double power = plus 3dB

OK I know the theory that when you double the power you add 3dB to the SPL, but I'm not sure how it works when you add speakers so lets take a theoretical example.

1) you start with an amp, rated at say 300 watts (mono) into 4 ohms.But to start with you only connect 1 x 8 ohm driver and put the volume up to say 3/4.......... So just for the sake of arguement you are putting 100 watts into an 8 ohm driver and getting say 115dB.

2) Now without altering the gain, you plug in a second identical 8 ohm driver in parallel. So the amp is now giving 200 watts into a 4 ohm load........... 100 watts to each driver You have doubled the power by virtue of halving the load so do you now get the extra 3dB making 118dB or is it more due to also having a second driver???????Edited by: markie

Youl get 3 db from doubleing of power + 3db from doubleing of sources
if they couple soyou get +6db, or nearly +6db depending on how well the
sources couple.

Yep aslong as they are in phase acoustically - and the drivers are perfect,which they are not.

I think a jbl 2241 or similar has 4dB of power compression at 1 x RMS rating.

3db = double the power. 6db = twice as loud.