Question on EPR Calculation - Distance

Looking for insight on proper calculation of electrical power required - specifically which distance to use
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Hi All,

Could a knowledgeable someone give me a quick assist?

When calculating EPR for speaker tap settings, the AVIXA CTS-D exam guide uses 20*log(distance) to determine the dB lost due to the inverse square law.
My question:  when calculating this for an in-ceiling speaker pattern with overlap, should I be using the distance to the edge of the dispersion cone, or the distance to the point where the neighboring loudspeaker provides equal loudness? 

Any insight would be welcome.

Best,

Chris

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Go to the profile of Greg Bronson CTS-D
over 1 year ago

Hi Chris - Good question; and the way you've phrased it shows you have a good understanding of the topic.  As you reference it's about accounting for max dB loss from source to listener(s).  Assuming uniform coverage pattern and listener positions your second choice - "...where the neighboring loudspeaker provides equal coverage" makes sense.  But for listener positions (if any) around outside edges of the coverage pattern area it could be your first choice; "..edge of dispersion cone".  Given headroom is also part of the equation, can't hurt to use that as the larger of the two.

Go to the profile of Christopher Eloranta
over 1 year ago

I never did properly thank Greg for his helpful reply.  Thank you Greg!