In trying to calibrate levels from my main speakers and sub, how do you read the SPL level of the sub? Maybe it's just my SPL meter, but the needle jumps up and down across the entire meter while playing pink noise through the sub.

I have a NADY analog SPL meter which looks to be identical to the radio shack analog meter.

Do you have the SPL meter set to "C" and "Slow"?

Yes. It works fine for pink noise on any other speakers I've tried it on, but on any sub it jumps rather wildly.

Are you holding it in your hand? Bass modes can result in huge measurement shifts with small changes in position, especially with pink noise. Get a stand/tripod and, since you have the SLM, consider using REW software with it and your PC.

Could it be room verberations? Mine is the same way. But at the end of the day I tune my sub by ears as I like it louder than calibrated anyways.

I've looked at REW, but never got it fully set up on my PC. Maybe I should look at that again.

The weird thing is 2 days later I tried again and the needle swing was still there, but it was only going up or down 1-2db. It's in a main living area, so it's not separated from anything -- maybe it wasn't as quiet as it should have been for testing and I was picking up background noise from some appliances or something...

When I did mine, the meter jumped as well. I just found an average of where the needle would settle the most amount of time. I figured it was the noise, and not the meter.