Sound box

from Wikipedia, the free encyclopedia
Sound box with Bakelite sound resonator of a microphone made by Paillard & Cie in Sainte-Croix, Switzerland.

A sound box , in English sound box , was an acoustic-mechanical component of the phonograph developed by Thomas Alva Edison , which was used to record and reproduce sound waves. With the advent of the electron tube and the associated possibility of amplifying sound signals, the mechanical sound boxes were gradually replaced by electrical sound boxes, from which the pick-up systems commonly used today emerged.

Mechanical sound box

General

In general it can be said that the operation is based a mechanical sound box on the recognition Edison that words spoken work to do. A thought that caught Edison when he experimented with the thin membranes that were built into the receivers of the telephones developed by Alexander Graham Bell and were used to convert sound. Realizing his idea structurally, Edison constructed a first sound box with a pin that sits vertically on the membrane surface and is centered in the middle. With this construction method, it was now possible to mechanically engrave the sinusoidal sound waves that hit the membrane in a sound carrier , to preserve them and to play them back as required.

In the course of their development history, the sound boxes used usually consisted of flat housings, made of brass or aluminum, sometimes also of wood, which had an opening on one side for the connection of a sound control system (funnel, hose or tonearm) on the opposite side were closed with a membrane mostly encased in rubber. It was important that the membrane, made of mica, glass, copper or aluminum, had to swing freely. It was only allowed to act on the lever system that connected it to the component (sapphire or needle) that either created the groove of the sound carrier or slid through it. Any contact with other fixed housing parts would have severely impaired the function of recording or reproducing sound.

Specific

Phonograph and Graphophon

The sound boxes for wax rollers developed by Edison were separated into recording and playback sound boxes, which were exchanged depending on the use, but in some cases were also mounted on a common carrier and then simply changed by turning sideways. They were always moved over the roller by a lead screw. This was necessary during the recording in order to be able to create a groove at all, and it was spared to a certain extent during playback. The recording sound box (recorder) was equipped with a funnel, the playback sound box (reproducer) with a hearing tube or funnel. In later models from various manufacturers, the lead screw was partly dispensed with, since devices such as the gramophone were only intended to reproduce sound.

As already mentioned, it was the case for all of these models that when recording the sharp-edged burin, which was almost perpendicular to the sound carrier - sinusoidally oscillating up and down in rhythm with the sound waves hitting the membrane - the sound information was dug into the depth of the recording medium and played back rounded sapphire caused the membrane of the specialized sound box to vibrate and thus converted the recorded sound signals back into audible sound. The described recording method is called deep or Edison script because of the direction of recording in the depth of the sound carrier.

The Graphophon , a further development of Edison's first phonograph by Chichester Bell and Charles Sumner Tainter , used sound boxes similar to that of the former and, as a result, also the subscript to record the sound waves in the recording medium. It should be noted that the one at the beginning of technical development made of a sheet of tin foil, stretched on a metal cylinder rotating around its own axis ( tin foil phonograph or tin foil phonograph ), later from a round cardboard roller ( graphophone ) and covered with a layer of wax again after its further development by Edison consisted entirely of wax. ( Improved Phonograph or Improved Phonograph ).

gramophone

With the rediscovery of the horizontal recording medium - Thomas Alva Edison, Chichester Bell and Charles Sumner Tainter already experimented with a flat disc on which the sound signals were engraved in subscript - by Emil Berliner and the gramophone he developed at the same time , the construction principle of the sound box changed to the effect that the needle, depending on the design of the gramophone, was at a forward inclined angle of up to 60 ° (relative to the vertical) to the sound carrier, while its membrane was in relation to this in a lateral, also vertical position to the playback medium so that its surface was parallel to the direction of the groove under the needle. The mechanical conversion of the audio signals recorded in a wavy line was now carried out using an additional angle lever that had become necessary.

The sound groove was no longer executed in the previously common subscript, but in the V-shaped side font introduced by Berliner as a major innovation. In connection with an exact needle guidance, this enabled the better conversion of the mechanical rotational force of the motor into acoustic energy and, as a result, higher volume than the phonograph and graphophone.

In contrast to the phonographs, the gramophones on sale in the trade were only intended for the playback of the now massively pressed sound carriers, the records , and were therefore only supplied with playback sound boxes. In addition, guide spindles could be dispensed with, which meant that the construction of the devices could be kept much simpler and therefore cheaper.

The weight of the page font preferred by Berliner and the associated positioning of the sound box is of particular importance. A sound box that was too light scanned the tone groove uncleanly, tended to jump and got audible resonance at low frequencies. On the other hand, sound boxes that were too heavy could permanently damage the shellac records due to increased wear. The same applied to the steel needles used, which were usually only suitable for playing the sound carrier once, as they quickly lost their original, rounded tip and adapted to the V-shape of the record groove. This effect is due to the deliberately chosen hard material mix of the shellac records in order to better protect them against conventional wear and tear.

Double sound boxes

Double sound boxes and the double-tone arms with the same technical aim of increasing the volume existed in a wide variety of designs. For example, the needles of two separate sound boxes were positioned one behind the other and the scanned sound information was fed into a common funnel. The combination of two membranes in a sound box housing, controlled by a scanning needle, is based on the same principle of doubling the sound generation area. Here, too, the emitted sound waves were emitted via a funnel, whereby it should generally be noted that experiments were carried out with a wide variety of constructions, including two and three funnels.

Electric sound box

Very early on after the development of the phonograph, it was possible to convert the engraved sound signals into electrical vibrations by letting the membrane of a microphone, mechanically connected to the stylus with a lever, scan the sound groove. However, the electrical signals were so weak that they could only be heard with the aid of headphones. This only changed with the introduction of the electron tube, which became more and more popular after 1918 in connection with radio equipment and the amplifiers and loudspeakers contained therein.

The replacement of the classic mechanical sound box by the electrical sound box, as the systems for electromagnetic scanning of records were initially called, was only due to the considerable advantages in terms of the record and needle protection, due to the lower weight, as well as the better and individually controllable frequency response a question of time. In the same period, by the transition from the mechanical-acoustic scanning toward the electrical to decrease occurred sound waves, is also the name patriated pickup a, which also there was consistently more appropriate than that no direct sound more generated within a sound box and by means of a Funnel was audibly released into the environment.

See also

literature

Web links