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Question about Sensitivity

adpopulum

adpopulum

Well-Known Member
Hi all,

I have a question about converting an expression of sensitivity presented as follows:

87dB/2w/3M

to the more universal form

??dB/1w/1M

Given the extion of distance to the speaker coupled with the increase in watts would this simply be a different way of expressing

87dB/1w/1M

I ask because the specs an AKer sent me on a pair of Braun speakers I recently picked up (see here) are 87dB/2w/3M and it is a bit hard to get my (thick) head around it.

Thanks
 
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Halving the power to 1W takes away 3dB, so we're now at 84dB/1W/3m. Taking the distance to 1m brings the figure to 88.8dB/1W/m according to my calculations, which sounds about right for these speakers IMHO.

az
 
You'll gain 3dB for a doubling of power so 87dB@2W3m would be 84dB@1W3m. You lose 6dB for a doubling of distance but since you don't have a simple doubling we'll have to go back to the actual equation which is 20*log(distance). In your case that's 20*log(1/3) = 9.5dB so to relate to 1W1m you'd have 93.5dB@1W1m.

edit: Az, the power equation is 10log(power ratio), spherical spreading is intensity based so it is 20log(distance ratio).
 
RayW said:
You'll gain 3dB for a doubling of power so 87dB@2W3m would be 84dB@1W3m. You lose 6dB for a doubling of distance but since you don't have a simple doubling we'll have to go back to the actual equation which is 20*log(distance). In your case that's 20*log(1/3) = 9.5dB so to relate to 1W1m you'd have 93.5dB@1W1m.
Click to expand...

I went with 10*log(1/3) for the distance, I guess I made a mistake there. :o

That figure does make more sense come to think of it: most one-woofer ADS speakers are ~90dB/W/m, so two woofers should pretty much be ~93dB.

Edit: RayW, I sort of knew that but got stuck in a stupid loop there! :) Thanks for correcting!

az
 
Last edited:
Thank you both, that is very helpful.

Wondering why, if it is universally true that better sensitivity is a good thing, Braun would relate that information in a way that downplays the speakers performance? Granted that I maybe just so indoctrinated regarding the convention of dB@1w/1m that I can't see past it!
 
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