Transcript Loudspeakers and Amplifiers

Loudspeakers and Amplifiers
How ‘good’ sound is created!
The loudspeaker….
A magnet and a coil produce motion
 This is also called a ‘linear motor’
 A paper or mylar cone is connected to the
coil to push air.
 The mass of the cone must be light to push
the air.
 The wire in the ‘electro-magnet’ has
resistance. ( 4, 8, 16, 130 Ohms)

This is ‘Energy Conversion’
Electrical energy is changed to magnetic
energy.
 Opposing magnetic fields produce motion.
 The moving ‘cone’ pushes air and sound is
created.
 Low frequencies use large ‘cones’
 High frequencies use very small ‘cones’

A battery can test a loudspeaker..
A 1.5 volt battery will move the speaker
cone.
 If it doesn’t move, it’s damaged!
 Alternating Current will move it back and
forth.
 Speakers have resistance due to the wire
used in the electro magnet.

“Frequency Response”
We expect the speaker to produce
frequencies in equal amounts..
 The ear can hear from 20 to 15,000 cycles
per second. (Hertz)
 A speaker must be able to reproduce these
frequencies.
 Not all can...

$$$$$$ determines the quality~!
An inexpensive speaker will produce sound
from 100 to 5000 Hz.
 An expensive speaker will go down to 15
and up to 18,000.
 Often, a speaker ‘system’ uses three
speakers. A BASS Woofer, a Mid Range
speaker, and a Tweeter.

The ‘Enclosure’
Speakers are put in large, non resonating
boxes.
 They are ‘tuned’ to help create a ‘flat’
response.
 A local company, McIntosh Laboratories,
has been building loud speakers for many
years. Yes, in Binghamton~!

The stereo system has ‘presence’
‘Presense’ is like being ‘there’.
 The microphones, the recording equipment,
the playback equipment, and the speakers
all have to have a ‘flat’ response.
 Otherwise, you’re not ‘there’ !

Magnetic Tape isn’t ‘flat’
Magnetic Tape emphasizes the ‘highs’
 The equipment must ‘de-emphasize’ the
highs.
 This creates a ‘flat’ response.

CD’s are flat!~

Not much to say here…..
When the signal is digitized, there is no
distortion of the signal!
 What is recorded, comes off the CD
perfectly. Almost.
 The process is full of corrected errors!

Signal Distortion - Ugh!
Microphones, Amplifiers, Recording
mediums, Speakers …. all introduce ‘signal
distortion.
 Two types of Distortion
1) Harmonic
2) Intermodulation

The Amplifier….
Takes a small signal (.001 Volts) and makes
it much larger (100 Volts?)
 You need 100 Volts to put ‘power’ into a
loud speaker.
 P=E²/R
 100²/8 = ? Watts

The Amplifer must be ‘Flat’
The frequency ‘response’ of the amplifier
must be flat. It’s not easy or cheap!
 15 Hz to 20,000 Hz.
 Much money is invested in doing this.
 At 1 Watt, the amplifier behaves differently
than 100 Watts.

How much is a Watt?
A cheeeep AM radio, produces .1 Watts
 Rock Concerts can use 5000 Watts +
 Typical home systems are 100 Watts/Side
 Some people have a lot of power in their
cars… P = ????

Tubes vs Transistors...
Really uncultured people argue about the
quality of amplifiers.
 We all know that transistors are better.
 Vacuum tubes are old and clunky and
produce a lot of heat and waste a lot of
energy and are obsolete.
 Most of the previous statement isn’t true.

Obsolete in the Electronics
Industry….
Simply means that new products are not
being designed with these devices.
 Actually, there are more vacuum tubes
produced today than ever per year.
 Every picture tube is a vacuum tube.
 There’s $$$$ in older tubes!
