C-weighting and calibration file questions

[stokasz]

I have been working with REW for a few days and have some questions even so I did some searching.

When I calibrate the soundcard (soundblaster live 24bit external) does it matter if the
c-weighting box is checked or unchecked in REW?

The results I have gotten do not seem to be right in that the subwoofer frequency response rolls off dramatically below 40 hz. I have an IB with 4 MJ-18’s soon to be replaced by IXL-18.4s so it is pretty impressive even without equalizing.

I have a Galaxy cm-140 meter and I have loaded the calibration curve. Should I use it
C-weighted or A-weighted and should I check or uncheck the REW C-weighted box? My sweeps have looked low using the meter A-weighted and REW C-weighted unchecked.

I read in another thread to press the Apply Windows button to recalculate the frequency response with a calibration file. I do not know where that button is and the having the calibration file loaded or unloaded in the settings makes no difference to the response.

I am also getting warnings about the impulse response but I think it may be related to what I am doing wrong here.

[brucek]

When I calibrate the soundcard (soundblaster live 24bit external) does it matter if the
c-weighting box is checked or unchecked in REW?

No..........

The results I have gotten do not seem to be right in that the subwoofer frequency response rolls off dramatically below 40 hz

Measure an RCA cable connected from line-out to line-in instead of the SPL meter connected to line-in and the subwoofer connected to line-out.

It should measure a flat response (with soundcard file loaded, and meter cal file cleared and C-weight box unchecked)................

I have a Galaxy cm-140 meter and I have loaded the calibration curve. Should I use it
C-weighted or A-weighted and should I check or uncheck the REW C-weighted box?

Set the Galaxy to C-Weight.

Leave the C-Weight box unchecked in REW. The cal file over-rides it at the cal files frequency extremes.

I read in another thread to press the Apply Windows button to recalculate the frequency response with a calibration file.

This is only required when you change cal files and want to recalculate the frequency response graph from the impulse response rather than take a new measure. The Apply button is in the IR Windows pop-up.

brucek

[stokasz]

Thanks for the help.

I had the meter at A-weighting and the REW box unchecked and was getting a low response. When I switched the meter to C-Weighting and checked the REW box the response looked high. I hope I get to work on it some more tonight.

Thanks again.