Have you ever wondered how speakers work? It may seem complicated on the surface, however, speakers utilize a couple of fairly simple concepts to achieve sound reproduction. By taking a closer look the anatomy of a speaker and understanding the basic specifications of audio technology helps you to be confident about your purchase. In this detailed blog-cum-guide, we help quickly understand the Science of Sound and the Anatomy of a Speaker. Let's have a look.
How do speakers work & how do we hear sounds?When the tweeter or woofer, also known as a driver or transducer, moves back and forth it creates vibrations in the air, otherwise known as sound waves. 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 a 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.
A closer look at the Anatomy of a speaker driver
Let’s take a more in-depth look at the components that make up just the driver and how each functions:
- 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 positively and negatively.
- Magnet: The non-changing magnetic field that allows the voice coil’s alternating magnetic force to be attracted or repelled.
- The 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 are needed to make a complete speaker. First, the cabinet which is just the box into which the drivers are installed. 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 one another and allows them to work efficiently.
Another feature you will see on many speakers is a port, which is merely an opening in the speaker which allows the long wavelengths of low frequencies to escape the cabinet and reinforces the speaker’s bass response. By including a port, the speaker will be able to reproduce bass at higher volumes than without it. Another method to increase a speaker’s bass response is to include a passive radiator, which has all the parts of a regular driver, except for a voice coil and magnet and is not wired to an amplifier. The passive radiator moves back and forth with bass sound waves created by the other drivers and allows for more bass output from the speaker. A passive radiator can be preferable to a port in some cases because it doesn’t have the same tendency to turbulence or port noise. It also allows the speaker cabinet to remain small, which is an engineering method that we at Aperion use for our small footprint subs and centre channels.
Finally speakers with more than one driver, that is nearly all loudspeakers, use crossover networks of circuitry to ensure that the different drivers play the frequencies for which they are designed. For instance, in a two-way speaker, which is a speaker with a tweeter and one or more woofers that play the same frequency range, the crossover will filter out low frequencies before the signal reaches the tweeter and then filter out high frequencies before they reach the woofer(s). This ensures that the drivers do not waste energy attempting to reproduce frequencies that are inaudible to our ears when produced by that driver. Commonly, capacitors are used to filter out lower frequencies and a coil or inductor is used to filter high frequencies. The crossover point is the frequency when one driver’s response falls off in decibels (dB) and another driver’s frequency response increases. You can think of the crossover point as the “handoff” of the sound from one driver to another. Using components to create an ideal crossover point for each driver is critical to ensure that the different drivers in a speaker blend together seamlessly while faithfully reproducing the full audio spectrum.