Dynamics device: circuit, dimensions, purpose

An electrodynamic loudspeaker is a device that converts an electrical signal into an audio signal through the motion of a coil with a current in the magnetic field of a permanent magnet. With these devices, we face every day. Even if you are not a big fan of music and do not spend half a day on headphones. Speakers are equipped with televisions, radios in cars and even telephones. This usual mechanism for us is actually a whole complex of elements, and its device is a real work of engineering art.

In this article we will take a closer look at the device dynamics. We will discuss what components make up this device and how they work.

History

The day began a small digression into the history of the invention of electrodynamics. Loudspeakers of a similar type were used in the late 1920s. Bella's phone worked in a similar way. It involved a membrane that moved in the magnetic field of a permanent magnet. These speakers had many serious flaws: frequency distortion, loss of sound. To solve the problems associated with the classical loudspeakers, Oliver Lorgge suggested using his experience. His coil moved across the lines of force. A little later, two of his colleagues adapted technology for the consumer market and patented a new design of electrodynamics, which is still used today.

Speaker unit

The speaker has a rather complex design and consists of many elements. The speaker unit diagram (see below) shows the key details, thanks to which the loudspeaker functions correctly.

The device of acoustic dynamics includes the following components:

• Suspension (or edge corrugation);
• Diffuser (or membrane);
• cap;
• Voice coil;
• Core;
• Magnetic system;
• Diffuser holder;
• Flexible conclusions.

In different models of speakers, different unique design elements can be used. The classic device of the speaker looks exactly like this.

Let's consider each separate element of the structure in more detail.

Edge corrugation

This element is also called a "collar". This plastic or rubber edging, describing the electrodynamic mechanism throughout the area. Sometimes as the main material is used natural fabrics with a special, vibration-relaxing coating. Corrugations are divided not only according to the type of material from which they are made, but also in shape. The most popular subtype is the semi-toroidal profiles.

The collar is presented with a number of requirements, the observance of which indicates its high quality. The first requirement is high flexibility. The resonance frequency of the corrugation should be low. The second requirement is that the corrugation should be well fixed and provide only one type of oscillation - parallel. The third requirement is reliability. "Collar" should adequately react to temperature changes and "normal" wear, keeping its shape for a long time.

To achieve the best balance of sound in low-frequency columns, rubber corrugations are used, and in high-frequency columns - paper corrugations.

Diffuser

The main radiating object in electrodynamics is the diffuser. Diffuser dynamics is a kind of piston, which moves in a straight up and down and maintains the amplitude-frequency response (further frequency response) in a linear form. As the frequency of oscillations increases, the diffuser begins to bend. Because of this, there are so-called standing waves, which, in turn, lead to failures and upsurge in the frequency response curve. To minimize this effect, designers use stiffer diffusers made from materials of lower density. If the speaker size is 12 inches, the frequency range in it will vary within 1 kHz for low frequencies, 3 kHz for medium and 16 kHz for high.

• Diffusers can be stiff. They are made of ceramics or aluminum. Such products provide the lowest level of distortion of sound. Dynamics with rigid diffusers are much more expensive than analogues.
• Soft diffusers are made of polypropylene. Such samples provide the softest and warmest sound due to the absorption of waves by soft material.
• Semi-rigid diffusers are a compromise option. They are made of Kevlar or fiberglass. Distortions provoked by such a diffuser are higher than those of hard diffusers, but lower than soft ones.

Cap

The cap is a sheath of synthetics or fabric, the main function of which is to protect the speakers from dust. In addition, the cap plays an important role in the formation of a certain sound. In particular, when reproducing middle frequencies. For the purpose of the most rigid fixation, the caps are rounded, giving them a slight bend. As you probably already understood, the variety of materials is just related to achieving a certain sound. In the course is a fabric with different impregnations, films, cellulose compositions and even metal nets. The latter, in turn, also fulfill the function of the radiator. Aluminum or metal mesh removes excess heat from the coil.

