REW hook up and set up help

[wackii]

Hi, this is my first time using REW. I'm trying to get the FR measurements for my subwoofer. I'm having trouble on how to set this up correctly. I got an error on "Set Input Volume" setting. When I clicked on "Set Input Volume" button. The comp is playing the pink noise tone for like 2 secs, then it will prompt a message saying "Input volume control is at its maximum....Wizard was not able to get the input signal RMS level to -18db even the volume control at its max setting..." Why is that? Please help. Thanks in advanced.

Al,

Edit: I'm using SB live! (not the 24bits live! but the older version) if that helps.

[brucek]

When I clicked on "Set Input Volume" button. The comp is playing the pink noise tone for like 2 secs, then it will prompt a message saying "Input volume control is at its maximum.

So you've used the SET MEASUREMENT LEVEL to play the pink noise and you adjusted your receiver to show about 80dbSPL on your Radio Shack Meter..

Then you've clicked the SET INPUT VOLUME and does the VU meter respond to the signal?

If not:

Is your souncard selected in the select device pull-down?
Do you have LINE_IN selected in the pull-down?
When you tap or speak into the RSmeter (it's a microphone), does the VU meter and SPL readout respond?

brucek

[wackii]

So you've used the SET MEASUREMENT LEVEL to play the pink noise and you adjusted your receiver to show about 80dbSPL on your Radio Shack Meter..

I did that part... set it to 75db though

Then you've clicked the SET INPUT VOLUME and does the VU meter respond to the signal?

I did not see the VU meter respond... maybe my sound card line-in is incorrect.

Is your souncard selected in the select device pull-down?

yes

Do you have LINE_IN selected in the pull-down?

yes

When you tap or speak into the RSmeter (it's a microphone), does the VU meter and SPL readout respond?

I did not check that... I will double check everything again.

Thanks for the help Bruce.

Al,

[wackii]

I got it to work Question is how come the corrected sub graph is the same as the measured sub graph? I thought C weight should be compensated? Do I need to download the C weight compensated values? Thanks.

Al,

[brucek]

Question is how come the corrected sub graph is the same as the measured sub graph?

The corrected graph is the result that will be achieved (in theory) after a BFD filter(s) is added.

Add a filter and you'll see that the corrected graph changes.

brucek

[wackii]

I see. How about the compensate values for the C-weight? Is it already applied?

Al,

[brucek]

I see. How about the compensate values for the C-weight? Is it already applied?

In the REW pull-down 'METER', there is a checkable entry to turn on C-weight compensation. The C-weight is applied outside the frequency boundaries of the meter calibration file when a calibration file is loaded.

You can read all about this and more in the REW HELP files. You should give these a read. They're really well written.

brucek

[Sonnie]

If you are using a correction file (*.cal file)... hopefully you are... then don't even concern yourself with C-weighting. It's really not going to matter whether you have it on or off. There is no significant C-weighting compensation above 100hz (-0.3 @ 125hz) until you get up to 5khz where it begins to compensate more than a db.

[wackii]

Thanks. One more question: How come my soundcard response graph looks like the u shape (not flat like the help file mentioned)? Eventhough I have cleared the calibration data and unchecked the c-weight compensate. Thanks.

Al,

[brucek]

Eventhough I have cleared the calibration data and unchecked the c-weight compensate

So the Calibration appeared to be successful, and then you selected the LEFT tab and left the loopback in place and did an Automatic Measurement with no cal file and C-Weight unchecked and you got the U shape?

brucek