So there seems to be some type of mystery out there amongst beginning engineers and musicians alike about the math of Ohms. I’m here to try and explain it.
You know those numbers on the back of your amp and speaker cabinet? 8, 16, 4, what not? Followed by the oh so powerful Omega Sign. Yea, Ω. Thats the symbol for Ohms. Which is a measurement of Impedance.
What does it mean? Its how much of a load (in this case, how many speakers) are in your signal’s path.
Ohms and Your Amp
Many amps (professional level) are rated at different power outputs at different Impedances (another term for measuring Ohms).
The general math involved here is if you half the Ohms, the Power Doubles.
Likewise, if you double the Ohms, the Power Halves.
Some amps DO NOT have ratings at different Impedances (only labeled for 8Ω output). In some cases this mean the amp is only meant to be used at this Impedance. In others, you can use it at different impedances, but be careful. Blowing up an amp is not as much fun as it may seem.
Wiring The Speakers to The Amp
This is the fun part. The part with all the copper, running cables and such. Best to set this up by example.
Almost all commercial cabinets are wired in Parallel (like Christmas tree lights, there is parallel and serial). This means whenever you wire two speaker cabinets together, the “Ohms” will half, and the power will double.
Say we have two Subs. Both rated at 8 Ohms, and to take 800 watts each. You have an amp that puts out 800 watts @ 8 Ohms. You CAN run both of these together at full power!
Simply connect the amp to the first cabinet, then the Out/Thru of the first cabinet to the second cabinet.
Waa Laa. Connecting these two cabinets makes the setup 4 Ohms. The Power output of the Amp is roughly 1600 Watts @ 4 Ohms. Nice.
Congrats. You’re learned something.
Oh, and this does apply to guitar/bass cabinets as well, given your Amp can handle it.
