Bass response in headphones
Normally high bass response is achieved with large speakers with heavy magnets and diaphragms. How is such response achieved in earphones and headphones?
PETER GEORGE
Thiruvananthapuram
Both the loud speakers and the earphones are devices to convert fluctuating electrical current into vibrations of a membrane or diaphragm which produces sound waves in the surrounding medium. There is normally a permanent magnet supplying constant magnetic flux and there is a conducting coil fixed on to a diaphragm. When the fluctuating current flows through the coil, the diaphragm is set into vibration producing sound.
The high frequency sound is termed as treble and the low frequency sound is known as bass. These types of sound are produced by vibrating reeds, diaphragms or columns of air; each of these work as a resonating system which efficiently absorb energy from the exciting source at a specific frequency known as the natural frequency of the system.
In the large size loud speakers, the vibrating diaphragm is often made up of soft material like paper constrained at the boundaries. The low elastic constant of the diaphragm enables it to vibrate at low frequencies. In the earphones the diaphragm is small in diameter, and is better suited to generate treble sound. But special care in design of both the diaphragm and the entire earphone enables one to get the bass sound too.
The old type bipolar earphones employed flat steel diaphragms and did not have very good frequency response and do not produce bass very faithfully.The newer models use thin aluminum diaphragms and can give fairly good low frequency sound. The bass performance is further improved by providing a dynamically shaped diaphragm, a properly shaped soft polymer ear-pad and properly shaped air chamber in front of the diaphragm.
Prof. H.K. SAHU
Scientific Officer
Indira Gandhi Centre for Atomic Research
Kalpakkam, Tamil Nadu
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