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How do the headphones
Fiction | How do the headphones?
It is difficult to find a common technical unit than the headphones. The variety of shapes, colors and designs at times striking. But that’s about “what’s inside” – is much less known. It is this gap I want to make up and talk about what are the types of headphones from the “inside” of why they invented, and how different.
Just specify that basically will consider the current state of the market headphones, with a few excursions into the history of the issue, as the story goes back to the headphone jack of the 19th century, and is worthy, perhaps, a single material.
For a start, it is necessary to discuss the form factors of the headphones, so you could make reference to what the emitters where applicable.
In English, it’s much easier, there is the basic form factors are divided names. Headphones worn on the head, called the headphones, is inserted into the ear canal – earphones, earbuds type of standard Apple-ovskih – earbuds. There is also a term for the separation of the two categories of headphones: circumaural – headphones, ear cushions that cover the entire ear, supra-aural – overhead headphones that have ear cups are usually made in the form of pillows, cuddle up to your ears.
In the Russian language there is no such order, and therefore there is a strong confusion and vacillation. For example by “the Monitor” headphones often understand circumaural headphones, but sometimes “the Monitor” is called headphones with a flat frequency response, is used to control the sound quality when recording. Some are called “inserts” or “insert” all the little headphones, others attribute the term to erabuds. Also confusing the term “overhead”, sometimes referring to all headphones, sometimes for only a supra-aural.
Since this article should be clearly distinguished from co-channel full-size headphones, and then I’ll call them, if necessary, by making a reservation.
The most popular scheme of radiators used in headphones – it’s remarkable dynamic moving coil transducers.
Динамический излучатель, вскрытие
The scheme of work is quite simple. By the earphone housing rigidly attached permanent magnet that generates a static magnetic field. Typically, frankly cheap headphones use ferrite magnets, most models of medium and high-level norm was to use neodymium (although some manufacturers still emphasize neodymium magnets as some outstanding feature of the models).
In a static magnetic field, there is a coil of wire through which an alternating current is modulated by an audible signal. Changing the current in the conductor causes changes in the electromagnetic fields surrounding it. In turn, the interaction of two magnetic fields (of permanent magnets and coils of the variable) causes the spool to move. The coil is attached to a thin membrane attached to the elastic suspension and the movement of the coil causes vibration of the membrane which is transferred through the air, and is perceived as sound world.
The membranes are made of different materials, and it will definitely affect the sound. In the cheap headphones use different synthetic polymer films in more expensive solutions is very popular Mylar, cellulose, and other materials. In some of the top models of earphones titanium, although now there are FA-003Ti , offering speakers with titanium diaphragm at an affordable price.
Here is an example of a typical dynamic headphone transducer.
Динамический излучатель в естественной среде обитания
This scheme is used with minimal changes in virtually all modern headphones all form factors, although there are sometimes surprising members of the family. For example, AKG K1000, in fact are not headphones, and two small speakers, hung over his head. Thanks to the suspension, they can rotate relative to the ears, adjusting the virtual scene, and used by emitters – to their full swing requires an amplifier for the speakers. Now these headphones out of production, but in the secondary market are sold at a price of about $ 1,300.
AKG K1000 — сложно, дорого и круто
Despite the prevalence, dynamic transducers have a number of drawbacks. The first of these – sometimes low reaction rate to change the sound, especially at low frequencies. This is typical for headphone inserts and inserts. Since it uses emitters diameter from 4 mm to 14 and somewhere (usually 7 to 10), to make such a membrane is equally good to play and low frequency and high – very hard. This has led to the emergence of dynamic models with two emitters, the most popular we have – Fischer Audio Tandem, Ritmix RH-145 Pro and Brainwavz R1 .
Just emitters suffer a similar design because of the uneven magnetic field that moves the coil, and the membrane itself with its suspension – also in the real world adds a irregularity and unpredictability.
Finally, another factor – the linear dimensions are large enough dynamic emitters. Like it or not – to make a compact circular diaphragm will not work.
Attempt to solve all of these problems has been the emergence of radiators with a balanced (balanced) anchor. They are the same – “reinforcement”, from their English name «balanced armature».
These heaters were invented in the 20s of the last century, and due to the small size almost immediately began to be used in medicine for hearing aids. During the Second World War, they are also extensively used in military phones, which are due to the “reinforcement” to provide a sound louder than 20-40% of the dynamic counterparts.
The device of the radiators is easy. As you can guess from the name, they are based on U-shaped plate-anchor coil positioned on the axis. This plate is suspended (equilibrated) in the magnetic field so that it can rotate. The rest is simple: an audio signal is applied to the coil, a magnetic field, the anchor deviates from its normal position. Through the movement of the armature connection is transferred to a membrane, which gives the sound.
