When talking about speakers, we will think
of sound waves and air. Speaker technology is simple, but knowledge of the
wavelength can help you put the speaker to optimal the sound.
The sound in general, whether it is music
from the speaker or sound of typing fingers on the keyboard, it is actually
moving air. Sound waves move the air and when the air comes to your ears, then your
brain considers it as sound.
Speakers, regardless of size, perform a
simple task is creating sound waves. In particular, speakers receive a power
form of an audio signal from the amplifier (amp), then they vibrate to generate
corresponding sound waves and reproduce original sound.
When music is recorded, sound is converted
to digital sound wave or similar thing. When playing music, you need equipment
to convert that data into suitable electric signals to be transfer to speakers.
Parts of the sound system or digital circuit and similar circuit of a device
are used for this purpose.
Speaker’s operation
In English, the term “speaker” has
ambiguous meaning. It can be used to refer individual speaker (also known as
driver) or a barrel for multiple driver speakers. In this article, the term
driver is used to talk about a speaker in a barrel or many speakers, and the
term speaker is used to refer a barrel containing one or more speakers.
The
smaller side of the speaker has a magnet, the bigger side has a vibrating
diaphragm by electrical signals.
Most speakers use a simple design. At the
rear of the speaker, a permanent magnet (usually has round shape) is fastened
in a fixed frame. When power is transfer to the speaker, the changes in
electric field make the magnet copper coil vibrate. Sticking with this copper
coil is a diaphragm, usually made of paper or plastic. This diaphragm vibrates
to move air in front of the speakers, then, sound waves are created. When these
sound waves reach to your ears, you will hear sound.
When the electric current flows in one
direction, the diaphragm vibrates away from the magnet. When the electric
current flows in opposite direction, the diaphragm also vibrates in opposite
direction. The flow of electric current is changed to match the frequency of
sound waves that speakers create. For low frequencies (bass), mobility changes
may be more than ten times per second. For high frequencies (treble), mobility
can change up to 20 thousand times or more per second.
The size of the speaker affects sound
frequency that it can reproduce best. Bigger speaker can move more air, but it
cannot move air quickly, making this speaker be used to create bass. Smaller
speakers do not move much air, but it can move much faster, so it’s used to
create the treble. Therefore, most hi-fi barrel or speakers often use many
kinds of speakers.
Some speakers just have a single speaker,
such as speaker of the phone. However, despite the single speaker can create
sound at almost all ranges, the speakers designed for listening to music often
use two or more speakers to create the full audible frequency range.
A
speaker set usually has many different component speakers inside.
A basic hi-fi speaker set has two speakers:
a woofer (for the lower frequencies - bass) and tweeter (for the higher
frequencies - treble). The mid-range frequencies (sounds by singing) are
usually renewable by tweeter, though some speakers have smaller woofer (such as
the speaker on shelf) for woofer to reproduce midrange audio.
The speaker set will decide what kind of
speaker will handle a frequency. A speaker set with many speakers has a circuit
called a crossover circuit to lead electrical signal to appropriate speaker
according to the frequency that speaker supports. For example, in a small
speaker on shelf, crossover circuit may send all the 3kHz or greater
frequencies to tweeter, and below 3kHz frequencies to woofer speaker.
Some hi-fi speakers have one or more
speakers to handle the midrange frequencies. Therefore, we need to have one or
more crossover circuits or even a subwoofer speaker in your speaker set (need a
subwoofer crossover circuit in signal chain). Each speaker or speaker set is
optimized to generate different frequencies. From low to high frequencies, it
means from bigger to smaller speakers, in order they are subwoofer, bass,
middle and treble.
Wavelength
The length of a separate sound wave depends
on its frequency. You may not notice much to the wavelength, but they are very
important when you decide the position of your speakers.
Speaker
creates sound waves and air movement. When sound waves come to your ear, the brain
will recognize that is sound.
About subwoofer, the speaker can create low
sound (bass) and has big wavelengths. The reason that you need a subwoofer is:
40Hz sound wave - a very low frequency needed subwoofer – is longer than 8.5 m.
In a normal sized room, you cannot listen
to music with that sound wave, so you only need a subwoofer. Besides, because
of the wavelength, your ears cannot know exactly where waves come from, that’s
why you can place the subwoofer anywhere (you’d better to put it in the same
side with other speakers).
About tweeter, a sound wave of 4000Hz
(4kHz) - equivalent to the highest note of the guitar or violin (excluding
harmonic) – is usually 86mm long. Because this sound is too short and vibrate
fast, you need to stay in their path to hear them clearly. That’s why the
tweeters are always in top of the barrel or speakers, so they are equal to the
ears. This means that you should put the left and right speakers so that the
tweeter is as high as the level of your ears when you listen to music or
watching TV.
If you use small speakers that cannot be
placed on the floor, you can place them on rack and shelf, so that the tweeter
is in equal position of your ears. The speakers connected to the desktop should
also be placed on shelf or rack and put tweeter toward your ears.
Woofer and mid-range speaker can create the
frequencies between treble and low bass, so their location is less important
than the tweeter placement. That’s why the speaker’s woofer is always at the
bottom. However, with higher frequencies, you will realize that your ears have
the same “axis” with speakers or not, that means it is on the wave path of the
speaker or not.
