Have you ever noticed that speaker elements seem to always be shaped like a cone with a portion of a sphere at the center? Have you ever wondered what is the physics reasoning behind this shape being so standard? Is it just a kind of general shape that “works well?” Well before I answer all of these questions that may have appeared in your head, let’s start off by talking about the essentials of speakers.
You have an enclosure (a box) into which speaker drivers are attached. The drivers are the round elements that many say are speaker but they’re not. Drivers look similar to cones or horns, and in fact the large surface area of the driver is called the cone or diaphragm. These surfaces move back and forth to produce sound. Drivers come in different sizes and modes. Generally, you will find 3 different types based on frequencies they handle. First being the Woofer Driver, these handle the low frequency bass range and usually are the largest out of the three. Next we have the Midrange driver which handles midrange frequencies and last we have the Tweeter driver which handles the high frequency treble range. Speaker drivers are typically made from paper, plastic or metal. This material moves back and forth and creates changes in the air pressure (sound waves) that ultimately arrives at your eardrum and causes it to move back and forth so you can hear sound.
Now that we know about drivers, let’s now start answering the questions. We know the shape of the diaphragm is a cone, but why? Try waving a large sheet of a paper, you will find it is impossible to move any air rapidly back and forth, wherever you hold the paper. But take a cone of paper and hold it by the center, where the coil drives a loudspeaker cone, and you will be able to push air back and forth with it much more easily, although it is just as light as the flat sheet. The conical shape gives rigidity. How big or small the cone should be depends on the wavelength of the sound we want to make. If the size of the diaphragm is smaller than a wavelength, the air tends to run round the edges instead of going back and forth with the diaphragm. If the diaphragm is large compared to the wavelength, the air will not have time to dodge around it during the passage of each wave.
As mentioned in the first blog post, low frequency tones have long wavelengths, whereas the high-frequency tones have short wavelengths. This essentially means that we require a large diaphragm for the lower frequencies, while a smaller diaphragm for the higher frequencies. Of course, a large diaphragm will also move air at the higher frequencies, unless it is too heavy to be driving effectively at the higher speeds. For this reason, many installations use two or more speakers of different sizes, each of which handles only the band of frequencies that it serves best. Due to the size of the wave at low frequencies, a diaphragm has to move a lot of air to produce sound. If you look at a loudspeaker diaphragm, you will notice that it moves quite a long way for the low frequencies, however the air load on the diaphragm is so great that the voice coil can hardly move. The high frequencies thus are not emitted. The reason for this difference in movement can best be understood by thinking of wavelengths. To create a pressure change, air must be pressed into a given space. When the wavelength is small (as at high frequencies), the space momentarily requiring the additional air is small, and the pressure can be increased by very small (but very rapid) air movement. When the wavelength is large, the area of increased or reduced pressure is large and requires the movement of a bigger of air to achieve it.
Coming back to why the diaphragm is cone shaped, is because a loudspeaker has physically to move a lot of air which means the diaphragm has to move a relatively long way. Thus, the diaphragms movement requires a very flexible surround and achieving that in a non-circular shape is a serious design headache. A cornered surround would be likely to introduce all sorts of unwanted issues, although it can be done and has been done. Sony manufactured flat square drive units for some of its consumer’s speakers many years ago. However, the idea was much more about the design than audio quality and was not a great success.
Speakers come in all shapes and sizes; we have floor-standing speakers, subwoofer, in-wall, bookshelf etc. However, one thing that all speakers have in common is the shape of their diaphragm which is shaped as a cone. Throughout this blog post, we have discussed about the importance of design of the diaphragm. Here’s what’s next; a blog post with detailed instructions on how to build a speaker with pictures and a video concluding everything we have discussed in this and previous blogs! Make sure you do check out the previous blog posts which are below, see you next week till then stay beautiful!!
You have an enclosure (a box) into which speaker drivers are attached. The drivers are the round elements that many say are speaker but they’re not. Drivers look similar to cones or horns, and in fact the large surface area of the driver is called the cone or diaphragm. These surfaces move back and forth to produce sound. Drivers come in different sizes and modes. Generally, you will find 3 different types based on frequencies they handle. First being the Woofer Driver, these handle the low frequency bass range and usually are the largest out of the three. Next we have the Midrange driver which handles midrange frequencies and last we have the Tweeter driver which handles the high frequency treble range. Speaker drivers are typically made from paper, plastic or metal. This material moves back and forth and creates changes in the air pressure (sound waves) that ultimately arrives at your eardrum and causes it to move back and forth so you can hear sound.
Now that we know about drivers, let’s now start answering the questions. We know the shape of the diaphragm is a cone, but why? Try waving a large sheet of a paper, you will find it is impossible to move any air rapidly back and forth, wherever you hold the paper. But take a cone of paper and hold it by the center, where the coil drives a loudspeaker cone, and you will be able to push air back and forth with it much more easily, although it is just as light as the flat sheet. The conical shape gives rigidity. How big or small the cone should be depends on the wavelength of the sound we want to make. If the size of the diaphragm is smaller than a wavelength, the air tends to run round the edges instead of going back and forth with the diaphragm. If the diaphragm is large compared to the wavelength, the air will not have time to dodge around it during the passage of each wave.
As mentioned in the first blog post, low frequency tones have long wavelengths, whereas the high-frequency tones have short wavelengths. This essentially means that we require a large diaphragm for the lower frequencies, while a smaller diaphragm for the higher frequencies. Of course, a large diaphragm will also move air at the higher frequencies, unless it is too heavy to be driving effectively at the higher speeds. For this reason, many installations use two or more speakers of different sizes, each of which handles only the band of frequencies that it serves best. Due to the size of the wave at low frequencies, a diaphragm has to move a lot of air to produce sound. If you look at a loudspeaker diaphragm, you will notice that it moves quite a long way for the low frequencies, however the air load on the diaphragm is so great that the voice coil can hardly move. The high frequencies thus are not emitted. The reason for this difference in movement can best be understood by thinking of wavelengths. To create a pressure change, air must be pressed into a given space. When the wavelength is small (as at high frequencies), the space momentarily requiring the additional air is small, and the pressure can be increased by very small (but very rapid) air movement. When the wavelength is large, the area of increased or reduced pressure is large and requires the movement of a bigger of air to achieve it.
Coming back to why the diaphragm is cone shaped, is because a loudspeaker has physically to move a lot of air which means the diaphragm has to move a relatively long way. Thus, the diaphragms movement requires a very flexible surround and achieving that in a non-circular shape is a serious design headache. A cornered surround would be likely to introduce all sorts of unwanted issues, although it can be done and has been done. Sony manufactured flat square drive units for some of its consumer’s speakers many years ago. However, the idea was much more about the design than audio quality and was not a great success.
Speakers come in all shapes and sizes; we have floor-standing speakers, subwoofer, in-wall, bookshelf etc. However, one thing that all speakers have in common is the shape of their diaphragm which is shaped as a cone. Throughout this blog post, we have discussed about the importance of design of the diaphragm. Here’s what’s next; a blog post with detailed instructions on how to build a speaker with pictures and a video concluding everything we have discussed in this and previous blogs! Make sure you do check out the previous blog posts which are below, see you next week till then stay beautiful!!