Basic knowledge of headphones

1. How are headphones classified?

According to the transducer principle, they are mainly divided into two categories: dynamic and electrostatic headphones. Although there are several other types besides these two categories, they have either been eliminated or have a very small market share for professional use, so they will not be discussed here.

Principle of dynamic headphones: At present, most (about 99% or more) of the headphone earplugs belong to this category. The principle is similar to that of ordinary speakers. The coil in the permanent magnetic field is connected to the diaphragm, and the coil drives the diaphragm to make sound under the drive of the signal current. Electrostatic

headphones: The diaphragm is in a changing electric field. The diaphragm is extremely thin and accurate to a few microns (the current new generation of electrostatic headphone diaphragms of STAX have been accurate to 1.35 microns). The coil drives the diaphragm to make sound under the drive of the electric field force.

2. According to the degree of openness,

they are mainly open, semi-open, and closed (sealed).

Open headphones generally sound natural and comfortable to wear. They are commonly seen in HIFI headphones for home appreciation. The sound can leak out, and vice versa, the sound from the outside world can also be heard. The headphones put less pressure on the ears.

Semi-open: There is no strict regulation. Sound can only go in but not out, or only go out but not in. Adjust accordingly according to needs.

Closed: The earmuffs exert great pressure on the ears to prevent sound from going in and out. The sound is correctly positioned and clear. This type of earphone is more common in the field of professional monitoring, but one disadvantage of this type of earphone is that the bass sound is seriously stained. W100 is an obvious example.

3. What do some related parameters and sound quality terms of earphones mean?

1. Related parameters of earphones

Impedance: Note the difference in meaning from resistance. In the world of direct current (DC), the effect of an object hindering the current is called resistance. However, in the field of alternating current (AC), in addition to resistance, capacitance and inductance will also hinder the flow of current. This effect is called reactance. The impedance we usually refer to is the vector sum of resistance and reactance. Generally speaking, low-impedance headphones are easier to drive, but when using them, you must first turn down the volume before plugging in the headphones, and then turn up the volume little by little. This can prevent the headphones from being overloaded and burned out, or the voice coil from deforming and misaligning and causing distortion. Therefore, portable and power-saving devices such as walkmans should choose low-impedance headphones, and at the same time, pay attention to high sensitivity. The sensitivity index is more important for walkmans.

Sensitivity: The sound pressure level that the headphones can emit when 1 milliwatt of power is input to the headphones (the unit of sound pressure is decibel, the greater the sound pressure, the greater the volume). Therefore, generally, the higher the sensitivity and the smaller the impedance, the easier it is for the headphones to make sound and the easier it is to drive.

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. Currently, mature headphone processes have met this requirement.

2. Sound quality evaluation terms

Range: The range between the highest and lowest sounds that a musical instrument or human voice can reach.

Tone: Also known as timbre, one of the basic properties of sound, such as erhu and pipa have different timbres. Coloration

: The opposite of natural neutrality of music, that is, the sound is stained with some characteristics that the program itself does not have. For example, the sound obtained by speaking into a can is a typical coloration. Coloration indicates that some components are added (or reduced) in the reproduced signal, which is obviously a distortion.

Distortion: The output of the device cannot completely reproduce its input, resulting in waveform distortion or increase or decrease of signal components.

Dynamics: The ratio of the maximum information to the minimum information allowed to be recorded.

Transient response: The ability of the equipment to follow the sudden signal in the music. Equipment with good transient response should respond immediately when the signal comes, and stop abruptly when the signal stops, without any drag. (Typical instrument: piano)

Signal-to-noise ratio: Also known as signal-to-noise ratio, the contrast between the useful components of the signal and the noise, often expressed in decibels. The higher the signal-to-noise ratio of the device, the less noise it produces.

Air sense: An acoustic term used to indicate the openness of the treble, or the space between instruments in the sound field. At this time, the high frequency response can extend to 15kHz-20kHz. Antonyms include "dull" and "thick".

Low-frequency extension: refers to the lowest frequency that audio equipment can reproduce. It is a measure used to determine how far the audio system or speaker can dive when reproducing bass. For example, the low frequency extension of a small subwoofer can reach 40Hz, while a large subwoofer can dive to 16Hz.

Bright: refers to the high frequency band of 4kHz-8kHz, at which time the harmonics are relatively stronger than the fundamental wave. There is nothing wrong with brightness itself. Live concerts all have bright sounds. The problem is to control the brightness in moderation. Too much brightness (even howling) will be annoying.

4. About headphone cables

Most headphone cables are made of copper. The higher the purity (usually expressed in a few N, such as 4N, 6N...), the better the conductivity and the smaller the signal distortion. Common ones are:

TPC (electrolytic copper): purity is 99.5%
OFC (oxygen-free copper): purity is 99.995%
LC-OFC (linear crystalline oxygen-free copper or crystalline oxygen-free copper): purity is above 99.995%
OCC (single crystal oxygen-free copper): the highest purity, above 99.996%, and is divided into PC-OCC and UP-OCC.