The Check Mate SPL Meter: For Good Measure Page 2



I checked the CM-140's accuracy by comparing it with measurements I obtained with my calibrated LinearX Loudspeaker Measurement System (better known as LMS), then compared both to a RadioShack 33-4050. I used C-weighting on the SPL meters, deactivated all the filters on the LMS, and adjusted the LMS's bass response results to compensate for its lack of a C-weighting filter. You can see the results in the accompanying graph. I wouldn't call this a lab-grade evaluation, but it's enough to give you a good general idea of how these meters perform.

Galaxy Audio claims a spec of ±1.5 dB from 31.5 Hz to 8 kHz, which is mighty impressive for such a cheap meter. Although its measurements ran a couple of dB out of spec at 4 kHz and above, the spec held true in the rest of the range. For room acoustics work, that's great; acousticians seldom concern themselves with frequencies as high as 4 kHz, anyway.

I sure enjoy using the CM-140 a lot more than I do my RadioShack meters. Most important is that I have a lot more faith in its accuracy - I'm now confident that what I'm reading on the meter is reasonably close to reality. Also, the CM-140's three operating ranges (32-80 dB, 50-100 dB, and 80-130 dB) make it more convenient to use than the 33-4050, which have seven scale ranges with a useful span of about 12 dB each. On the RadioShack meter, you're constantly flicking a big adjustment knob to find the right range. With the CM-140, it's pretty much set and forget.

One thing I can tell you for sure: Audio manufacturers who see this meter when they visit my listening room will order one right away. If you're into audio - which surely you must be if you've read this far - then you should, too.