How to measure Headphone & Earbuds quality

Headphone Sound Quality

Measuring the earphones & earbuds can use some methods of evaluating the speakers, but the listening sound of the headphones is different from that of the speakers. The sound waves emitted by the speakers are attenuated in the air, interfere with each other, interact with the head and ears of the person, and the sound of the earphones directly enters the ear. 

 

The sound quality of the earphone is more important than its technical performance. Because the shape of the human head and the ear are different, a pair of headphones will have different hearing feelings for different people, so the recommendation can only be used as a reference. There is a chance to listen to it personally. Only then can you really feel the sound of the headphones.

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What is a high fidelity headset? The main performance of the high-fidelity headphones recommended by the International Electrotechnical Commission IEC581-10 is: the frequency range is not less than 50Hz-12500Hz, the optimal frequency response of the current dynamic headphones is about 5-45,000Hz; the allowable error of the typical frequency response is positive and negative. 3dB; the slope of the frequency response curve does not exceed 9dB per octave; the difference between the average sound pressure level of the unit in the same octave band is less than 2dB in the range of 250Hz-800Hz; the sound pressure level is 94dB in the range of 100Hz-5000Hz. When the harmonic distortion does not exceed 1%, it does not exceed 3% at 100db; the biggest advantage of the earphone relative to the speaker is in the details. Actually listening to an excellent earphone should be clear, rich in detail, and audible distortion; low frequency deep The potential is clear and effective, and the entire frequency band is smooth and flat, and the high frequency is not too bright or too dark. For any pair of headphones, tri-bands are not perfect, and the smooth and natural connection between them is the most important.

 

Headphone Comfort

The comfort of the headphones or earbuds is also very important. If you use headphones, you should also consider other activities. A pair of headphones should not be too tight or too loose, and should be worn for a long time. The adjustability of the headband and the unit can ensure the use of different head shapes and different uses. Professional audio personnel sometimes need a single unit to monitor, the unit needs to be able to rotate, and the length of the line and the way the unit is connected also affect the use. A factor. Pay attention when adjusting the length of the headband: the headband is short, the pressure on the top of the head is large, the pressure on the head is small, and the headband is opposite in length. The pressure of the three points is balanced to be the most comfortable for the adaptive head. Bringing this problem does not exist. Some earmuffs have a pentagon design that fits the human ear more comfortably.

Headphone Durability

Durability is very important in portable audio and professional fields. Portable audio headphones & earbuds are light and easy to be damaged; professional headphones use and move frequently, and the wires are easily broken and broken, requiring the headphones to be very strong, and Parts are easy to repair and replace.

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Another related to durability is the power consumption. With a small power, the headphones can be pushed very loudly. When the power is exceeded, the earphones may be damaged. Generally, the power consumption of the civilian headphones is less than 100mW, and the professional headphones are 100mW-1000mW. . High-impedance headphones have strong voice coil resistance, unlike low-impedance earphone voice coils that are as sensitive to power changes and more durable.

Headphone Parameter

The technical parameters of the earphones are very important, but they may also be misleading. The sound quality of the headphones with good parameters may not be good, and the sound of the headphones with flat parameters may not be bad.

impedance:

The impedance of the earphone is the abbreviation of its AC impedance, and its size is the sum of the DC resistance of the coil and the inductive reactance of the coil: Z = (R2 + ω2L2) 1/2.

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The impedance of civilian headphones and professional headphones is generally below 100Ω, and some professional headphones have impedances above 200Ω. This is to reduce the load of the amplifier when a single amplifier drives multiple headphones. A headphone with a high drive impedance requires more power. The relative impedance of Japanese headphones is low. Even the flagship headphones like the Denon D7100 have an impedance of only 25 ohms and are very easy to drive.

 

Headphone Sensitivity

Usually, the sensitivity of the earphone is actually the sensitivity level of the earphone. When it is applied to the electric power of 1 mW on the earphone, the sound pressure level generated by the earphone coupled to the artificial ear (dummy head), the power of 1 mW is the frequency. The standard impedance of the headphones at 1000 Hz is calculated based on the basis. The unit of sensitivity is dB/mW, and the other one that is not commonly used is dB/Vrms, which is the sound pressure level produced by the 1Vrms voltage applied to the headphones. High sensitivity means that the power required to reach a certain sound pressure level is small, and the sensitivity of the dynamic earphone is generally above 90dB/mW. If it is for the Walkman, the sensitivity is preferably around 100dB/mW or higher.

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The sensitivity of the speaker is the sound pressure level generated by inputting 1W power at 1 meter. For headphones and speakers with similar sensitivity values, the power required by the earphone is equivalent to 1/1000 of the speaker. In fact, this value is even smaller because it is rarely Someone listened to the speaker at a distance of 1 meter.

 

Headphone Distortion

The distortion of the earphone is generally small, and the total harmonic distortion (THD) is less than or equal to 1% at the maximum withstand power, which is basically inaudible and much less distorted than the speaker.

 

Frequency Response

 

Sensitivity has different values at different frequencies. This is the frequency response. The dependence of the sensitivity on the frequency is represented by a curve, which is called the frequency response curve. The human hearing range is 20Hz-20000Hz. Most people who are out of this range can't hear the sound. The frequency band that the earphone can reproduce is quite wide. The excellent earphone can reach 5Hz-45000Hz. Generally, the frequency response given by the earphone is positive or negative 10dB. The unevenness of the frequency response given by professional headphones and some high-end headphones is plus or minus 3dB, which causes many medium and low-end headphones to have a striking frequency response. The frequency response of the headphones is flat. A sound with a true frequency response curve is not good, because the sound has already occurred with the head before the sound enters the ear canal, resulting in peaks and valleys. Therefore, the earphone design is often balanced to make the ear The received frequency response curve is relatively flat.

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Diffusion Field Equilibrium

There are two ways to balance the headphones: free-field equalization and diffusion-field equalization. The free-field equalization assumes that the environment is not reflective, such as the wilderness; the diffuse field equalization simulates a room with reflection, and its sense of hearing is more natural than the free-field equilibrium. . The International Electrotechnical Commission's method for testing the flatness of a diffused field can be found in the standard IEC 60268-7. However, the diffusion field equalization is modeled on a standard head shape and a room model. It does not satisfy all users and is not suitable for some recordings, such as dummy head recording.

Headphone selection

Different headphones should be used depending on the application. If you are learning and listening to news, choose a head-mounted, ordinary electromagnetic headset. If you are listening to music, you should use mid-range headphones. If you want to enjoy high-quality music, you should use high-fidelity headphones, such as high-quality moving coil or condenser headphones. Easy to use, optional wireless headphones, no connection. In addition to the headphones of the radio, you can listen to the program.