Many sound-shaping mechanisms have been tried. However, in mainstream use, the three best dynamic drivers, ribbon loudspeakers, and electrostatic drivers have taken hold. In this article, we have tried to collect only interesting facts about these types of speakers.
Dynamic drivers have a recognizable shape that is difficult to confuse with something, these are cones and domes of diffusers. This type of emitter is widespread and popular due to its characteristics such as wide dynamic range and high sensitivity. However, an important aspect of the high popularity of these speakers is their reliability.
Speaker systems based on such speakers are created from a combination of speakers of different sizes. This is since the size depends on which frequencies will be reproduced. Low frequencies are reproduced by large diameter, dense diaphragm drivers. But high frequencies are the prerogative of small drivers with small, metal, or fabric diaphragms. And there is also a separate view for reproducing the midrange.
Principle of operation
Let’s take a closer look at the principle of operation. The speaker has a voice coil that sits inside the magnet system. It is connected to a diffuser, which creates air vibrations as a result of its movement. An electrical signal from an amplifier is supplied to the speaker circuit. As a result of its interaction with the magnetic field, the coil and with it the diffuser move back and forth. Thus, sound vibrations of the air are obtained.
The most common material for making diffusers is paper. But many speakers are also made with polypropylene or metal cones. In the Hi-End segment, there are also more unusual materials – carbon fiber or even unique composite materials.
This variety of materials is driven by the search for the perfect combination of lightness and rigidity. The lighter cone has less inertia, which allows it to respond more quickly to an audio signal and stop faster when it stops. The stiffness is required for the diaphragm to prevent distortions called bending waves: they occur when the diaphragm material bends instead of moving like a perfect piston.
Like any electrical technique, dynamic speakers can break down. The most common problem is a burnt coil. Speakers often fail due to too much current flowing through their voice coils. Another common cause of speaker failure is a rattle from a weakened voice coil. Too much current through the coil melts the adhesive and weakens the wire winding, which then rubs against the magnet, causing a humming noise.
Electromagnetic dynamic driver
Another type of common speaker is electromagnetic drivers. This type uses a large coil instead of permanent magnets, which works as an electromagnet. The magnetic field is created by the current that flows into the coil circuit, and it also drives the diffuser.
The advantages of an electromagnet are obvious here. The first thing to note is the high power. With this approach, the cone itself can be made from heavier materials, which has a positive effect on sound depth.
Besides, the sound of the electromagnetic speakers can be finely adjusted, and all thanks to the same electromagnetic coil. Such adjustment is carried out by changing the strength of the current passing through the coil using a regulator on the mains power supply.
The ribbon loudspeaker design was patented in 1928 by a Gerlach engineer from European Acoustic Laboratories. Typically ribbon loudspeakers are used as a tweeter in combination with a woofer dynamic loudspeaker unit, however, broadband ribbon loudspeaker models are available.
Principle of operation
The operating principle of such a speaker is very simple. When an alternating current is applied to a corrugated aluminum conductor in a magnetic field, the mechanical Lorentz force begins to act on it, directed perpendicular to the surface of the ribbon. Since the ribbon is very light, it receives a fairly large displacement with a small amount of applied current.
To reduce distortion caused by asymmetry and non-uniformity of the magnetic field in the gap (which is a big problem for conventional electrodynamic loudspeakers), the design of the magnetic circuit poles is optimized to obtain the most uniform field in the gap.
After familiarizing yourself with all three types of speakers, it must be said that despite all the design flaws and possible breakdowns, dynamic speakers remain the most popular. Balance and versatility play into their hands, as well as the relative cheapness in manufacturing.