# sub amplifier question...



## Vader (Jul 8, 2006)

Hi all,

I am somewhat confused (no suprise there) concerning the power requirements as it relates to acoustic levels. I know that an increase of 6dB translates to doubling the acoustic power, but when reading SVS's FAQ, I can up with the following:



> Each 3dB boost of broad-band bass roughly halves the effective power of any given amp.


So, obviously my wires are crossed somewhere, and I am equating apples to oranges. How can 6dB represent twice the acoustic energy, and yet an increase of 3dB also doubles the effective power? This is probably a case of not seeing the forrest through the trees, but before trying to explain why to a friend why those tiny sub "bass modules" don't cut it, I want to understand it.... :scratch: :scratch:


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## Danny (May 3, 2006)

Hey Vader

Hopefully this will answer your Question, if there is anything that you don't understand feel free to ask.


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## Ayreonaut (Apr 26, 2006)

When talking about power, 3dB represents a ratio of two to one or a doubling of power. 

When talking about voltage, 6dB represents a ratio of two to one or a doubling of voltage.

When talking about Sound Pressure Level, 6dB represents a ratio of two to one or a doubling of sound pressure.

Interestingly, our perception of loudness is not the same as sound pressure level. Although the actual formulae is somewhat complex, as a rough rule of thumb, an increase of 10db SPL is perceived to be approximately twice as loud.

link


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## bobgpsr (Apr 20, 2006)

Ayreonaut said:


> ...as a rough rule of thumb, an increase of 10db SPL is perceived to be approximately twice as loud...


Yes, I've read that also and generally agree from personal experience. Except that I have also heard that for low freqs ( < 100 Hz? ) that the 10 dB rule no longer applies and we are back to something less (6 dB? 3 dB?). Perhaps Mark or Tom have some thoughts? :scratchhead: 

Bob


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## Vader (Jul 8, 2006)

Thanx, Guys!

What I was missing was the factor of 2 due to a square in logarithmic land....


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