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Discussion Starter · #1 ·
Here's what I'm doing:

I set the volume on the receiver by playing the speaker targeted pink noise in REW's signal generator.

Then I go about my measurements, attempting to hit a target of 75 dB.

After that, I play the pink noise targeted at the subwoofer in an attempt to set the gain on the subwoofer to hit 75.

1. In order to do that though, I have to turn the sub's volume control up quite a bit. When I take another measurement, the curve is about 6 dBs louder? It also sounds really boomy now.

2. I've been informed that the SPL meter reading in the program doesn't take into account the mic/meter or soundcard calibration files. Does this mean that using the meter in the program is inaccurate with subwoofer pink noise?

3. Why use pink noise to set the level instead of setting the level to hit the targeted curve? Because isn't the idea to have the subwoofer play certain it's allotted frequencies at a specified loudness relative to the rest of the system?

Thanks for answering all of these questions. To say the least, I'm a little confused, but I think clearing up these basic concepts will go a long ways. I've spent a lot of time calibrating but it still doesn't sound good.
 

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It’s hard to tell from your post if you’re trying to get a full-range or just a subwoofer measurement, but it appears you’re going through more trouble than necessary.

Just open the “Settings” window and run the “Check Levels” routine under the “Soundcard” tab. Use the tone generated when you click through the steps; no need to use the REW signal generator separately. The appropriate test signal is determined by what you select in the field - “Use Subwoofer” or “Use Main Speaker.”

After that, run the “Calibrate SPL” routine under the “Mic/Meter” tab. Once again, select “Subwoofer” or “Speaker” in the field, and the program will generate the appropriate signal.

Regards,
Wayne
 

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Discussion Starter · #3 ·
Thanks for your responses, Wayne.

I'm asking about the general concept of "pink noise" and using it to set the level of the subwoofer.

Once I had used the BFD to get the appropriate curve for the subwoofer, it measures low in pink noise, maybe 65 dB despite the graph tracking from 76 to 70 between 30 and 80 Hz. I was asking if this is because the meter is inaccurate due to the lower frequencied pink noise, or if I ultimately need to raise the gain control on the sub.

Or, should I even bother with the pink noise at all once I have it tracking the curve properly?
 

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The “proper” process would be to first determine the house curve slope you need, then load a house curve file (that you create) into REW. Measure with REW, then EQ the subwoofer. After equalizing, the sub’s response should track the Target house curve (you’ll typically have to re-calibrate REW’s levels for new measurements taken after equalization).

After you’re satisfied with your EQ settings, then the sub’s level needs to be re-adjusted to correctly blend with the main speakers. Whatever process you used to accomplish that before equalizing –calibration disc, the receiver’s internal test tones, etc. - use it again.

Regards,
Wayne
 

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Discussion Starter · #5 ·
Thank you so much Wayne, you've been a great help.

Is checking the sub's level with pink noise via the SPL meter in REW inaccurate because the RS meter measures lower frequencies incorrectly (and because the calibration file is not taken into account with the REW's SPL meter)?

Loren
 

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Any measurements taken in REW using the Radio Shack SPL meter will be as accurate as a Class 3 meter can be (±2 dB in the case of the RS meter). All the calibration file does is flatten the meter’s C-weighted frequency response, for the purposes of using it to take a frequency response reading. That’s not the same as taking a basic SPL reading.

I say “in REW” because you’re asking about using the meter to check the sub’s level, and that’s typically not done “in REW.” If you’re using the meter’s built-in display (i.e., during the “Calibrate SPL” routine), that’s not “in REW.” “In REW” would mean you’re using the program’s own SPL display. Which of course is set during the “Calibrate SPL” routine using an “uncalibrated” SPL meter...

I don’t know if REW’s on-screen SPL display uses the calibration file or not. I would expect not, as SPL-measuring protocol typically requires A- or C-weighting. So, adding a calibration file would technically render REW’s SPL reading inaccurate. Again, getting a basic SPL reading is not the same as taking a frequency response measurement.

Clear as mud? :D

Bottom line, the calibration file is only relevant for using the SPL meter as a measurement mic in REW. You don’t use REW to “set the sub level” (you could use it for sub/main calibration, but that’s a discussion for another day). You use the SPL meter itself. Its C-weighted response curve is perfectly fine for subwoofer level-setting using a pink noise signal. “Accuracy” would only be an issue if you’re measuring frequency-specific sine waves below ~50-60 Hz. If that’s what you’re doing, then the Correction Values you can find on-line are needed.

Regards,
Wayne
 
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