Basic knowledge of headphones

1. How are headphones classified?
1. According to the principle of transducer (Transducer)
Mainly there are two types of dynamic and electrostatic headphones. Although there are several types of equal magnetic types in addition to these two types, they have either been eliminated or have a very small market share for professional use. , Do not discuss here.
Principle of moving coil earphones: At present, most (about 99%) earphone earplugs are of this type. The principle is similar to ordinary speakers. The coil in the permanent magnetic field is connected to the diaphragm, and the coil drives the diaphragm to sound under the signal current.
Electrostatic earphones: The diaphragm is in a changing electric field. The diaphragm is extremely thin and fine to a few micrometers (currently the diaphragm of STAX's new generation of electrostatic earphones is as fine as 1.35 micrometers). The coil drives the diaphragm to sound under the drive of the electric field.

2. According to the degree of openness
Mainly open, semi-open, closed (closed)
Open earphones generally have a natural sense of hearing and are comfortable to wear. HIFI earphones commonly used at home can leak sound, and vice versa. The outside sound can also be heard. The earphones have less pressure on the ears.
Semi-open: There are no strict regulations, the sound can only enter but not exit, or only exit but not enter, and make corresponding adjustments according to needs
Closed type: The earmuffs put a lot of pressure on the ears to prevent the sound from entering and exiting, and the sound is correctly positioned and clear. This is more common in the professional monitoring field. However, this type of earphone has a disadvantage that the bass sound is severely stained. The W100 is an obvious example.

3. According to the purpose
Mainly home (Home), portable (Portable), monitor (Monitor), mixing (Mix), human head record (Binaural　Recording)

2. What are the meanings of some related parameters and sound quality terms of headphones?

1. Headphone related parameters

Impedance: Pay attention to the difference between the meaning of resistance. In the world of direct current (DC), the effect of objects on the current is called resistance, but in the field of alternating current (AC), in addition to resistance hindering current, capacitance and inductance It will also hinder the flow of current. This effect is called reactance, and what we call impedance is the sum of resistance and reactance in a vector.
Sensitivity: The sound pressure level that the earphone can emit when the power of 1 milliwatt is input to the earphone (the unit of sound pressure is decibels, the greater the sound pressure, the greater the volume), so generally the higher the sensitivity and the lower the impedance, the earphone The easier it is to make a sound, the easier it is to drive.
Frequency Response (Frequency Response): The sensitivity value corresponding to the frequency is the frequency response, and the graph is the frequency response curve. The range that human hearing can reach is about 20Hz-20000Hz. The current mature headset technology has reached this Claim.
2. Sound quality evaluation terms

Range: the range between the highest and lowest notes that an instrument or human voice can reach
Tone: also known as timbre, one of the basic properties of sound, such as erhu and pipa are different timbres
Sound dyeing: The opposite of the natural neutrality of music, that is, the sound has some characteristics that the program does not have. For example, the kind of sound obtained by speaking into a jar is a typical sound dyeing. Sound coloration indicates that some components are added (or reduced) in the replayed signal, which is obviously a kind of distortion.
Distortion: The output of the device cannot fully reproduce its input, resulting in distortion of the waveform or increase or decrease of signal components.
Dynamic: Allow to record the ratio of the largest information to the smaller information
Transient response: the ability of the equipment to follow the sudden signal in music. The equipment with good transient response should respond immediately as soon as the signal comes, and stop abruptly when the signal stops. (Typical musical instrument: piano)
Signal-to-noise ratio: also known as signal-to-noise ratio, the contrast between the useful components of the signal and the strength of the noise, often expressed in decibels. The higher the signal-to-noise ratio of the device, the less noise it produces.
Air: An acoustic term used to express the openness of the treble, or the space between the instruments in the sound field. At this time, the high frequency response can be extended to 15kHz-20kHz. Antonyms include "dull" and "thick".
Low frequency extension: Refers to the lowest frequency that audio equipment can reproduce. It is a scale used to determine how deep a sound system or speakers can dive when reproducing bass. For example, the low frequency of a small subwoofer can extend to 40Hz, while a large subwoofer can dive to 16Hz.
Bright: refers to highlight the high frequency range of 4kHz-8kHz, when the harmonics are relatively stronger than the fundamental wave. Brightness itself is not a problem. Live concerts have bright sounds. The problem is that they are bright enough to be well controlled. Too bright (or even howling) is annoying.

3. Related knowledge about amplifiers

1. General amplifiers can be divided into two types: transistor (stone machine) and tube (tube amplifier) amplifiers

2. Amplifier
The collective term for preamplifier and power amplifier.
Power amplifier
Abbreviated as power amplifier, an electronic device used to increase signal power to drive speakers to produce sound. The power amplifier without auxiliary functions such as signal source selection and volume control is called the post-stage.
Preamplifier
The pre-amplification and control part before the power amplifier is used to enhance the voltage amplitude of the signal and provide functions such as input signal selection, tone adjustment and volume control. The preamplifier is also called the preamplifier.

3. Class A amplification (class-A)
Also called Class A amplification. It is a working state of the amplifier. At this time, the transistor or tube amplifier will amplify the entire audio signal.
Class B zoom (class-B)
Also called Class B amplification. It is a working state of the amplifier. At this time, one transistor or tube amplifier will amplify the positive half of the audio signal, and the other transistor or tube amplifier will amplify the negative half of the signal.
Class A and B zoom (class AB)
Also called Class AB amplification. A working state of the amplifier. At this time, the output stage of the amplifier is in the Class A amplification state when the output power is low, and it is converted to Class B amplification when the output power is high.

Four, about the earphone wire
1. Most of the earphone cables are made of copper, and the general purity (usually expressed by a few N, such as 4N, 6N...) The higher the conductivity, the smaller the signal distortion, and the common ones are:
TPC (electrolytic copper): 99.5% purity
OFC (Oxygen Free Copper): The purity is 99.995%
LC-OFC (linear crystalline oxygen-free copper or crystalline oxygen-free copper): purity above 99.995%
OCC (single crystal oxygen-free copper): the highest purity, above 99.996%, is divided into PC-OCC and UP-OCC
2. The plug part of the earphone
One is the left channel, the second part is the right channel, and the third is the ground

Five, about front-end equipment
Many HIFI enthusiasts are used to separating the turntable and decoder into two parts to get better sound quality music
Front end: refers to the signal source in the audio system, such as LP compact slow turn phonograph or CD player, sometimes also refers to the front stage of the tuner (radio head) that processes the signal received from the wireless.
CD turntable: a machine that separates the mechanical transmission part of the CD player.
D/A converter: A device that converts digital audio signals into analog audio signals in digital audio products (such as CDs, DVDs). The D/A converter can be made into an independent machine to work with CD turntables, and is often called a decoder (DAC) at this time.

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