solution was found in 1943 in the form of the Type AXB with internal wiring balanced to secure cancellation of externally induced interference

The final step in this evolutionary series was the Type AXBT of 1944, with improved Alcomax magnets (aluminium.cobalt/nickel) in place of the original cobalt/steel. Alcomax gave twice the flux density and hence doubled the sensitivity. The A-AXBT series embodied an end casing with a lining of plasticine to avoid ringing, and an outer case with silk lining to screen from draughts. The very low impedence of the ribbon was stepped up by a built-in transformer to give 300 ohm output impedence.

The PGS ribbon microphone

The PGS (pressure Gradient Single) microphone was designed by the BBC and manufactured by STC in 1952 as type 4038. It was very much smaller and lighter than the AXBT, but retained the excellent performance of its predecessor.

1928
Shure grows to more than 75 employees. Sidney N. Shure's brother, Samuel J. Shure, joins the company. Shure Radio Company becomes Shure Brothers Company, moving to more spacious quarters at 335 West Madison Street, Chicago.

1929
The Great Depression grips the United States. Market for radio parts kits declines when factory-built radio sets become available. Staff is reduced to a few people. Shure becomes exclusive distributor for a small microphone manufacturer.

1930
Samuel J. Shure leaves to pursue a career in heating and ventilation engineering, his college major, joining a prominent company in St. Louis, Missouri.

1931
Shure begins development of its own microphone under the direction of a young engineer named Ralph Glover.

1932
Shure becomes one of only four U. S. microphone manufacturers with the introduction of the Model 33N Two-Button Carbon Microphone. It is the first lightweight, high-performance product in a market dominated by large, costly devices.

1933
Model 40D is the company's first condenser microphone.

1935
Model 70 is Shure's first crystal microphone.

1936
First patent is received for a stylish and practical suspension support system for microphones.

1939
Model 55 Unidyne Microphone is the first single-element unidirectional microphone. Its performance qualities and distinctive styling ultimately make it "the most recognized microphone in the world." Notably, the single-element design makes microphones smaller, less expensive, and, therefore, more accessible to all.

1941
Shure secures contracts to supply microphones for United States armed forces in World War II.

1942
T-17B Microphone becomes the most widely used microphone by the U.S. Army and Navy. Shure develops plastic cases for these mics, preventing them from getting too hot to handle in tanks and, also, conserving scarce metal for the war effort.
1942-1944
T-30 Throat Microphone, HS-33 and HS-38 Headset Microphone, M-CI Microphone for oxygen masks, and Battle Announce Microphone are all made for the military. Using T-30s, bomber crews could communicate over the noise inside the planes. Shure adopts strict military standards (MILSPEC) as the standard of reliability for all Shure microphones.
1946
Shure is the largest producer of phonograph cartridges in the U.S., supplying cartridges to major phonograph manufacturers, including Philco, RCA, Emerson, Magnavox, Admiral, and Motorola.

1946
Shure Brothers Company becomes Shure Brothers Incorporated.

1948
First phonograph cartridge capable of playing both long-playing (LP) and 78 rpm (revolutions per minute) records.

1951
Unidyne 55S is a smaller version of the renowned Unidyne 55.

1952
First Shure ribbon microphone, Model 300.

1953
First wireless microphone system for performers, called the Vagabond. Powered by two hearing aid batteries, the system could transmit within a "performance circle" of approximately 700 square feet.

1954
M12 Dynetic Phono Reproducer is a tone arm/phono cartridge combination that set a new industry standard with its tracking force of only one gram.

1955
First mobile communications microphone designed to also function as a loudspeaker.

1956
Shure moves from downtown Chicago to its present corporate headquarters in Evanston, Illinois.

1958
M3D Phonograph Cartridge is the world's first cartridge to successfully meet performance requirements of stereo recording.

1959
Unidyne III Microphone is the first high-quality unidirectional microphone that is used by speaking into the end ("end-firing") rather than the side of the microphone. It was the predecessor to the SM57.

530 DX

Legendary among harmonica players

Over the years the company expanded and in April 1949 it was re-organised with a capital of 500,000 yen and Mr Tsunettaro Nakataro became its first President; at the same time the factory moved to 14 Shimosawa-Dori, 5-Chome, Hyogo-KU, Kobe, Japan.

