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5 Nov 2024 22:22:13 EST (-0500)
  A question of physics (Message 1 to 4 of 4)  
From: Invisible
Subject: A question of physics
Date: 17 Oct 2008 05:55:13
Message: <48f86101$1@news.povray.org>
OK, so I need to buy a set of PC speakers. It doesn't really matter how 
good they sound, but they need to be loud enough for a crowded room full 
of people to hear them.

The trouble is, I'm looking at the product catelogue, and although every 
single product clearly states how many Watts it gives you, not one 
single one seems to say HOW LOUD THEY ARE! >_<

Is there any way to infer the approximate loudness of a cheap PC speaker 
from the Wattage rating? I realise that it's quite possible to make an 
8W speaker that is deafening, but most manufacturers "typically" don't 
od this, so... is there any way I can figure out the data I need?


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From: scott
Subject: Re: A question of physics
Date: 17 Oct 2008 06:01:46
Message: <48f8628a$1@news.povray.org>
> Is there any way to infer the approximate loudness of a cheap PC speaker 
> from the Wattage rating? I realise that it's quite possible to make an 8W 
> speaker that is deafening, but most manufacturers "typically" don't od 
> this, so... is there any way I can figure out the data I need?

Speaker sensitivity is the parameter you are after, tells you the "loudness" 
in dB 1 metre away from the speaker when you apply 1 Watt of electrical 
power to it.  Typical values are from 80 - 100, so I guess you could use 90 
to work out the dB.  I doubt cheap PC speakers will tell you the actual 
value.


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From: Invisible
Subject: Re: A question of physics
Date: 17 Oct 2008 06:11:55
Message: <48f864eb$1@news.povray.org>
scott wrote:

> Speaker sensitivity is the parameter you are after

Indeed. But it isn't quoted.

> Typical values are from 80 - 100, so I guess you could use 90 to work out the dB.

Heh. Yeah. Now I just have to figure out how many dB I actually need to 
fill a room...

> I doubt cheap PC speakers will tell you the actual value.

That's the problem. :-/

OTOH, at least the Wattage ratings are all RMS. (Although it doesn't 
tell you at what frequency...) Some even state the impedance - which 
seems a little redundant in an active speaker system...


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From: m a r c
Subject: Re: A question of physics
Date: 17 Oct 2008 09:06:00
Message: <48f88db8@news.povray.org>

48f864eb$1@news.povray.org...
>
> Heh. Yeah. Now I just have to figure out how many dB I actually need to 
> fill a room...
>
Consider a 6dB fade every time you double distance in free field* from a 
point source (fade_power 2)

*Obviously a room full of people is NOT a free field : walls reflect a part 
of the sound and people absorb another part.

For a better intelligibility try to put your speakers  above head level so 
people get sound coming in straight line from speakers.

Marc


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