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Amp heads and Cabs

Maybe i have this wrong but lets say i had a 500w head at 4 ohms. And that went into a cab rated at 500w at 8 ohms. i would get less than 500w of power because of the resistance? so if i wanted to make the most of my cab could i buy a 600w head at 4 ohms to make up for the lost watts due to resistance?? correct me if i got that totally wrong :p lol and if i was right about the ohms, would that be a good idea?. cheers!
 
If the amp is rated at 500 W into 4 Ohms, it would typically be around 60% of that, or about 300 W into 8 Ohms. The wattage isn't really lost. Instead, the higher impedance speaker is simply drawing less current from the amp.

I would not split hairs over this. Is the rig loud enough? Does it sound good?
 
You're confusing yourself. Your head has the capacity to push out 500 watts @ 4 ohms. You have an 8 ohm cab, so as fdeck said, you're probably getting around 300 watts max from the amp. If it's working out, everything's fine. If you need more volume, just add another 8 ohm cab, and you'll get the whole 500 watts. Or, dump the cab, and get a single 4 ohm cab, same difference. Buying another Amp with more power would be silly, since you'd still be using an 8 ohm cab. If you're set on getting max power and volume, buy another cab just like the one you already have.
 
Good first answer. The second one got in before I noticed... Anyway, ratings vary from manufacturer to manufacturer, so it's not exactly good science. Really, you're going to find out that your ears will not lie.

500w is enough generally speaking for most use. Need more volume get another 8 ohm cab...