Anglicky v odborných předmětech"Support of teaching technical subjects in English“ Educational program: Mechanic - electrician Title of program: Technical training II. class The loudspeakers Worked out: Bc. Chumchal Miroslav Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.
The loudspeaker • Function of loudspeaker • Types of loudspeakers • Speakers according to the frequency range • Cross- section of speaker´s basket • Students activities • Literature used
Function of the loudspeakers • Loudspeakers are electro- acoustic exchangers, which converted an electric power on mechanic power in sound form. • It consist from membrane, drive unit, which is supplied by input voltage from the final stage of the amplifier. • Earpieces are similar device. • Loudspeakers are divided by the form of emission on: - Directly emitting ( oscillating membrane is directly connected on setting, in which are acoustic energy emitting ) - Indirectly emitting pressure ( auditory is insert between membrane and surroundings. These loudspeakers have high efficiency and high emitted power.
Types of loudspeakers • Loudspeakers are divided on: electrodynamics – by oscillating coil passing current in magnetic field and it cause membrane moving. electromagnetic – firmly placed electromagnet attracted membrane from thin iron sheet metal, electromagnet placed in the field cause the coils activities and membrane moving. electrostatic - membrane with conductive layer is placed between two electrodes. The loudspeaker working on attracting and repelling principle of electric charge desks . piezoelectric – desk from piezoelectric material is mechanically joined with membrane or it right constitute the membrane. plasma – without membrane. Use change in air pressure, caused by arc discharge.
The loudspeakers according to the frequency range • Broadband – range 20 – 20 KHz • Deep tone ( bass ) 20 – 5 KHz • Middle band ( centre tone ) 100 – 12 KHz • High tone ( high ) 2 KHz – 20 KHz, but even more
The loudspeaker Airflowing by loudspeaker
Parts of the electromagnetic loudspeaker Cross- section of speaker basket Oscillating coil with centr- tend membrane
Questions for students • Explain the function of the loudspeaker. • What types of the loudspeaker do you know? Explain theirs function. • Give the frequency ranges by individual loudspeakers. • How difference is between the loudspeaker and earpiece.
Sample students exercises • Show and describe individual parts of loudspeaker on sample. • How behave the speaker, when the low voltage is bringing on it from the source? • Verify on a template.
Literature used • www.cs.wikipedia.org./wiki/Reproduktor • Vlastní poznámkový sešit