Сбалансированный якорь, схема работы
This scheme provides several advantages. First, it is compact, anchor emitters are performed in a very small package, enclosed on all sides except for a small sound guide. Because of this, headphones with such emitters can be made very small and use multiple transmitters in one ear (about that later). In addition, due to the closed design of the sound emitter is less dependent on the shape and materials of the shell headphones. Secondly, fittings free from distortion caused by the shape of the diffuser due to the large mass of the anchor. Thus, these emitters bypass similar to the dynamic sensitivity, volume and clarity of sound. Also, usually (though not always) armaturki have a flat frequency response.
As usual, there are no advantages without disadvantages, minus these radiators – a narrower frequency range than the “dynamo”. Manufacturers overcome this in different ways. Some TUNING emitters, achieving a maximum range (for example, one of the recognized leaders in the market Phonak hearing aids with their line of headphones Audeo). Other manufacturers are combined in one ear several emitters are responsible for different parts of the frequency range. This task is easier and producers themselves emitters, releasing dual model in a single package. The arms race has reached incredible heights, and now there are models of headphones with 4 drivers per ear (Sony, Westone, etc.), and of custom headphones, casts produced by the ears, and in general there are popular models from 6 to 10 drivers.
Ambient Acoustics AM4
By the way, about the Custom mnogodrayvernye headphones I wrote a review on AppleInsider .
Recently, many companies produce hybrid headphones, in which the dynamic transducer for low frequency combined with a reinforcement for the middle and high frequency ranges. I have listened to so far only one model, but we have to admit, the results are interesting.
Wearing headphones is often the case that everything is new – it is well forgotten old. As happened with the following types of radiators: isodynamic and orthodinamic (sometimes found the name “planar”). About 30 years ago, they were very popular, even in the Soviet Union produced several models of such emitters under the name of TDS, which are now looking for lovers of quality sound and restored.
With the departure of the 80s, these radiators are somehow “forgotten”, and yielded the palm dynamic, but the last 5-7 years there is a return of interest in them, they have strongly taken place in the pantheon of top-end models, primarily due to the efforts of companies HiFiMan and Audeze.
Principle and iso-and orthodinamic models is identical, differ only in the shape of the emitter. On the thin membrane is applied conductive spiral wrap, the membrane itself is sandwiched between two magnetic lattices. Then everything traditionally – the coil is energized, the electromagnetic field interacts with the field coil magnets, the membrane oscillates, it turns out the sound.
Here is a membrane of the most popular models isodynamic headphones – Fostex T50RP.
Мембрана Fostex T50RP
Orthodinamic transducers operate on the same principle, but have a circular shape.
In general, isodynamic headphones have higher levels of detail, but generally require a good amplifier their ability to expand.
Another little-known type of emitters – electrostatic. Humor of the situation is that there were the first such model in the 80’s of the 19th century, but as ways of reproducing electrical signals then it was not, then they were used mainly for experiments with ultrasound. Powerful magnets then still do not learn, so the technology of electrostatic gave better results in comparison with dynamic transducers. Already in the early 20th century, with the advent of tube amps made by the first electrostatic sound system, used for cinema.
With the advent of normal ferromagnets, dynamic transducers took the lead, as for electrostatic need a very thin membrane, which was impossible to produce at the time.
Return to the widespread use of steel electrostats somewhere in the 1950s, mainly in the form of large speakers. In 1960, the Japanese company released its first Stax electrostatic headphones model SR-1, and at the present time and the Stax electrostatic headphones have become almost synonymous, although electrostats release and other companies, including Koss, AKG and Sennheiser (Sennheiser Orpheus their system is unhealthy 12,000 dollars).
How does this masterpiece audiophile industry? The membrane is made of the finest polymer located between two electrodes-grid coated with an insulating varnish. These electrodes beeps, however, in contrast to other types of radiators – with a very large voltage (100 to 1000 volts), an electric field which causes the vibrations of the membrane. Through apertures in the electrodes sound comes out. Because of the need for high voltage, electrostatic headphones that require special amplifiers (or special devices, “energizers”, which are essentially step-up transformers).
Electrostatic headphones are expensive (some – just not realistic), require special equipment and are not designed for portable use (although there are exceptions). Instead, they have a large dynamic range: 20 Hz to 20 kHz, and even more, very flat frequency response, low distortion, especially in the area of high-frequency, where the rest of the headphones are not as good, and a host of other advantages.
Sometimes the secondary market there are electrostatic headphones b / y in good condition and it is a way to get them for sane money. For example, I bought a very inexpensive vintage “gold» Stax SR-5 with Energizer and is very pleased with the purchase.
Here are the main types of emitters are used in modern headphones. Do not fall into consideration some exotic solutions such as plasma emitters, piezoelectrics, and a number of others, but they are perhaps worthy of special consideration, if I gather enough material about them.
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Tags: Audio , Headphones .
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