Nominal watt


Nominal watt

Nominal wattage is used to simplify the measurement of the efficiency of a loudspeaker.

The impedance of a loudspeaker varies with frequency. This means that if different sine wave tones are fed into the loudspeaker at the same voltage (or the same current), the amount of electric power consumed will vary.

By convention, loudspeakers are designed to generate the same sound pressure level (SPL) at the listener for the same voltage at varying frequencies - regardless of the variation in electric power. This permits a loudspeaker to be used with an amplifier having a low internal impedance and a flat frequency response is realized for the combined amplifier/loudspeaker system.

However, an amplifier with a low internal impedance delivers more electrical output power when the load impedance reduces (until the impedances become approximately matched). Such high power levels could cause damage to either the amplifier or the amplifier's power supply, or the circuit connected to the amplifier's output (including the loudspeaker).

Therefore, an additional convention exists whereby loudspeaker manufacturers specify a conservative estimate of the average impedance that the loudspeaker will present while playing typical music. This is called the nominal impedance. Amplifiers can therefore be safely specified to operate into a load that has this nominal impedance (or higher, but not lower).

Typical nominal impedances for speakers include 4, 6, 8 and 16Ω (ohms), with 4Ω being most common in in-car loudspeakers, and 8Ω being most common elsewhere. A loudspeaker with an 8Ω nominal impedance may exhibit actual impedances ranging from approximately 5 to 100Ω depending on frequency.

In this context, the nominal wattage is the theoretical electric power that would be transferred from amplifier to speaker if the loudspeaker was actually exhibiting its nominal impedance. The actual electric power may vary from about twice the nominal power down to less than one tenth.

Loudspeaker efficiency is measured with respect to nominal power in order to emulate the situation outlined above where a low internal impedance amplifier is used with a loudspeaker. The convention is to supply one nominal watt during testing. If the nominal impedance is 4 ohms, the voltage would be 2 volts. If the nominal impedance is 8Ω, the voltage would be 2.83 volts.

References

  • EIA RS-299-A, Loudspeakers, Dynamic, Magnet Structures and Impedance
  • IEC 60268-5, Sound System Equipment - Part 5: Loudspeakers

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Watt (disambiguation) — Watt may refer to:*Watt, the SI (Système International) unit of power, named for James Watt, which has several associated measures or quantities: **Watt hour **Watt balance **Nominal watt *Watt (novel), a book by Samuel Beckett *Watt (album), by… …   Wikipedia

  • Watt-peak — (Wp) is a measure of the nominal power of a photovoltaic solar energy device under laboratory illumination conditions. Related units such as kilowatt peak or kilowatts peak (kWp) and megawatts peak are also used, and in the context of domestic… …   Wikipedia

  • Nominal Horse Power — (deutsch: nominale Pferdestärke) abgekürzt nhp, manchmal auch NHP oder deutsch PSnom, ist eine ehemalige Einheit zur Leistungsbenennung von Dampfmaschinen, später auch von anderen Kraftmaschinen. Inhaltsverzeichnis 1 Einzelheiten 2 Umrechnungen 3 …   Deutsch Wikipedia

  • nominal usable power — vardinė naudojamoji galia statusas T sritis radioelektronika atitikmenys: angl. nominal usable power; rated watt consumption; rated wattage vok. Nennleistungsaufnahme, f rus. номинальная потребляемая мощность, f pranc. puissance consommée… …   Radioelektronikos terminų žodynas

  • James Watt — Infobox Person name = James Watt caption = Inventor and Mechanical Engineer birth date = birth date|1736|1|19 birth place = Greenock, Firth of Clyde, Scotland, Kingdom of Great Britain death date = death date |1819|8|25| Although a number of… …   Wikipedia

  • rated watt consumption — vardinė naudojamoji galia statusas T sritis radioelektronika atitikmenys: angl. nominal usable power; rated watt consumption; rated wattage vok. Nennleistungsaufnahme, f rus. номинальная потребляемая мощность, f pranc. puissance consommée… …   Radioelektronikos terminų žodynas

  • Peak Watt —   A unit used to rate the performance of a solar photovoltaic (PV) cells, modules, or arrays; the maximum nominal output of a PV device, in Watts (Wp) under standardized test conditions, usually 1000 Watts per square meter of sunlight with other… …   Energy terms

  • Cassini-Huygens — Künstlerische Darstellung von Cassini (große Sonde) und Huygens (links) vor Titan (Vordergrund) und Saturn (Hintergrund) …   Deutsch Wikipedia

  • Horsepower — hp redirects here. For other uses, see HP (disambiguation). Horsepower (HP) is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.[1] Horsepower was originally defined to compare the… …   Wikipedia

  • Pferdestärke — Einheit Norm Alte Maße und Gewichte Einheitenname Pferdestärke Beschriebene Größe(n) Leistung Größensymbol(e) P In SI Einheiten 1 PS = 735,498 75 W …   Deutsch Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.