A combination of the mechanical properties of the driver and the size of the box define the low-frequency behavior of an assembled closed box loudspeaker system. Without getting super technical, the air in the box acts like a spring that the cone pushes and pulls against, and that system has a resonant frequency below which its output drops off considerably. You may have noticed lots of speaker boxes have circular holes, or sometimes slots, usually in the front or back. What you are seeing are ports, or vents, and this identifies what is known as a bass reflex enclosure.
A bass reflex enclosure works essentially the same way as when you blow air over an open beer bottle and a note sounds. The note changes with the amount of liquid in the bottle because the volume of air inside the bottle changes.
If you were able to stretch the glass neck of the bottle, that would change the note too. This bass reflex speaker has a rear firing bass port. If tuned correctly, what this does is create a resonance just below the point at which the loudspeaker response would normally roll off, effectively extending the bass performance of the system.
For this to work correctly, the port tuning is calculated for the specific driver in the specific enclosure. Loudspeakers that use passive radiators work on the same basic principle but with a mass loaded, unpowered speaker cone creating the bass resonance with the enclosed air volume.
Now, you may have noticed that in most loudspeakers, particularly as they get larger than little portable boom boxes , you can see more than one speaker driver—usually a smaller diameter one atop a larger one.
These speakers have two sizes of speaker driver: tweeters above and woofers below. There are several reasons why speakers use multiple drivers in different sizes. While it is true that a single driver can cover almost all the audible spectrum by itself, there are a number of limitations it runs up against. Unlike standard conductors, as the voice coil is tightly wound in a coil the makes this complicates things because it adds inductance.
Inductance is different from resistance as it changes as the frequency changes and this is called inductive reactance. In other words, when the magnetic fields of the voice coil are created they oppose the flow of electrical current a bit. If you like fancy math, you can see here how speaker impedance is calculated.
It is the geometric sum of the resistance in the voice copper wire winding and the resistance caused by its inductance at a given frequency. Image showing how to measure speaker impedance with an Ohm meter. This measures only the direct current DC resistance of the wire in the voice coil, not the total impedance of it with music playing due to inductance.
The practice began long ago when radios and speakers were first installed from the factory when cars were built. In both cases these Ohm ratings became common for home and car speakers. While a subwoofer or mid range speaker needs to be used in a sealed structure tweeters do not. In some cases like for surround speakers they may be smaller than the front main speaker cabinet pair. An example of a typical speaker frequency response graph is shown here.
Speaker frequency response is the measured performance of a speaker, in decibels dB of volume, over a range of sound frequencies. While some speakers include a graph or other specifications to help you understand how they perform, not all do. More expensive speakers may do so, however. If you have the right equipment you can also measure it yourself at home using a real-time analyzer RTA program and a high-quality microphone for this purpose.
Speaker sensitivity is a manufacturer-provided specification useful for comparing or matching speakers. In most cases, the standard measurement is the dB volume at one watt of power at 1 meter distance and often a sound frequency like 1KHz depending on the type of speaker may be used.
Subwoofers tend to have a sensitivity around 87dB, midrange speakers around 89dB or so, and tweeters as high at dB depending on the type. Sensitivity is sometimes measured slightly differently. Larger speakers are, on average, much better in terms of their frequency response and distortion but a big improvement would be to be able to produce better, more accurate sound from smaller speakers.
Graphene is a cool new material that was first discovered in It significantly improves loudspeaker performance. Graphene is the strongest and lightest material in existence. Traditional speakers are actually less efficient than incandescent lightbulbs, which are pretty much outlawed at this point!
Traditional speakers are actually one of the least efficient technologies that we still use today. Most of the energy gets converted into heat. New materials and their applications are the future of speaker technology. They will solve the problems of efficiency and sound that speakers have endured for decades. Skip to primary navigation Skip to main content.
Look around your studio. How does sound work in relation to speakers? What are the parts of a speaker? The parts of a speaker are: The cone and the dust cap the parts that move air and produce sound The spider and the surround also called the suspension, these are the parts that hold the cone in place while still allowing them to move The magnet and the voice coil the parts that interact to convert electric energy into motion The basket The pole and top plate And finally the frame that mounts everything together How do speakers work?
It is represented by a waveform defined, typically, by voltage. Here is an example of a simple 1 kHz sinusoidal audio signal. We see that there is a positive voltage for half the period, and for the other half, there is a negative voltage.
This tells us that audio is made of alternating current. Here is an example of a simple 1 kHz sinusoidal digital audio signal. What we end up with is a very close representation of the analog signal.
So how do we, ourselves, and our technologies interact between sound and audio? The answer is with transducers. A transducer is a device or system that converts one form of energy to another form of energy.
Remember that sound is mechanical waves energy, and audio is electrical energy. Our ears pick up the vibrations in the medium caused by sound waves and convert these vibrations into electrical impulses that our brains can understand. In other words, our ears are transducers.
Microphones work similarly with diaphragms that move in reaction to the sound waves around them. Their capsules cartridges, motors use this diaphragm movement to create electrical audio signals that represent the sound waves. Loudspeakers and headphones work in the opposite manner. Their transducer elements, known as drivers, are designed to receive audio signals and move their diaphragms to reproduce these audio waveforms as sound waves.
For a more detailed article on the differences and similarities between sound and audio, check out my article What Is The Difference Between Sound And Audio?
Though there are certainly variations in the design of speaker drivers, the vast majority will be of the dynamic variety also known as moving-coil or electrodynamic. To learn how each type of speaker driver works, check out my article What Are Speaker Drivers?
How All Driver Types Work. The Dayton Audio RS link to check the price on Amazon is an example of a moving-coil speaker driver. So how does this seemingly complicated transducer with multiple components produce sound? The magnetic structure is made of the main magnet and several pole pieces.
The pole pieces extend the magnetic poles of the main magnet and form a small ring-shaped cutaway just slightly larger than the voice coil. This concentrates the magnetic field around the voice coil while still allowing it to move freely inwardly and outwardly.
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