Just in case anyone is interested, recently I "blew" my RS Digital SPL Meter via a static electricity discharge. I was going to toss it out, but I decided to "repair" it. The mike element went bad, so I replaced it.


Now, the interesting part. A few days after I repaired the SPL meter, I thought that with all the so called calibration files out there how much of the error is electronic and how much of it is mike related.


Here is the answer. I removed the mike, and swept the electronics via True RTA (1/24 octave no smoothing). Green is C scale, Red is A scale. This proves that the basic filters are pretty accurate A scale and C scale filters.


The accuracy of the mike used in the SPL meter determines SPL meter "accuracy" relative to the well known electronic A scale and C scale filters in the SPL meter.


http://hyperphysics.phy-astr.gsu.edu/hbase/sound/acont.html#c1



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Very true. The electronics are just a form of sound card. And most if not all soundcards are really flat. The mics are what need the calibrating not the soundcards.

So what is the take-home message here? Are the 'correction factors' needed or not? If not, why is it sort of dogma that they be used?

There have been some claims that if you use the audio output jack of the RS Digital SPL meters with REW or TrueRTA, then C scale is not applied to the audio output jack. As the sweeps show, C scale and A scale are obviously being applied to that jack.

If you are using the SPL meter to do a FR chart by hand or via REW or TrueRTA, at a minimum you need to use the C scale compensation.


Here is a discussion on the accuracy of various RS SPL meters:

http://www.audioxpress.com/magsdirx/ax/addenda/media/koya2811.pdf


What I am looking to pickup is a better quality mike element for my SPL meter. I replaced the blown unit with a standard RS mike element, but it is not the flattest mike out there.

So what is the take-home message here? Are the 'correction factors' needed or not? If not, why is it sort of dogma that they be used?


Correction factors for what, "calibration" of speaker levels?


FR curves of calibration tones of my STR-DA4ES taken from pre-amp level output jacks. What do you use for a compensation frequency for the subwoofer?


Green = main channels

Red = subwoofer with LP set to 80 Hz

Yellow = subwoofer with LP set to 120 Hz

Purple = subwoofer with LP set to 200 Hz



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Correction factors for what, "calibration" of speaker levels?No, for the sub.


FR curves of calibration tones of my STR-DA4ES taken from pre-amp level output jacks. What do you use for a compensation frequency for the subwoofer?~3dB is often sited as the figure. Of course, everyone's subwoofer is going to reproduce pink noise differently. My impression is that that is sort of a ballpark figure that encompasses or approximates a reasonable average correction factor for the sub's output with pink noise based upon the correction factors that are supposed to be used with pure tones:

10Hz add 20dB
12Hz add 16.5dB
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dB


Perhaps AVIA's subwoofer tone is ~30Hz which, according to this table, would correspond to a 3dB 'correction'.



HERE (http://www.avsforum.com/avs-vb/showthread.php?t=505236) is an extensive thread regarding the subject.