If you do a Google search for "Radio Shack SPL meter corrections" you find links to lots of discussions about this topic on AVS forum. I've got both the Stereophile and Rives Audio test cds (the Rives cd has tracks that are supposedly corrected for the anomalies inherent in the meter.) My JL Audio Fathom has a calibration mode that purportedly corrects and equalizes in room response. If I accept the measurements I make with the Stereophile cd, my room is plus/minus 1.5 db from 50-25 hz and down 3 db. at 20 hz. The Rives cd tests have such a wide variance from this I wonder if it is calibrated to the model db tester I have (There are analog and at least two digital versions.) I wrote Rives and asked what model meter they are using for their calibrations, but they never replied to my question. Bottom line is, it's hard to know how accurate any given RS meter is (but its measurements are consistent and are good for seeing the comparative results of adding room treatments, moving subs to new positions, etc. ) If one wants to do better, I guess you have to step up to the next level and buy something like the calibrated Dayton Omnimic measurement system Parts Express sells.
Using a RS SPL meter
What is the proper way to use a RS SPL meter in order to measure the room response. What I have done is set the meter to "C" weighting, "fast response". In particular, I wanted to see what was happening in my room from 200 Hz down (my room is 14'5" wide x 19' long with coffered ceiling).
This is the part I'm not sure I did correctly. Using a Sterophile Test CD, I played 200Hz track, and adjusted the volume of my preamp in my room until the RS SPL measured 90 db. I then played each of the following tracks (with lower freqs), and recorded the db reading from the SPL. I put the RS SPL on a tripod, at ear level, from my listening position, and pointed the meter directly forward (aimed between the two speakers).
Wow, the response dropped significantly below 60 Hz? I'm talking about a drop of 18db by the time i got down to 25 Hz. (My speakers are Acoustic Zen Crescendos, which are full range). I understand (from another thread here on A'gon) that the RS SPL is deficient in the lower frequencies, and that I need to add db's to the reading I get (however, even after db's to the response, the response below 50 would still be down over 12 db).
So,
#1 Am I using the meter correctly?
#2 If not, what is the correct way to measure room response using the RS SPL meter?
#3. Any thing else you want, to add or need to know?
In advance, thanks!
Louis
This is the part I'm not sure I did correctly. Using a Sterophile Test CD, I played 200Hz track, and adjusted the volume of my preamp in my room until the RS SPL measured 90 db. I then played each of the following tracks (with lower freqs), and recorded the db reading from the SPL. I put the RS SPL on a tripod, at ear level, from my listening position, and pointed the meter directly forward (aimed between the two speakers).
Wow, the response dropped significantly below 60 Hz? I'm talking about a drop of 18db by the time i got down to 25 Hz. (My speakers are Acoustic Zen Crescendos, which are full range). I understand (from another thread here on A'gon) that the RS SPL is deficient in the lower frequencies, and that I need to add db's to the reading I get (however, even after db's to the response, the response below 50 would still be down over 12 db).
So,
#1 Am I using the meter correctly?
#2 If not, what is the correct way to measure room response using the RS SPL meter?
#3. Any thing else you want, to add or need to know?
In advance, thanks!
Louis
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- 13 posts total
- 13 posts total