Practical Application for your Speaker's Sens. Rating

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Practical Application for your Speaker's Sens. Rating

Postby JackD201 » Mon Dec 05, 2005 2:11 pm

This was compiled by myself with the following as resources:

My old notes
Turbosound Inc.
Hyperphysics.

Links to be provided

We often wonder what say 83dB/1w/1m/2.83V really SOUNDS like since I would venture to guess none of us listen to one speaker on-axis at 1m :roll:

*Note that these are general approximations since these are anechoic measurments that can be mitigated by room reverberations. Thankfully, we are dealing with short distances so they pretty much stay close.

We listen with stereo pairs so rule number one:

Add another 3dB to your Sensitivity rating. Say 90dB is now 93dB.

Now. Sound intensity reduces rapidly in intensity at a distance from the source according to the inverse square law, which predicts that a doubling of distance will result in a reduction of ΒΌ the original.

Important:Because SPL in dB is logarithmic that 1/4 doesnt mean your 100dB will be come a measly 75dB.

So lets pick a common sensitivity rating of 89dB 1w/1m

we use the Inverse Square Law (by ratio) calculator at http://hyperphysics.phy-astr.gsu.edu/hb ... ob.html#c3

We want to find out at 2 meters so plug in 2 (Double of 1 meter)

89+3 kasi stereo

Abracadabra!!! You get a shade under 86dB at your listening position.

Hope this helps you guys.
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Postby Jon Agner » Mon Dec 05, 2005 4:44 pm

Galeng!!!

I recalled somebody telling me that when the distance from the listening source is doubled, there's a 6 dB loss on the sound.... the calculator verified it :)
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Postby Guest » Mon Dec 05, 2005 7:37 pm

Siguro nabasa niya sa musical fidelity broschureng New A5 Series page 8
I quote:
"Loudspeaker are usually specified by their efficiency: they produce a certain number
of dB for 1W at one metre. However, as you move away from the loudspeaker, you
lose about 5db for each metre over one meter."
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Postby JackD201 » Mon Dec 05, 2005 11:19 pm

No guest. I do not read brochures of items that do not interest me.

The question came up a few weeks ago when Hyperion, Bogart and Myself were hanging out after installing a piece of gear in my system. When training abroad I did not elect to take Sound Reinforcement and opted for Advanced Recording Engineering instead so I couldn't come up with anything but a guestimate mali pa I guessed 4dB. I needed a break so I pieced this together today by accident because I was looking in the Turbosound website to see what advances they've made in compression drivers over the years. I happened to see the Intensity loss calculations via the Inverse Square Law in of all places the FAQ section. I followed it up by checking for formulae at Hyperphysics since most ISL formulae deal with light propogation and not sound. I double checked my old notes to check the dB boost for dual pointsources and it was indeed 3dB.

So there you have it.

Proper resources and acknowledgements made on original post, as is the rule at WS. Credit goes to Turbosound UK and Hyperphysics at GSU.

Please register and join the community.

To everyone else again I hope this proves usefull in any way.

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