REW - sets up right but then "check levels" too low

[Schwingding]

I'm very frustrated and appreciate your help. I have set up REW painstakingly carefully, with a SB Live external, following the instructions to the letter. The card calibrates well, gives me the expected curve, and the mic and levels all calibrate out well. Everything is going smoothly. I use 75db as the ref point as indicated. But then when I go to take a measurment, and first "check levels", I am returned with a "level too low" message, and if I proceed to take a measurement I'll get a warning half way through that tells me my levels are significantly low like -90db. If I adjust the volume to a point where the check levels don't report an error, the decibel level is WAY TOO HIGH to tolerate even during a test, and the results are off the chart.

I really don't know what I'm doing wrong here. Help please. Thanks.

[brucek]

But then when I go to take a measurment, and first "check levels", I am returned with a "level too low" message

That's because the Check Levels in the Measurement screen and the Check Levels in the Settings screen use different values to generate the pink noise.

The Check Levels in the the settings screen uses the fact that you have the 'check/set levels with subwoofer' pull-down set. To double check and verify that the end sweep frequency that you have set in the Measurement panel matches that subwoofer setting, its' Check Level uses the end frequency as the pink noise hi-limit cutoff. So if you had 20KHz as the end frequency to measure for your sweep, you can see how the pink noise would be different (between the two Check Levels) and as such the low level signal you're experiencing.

Set the End Frequency in the Measurement panel to 200Hz..................

brucek

[Schwingding]

Thats it? I would have never figured that out. I'll check later on, and thanks for the help.

[Schwingding]

Went back to check things out as suggested. The end freq had been set to 200Hz as I suspected. It was there all along. I'm still totally stumped. Went back and started from scratch again - same result.

[brucek]

Makes no sense.

I'm going to suggest you start REW and then select Delete Settings and Shutdown (in the settings pull down) and then restart REW and go through the whole setup. You'll have to reload your cal files etc.......
Can you try that before we continue..

brucek

[Schwingding]

Yes, surely, but I did that last night. I do that regularly it seems! Appreciate your continued help. I was able to fudge with settings enough to make a measurement, but it is way off the chart, I can't even read the peaks as they are being interpreted as over 140db - not a chance, even given dual pb12+/2s.

Is this normal behavior - in the soundcard cal menus, I am unable to much affect the "output" vertical bar, even through manipulation of the output wave and sweep options. The only way I can get output to change is by changing the input sweep. I am able to get input and output no closer then 3db away from each other.

[brucek]

I am unable to much affect the "output" vertical bar,

The output VU meter is set with the sweep level. Set it to about -12dB FS and that should produce -12dB on the output VU meter. The Output Volume should be set to 0.500 and the Wave Volume set to 1.000. Neither of these latter two control have any effect on the output VU meter.

Once that's set, adjust the volume on your receiver to create 75dBSPL on your RS meter.

Now set the Input Volume until the Input VU meter reads about -3dB or about the same as the output VU meter.

Now set the CALIBRATE SPL using the button on the Settings tabs.

Now set the TARGET LEVEL using the button in Target settings pull down (left panel).

Now go to MEASURE and see what the Check Levels says... (ensure end freq = 200Hz

brucek

edit: you can set the Output Volume higher if you find the receiver volume dial is too high for your liking to get the 75dB. The 0.500 is a good starting point though.

[Schwingding]

Well nothing I do seems to affect this particular issue, even replacing a few key cables does nothing other than alter the input signal a few db.

Here's what I do. Ensure the creative sound card settings are identical to those in the REW manual. Fire up REW. Set the input and output devices as specified in manual. Check levels with sub pink noise gen to attain 75db on the RS meter. Begin calibration of sound card by connecting input/ouputs and then matching input/output signals within 3db. Calibrate card, save. Enter microphone calibration file. Calibrate SPL. Begin measurements and get the "input too low".

Despite this, I have been able to get readings that are similar enough to my manual plots that I believe they are accurate, just not reading correctly on the db scale on REW.

I had a massive spike of which I was aware in the 20Hz range and a large dip at 28Hz. By messing with my subs PEQ (dual PB 12 +/2 s) I was able to tame the peak. But I discovered a remarkably flatter curve when I set one of the subs to its native tune of 20Hz and the other to a native tune of 16Hz. When I set them both to 20Hz (they were both at 16), the problem grew worse, but setting them each differently cured that peak. So REW is already helping me, but moo if I can get it set up correctly! Thanks again for your help.

[JohnM]

Can you post a screen shot of the Scope page after you take a measurement? For the SB Live the input volume, wave volume and output volume generally all end up set to 1.000, what figures have you ended up with?

[brucek]

Yeah, I am baffled for sure......

As long as the Settings page shows Input/Output levels that are like this:

settings_panel.jpg

And if you have an end sweep of 200Hz you should see the same levels like this when you push the Check button

measure_1.jpg

Then it should say:

measure_2.jpg

What are the levels when you do it?

brucek

[Schwingding]

Thanks everyone. Bruce, the first screen shot is nearly identical to my setup, but my levels are nearer to -14. The second screen - WAY DIFF. the output level is normal as shown, but the input level never even registers anything.

I don't normally have difficulty with these types of things, and man is it frustrating! Thanks for your continued assistance.

[brucek]

The second screen - WAY DIFF.

I have overlayed my Windows playback and record mixers with REW below. You can see which controls affect which REW settings. Its dynamic. When you have the settings screen up, look at the mixers and their slider levels. You see mine match the REW levels.

Now go to the Measure panel in REW and do a check levels. Do the Windows mixer sliders stay put?
Does the input level remain the same?
Does the pink noise sound the same between the two Check Level tests (i.e. output still OK)?

settings_control copy.jpg

brucek

BTW. You can do this testing with a simple short from line_out to Line_in on the right channel instead of the usual microphone and receiver setup on the right channel. I saves all the noise.......

[JohnM]

Make sure the SPL meter is connected to the correct channel, some 1/8" to phono leads have left/right swapped.

[Schwingding]

JohnM wrote:

Make sure the SPL meter is connected to the correct channel, some 1/8" to phono leads have left/right swapped.

Now you've stumped me. The RS meter output is a single channel, how would a reversal work? The 3.5mm jack is also mono.

[brucek]

The 3.5mm jack is also mono

Nope, this is likely your problem. The line_in jack and line_out (front out) jacks are stereo. You need a stereo plug for a stereo jack to ensure the contacts mate. Everyone usually uses an adapter (as specified in the help files) that splits the stereo out to two channels so you can use the right channel. get a couple of adapters (as specified in the help files)

24BitSB.jpg

brucek

[Schwingding]

Son of a gun. I'm sorry for being so much trouble, but I think we (you) two have finally nailed it. Will report back. Thanks again.

[Schwingding]

Welp, that fixed it. Thanks very much for everyone's help!