Yes, your receiver does send everything out at the same time, but it does not compensate for your room acoustics and speaker placement. The placement of your subwoofer in relation to your front speakers may cause a phase issue, as the sound waves from each speaker will interact differently with your room and reach your ears at different times. The best way to adjust your phase will require an audio test tone CD and two people. You will need to wire your main speakers out of phase (i.e. reverse the + and - wires on the back of the speaker), then play the test tone at the crossover frequency (typically 80Hz). While you are seated in your typical listening position, have a buddy slowly turn the phase adjustment knob on the back of the subwoofer until you hear the LEAST amount of bass. At this point, your main speakers are completely (180 degrees) out of phase with your subwoofer. When you have reached this point, you will want to switch the wires back to normal on your main speakers, thus putting your main speakers perfectly in phase (0 degrees) with your subwoofer.