Washer

Sometimes it is also called a "spider". This is a heavy piece, located between the speaker cone and its housing. The task of the washer is to maintain a stable resonance for low-frequency speakers. This is especially important if there are sudden temperature changes in the room. The washer fixes the position of the coil and the entire mobile system, and also closes the magnetic gap, preventing dust from entering it. Classic washers are a round corrugated disc. More modern options look a little different. Some manufacturers intentionally change the shape of the corrugation so that to increase the linearity of the frequencies and stabilize the shape of the washer. This design greatly affects the price of the speaker. Washers are made of nylon, calico or copper. The latter option, as in the case with the cap, performs the function of a mini radiator.

Voice coil and magnetic system

So we got to the element, which, in fact, is responsible for the reproduction of the sound. The magnetic system is located in a small gap of the magnetic circuit and, together with the coil, converts electrical energy. The very magnetic system is a system of a magnet in the form of a ring and a core. Between them at the time of sound reproduction, the voice coil moves. An important task of designers is to create a uniform magnetic field in a magnetic system. To do this, speaker manufacturers thoroughly verify the poles and equip the core with a copper tip. Current in the voice coil comes through the flexible terminals of the speaker - ordinary wire wound over the synthetic thread.

Principle of operation

With the device the speaker is sorted out, we move on to the principle of work. The principle of the dynamics is as follows: the current going to the coil causes it to perform perpendicular oscillations within the magnetic field. This system entrains the diffuser, causing it to oscillate with the frequency of the supplied current, and creates discharged waves. The diffuser begins to oscillate and creates sound waves that can be perceived by the human ear. They are transmitted as an electrical signal to the amplifier. Hence the sound appears.

The range of frequencies reproduced directly depends on the thickness of the magnetic circuits and the size of the speaker. With a larger magnitude of the magnetic circuit, the gap in the magnetic system increases, and with it the effective part of the coil also increases. That's why compact speakers can not cope with low frequencies in the range of 16-250 hertz. Their minimum frequency threshold starts at 300 Hz and ends at 12,000 hertz. That's why the speakers wheeze when you twist the sound to the maximum.

Rated electrical resistance

The wire that feeds the coil has active and reactive resistance. To determine the level of the latter, engineers measure it at a frequency of 1000 hertz and add to the resulting value the active resistance of the voice coil. In most speakers, the resistance level is 2, 4, 6 or 8 ohms. This parameter must be taken into account when buying an amplifier. It is important to reconcile the load level.

Frequency range

It has already been said above that most of the electrodynamics reproduces only a part of the frequencies that a person can perceive. Make a universal speaker, capable of reproducing the entire range from 16 Hz to 20 kilohertz is impossible, so the frequencies are divided into three groups: low, medium and high. After that, the designers started creating the speakers separately for each frequency. This means that low-frequency speakers are best able to cope with bass. They operate on a range of 25 hertz - 5 kilohertz. High-frequency ones are designed to work with screeching tops (hence the common name - "pyshalka"). They operate in the frequency range of 2 kHz - 20 kilohertz. Mid-frequency speakers operate in the range of 200 hertz - 7 kilohertz. Engineers are still trying to create a high-quality broadband speaker. Alas, the price of the dynamics goes against its quality and does not justify it at all.

A little bit about mobile speakers

The speakers for the phone differ from the "adult" models constructively. To arrange such a complex mechanism in the mobile casing is unrealistic, so engineers went to the trick and replaced a number of elements. For example, the coils become fixed, and instead of the diffuser a membrane is used. Speakers for the phone are greatly simplified, so expect from them a high quality sound is not worth it.

The range of frequencies that can cover such an element is significantly narrowed. In its sound, it is closer to high-frequency devices, since there is no additional space in the phone casing for installing thick magnetic circuits.

The device of a speaker in a mobile phone differs not only in size, but also in the absence of independence. The possibilities of the device are limited to the software. This is done to protect the design of the speakers. Many take this limit manually, and then they ask themselves: "Why do they wheeze the speakers?"

In an average smartphone, two such elements are installed. One spoken, the other musical. Sometimes they are combined to achieve a stereo effect. Anyway, to achieve depth and saturation in the sound can only be a full stereo system.