How do I measure it?

I have a pair of 1500s strapped on three Fi Bl 18s (dual 2ohm) in a series/parallel configuration. I've already clamped the amplifiers and they are pulling 460a of current, voltage drops from 14.4 to 11.8, and resting resistance is 1ohm. What else is there?

ok, here it is, the secret of impedance rise, hehe-

You will need an Ammeter which you have and a DMM(Digital Multimeter)

You can only measure impedance rise on single test tones. IF you try to do it when playing music, the resistance will change repeatedly before the test tools retrieve the present info. So one tone at a time.

Also take note that if you need to test a lot of tones, allow the subs to cool down or else resistance will be higher than normal.

Take the DMM and put it's probes on the speaker output terminal.

Take the ammeter and clamp it around the positive wire ONLY.

Burp a test tone long enough for you to get readings. At a split second, visually record your voltage and current output from the amp. Make sure that they stay steady instead of changing erratically.

Write these numbers down before you forget.

Let's say you got 63.2V and 46.1A

All you do now is divide the amps INTO the voltage.

The answer in this example is - 1.37 ohms

That is what rise is, amps divided into voltage and can be found only by measuring the output from the amp(s) itself.

Now since you know... and everyone else who read this, start doing your tests. You will start to gain some knowledge about how things work in your install environment for comp reference if you are going that route.

For amps that are strapped, is it a little different since the positive from both amps are used? The clamped amperage of the amplifier connected to my positive terminal was 48.6. The AC voltage was 37.5. That = 0.77 ohms but that has to be per amp, right? That also = 1822watts of power. If that is per amp then thats 3644watts of power with rise up to 1.54ohms at about 67% efficiency.