Radio Shack Sound Meter Calibration

[rlam01]

Does the Radio Shack Digital Sound Meter need to be calibrated?

If so, how does one accomplish this?

[gmorris]

I could be way off with this, so take it as info only.

I'd say the Rat Shack meter does NOT need to be calibrated. You are using it to adjust the relative volume levels of the speakers. Therefore, the meter could be off by 99% and it would not matter, the speakers will still be set relative to each other.

Now, if the meter is not working correctly and you are not getting a consistent reading, that is a different story. But as long as you set the speaker levels to the same relative value, they will be balanced regargless if the reading on the meter is correct or not.

If you set your level at 80 Db's and balance all speakers to 80 Db's, they are balanced relative to each other. It makes no difference if the 80 Db reading is actually 70, 75, 85 or 100....

[Dr. Spec]

Yes, the difference between accurate and precise.

The meters are factory calibrated, and I have checked them to be within 1 dB of the actual SPL, at least at 1000 Hz. You need a "sound level calibrator" to calibrate a sound meter for "absolute" sound pressure. Otherwise, relative works fine.

Absolute SPL is critical for certain types of audio measurements, but as discussed above, not needed for system balancing.

The meter itself is c-weighted and will read prgressively LOWER than the actual SPL as the frequency drops much below about 90 Hz. There are correction factors to compensate for this, and they are mostly useful for people plotting the FR of their subwoofer. Otherwise, don't bother.

[Lee Bailey]

If you're good with a soldering iron, you can modify your RS meter to make it have a flat response. The docs are here: Eric Wallin's Audio DIY Projects (http://www.gti.net/wallin/audio/audio.html) .

[rlam01]

Uh, I don't have a MSEE. :( That looks like something I would 'attempt'. Not sure about being able to finish.

So many talented people around here.