weird amp readings

So I have a Fluke 115 multimeter and recently bought a Uni-Trend UT202A AC clamp meter. Decided to go out today and tune my amps via multimeter for voltage and ac clamp for current, but got some weird readings. With a 0db 50hz test tone playing, the voltage was reading about 8 volts and current at .18 amps. That math doesn't work out to almost fully pushing an alpine type r 12. Since this was weird, I tested voltage on my 4 channel amp and only saw 1.13 volts. I'm completely baffled as gains are in the general right area and the sound coming out was loud and clear. Any ideas of what's going on?

Does the AC clamp meter read DC current? You need to figure out why the amp is getting only 8 volts.

I think I was misleading, I'm testing the speaker outputs, not DC power in from the battery. And no, it's only an AC clamp meter. The amp is getting a constant 13.6v from the alt/battery.

Did you have the clamp meter over both the positive and negative speaker wires?   Only one of the 2 can pass through the clamp.

When checking your 4 channel amp, was it playing music, or a test tone?  The sampling rate of the meter will not allow an accurate reading with music. 

Is there a way to manually set a range on the meter?  With fluctuating voltages, those meters spend most of their time changing ranges.

Clamp was only over the positive speaker wire. And I had a test tone going for each. Obviously a lower frequency for sub and midrange for the others. The clamp meter has 20A, 200A, and 600A I believe. Checked on both 20A and 200A to make sure I wasn't going crazy.

In order to measure amplifier output power with any meaning, you need to use a dummy load of a fixed resistance and simply measure the true AC RMS voltage drop across it. Power = voltage-squared divided by the resistance. Trying to use a clamp on ammeter will give you a different reading at every frequency since a speaker's impedance changed with frequency. A resister remains fixed.Support the12volt.com

I'd suggest an in-line current measurement since clamp meters often have an absolute +/- n-Amp inaccuracy. And they are less accurate at lower values. Plus yours is not true RMS and may be centered on mains frequencies (50, 60, 400Hz etc).    However as per DYohn, by measuring true RMS voltage across a known resistance you don't need to know the current (it can be calculated - as can the power). True RMS voltage across the speakers alone may be sufficient for your purposes. (Measure or obtain the resistance of your speaker(s) - as opposed to its/their impedance.)

So I should just scrap what I was trying to do, make like a resistor array with a bunch of 100W aluminum resistors that the equivalent resistance measures to ~1 ohm and then I can simply measure voltage and calculate power like that (or set gains to a certain power)? Obviously an oscope would be needed to make sure there isn't any distortion, but just the voltage will get it in the right area it seems.

IMO no, tho it depends what you are trying to do. If it's the max power without distortion, then various test tones into the speakers and watch the CRO or meters or listen to you ears for distortion. If it's to test max power I'd argue the same since IMO testing into a pure resistance is not the same as a speaker - ie, higher current due to inductance, or speaker/inductive distortion effects.