# Need A 5v Or 12v Audio Amplifier To Get 100 Db Out Of 1 Or 2 Speakers

Discussion in 'Audio' started by Jamesmc1120, Apr 4, 2017.

1. ### Jamesmc1120

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Apr 4, 2017
I have a raspberry pi 2, could use a 3 if needed. i am looking for an audio amplifier and whichever speakers i would need, could be 1 or 2 speakers, to get 100 db out of the speakers. on the RPI i am using the pigame mixer in my code to play .wav files. please let me know if more info is needed or if a question like this has been answered before. thanks

2. ### Harald KappModeratorModerator

9,669
2,020
Nov 17, 2011
100dB with reference to what?
Decibel (dB) is a logarithmic measure of a ratio. You therefore need a reference level which results in 0dB.

3. ### davennModerator

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Sep 5, 2009
it is when referring to gain or loss in a circuit as in dBm, power relative to 1mW

sound level, on the other hand, is referred to in dB

an example
http://au.noisemeters.com/product/tm102/sound-meter.asp

the sound level monitor systems I build for clubs and pubs etc are calibrated in dB

4. ### Audioguru

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Sep 24, 2016
The dB sound level from a speaker is determined at a certain distance (usually 1 metre, it is much louder if you hold it against your ear and it is less by -6dB per doubling of distance when no echoes), the power and the frequency.
Most speakers are rated at about 86dB to 94dB at 1W, 1m. Doubling or halving the power results in +3dB and -3dB.
I measured 120dB in a disco about 40 years ago. 4 speakers were about 5m away from me.

Then if one speaker is 90dB at 1W, 1m it produces 84dB at 2m and 78dB at 4m and maybe 76dB at 5m. At 5m an amplifier power of 10W produces 86dB and power of 200W produces 99dB.

A speaker with a rating of 90dB at 1W, 1m will produce 100dB at 10W, 1m.

An ordinary amplifier powered from only 5V will produce about 3V peak-to-peak which is 1.06V RMS. Its power into 8 ohms is only 0.14W and is about 0.25W into 4 ohms. If the amplifier is class-D with very low losses and is bridged then with a 12V supply its output is 23V p-p which is 8.13V RMS that creates 8.3W into 8 ohms or 15W into 4 ohms.

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