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: ''The term damping factor can also refer to the amount of Damping in an oscillatory system'' In Audio Amplifier terminology the damping factor gives the ratio of the impedances of the loudspeaker and the amplifier. Only the resistive part of the loudpeaker imedance is used. The amplifier output impedance is also assumed totally resistive. The Load Impedance (input impedance) and the Source Impedance (output impedance) are shown in the diagram. The damping factor is: : EXPLANATION For ) is generally smaller than 0.1 Ω (ohms), and can be seen from the point of view of the loudspeaker as a near short-circuit. This low impedance very rapidly absorbs any unwanted currents induced by the mechanical resonance of the speaker's voice coil, acting as a very effective 'brake' on the speaker (just as a short circuit across the terminals of a generator will make it very hard to turn). The loudspeaker's Load Impedance (input impedance) of is usually around 4 to 8 Ω although other impedance speakers are available. Solving for : : The output impedance of an amplifier can therefore be calculated from the damping factor and the loudspeaker impedance. Note that modern amplifiers, employing relatively high levels of Negative Feedback , generally exhibit extremely low output impedances — one of the many beneficial consequences of using negative feedback. Thus "damping factor" figures in themselves do not say very much about the quality of a system. Given the controversy that has surrounded the topic of feedback for many years, some may see a high damping factor as a mark of poor quality because it implies a high level of NFB in the amplifier. IN PRACTICE A speaker diaphragm has mass, and the surround has stiffness. Together these form a Resonant system and the cone may resonate in response to short Pulse s, such as from a bass (kick) drum. Damping factor describes the ability of the amplifier to control undesirable movement of the speaker cone near the resonant frequency of the speaker system. A high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone, particularly in the bass region where the resonant frequency of the speaker system will lie. This damping gives a "tight bass" sound from the sound system. The damping factor is affected to a small extent by the resistance of the speaker cables. The higher the resistance of the speaker cables, the lower the damping factor. A large damping factor(greater than about 10) is no advantage to most listeners. Thus provided that the return path of the cables measures less than about 0.8 Ω , thicker or better cables will make no perceptible difference. The difference in damping with a factor of 10 is the difference between 8 Ω and 8.8 Ω, which is unlikely to give more than a fraction of a dB difference in sound pressure level at the low frequency resonance of the speaker. ZERO ELECTRICAL DAMPING FACTOR There is also a good case to be made for a loudspeaker system with zero electrical damping. In the case of a speaker in a small sealed box, there is no way to reduce the system resonance below a few hundred Hz (even if the speaker itself has a very low free air resonance) because of the low compliance of the air in the box. However, because of the high system resonance, other losses being equal, the acoustic cone damping will be high. All that is needed is then to electrically drive the speaker from an amplifier with a high output impedance (a current source) for a flat response all the way down to DC. {Link without Title} One advantage of the system is that whether it is being operated above or below the system resonance, the cone excursion is current controlled and is therefore linear (independent of surround nonlinearities). The only slight problem with this scheme is that the efficiency may not be too high. SEE ALSO
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