Created on 25.11.2019 15:31.
Author: Pavel Sayk.
- Scheme / design
- Pros / Cons
- Where apply or may apply
Living in the world of sounds, a person is so accustomed to their perception that he quite clearly defines any distortions. Considering that when transmitting any sounds, the process must end with an element emitting the received signal, special attention is required to its design.
The loudspeaker acts as such a final chord, which is the invention of the human intellect, without which it is difficult to imagine modern life today. The first theoretical developments in this direction began at the end of the 19th century by the founder of Siemens, a world famous company.
Ernst Werner von Siemens, an engineer from Germany, calculated an original magnetoelectric device in the form of a round coil wrapped with wire.
The product was placed in a radial magnetic field, thus providing vertical displacement. Such an unusual design at that time was used to receive a sound signal. However, so far this remained a theoretical development.
Within a few years, Siemens described the basic principles of the functioning of an electrodynamic loudspeaker, which was already used in the industry in the form of finished products. It took more than a dozen years until, after a series of inventions and protected patents, the loudspeaker acquired structural elements that are more familiar to modern users: a diaphragm (conical), centering washers, etc.
The mankind appreciated all the power of the invention decades later and at the moment has come to the conclusion that modern loudspeakers are the most widespread type of sound equipment, the quantitative production of which reaches 0.5 billion pieces per year of various modifications and purposes. Almost everything that a person hears, apart from natural natural sounds, reaches us from loudspeakers.
Scheme, principle of operation of the woofer with a flat diffuser
The design of a classic woofer includes a cone, cone suspension, magnetic system, oscillating coil, suspension.
The principle of operation of an acoustic transducer is to convert an electrical signal into sound waves. This transformation is carried out by moving the oscillating coil with a winding in a magnetic field. Most often, a direct current magnetic field is used, less often an electromagnet. The resulting mechanical vibration is converted with the help of a diffuser into ambient air vibrations (sound waves), which are perceived by the human ear. The vibration amplitude depends on the frequency of the supplied current.
Special attention should be paid to an important component of the woofer design: it is a diffuser, like the main radiator.
Flat diffuser: pros and cons
In a low-frequency speaker, the diffuser should provide a linear amplitude-frequency characteristic (AFC) in the middle frequency range (up to 1 kHz).
There are four main types of materials from which a flat diffuser is made:
- metal, tough… Such material guarantees minimal distortion due to the strength of the entire structure, but at the same time there is an increased Q factor (a measure of attenuation of the oscillations of the head), that is, a pronounced peak value of the resonance.
- semi-rigid “Layered” structures. Kevlar or fiberglass is used in combination with a binder resin. The result is a cross between a hard and soft cone. At high distortions, they show a lower resonance overshoot (at low frequencies);
- soft… These diffusers are made of polypropylene or polymethylpentene. The latter is distinguished by a sufficiently high melting point and high heat resistance. The material has low density and optical transparency. Among the advantages of low-frequency loudspeakers of such materials should be noted an even frequency response, soft and pleasant sounding in the entire middle range. Such a diffuser is attached to the holder without a suspension;
- paper… A separate type of diffusers. To improve the sound, natural / synthetic fibers are added to the material (natural / mental0), and the cone itself is covered with varnishes. Considering that the diffuser, suspension and cap can be made from the same material, the cost price of such a product is very low, as is the simplicity of production.
Without this element, it is impossible to organize the functioning of the loudspeaker. The head usually includes a radiating diaphragm, a voice coil, and a magnetic system. It is in the head that the electrical signals of the sound wave are converted into acoustic vibrations, which are perceived by a person.
According to the principle of converting an electrical signal into acoustic vibrations, several types of loudspeaker heads are distinguished. The overwhelming part of the loudspeaker market (about 90%) is occupied by woofers with electrodynamic diffuser heads. The rest is accounted for by other types, including electrostatic and piezoceramic.
In addition to the principle of conversion, two types of radiation are distinguished in the heads. This is horn and direct radiation. The horn design of the head contains a pre-horn chamber and a horn through which sound is emitted. In the case of the direct version, the sound is radiated directly into the environment.
Application of low frequency loudspeakers
The classic version of the woofer can be used in technology that does not require high sound quality. Considering that the human hearing aid perceives all types of sounds, be it ordinary noise, tonal and note signals, as well as a number of other sounds, then low-frequency loudspeakers, being acoustic transducers, have found the widest application.
These are sound systems in cinemas, speakers in TVs, in radio devices (including portable ones) and, of course, in subwoofers. Since all the indicated devices have completely different sizes, then the sizes of the woofers vary greatly, as well as the quality of the sound emitted.
The sound range, which is the working range for low-frequency loudspeakers, determines the widest scope of their application.
Considering the dimensions of the products, as well as wanting to get the highest quality sound, the design is constantly being improved. Amplifiers are added (then the system becomes active), several are applied …