Due to continued rapid growth in both domestic and overseas sales in 1962 a new factory had to be built and since that date the factory and offices have been considerably expanded and today have 166,842 square feet of site 107,640 square feet of building space and Mr Taro Nakatani is president of the Toa Electric Group of Companies which has a work force in Japan of approximately 1100 people.

The Toa Electric Group is split into various product operating companies all of which are independently managed. This means that the staff can appreciate the rapidly changing world of technological advancement, customers requirements and the day to day economic situation throughout the world; plus each company has its own unique creativeness in it's specific field, but is still working for a common purpose which is the Toa Group of Companies.

The main Companies are:

Acous Ltd Radio Microphones and Receivers

Toa Communications Industries Co Ltd Automatic
Broadcasting Systems

Pasco Ltd Indoor Loudspeakers

Ikegami Metal Co Ltd Spinnings for Loudspeakers

Takarazuka Metal Co Ltd All metal work for Toa
products

Takeo Toa Co Ltd Dynamic Loudspeakers and
Diaphragms

Musashino Communicatioins Ltd All types of
Transformers used in Toa products

Taktisu Co Ltd Amplifier assembly

The Takarazuka factory produces outdoor speaker racks and console amplifiers, plus is responsible for the initial production of all newly developed products.

1934

Mr Tsunettaro Nakataro insisted that four words would govern his business activities and of what is now the Toe Electric Group of Companies and they are; SINCERITY-UNITY-RELIABILITY-COURAGE
And is worth noting the definitions of each one of these words:

SINCERITY- develops a lasting trust. Trust is a prize possession that takes years to earn, but can be destroyed in a single day. It must be carefully preserved and cultivated.

UNITY- is the harmoneous effort of the entire company. It replaces the flash of individual bright stars with the brighter, steadier glow of co-operation.

RELIABILITY- is based on self knowledge. It requires complete honesty concerning oneself and ones talents, and a desire to proceed steadily after calculating the risk.

COURAGE- requires foresight. It is a willingness to do what one has never done, to challenge the unknown and to move ahead, even if it is only half a step.

By coupling with the above four words the other phrase 'The Sound of Toa' it can be seen why constant stress has been put on technical developments. Since its very beginning, Toa has pioneered to research into a number of vexing technical audio problems in order to effectively satisfy the demands of PA Equipment users, and this single minded determination has paid off.

'Quality first' is realised through stringent quality control and a firm determination that every member of the Toa family whether Toa staff or a member of the overseas dealer network staff, labours diligently at his job, studies constantly and does his utmost to eliminate errors and imperfections.

'Quality first' is perhaps an over-used and thread-bare phrase but not at Toa, a constant determination to produce better products has made 'quality first' a way of life.

Toa Electric was the first Company to form its own Sound Research Institute and so far, over 5000 engineers have attended courses to learn about sound, sound system designing and the range of Toa products.

By this constant effort the Toa Electric Company now holds 497 industrial registrations made up of 64 patents, 152 technical innovations, 71 designs and 210 trade marks.

This is why the product list of Toa 'first' is prolific such
as:

1954 Valve megaphones

1957 Transistorised megaphones

1961 High output transistorised megaphones

1968 Emergency megaphones approved for aircraft use

1971 Police Motor Cycle - Mounted Public Address Equipment

1972 Ultra compact transistorised megaphone (same weight as half bottle of beer)

1973 Mini computerised automatic broadcasting systems

1975 Compact wall mounting fire alarm

In 42 years Toa Electric Company is now possibly the largest manufacturer of Public Address Equipment, both portable, cabinet, rack and business consoles to supply the markets of the world.

Chime Paging Microphone 1960's

AMPLIFIER PRODUCTION

THE FIELDS OF AUTUMN BY JIRD TAKIDAIRA

1976

WIRELESS MEETING AMPLIFIER 1976

WIRELESS MICROPHONE 1976

(The Toa Electric Group of Companies is now the TOA Corporation Co Ltd 2002)

Grampian established a reputation for 'Firsts' way back in 1932 with the development of moving coil microphones, a further 'First' was the pioneering of a sound package for ENSA in 1940, but possibly the most notable 'First' was the application of solid state switching to audio systems leading to the development of their highly successful; Series 7 System

The Extended Type 73 System was developed and engineered by Grampian Reproducers Ltd in conjunction with Telephone Rentals Ltd.

Moving Coil 1939

At last we have it...

Ken F Yaxley 4th April 2004