Have you ever wondered how speakers work? It main seem complicated on the surface, but actually speakers utilize a couple of fairly simple concepts to achieve sound reproduction.
The Science of Sound and Anatomy of a Speaker
Jason Hicks | Aperion Audio
From Sound to Electrical Current and Back Again
It’s pretty incredible when you think about it, magnets attached to a tweeter or woofer, the basic components of a speaker, can reproduce any sound simply by moving back and forth in a precise fashion. When the tweeter or woofer, also known as a driver, moves back and forth it creates vibrations in the air, otherwise known as sound waves. How does the driver move in just the right way so as to faithfully reproduce the recording that is being played? The recording contains an encoding of the sound wave in some method, either by transforming the sound waves into grooves on a record, pits on a CD or just binary data in digital file. That encoded translation of the sound wave is then converted into an electrical signal which goes from the playback device and is then amplified either at an external amp, receiver or at an amp inside the speakers. It’s these electrical signals, also known as current, that change the polarity of a magnet inside the speaker called a voice coil. As the polarity of the voice coil is switched back and forth by the current, it moves closer or further away to another magnet next to it. Since the voice coil is attached to the driver, they both move together and the current is transformed back into sound waves.
One of the more interesting parts of the process is that once the sound reaches our ears, our nervous system once again translates the vibrations from sound back into an electrical current which is then processed by our brain where the truly mysterious part begins as we interpret that sound through perception. So basically the whole process of recording, sound reproduction and even our hearing is merely the conversion of vibration to electrical current and vice versa. The one exception is the storage of the information on a disc, piece of vinyl, etc until it can be played back, or converted back to current, at a later time.
Let’s take a more in depth look at the components that make up just the driver and how each functions:
The Anatomy of a Speaker Driver
- Cone: The cone is connected to the voice coil and moves air to create sound waves. Most modern tweeters move air with a dome rather than a cone.
- Voice coil: The electromagnet that drives the cone and is alternately charged postively and negatively
- Magnet: The non-changing magnetic field that allows the voice coil’s alternating magnetic force to be attracted or repelled.
- Top plate, back plate and pole piece: The magnetically conductive parts that efficiently concentrate the magnet’s energy around the voice coil.
- Spider: A springy cloth disc that keeps the voice coil and bottom of the cone from moving off to the side and focuses the coils motion in a forward and backward motion.
- Surround: A flexible ring that keeps the cone from moving side to side while allowing it to push forward and backwards. Together with the spider, a suspension system is formed for the parts that move, the moving parts being the cone and voice coil.
- Flex wires and wire terminals: These components move the electrical current from the amplifier to the voice coil.
- Dust cap: Covers the middle section of the cone and keeps debris from getting into the gap between the magnet and the pole piece where the voice coil resides.
- Frame (or basket): Holds the entire speaker assembly together and attaches it to the cabinet.
In addition to the driver there are a couple other parts that we need to make a complete speaker. First the cabinet which is just the box into which the drivers are installed. Why do we need a cabinet? The main purpose is to trap the sound waves that come off the backside of the driver and to ensure that they do not cancel out the sound coming from the front of the driver. The cabinet also ensures that the drivers are positioned properly with respect to o