[thewire]

Andysu wrote:

One thing I’ve noticed is when conducting (sound check before frequency sweep) is that the sound check is never the same twice when repeating the test in the same position. That is the level is too low or it’s okay. Now is there a reason for this?

Thanks.

Your pink noise level for example when using the subwoofer level in the generator (in tools) or as when you setup the settings such as when doing the "check levels" there should = 75dB on your SPL meter and also 75dB in REW. Try lowering the wav volume then gradually (very slowly) adjust the level until your meter says 75dB. I have found it can take anywhere from 5 seconds up to 30 seconds to get this proper. Determining the proper sweep level can be indicated at the top of the bars during the check levels setup. Watch that each does not go red as this will cause clipping during the test proccess. Even better yet turn on the SPL meter in REW by pressing the red button and watch this reading costantly. During the setup proccess it will tell you if the sweep is appropriate because your reading at 75dB will not fluctuate. The different numbers bellow should be within 10dB from eachother. Then when you go to check levels watch again and if the SPL reading has not settled correctly to within at least .5 of your target (being 75dB for example 74.8 is acceptable IMO). Don't forget to calibrate the SPL meter when you begin to see it stabilize. If anything goes wrong, check your soundcard or try using different sweep levels with the generator again to see what is most stable and how smooth sounding the noise from the subwoofer has become.

Taking the time to verify the inputs accuracy and setup REW much slower than one might think to do so will result in my better testing over longer lengths of time as I have discovered spending almost full days doing so. Watching movies before testing helps also. I hope this makes since.