Thanks! I have that part of the equation down. My confusion is when bridging. For a normal 252, Hypex uses the ohms and power of one of the channels to calculate the input sensitivity (so their datasheet example is sqrt(150*8)/10^(25.6/20) = 1.82Vrms
But when bridging, each channel of the amp now see's half impedance. So if I bridge a 252 and use it to power a single 8ohm speaker, technically each amp on the module is seeing 4ohms but combined the overall impedance is 8ohm @ 500w. Do I use 500*8 for the sqrt() now? Or 500*4? Or 250*4 (since each module is outputting max power of 250w)?
125W x 2 @ 8 ohms
input sensitivity = sqrt(125*8)/10^(25.5/20) = 1.7V
250W x 2 @ 4 ohms
input sensitivity = sqrt(250*4)/10^(25.5/20) = 1.7V
500W x 1 @ 8 ohms
input sensitivity = sqrt(500*8)/10^(31.5/20) = 1.7V
Input sensitivity is always calculated on a per channel basis. As long as power doubles in to half the impedance the input sensitivity will be the same. Input sensitivity for 8 ohms bridged will always be the same as the input sensitivity in to 4 ohms stereo.
Just for demonstration let's say power does not quite double in to 4 ohms and you only get 200W x 2 @ 4 ohms (400W x 1 @ 8 ohms).
200W x 2 @ 4 ohms
input sensitivity = sqrt(200*4)/10^(25.5/20) = 1.5V
400W x 1 @ 8 ohms
input sensitivity = sqrt(400*8)/10^(31.5/20) = 1.5V
IMHO gain is a much more useful concept than input sensitivity.
Michael