Lighting Audio Amp

[BlueZXTwo]

I have a L/A amp and I was looking at the RMS for it. It says it's 85W x 2 @ 4 ohms or 250W x 1 @ 4 ohms. I don't get it. I would have expected it to be 170W RMS and not 250W. Why is this?

[SimpleAudio]

lightning audio is a lower subdivision of rockford fosgate. often times their amps are over rated. the newer the amp is the worse it probably is. also bridging the amp at 4ohms is equivalent to running the amp in stereo at 2ohms....i bet its rated for 170rms x 2 at 2ohms.

[BlueZXTwo]

I actually just hooked it up to a single 10" sub rated at 150W. It's also a Lightning Audio and so far, it sounds pretty good. I just wonder how long it will last.....

Oh well, just another reason to go buy something better.

[JonsZX2SR]

More likely it's 85W X 2 @ 4 ohms, 125W X 2 @ 2 ohms and 250W X 1 @ 4 ohms bridged.

If you bridge the amp across a given load, each channel effectively sees half the impedance. If the amp provides 250W X1 @ 4 ohms, each channel provides equal current, but half the voltage. Since the two channels are out of phase in bridged mode, the voltages add.

http://www.teamzx2.com/attachment.php?attachmentid=625&stc=1&d=1211113532

Power = E*I*Cos(theta) Assume the voltage and current are in phase so theta= 0 and Cos(0) = 1

If Power = E*I = E*E/Z = 250 = (E*E)/4 then Erms = 31.6 V and Irms = 7.9 A.

Checking the calculations if Erms/2 = 18.8 and Z/2 = 2

Power = 18.8*18.8/2 = 125 and Irms = E/Z =18.8/2 = 7.9 A