I'm learning LTSpice, and I am confused about why this simulation gives different results from real life.
The circuit is an opamp bandpass filter for an engine knock sensor. I believe that knocking on this engine would be in the 5.7Khz range. I hooked up a function generator to the input and swept the frequency from a few Khz up to around 12Khz, and what I found was that at around 5.5 the response suddenly goes up quickly, and keeps increasing until around 7Khz, and then drops off very quickly above that.
So, it seems to be centered around 5.5 - 7 Khz, which is a tad higher than I expected, but close enough.
But the spice simulation of the circuit shows that the filter should be most sensitive around 4Khz. So I'm trying to understand what other factors affect this that I haven't taken into account. The capacitors are marked only as "0.01", but I think it has to be uF because otherwise I'd be off by a factor of 1000 which could not work. The resistor values, I measured.
I'm attaching screenshots of both decibel and linear scales (I find the linear one clearer)
Any ideas where I've gone wrong?
EDIT: changed the screenshots to correct a mistake (which didn't make any difference to where the filter is centered)