Definition: Speaker – An electro acoustic device (often, but not always, housed in a cabinet) that is connected as a component in an audio system and functions to reproduce recorded sound.

Synonyms: Driver, Loudspeaker, transducer.

Parts List (labeled on picture)

1)      Cone

2)      Dust Cap

3)      Surround

4)      Basket

5)      Spider

6)      Motor Structure

7)      Pole Piece

8)      Voice Coil

9)      Magnet

10)  Terminals

11)  Tinsel Leads

The Cone – expands the area swept by the movement of the voice coil. A 2″ voice coil can be attached to many different cone sizes depending on the purpose of the speaker.The ideal cone is light, strong, and well dampened. If the cone is too heavy it will be slow to respond to the movement of the voice coil. If the cone is weak it will flex or bend. If the cone is not well dampened it will color the sound with harmonics or resonances. Many cones are made from types of treated paper.

The Dust Cap – is a small dome (or inverted dome) over the middle of the cone. Underneath it lays the center of the voice coil former and the pole piece. The dust cap keeps harmful things from entering the speaker’s internals and damaging them. If anything solid gets into the gap it’s game over for your speaker..

The Surround - attaches the top of the cone to the basket. This also seals the front of the cone from the rear. Surrounds are usually made of butyl rubber, foam, or sometimes cloth.

The Basket – holds all of the speaker’s parts together and gives them something to mount to. Additionally, the basket also offers a flange to allow the speaker to be mounted to a baffle of some kind.

The Spider – in this case does not have eight legs and spin webs. This is a device that centers the moving parts of the speaker. Usually made from cotton, it allows the moving parts to move in and out but not side to side. Without a spider the speaker’s movement would be uncontrolled and it would easily destroy itself.

The Motor Structure – is a general term referring to the sum of the lower parts of the speaker that produce motion. This includes the magnet, pole piece and the gap. The gap is the area around the pole piece between it and the magnet. The voice coil fits into this very small area. This is centered between the north and south poles of the magnets magnetic field.

The Pole Piece – acts as a guide for the voice coil former to move in and out.

The Voice Coil and Former – are a single unit. The former is a cylinder that the voice coil is wound around. It is attached to the back of the cone so that when the voice coil is moved the cone moves as well. The voice coil is a coil of wire that changes its polarity when electric current is run through it. The coil, at rest, sits between the magnet’s polar north and south. When it’s polarity changes it repels the polarity of the magnet and moves.

The Magnet – creates a magnetic field (surprising I know) around the gap. This field causes the voice coil to move when it is charged. There are two types of common magnets used in speakers. The most common ones are ferrite magnets, which are quite heavy and will loose their magnetism over time and if they are dropped. Neodymium magnets are the most powerful permanent magnets and weigh a lot less than ferrite magnets. This makes them perfect for car audio applications where lower reducing weight is always a goal.

The Terminals – are where you connect your signal wires to the speaker. These wires come directly from the amplifier. There will be a positive and a negative terminal for each voice coil that the speaker has. The subwoofer pictured above has two voice coils and has another pair of terminals on the other side of the speaker.

The Tinsel Leads – are the wires connect the terminals to the voice coil. These are sometimes woven into the spider to prevent noise.

How It Works

Now that we know what makes up a speaker and what it does, let’s attempt to understand HOW it works so we can attain better sound. While there are many different types of speakers, my explanation will cover the most common kind which is the cone driver. Let’s start by explaining how a speaker creates sound.

A cone speaker creates sound waves by pushing its cone in and out. As the cone moves, it creates pressure waves in the air that our ears perceive as sound. As we learned in Part 1, Sound Explained, we use the hertz as our metric to determine how high or low a sounds’ frequency is. To produce a 100 Hz tone, 100cycles, a speaker must move in and out 100 times per second. A speaker’s ability to create sound largely depends on its ability to move at will.

So now you might be wondering what makes a speaker move and what controls its motion. If you aren’t, you should be. It’s actually quite simple and it involves the change in polarity of the voice coil. Changing the polarity of the electrical current moving through the coil you change the polarity of its magnetic field and it will move between the magnet’s magnetic fields. We will go over the concepts surrounding electricity on the next page.

Next>>Understanding Electricity

Content written by Steven Solazzo