# Calculation of Receiver Power / Watts

Discussion in 'Home Theater Projects' started by JackB, Jan 5, 2004.

1. ### JackB Extra

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I would like to know if htere is a formula to calculate the receiver power per channel needed based on room volume. ( I mean just as a rule of thumb, speaker efficency, etc will complicate it.) Does anyone know of such a formula, I've tried searching for it here, so far, I haven't found it.

2. ### ThomasW Cinematographer

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There is no such 'formula'.

This is like asking how much horsepower should my car have?

There are just too many variables involved, (the size of the room, efficiency of the speakers, desired SPL's, construction materials used in the room, amount and type of furniture in the room, number of people in the room, etc, etc, etc........

For most people, their speakers, and their rooms, 75-100 watts/channels is more than adequate. Obviously YMMV.....

3. ### Tom Rosback Stunt Coordinator

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Jack,
I have posted a nomograph here:

http://home.mn.rr.com/hometheater/acoustics.htm

This is based on a 'normal' small room (no such thing, really) with a reverb time of from .2 to .4 seconds. You can, based on room volume, calculate an acoustic power you will need to reach a given SPL in the room. You can then work backward, based on speaker efficeincy, to get to an electrical power needed to achieve the SPL you want.

The nomograph is based on a listening position in the 'transition zone', an area equally influenced by the direct sound coming from the loudspeakers, and the indirect sound coming from room reflections.

It's rough, but it may get you the answer you're looking for. Let me know what you think.