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Old 15th December 2012, 08:17 AM   #1
Shelah is offline Shelah  Zambia
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Default comparison between volume and power

dear all,

is there a way of finding out how amplifier power and the volume of a sound box are matched?
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Old 15th December 2012, 08:19 AM   #2
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It's called sensitivity.
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Old 15th December 2012, 08:35 AM   #3
Shelah is offline Shelah  Zambia
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okay now lets say i have a 18'' sub cabinet that is about 160 litres, what power do i need in this case?
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Old 15th December 2012, 08:42 AM   #4
freax is offline freax  Australia
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haha, maybe a bit more information about the speaker driver would be a good start.
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Last edited by freax; 15th December 2012 at 08:49 AM.
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Old 15th December 2012, 02:49 PM   #5
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You need to find out how sensitive your speaker system is.

Build it without an amplifier to start with. I'm at work at the moment so I don't have the exact figures in front of me. Most speakers are quoted at a dB level at 1m when fed with a signal of 2.83V RMS.

So, if you feed it with a signal of 2.83V RMS and get 88 dB of sound, your speaker will have a sensitivity of 88 dB/W at 1m.

Once you have this figure you can then ascertain how much power you need to obtain the volume that you looking for.
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Old 16th December 2012, 06:16 AM   #6
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+1 What KatieandDad said. And each time you double the power, ad 3dB.
so:
2W - 91dB
4W - 94dB
8W - 97dB
16W ...
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Old 17th December 2012, 08:29 AM   #7
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Quote:
Originally Posted by KatieandDad View Post
You need to find out how sensitive your speaker system is.

Build it without an amplifier to start with. I'm at work at the moment so I don't have the exact figures in front of me. Most speakers are quoted at a dB level at 1m when fed with a signal of 2.83V RMS.

So, if you feed it with a signal of 2.83V RMS and get 88 dB of sound, your speaker will have a sensitivity of 88 dB/W at 1m.

Once you have this figure you can then ascertain how much power you need to obtain the volume that you looking for.
I like to add 1 thing here, this only holds true for an 8 Ohm driver. Usually sensitivity is spec'd xdB/W @1m. Important is whether this is into half space or full space. And don't forget to take power compression into consideration.
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Old 17th December 2012, 08:35 AM   #8
more10 is offline more10  Sweden
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Quote:
okay now lets say i have a 18'' sub cabinet that is about 160 litres, what power do i need in this case?
You cannot have too much power :-). An amp with more power has better damping factor, so it will sound better even if you don't use all power. A bigger amp will have better power supply, helping out in transients at lower power levels. Also a big amp will not clip. Clipping is very bad for you drivers.
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