Neodymium magnets are stronger for their size denser magnetic fields but ceramic magnets, while larger, are more cost-effective. Some, but not all, speaker magnets have a hole in the center to help ventilate the voice coil and keep it cool.
Dual voice coil speakers offer a second voice coil winding in the same speaker and on the same voice coil bobbin assembly. These types of speakers allow some additional options that single coil speakers do not:. Examples of two speaker bobbins with dual voice coils. In this animated diagram, you can see how a loudspeaker works. A stereo or amplifier drives the speaker with an electrical signal that alternates from positive to negative in the shape of the musical signal.
This moves cone assembly that creates sound waves as the air moves rapidly. Speakers use alternating current AC that changes direction polarity just like sound waves in real life. A speaker also referred to as a loudspeaker, a name from back in the day uses an alternating current AC electrical power signal and are driven by a stereo or amplifier. In a matter of speaking, speakers are just an electric motor of sorts: they are powered by an electrical signal and change it into a mechanical output: moving air to create musical sounds.
Speaker impedance, measured in Ohms, is the total resistance to the flow of electric current through a speaker voice coil. 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. That is, can the loudspeaker be used as a microphone which detects sound? In the video of the jumping wire demonstration, we moved a wire in the magnetic field and observed a voltage on an oscilloscope. The jumping wire is reversible. Essentially the same effect should occur for a loudspeaker!
Incoming sound causes motion of the cone and thus the voice coil. The motion of the voice coil in the magnetic field should produce a voltage across the coil, but the effect may be too small to observe. The loudspeaker is now directly connected to an oscilloscope.
Touching the cone also produces a voltage. For more mature audiences, we connect the amplifier to another loudspeaker, which is used to produce sound that is detected by the original loudspeaker, as you can see. It is interesting that a loudspeaker acting as a microphone can actually be useful. This was done during World War II for the first detonation of a nuclear weapon.
A normal microphone could have been overloaded or damaged by the blast wave. A conventional loudspeaker has a circular coil of wire in the gap of a circular magnet. The coil is attached to a cone. When an oscillatory electric current is passed through the coil, there is an oscillatory magnetic force on the coil, which moves the coil and cone, thus causing sound to be emitted. The loudspeaker can act in reverse, as a microphone, although it is not very sensitive and is subject to noise.
A conventional loudspeaker is not the only kind of loudspeaker! An unusual and interesting type is an electrostatic loudspeaker. This works in a fundamentally different way than a conventional loudspeaker, and has its own advantages and disadvantages. We will demonstrate and explain an electrostatic loudspeaker in another video. They can only convert 0.
Most of the energy lost is given off as heat emanating from the voice coil and other electric circuits inside the speaker. In particular, one group of circuits , called the crossover , dissipates a large percent how much? The crossover is comprised of capacitors, resistors, and inductors, and it has the function of sending high frequency signal to the tweeter and low frequency to the woofer.
All of these circuit components take some electric power and convert it to heat. They are all around us -- in our TV's, computers, alarm clocks, cars, stereos, headphones, etc. The ultimate test of fidelity for a speaker is how similar the waveform in the air the pressure wave is to the electronic signal the sound recording that was sent into the amplifier. There are several factors that determine how accurate the listening experience will be including the frequency response , the amount of distortion , and the directionality dispersion of the speaker.
A typical test for frequency response sends out a sweep of frequencies from the bass to the mids, and up to the treble range to see if the sound from the speaker is the same in all these areas. The ideal frequency response for a speaker is very flat. This means the speaker would be the same level at low frequency as it is in the mids or highs.
The goal of a flat frequency response is to ensure that the people listening to your music experience it the way you intended it. If your track is well mastered and sounds good on speakers with a flat response, you can be sure that it will sound its best on any playback system. Many speakers are not flat. Some do not have enough treble or enough bass, or they have peaks or dips in their frequency response where certain frequency ranges are over emphasized or hidden or masked. If this happens some instruments may be louder or softer than you intended them to be and the mix you worked so hard on will not be properly represented.
For high frequencies, speakers must move very quickly. For low frequencies, speakers must push a lot of air. This is why tweeters high-frequency drivers are typically small domes and woofers low frequency drivers are usually large cones. We hear 10 octaves 20hzkHz that is a very wide range for comparison, we can only see less than one octave of light.
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