How Many Amps Does a Subwoofer Use


There are two forms of sensory inputs that our brain mainly relies on for information, entertainment, and a concept of reality, out of the five actually available. These are the Visual and the Audio sensations. While the Visual has for long been the main target of research and advancement of sensory scientists and developers, the Audio sensation gradually equals the focus of the Visual. The Sound we hear usually travels through the Air in the form of spheroid pressure waves, though mediums like water and metals can also transmit sound at varying speeds. Sound Systems have both high and low frequency outputs, both of which are mixed in suitable proportions in a typical Speaker equipment, to produce realistic sound in our ears. In general parlance, while Tweeters handle the high audio frequencies, Woofers are used to reproduce low frequency audio outputs, or “Bass”, to our ears. The range is typically 50 Hz (Hertz) to 1000 Hz. The common name of “Woofer” is derived from the onomatopoeic English for a dog’s bark, “Woof”. But 50 Hz is higher than the real lowest frequency of sound that we can hear at ordinary SPL (Sound Pressure Levels), which is more like 20 Hz. Drivers handling low frequencies in Two-way speakers have to cover a substantial part of the midrange frequencies also, going up to even 5000 Hz (from 2000 Hz). But it was slowly realized that the lowest frequencies were also important to produce the “surround sound” necessary for realistic audio reproduction. Thus, from the 1990’s, a new driver came into being, called the “Subwoofer”, which handled the lowest frequencies selectively, right down to 20 Hz. But the power output from a typical Subwoofer is generally lower than desired, as the lowest frequencies are harder to hear by normal ears.  The number of Amps required is a moot question in the design of Subwoofers. The question asked is: How Many Amps Does a Subwoofer Use? 

The Amp Factor

Some of the main factors by which the Amps can be determined are discussed and explained below:

  • The rating of the Amp is measured by the impedance (measured in ohms) that the Subwoofer Power Amplifier sees as the “load” on its output. This Amplifier generates different amounts of power (in Watts RMS) based on the load impedance it senses.
  • The word “Amp” stands for the abbreviation for the base unit of measurement of the strength of the Electric Current, (symbol I), in “Amperes”, in the International System of Units (SI). It is named after the father of Electromagnetism and mathematical genius, Andre-Marie Ampere.  
  • Ohm was the other genius of electromagnetic science, and the base unit of impedance/resistance is named “Ohms” (symbol R), after him. 
  • Similarly, the base unit of the potential electrical energy of an electrical circuit (symbol V) is named after the Italian maestro Alessandro Volta.
  • Ohm’s Law is the fundamental formula in all studies of Electricity, Electromagnetism, and Electronics, and describes the relationship of Current I, Voltage V, and Resistance/Impedance R, as: V = I X R.
  • R is the Constant of Proportionality, while V is fixed by the Electrical Authorities of the country. I is the Variable.
  • Now, of the standard impedance values of Subwoofers (and similar devices) used in the market for domestic and office devices, 8 Ohms is the most common. Using Ohm’s Law, and 120 Volts as the standard Electricity Board-rated single-phase voltage at all domestic devices and switchboards, (which is common for the major countries like USA, Europe and so on), the Amp Rating of a typical 1,000 Watt power Subwoofer would be 11 Amps RMS (Root Mean Square value), or Peak 15 Amps ( for Sinusoidal Current Wave).
  • This “Current Rating” will determine the designed capacity and size of all intermediate switching and main-line control components,  such as the insulated wires, switches, fuses and MCB’s (Miniature Circuit Breakers) and other protection devices for the rated standard voltage in use.
  • The usual standard impedance/resistance values used for subwoofers are 2, 4, 6, and 8 Ohms.
  • Of these, 8 Ohms is most common, though theoretically, 4 Ohms is reckoned to be the best.
  • This is because the other components of the complete electrical power circuit incorporating the 8 Ohm Subwoofer are most popular and easily accessible in the market.    


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