The Dynamic Speaker

Joshua Gurganious

Why I Chose This

• I’ve always had a system in all the cars I’ve driven

• It’s one of my hobbies

• Already knew a little about them

What Is A Speaker•A speaker is a device that reproduces sound waves obtained from a source.

•Sound waves are reproduced by converting the electrical signal in the workings of the speaker.

Sound Waves

• A sound wave is a pressure variation in air molecules.

• The molecules hit the ear, travel through ear canal and vibrate the ear drum.

• Nerves send this vibration to the brain which interprets them as sound.

Sound Waves cont.

•Frequency- higher frequency means faster air pressure variation, which in turn means a higher pitch. Lower frequency, lower pitch. The human ear can detect 20-20000Hz

•Air Pressure Level- the amplitude of the sound wave. A higher amplitude wave vibrates the ear drum more, producing a greater sensation.

•Levels are measured in SPL (dB)

Outer Parts

• Cone- is the part that actually pushes the air creating sound waves

• Surround- is attached to the cone and the basket. It allows the cone to move

• Basket- is the frame that houses all the parts

• Dust Cap- covers the top of the voice coil and provides rigidity to the cone. Some speakers have no dust cap.

Inner Parts

• Spider-attached to the basket and holds the voice coil in position

• Voice coil-a coil of wire that the alternating current is passed through. This changes the polarity of the coil

• Magnetic-the field of the magnet causes the voice coil to move when the polarity of the coil is changed

How It WorksAs alternating current passes through the voice coil, the coils polarity changes. The top and the bottom of the coil switch between north and south. Since the coil is in a magnetic field, it is attracted and repelled from the magnet. This causes the coil to vibrate at the given frequency of the current. The spider and the surround maintain the speakers stability and the cone produces sound waves.

Other Types of Speakers

An Electrostatic Speaker-alternatively charged film in

between two charged plates

-a thin, low mass film produces clear, high frequencies

A Planar Magnetic speaker works the same way, with a magnetic field instead of electric

Applications To Engineering

• Electrical Engineering– Inductance, current, P=IV, etc.– Crossovers, Filters

• Mechanical Engineering– Vibrations– Energy– Acoustics?

• Would be a nice senior elective?

References

• http://www.rockfordfosgate.com/home

• http://electronics.howstuffworks.com/speaker.htm

• http://www.memphiscaraudio.com/

Questions