Your data makes sense and looks good. I agree that things are much better once you individually calibrate each sound level meter.
My impression from reading the messages on this thread is that people are making calibration tables and telling everyone "Here, this is the calibration data for this model of SPL meter". That is what is so terrifying. The models simply vary too much from one to the other. Not just in response, but in level. I looked up the specs at Radio Snack and they only say +-3dB from 50Hz to something in the several k range. That means that one meter could be off by as much as 6dB in comparison to another meter....in their "mid-band". Outside of this range, that difference will increase rapidly. Incedentally, even the R/S lit says the response drops like a rock at very high frequencies.
Acoustical Measurements is an area of expertise of mine...and the readers here need some help. Here we go:
BTW, for everyone out there. In case you did not know this. The "GOOD", low cost electric condesner mic is the Panasonic WM-61A available for less then $2.00 at DigiKey. DON'T BUY ANOTHER MIC CAPSULE. Many people don't know that companies such as Earthworks simply buy this mic, dress it up and add some good electronics around it, and sill them for $2,000.00
. Quite a nice mark-up. Just put the mic itself in a small diameter brass or AL tube from the local hobby store. Use the default mic circuit that Panasonic recommends, and you have yourself a pretty decent microphone
. It is so cheap and easy to do, I always encourage people to go ahead a make several of them at a time. Many of the $100-$250 Measurement mics out their are exacly this.
There are several small companies (people) that make inexpensive test and measurement gear. One of them is Here
This software is $150.00 and works with a sound card. Do any of you guys have sound cards in your PC
Seriously, be careful. When talking to this guy, or any other similar outfit, ask them what cards they recommend. Honestly, it may well be worth it to buy the card they recommend.
SO THERE YOU HAVE IT. A reasonable OPTION FOR AROUND $200.00 (WITH misc. hardware and electronics for the microphone). This set-up will measure LOTS of different things with REASONABLE accuracy.
BTW, I am not recomending the etfacoustic outfit over anything else. I have no experience with them. I do know that there are a few outfits like them out there. Just do an internet search like "Audio Measurement System PC Low Cost" and things will pop up.
Also, there are many options for low cost dedicated hardware items. Such as the Clio Lite System
. This particular one is very good and is $650.00. Other can be found in the several hundred dollar range.
Anyhow, I hope this helps.