Hey Roy, I have used a couple of different scenarios. I am currently using the Checkmate Galaxy CM-140, but I have also used the Radio Shack analog meter and the Behringer ECM8000. So far, the CM-140 is my favorite as it has an great built in condensor mic inside.
I use a Radio Shack SPL, but that doesn't have anything to do with why the card showed itself to be 9db down at 20hz before I made the correction calibration. When I ran the calibration test for the card the meter wasn't connected. I am aware that the figure closely resembles the generic correction figure for the RS Meter which could have someone misunderstand.
Once I caliblrated the card I was flat from 20-20,000, and there was some variance lower than 20hz.
I'm trying to see if this cards performance shows itself not well suited for movies or music with content less than 30hz, as this is where the roll off starts with my particular card. Since you can use REW to see how a sound card performs, I am just asking if any other users of this card can verify rolled off response starting as high as 30-40hz. I know most sound cards tend to have roll offs at the upper and lower limits of their bandwidth, but it is a $65 card that we are trying out amongst others to see how well it performs.
ok thank you, would the crossover introduce a roll off starting around 40hz, or should I say be detrimental to the cards native frequency response? I ask because these types of roll offs are typical with sound cards but usually start more commonly around 20hz. I didn't have the sound cards crossover activated when I did the calibration with left channel loopback. I just noticed that the card doesn't seem to have a very good native FR.
In the setup I am using, I am measuring room response with powered monitors in a home recording, reference monitor setup. So I have the left and right RCA line outs going to the powered monitors, the line out for the sub is done through a mini jack to RCA adapter. This way he will have full range with his system. The monitors roll off around 50hz.
When taking measurements I use the internal crossover in the sound card set to 80hz and can run sweeps showing me how well the speakers integrate with the sub. We have achieved pretty good results. Any change I make to the crossover clearly shows up in the graphs. I have graphed each speaker independently, as a full range stereo pair, and as a 3.1 setup. All graphs show a proper 4th order crossover slope when it is activated and the sweeps are independent to one speaker, the monitors running in stereo, or just the sub itself.
9db down at 20hz native response doesn't seem too abnormal to me for a $65 External Sound Card, but I will check each configuration as you suggested so that we may have a better understanding of what this card is capable of.