Top of SPL meter or bottom.

I can't comment upon whether this is a problem with the meter or not. But it is all relative. So, use one or the other.

Did you consider that the Ratshack device is a POS?

Borrow a real SPL meter.

It does not matter for calibration purposes. Use one or the other scale. Anyone who thinks that 75 dB on any SPL meter is exactly 75 dB is just fooling themselves. Look at the tolerance specified in the instruction book. That is why no SPL meter should be trusted to give you any precise number. They don't give you those tolerance numbers just for fun!

By the way, I had to change the mike element in my RS SPL meter (static discharge blew it). The CAL adjustment on the side of the Digital meter is used to make 75 dB read the same number on different scales. The actual "calibration" adjustment is inside the meter so people can not play with it.

Also, make sure your batteries are not getting weak. The first thing that is done at a calibration lab before calibration is performed is to install fresh batteries!

Why? Use something like True RTA instead of a toy SPL meter!

I can't disagree.

True, not accurate but the results are pretty darned reproducible for a toy.

"reproducible"

Is it safe to say that the rs meter is reliably inaccurate when calibrating speaker levels with pink noise? For example, it is -2db off across the board. I dont really care if I am at 75db or 73db as long as all my speakers are calibrated to the same level. Or is the rs meter completely all over the place?

Yes, provided you don't move the meter, there is very little variance between successive measurements. It is not accurate, but it IS precise. If you calibrate all the speakers to 75dB, the SPL that is being measured by the meter's mic, at the meter's exact location and position, IS identical. So, no, it is not "all over the place".

A stopped clock is precisely accurate twice a day!

very true

Although Heisenberg may disagree.

There is nothing wrong whatsoever with using the RS meter for calibrating speaker levels. It is very valid for a comparison measurement, which is all you really need it for. Who cares if the absolute level is off 1-2 dB?

Hmmm ... I'm "uncertain" about that!

Well, it's the "principle" of the matter...

Is this what you intended??

This is the right answer. The RS meter is not a POS. There are more accurate devices but they cost a lot more. And they're more accurate mainly at high frequencies which are difficult to measure even with a better device. For balancing speaker volumes at low and mid frequencies the RS meter is perfectly adequate.

--Ethan

I agree with Ethan on the utility of the RS meter.

As for True RTA, it is an extremely useful tool. But it must be calibrated to some absolute reference sound level, because otherwise, all frequency measurements with it are only relative.

And where does that absolute level come from? You could use a reference microphone with a calibrator attachment matched to its capsule. But these are rather expensive, and we acousticians are generally the only ones who need them.

Or you could use a cheap RS meter, and be within a dB or two of absolute sound level.

Regards,
Terry