Please help, I may be having problems setting up REW correctly

I can post graphs if you all would find that helpful. I am using a realtek sound card, Radioshack Digital SPL meter, and the current version of REW. I set it up as I thought it was supposed to be, and I am getting accurate SPL readings I believe, once I set the reference, but I don't seem to be getting accurate bass measurements. Instead of the expected lumpy response, I have a very smooth graph which from 20hz to DC has an ever increasing slope, I believe in the 24db per octave range. This obvisouly makes no sense, so I must assume something is wrong.

I calibrated the soundcard, I thought, but may need to redo that. I also loaded the SPL meter file, and set levels accordingly. I seem to be getting an impulse response, though I don't know if its accurate, it at least looks plausible.

[JohnM]

Sounds like you might have selected an internal or external loopback as your input so you are just seeing the inverse C weighting on top of the flat response of the loopback. Make sure you have selected the correct input channel (i.e. left or right according to which input channel your meter is connected to) and the correct input on your sound card (usually Line In) and if your soundcard has 1/8" connections make sure you are using stereo jack plugs.