Originally Posted by Digital_Chris
I have my SR5003 reciever, "component SW out" to subwoofer amp which then connects to the sub across the room via 12ga speaker wire. For the test, I'm running a PC laptop with SoundBlaster USB sound card. RShack meter "out" to soundcard "in", "out" of sound card into left channel of front AUX input on receiver via RCA cable. Mic mouth is about 6-7 feet from "mouth" of subwoofer cab.
If you're game, I'd like to strip things down a bit, and measure the direct electrical response of the 5003.
1) Turn off any Audyssey modes. Turn off surround modes. Do not use "Direct" modes. Plain stereo, bass management turned on.
2) Feed the soundcard output to Aux 1 (on front panel), either channel.
3) Connect the 5003 SW output to soundcard input. Adjust volume to get decent REW readings.
4) Run REW sweep. It should show the 60 Hz LPF response.
If the 60 Hz filter looks right, then you can re-connect the SW output to the sub amp, and again measure the SPL with the RS meter. The same general filter shape should result. But if it looks like your original plot, there's something odd happening.