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08-31-2023, 01:56 PM
Hi Guys
Headphones are primarily of one type using small transducers that are electromagnetic motors; tiny versions of the dynamic drivers fitted in our stereo speakers, in our cars and for computer speakers. They do not have to handle much power but they do have to be full-range.
The dynamic driver is cone shaped, with a voice coil at the apex working against a small magnet. The surround of the cone is flexible so the entire cone can move as a unit. In general, the cone should be able to retain its stiffness over the entire Human audio range of 20Hz to 20kHz, and this will provide the least distortion. Some transducers may experience cone break-up modes, where the outer part of the cone decouples from the central portion at higher frequencies. This may appear as a peak or dip in the frequency response. Dynamic drivers are very inexpensive to manufacture and may use a variety of materials for the cone, with paper being the most common.
Planar drivers are flat and can produce lower distortion than dynamic drivers. This is not a general statement, simply a reflection of the fact that the lowest-THD measurements of any acoustic driver have been with planar types. Of the available planar headphones, there are two types" electrostatic and planar magnetic.
Electrostatic headphones use a metalised film as the acoustic transducer, with stationary very fine wire coils on either side. A high-voltage is applied to the film and symmetric audio signals are applied to the coils. The film can move all as one in the varying electrostatic field between it and each coil - one coil 'pulls' while the other 'pushes'. The film moves uniformly and THD is extremely low. The coils here are incomplete inasmuch as only one wire end has applied voltage and only relays electrostatic potential. The coils are referred to as 'stators' and appear capacitive to the amplifier.
Planar magnetics use a flat film as the transducer, which has laid upon it the voice coil. In front of and to the rear of the transducer are narrow magnets that the coil works against magnetically. The force over the area of the film is slightly less uniform than for the electrostatic driver as force is only applied where the coil trace is laid. The coil presents a resistive load to the amplifier and is often differentially driven.
Planar headphones have larger transducers than most dynamic headphones, and thus, tend to produce better bass response. They can also play quite loud - far louder than any Human should subject themselves to.
Dynamic headphones have nominal speaker impedances values from 8-ohms to 600-ohms. With typical 100dB/1mW sensitivity, these headphones can often be driven by opamps or simple circuits. Planar magnetics are between 20 and 130 ohms. Electrostatics look like 100pF per stator and require a high bias voltage of 200-500V with signals of up to 70Vrms/stator.
Headphones are primarily of one type using small transducers that are electromagnetic motors; tiny versions of the dynamic drivers fitted in our stereo speakers, in our cars and for computer speakers. They do not have to handle much power but they do have to be full-range.
The dynamic driver is cone shaped, with a voice coil at the apex working against a small magnet. The surround of the cone is flexible so the entire cone can move as a unit. In general, the cone should be able to retain its stiffness over the entire Human audio range of 20Hz to 20kHz, and this will provide the least distortion. Some transducers may experience cone break-up modes, where the outer part of the cone decouples from the central portion at higher frequencies. This may appear as a peak or dip in the frequency response. Dynamic drivers are very inexpensive to manufacture and may use a variety of materials for the cone, with paper being the most common.
Planar drivers are flat and can produce lower distortion than dynamic drivers. This is not a general statement, simply a reflection of the fact that the lowest-THD measurements of any acoustic driver have been with planar types. Of the available planar headphones, there are two types" electrostatic and planar magnetic.
Electrostatic headphones use a metalised film as the acoustic transducer, with stationary very fine wire coils on either side. A high-voltage is applied to the film and symmetric audio signals are applied to the coils. The film can move all as one in the varying electrostatic field between it and each coil - one coil 'pulls' while the other 'pushes'. The film moves uniformly and THD is extremely low. The coils here are incomplete inasmuch as only one wire end has applied voltage and only relays electrostatic potential. The coils are referred to as 'stators' and appear capacitive to the amplifier.
Planar magnetics use a flat film as the transducer, which has laid upon it the voice coil. In front of and to the rear of the transducer are narrow magnets that the coil works against magnetically. The force over the area of the film is slightly less uniform than for the electrostatic driver as force is only applied where the coil trace is laid. The coil presents a resistive load to the amplifier and is often differentially driven.
Planar headphones have larger transducers than most dynamic headphones, and thus, tend to produce better bass response. They can also play quite loud - far louder than any Human should subject themselves to.
Dynamic headphones have nominal speaker impedances values from 8-ohms to 600-ohms. With typical 100dB/1mW sensitivity, these headphones can often be driven by opamps or simple circuits. Planar magnetics are between 20 and 130 ohms. Electrostatics look like 100pF per stator and require a high bias voltage of 200-500V with signals of up to 70Vrms/stator.
