Design and characteristics of dynamic loudspeakers (speakers). Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Speakers

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Consider the design and characteristics of a typical dynamic loudspeaker (speaker).

External dimensions - usually from 5 to 30 cm in terms of the diameter of the diffuser, the weight corresponds to the dimensions.

Diffuser - This thing plays sound. The diffuser material is most often pressed paper (cellulose) impregnated for consumer models. The main thing is that the diffuser is not subjected to deformation during operation. For models designed to work in cars, foamed plastics are often used, as the material is not hygroscopic and has sufficient rigidity. For expensive models, the choice of diffuser material is wider, and is determined mainly by the "steepness" of the developer. The manufacture of a diffuser made of aluminum has come into fashion; combined materials (sandwich) are often used.

corrugation - through it the diffuser is attached to the frame - body (diffuser holder). It can be molded together with the diffuser during its molding, or it can be made separately from another material - latex, polyurethane foam. The main thing is that it should provide minimal resistance to the movement of the diffuser during operation. Often, paper corrugation is impregnated with special compounds for greater flexibility and at the same time damping parasitic resonant vibrations. Usually the corrugation is glued to the diffuser holder, but earlier there were designs with fastening with a clamping ring.

Magnetic system - creates a magnetic field in which the coil moves. Obviously, the stronger this field, the louder the "yelling" speaker, so designers tend to use highly efficient magnetic materials. In case of impacts, self-disassembly of the magnetic system, high temperature - the characteristics may deteriorate irreversibly. Sometimes the magnetic system is shielded from above (for example, for speakers built into TVs and monitors). Previously, there were designs where, in order to amplify the magnetic field, an additional coil was wound on the magnetic system, powered from an auxiliary source.

Kern - transfers the magnetic field inside the coil, but should not be magnetized itself, therefore it is made of a magnetically soft material.

coil frame - the "carrier" of the coil is made of a thin, durable material that does not shield the magnetic field and has a minimum mass. In the old designs - exclusively electric cardboard, in the new ones - aluminum.

voice coil - the power developed by the amplifier is supplied to it. Coil active resistance (DC):

from 2 Ohm (for car speakers);

4 - 6 - 8 ohm (most common);

16 - 32 Ohm (for economical or special purposes).

The coil is most often wound in two layers with ordinary wire in lacquer insulation, but in especially powerful designs, the wire can also be of rectangular cross section - to increase the effective filling of the gap. The coil is glued to the frame. With poor-quality sizing, or if the speaker is overloaded, some of the turns can "dangle" inside and create sound effects that do not belong to the category of high-quality sound reproduction. In the last century, radio amateurs independently rewound voice coils, especially since the design of many speakers allowed this.

Centering washer - the purpose is clear from the name. The main thing is not to interfere with the movement of the voice coil, and to be breathable, otherwise a closed volume is formed inside the magnetic system where the coil is located. But we will remember about its harm further when we consider the acoustic design of the loudspeakers. The material of the washer - something like impregnated gauze - for consumer goods, and anything - for the exclusive.

Due to high humidity or other bad influences, alignment may be disturbed, the defect cannot be eliminated without disassembling the speaker. You can check the alignment by gently pressing the diffuser and listening to the sounds inside - they should not be!

Coil terminals - are performed with a special wire "tinsel" of mixed thin copper and silk threads. The conclusions should not interfere with the movement of the diffuser. Due to constant movement, they tend to break near the contact patches, where they are soldered to the voice coil leads. A good alternative is the stripped MGTF wire. Leads that are too long can rub against the cone and create interesting sounds that add flavor to your speaker but are not appreciated by other listeners.

Gap - the gap between the magnetic system and the core, where the voice coil moves. The smaller the gap, the higher the inductance in it, and the higher the efficiency of the speaker.

Repeated attempts have been made to increase the inductance without increasing the gap by introducing a magnetic fluid there. But this led to an increase in the resistance to the movement of the diffuser and an increase in the lower limit of the reproducible frequencies. Debris entering the gap is fraught with sound distortion, so the gap is usually closed with a cap (not shown in the figure). At the same time, the cap improves the reproduction of upper sound frequencies.

Frame - she is a frame, she is a diffuser holder. In cheap designs - from plastic, in consumer goods - from a stamped sheet, in more expensive designs - casting from aluminum alloys. Usually there are "windows" in the frame for the free movement of air, but in tweeters this is not necessary. The frame should be very rigid, not resonate, be comfortable when installing the speaker in the case and please the eye of the happy owner of the device.

We will talk about the characteristics that directly affect the sound in the next article.

We've covered the general issues of speaker design, now let's look at some exotic designs.

The shape of the speaker cone is the correct circle, as the most technologically advanced element.

Elliptical shapes are just to reduce the size, and do not have any advantages. And the Japanese were even able to make a square one, which fits very nicely into a rectangular case. The material of the diffuser is the thinnest cut of birch aged in sake*****. True gourmets, of course, appreciate this device.

NASA (which is in the USA) for testing the Gemini descent vehicles built a speaker more than a meter in diameter with a MECHANICAL DRIVE. Subsequently, it was transferred to a disco in Atlanta. The sound of this monster shook to the core in the truest sense of the word.

For high-frequency speakers (tweeters), the diffuser as a concept is practically absent, the sound is reproduced by a spherical cap glued to the coil. To reduce the mass, the cap is made of silk, sometimes of beryllium, ceramic or even diamond coating is applied in order to obtain a transparent, like a diamond, sound.

ELECTROSTATIC sound emitters are produced in a very limited edition, which can no longer be called speakers. In them, the role of a diffuser is played by a thin film with sputtered foil, and all this is placed in a giant capacitor, polarized by a voltage of 1000 volts. This design does not require special acoustic design and sounds great at frequencies above 100 Hz.

In our country, ISODYNAMIC emitters were produced - also a film with sputtered conductors, but everything is located between two multi-pole magnets. An ideal radiator for frequencies above 5 kHz.

Piezoceramic radiators and exotic speakers are common (see boomboxes with two or three-way radiators). My cat has never heard a single piezo emitter claiming to be Hi-Fi sound reproduction. All of them can be classified as Hi-Hi.

And the most exotic emitter is the ionophone. It was demonstrated at the All-Union Exhibition of the creativity of radio amateurs somewhere in the 50s of the last century. The flow of air ions was modulated by sound frequency. The sound quality is beyond praise. Disadvantages - large dimensions and harmful air ionization. It seems that foreign countries are sometimes trying to revive such emitters, but they will not go into production - ordinary speakers are much simpler and cheaper, and trained ears are needed to catch the difference in sound. A special article is planned on a set of exercises that develop the ears.

Publication: radiokot.ru

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