Created on 18.11.2019 23:03.
Updated on 16.02.2020 15:51.
Author: Dmitry Pirozhkov.
It is difficult to imagine the modern world without acoustic systems, represented by the widest assortment that satisfies the most sophisticated needs of real music lovers. But it all started with a banal attempt at all to hear something at a distance. Speech about the quality of sound, about its high, medium or low frequency range did not go, in principle, due to complete ignorance.
The physical laws have remained the same, so that since the invention of the telephone by T. Watson and A. G. Bell (1876), little has changed, although since then the improvement of speakers (electro-acoustic transducers) has reached incredible heights.
In the designs of the first electrodynamic speakers, a fabric suspension was used, electromagnets were powered by direct current, and the coils were high-resistance. Only in 1925 the company’s engineers General Electric developed and patented an electrodynamic head, which is very similar to modern mid-range speakers.
The midrange speakers (midrange) are very similar to the woofers – they are, as it were, a reduced version of them. The main task of these speakers is to reproduce frequencies in the middle range, from about 200 to 8 kHz.
Midrange speaker design
Considering that the human voice mainly falls on the middle frequencies of the audio range, it was the quality component of the midrange speaker design that was the main task. The human brain is absolutely adapted precisely to the middle frequencies, since they receive the lion’s share of sound information. This led to high requirements for mid-range speaker systems in general and midrange speakers in particular.
Considering the general principles, the design of the speaker is similar to the products related to the woofer. The difference lies in the overall dimensions, which are smaller and more compact. This is necessary to expand the radiation pattern at the upper echelons of the sound range.
As a rule, a mid-range speaker contains in its design (see Fig. 1.):
- centering washer (1);
- diffuser (2);
- corrugated suspension (3);
- voice coil (4);
- bottom plate (5);
- magnetic system (6);
- top plate (7);
- basket (8);
- dust cap (9).
The midrange speakers have a cone-shaped (conical) diaphragm, less often there is a dome variation. The latter serves to ensure high-quality sound in the high frequencies of the range. A tapered diaphragm has a wider pick-up pattern at high frequencies. Distinguish between hard and soft diaphragms.
In the manufacture of the former, foil made of aluminum, beryllium or titanium is used. And in the second version, cellulose, silk or polypropylene is used.
The cone-shaped diffusers are designed for frequencies ranging from 200 Hz to 5 kHz. At the same time, the dimensions of such midrange speakers are limited to 12.5–20 cm, since a rather narrow directivity is observed. The size of the dome variations of the diffusers is measured in the range of 4–8 cm, and the range is from 600 Hz to 8 kHz.
Research is also being carried out on new materials that are used as fillers in the creation of combined diffusers. This achieves an even greater degree of dispersion of the sound wave in all directions. The goal is to achieve a uniform sound field.
Pros / cons of midrange speakers
There are a number of advantages and disadvantages depending on the design of the midrange speakers.
So, in the case of using small midrange speakers (tweeters with soft domes), good damping, smoothing (self-damping), as well as a fairly flat frequency response (AFC) can be considered an advantage. The excellent impulse response allows for an open, natural sound without resonance. Among the disadvantages are dull sound and low power characteristics.
When operating the metal dome tweeters, one can note the sound of a very high resolution, thanks to the flat profiles, in contrast to the soft structures of the midrange, which have high distortion and limited power capabilities.
If, however, mid-bass and broadband speakers with paper cones are used as mid-range speakers, then they have a very flat frequency response, excellent resolution and detail, as well as smoothing.
Considering the material (paper), which is less rigid than Kevlar or metals, such products are less loud.
If we rely on the design of the diaphragm (cone-shaped and domed), then the following are distinguished:
- domed diffusers have lower modulation distortion, while their radiation pattern is less dependent on frequency. Products differ in a small range of reproducible frequencies, starting from 800-1000Hz, which causes certain inconvenience in settings.
- for cone heads in midrange speakers, it is necessary to provide a given volume of the cabinet. Otherwise, the “golden” median size of 10 cm is considered the optimal diameter of the cone head.
Scope of midrange speakers
In the original (English) version of the name of the midrange speakers, the phrase “midrange speaker” (or midrange) comes from the car audio. The midrange speaker operates in the most comfortable human range, so any distortion is clearly identified by the human hearing. The scope of application is unusually wide, since a huge spectrum of human activity is associated with sound.
These are concert acoustics and acoustic car systems. At home, the midrange speakers have proven themselves to be both active and passive speaker systems. Estrada also uses a variety of types of mid-range speakers.
The high popularity and breadth of application of midrange speakers is primarily due to the structure of the human body, in general, the organs of hearing and the speech apparatus, in particular. It so happened that humans and most living beings emit sounds in the middle range of sound frequencies. The human hearing aid is ideally designed for them.
The mid-range speakers cover the specified range completely. Regardless of design, cone-shaped or domed mid-frequencies are fully capable of transmitting the finest edges of sound waves. Given the development of modern technologies, information, including sound, is becoming more and more. This, in turn, guarantees further improvement of the midrange speaker designs, the search for new materials, as well as innovations in the field of product design.