In the ongoing effort to provide ever increasing accuracy and legitimacy of my test results, there were two rather exciting additions to my test "bench" today.
The first isn't a big deal to you, but it's a "must have" for me in the DC voltage drop battle since I've been using a cheapo batt charger for power. Caps are fine for short bursts, but even a rather healthy number of banks starts to drop pretty low on sustained testing. And it takes my little charger forever to keep up. So... a 100A / 13.8v power supply gets to handle voltage duty now. I hope to add more powa, but holy hell these things are pricey.
This thing is my new best friend.
Second, and more importantly... I got a bank of fixed resistance. What you see here is 5,000w worth of fixed resistors with different ohm loads available depending on how I configure them.
What's the big deal, you say? Well... I'll tell you. One really awesome thing about these is that I don't have to tear up subs to test amps. Or wake the dead while doing it. But that's just a bonus.
The other thing that's cool here is the "fixed" part. As in, a purely resistive load as opposed to an inductive load (like subs). If I configure these to a 1 ohm load... that's what I get. 1 ohm. No "rise."
Now we will science...
When we measure the current and voltage on an inductive load like subs, the current and voltage are out of phase. It's just the nature of the beast. Basically what that means is that we are measuring them at different times. The further they are out of phase, the larger the difference between the "real" power and the "apparent" power.
Real power, apparent power and power factor are sort of a difficult concpet to grasp, so if you need to Google, I'll wait...
Here's a pic to illustrate what I mean. Even though the peaks are the same here... you can see the difference in the phase. Known as the "phasor angle." And actually... if you can measure or know this angle, you can calculate the real power. Fwiw, these look to be ~ 50* out of phase.
If you measured these two, you'd wind up with a false high reading of about 36%. This is why we see 1k's doing 1.5k "apparent" power.
Here's another pic. You can see in the first one that even though the current and voltage have different peaks, they're in phase. These are the same two measurements except that one is a purely resistive load and the other is an inductive load. These happen to be 90* out of phase. It's just for illustrative purposes since all this would probably do is generate heat. Lol.
Aaaaaaanyway. This all means that all of our clamps on subs are false high readings. How false? That's difficult to say for your clamps, but I can show you on an amp I tested today.
The amp in question is irrelevant, but it was setup exactly the same in both tests. The only major difference is that one test is on a sub and the other is on the resistors. The difference between the "rise" and the resistance here is pretty negligible. As is the .3 dcv difference.
Here we have the inductive test. As in... clamped on a sub. The result I got here is 789w rising
to 2.3 ohms.
Now, here's the exact same amp and the exact same settings- except on the resistors wired to 2.5 ohms. Result... 542w @ 2.7 ohms. (note: the "rise" from 2.5 to 2.7 is due to the inaccuracy of this type of current clamp.)
Holy hell I can get long winded.
So, this amp is doing 789w "apparent" power, but it's really only doing 542w "real" power. You guys following me here?
This is the concept behind the AD-1 amp dyno. And why they are all high and mighty about it being the only "real" results and being superior to "clamping" blah blah blah. And technically... they're right. BUT.... since clamping on subs is the end user industry standard across the board, I will continue to include apparent power clamps in my results. Only now, I have another data point to include in my testing.
tl;dr. I haz meters and stuff. Suck it.