Hi guys, I've posted on this many times in the past, but most will have a hard time grasping the situation until you start looking at Energy Time Curves and real measurements beyond the Radio Shack meter. Your receiver is likely correct relative to where you located the mic. What many forget is that any low pass filter results in what is known as group delay which is frequency dependent. What this means in the real world is that if we place a common tweeter and a subwoofer at the same distance from a mic and send them the same test signal, the sound from the subwoofer will arrive at the mic later than from the tweeter. If we have measurement equipment capable, we can also see that group delay is rarely constant, and below some high frequency, generally increases with lowering frequency. When we design a loudspeaker or optomize a loudspeaker system, we would prefer that in the range where two drivers cross over(and are both playing), the sound arrive at nearly the same time from both drivers. The fact that this "fixed delay" changes with frequency makes this more difficult, but we generally find that as we lower the crossover frequencies, the delays grow longer. We find that we would like to delay the higher frequency sections to better match with the lower frequency sections. Before I go further, let me clarify that this is different than how the distance settings are used for the 5 or 7 channels in a home theater. For the main speakers we are primarily looking to equate arrival times in the interest of not skewing the image. Curiously, we find a distance setting for the subwoofer as well... This obviously is not to aid in directional confusion, as there is commonly only 1 subwoofer, and directional ques are dominated by higher frequencies. This delay/distance setting can only be meant to adjust the relative arrival of the subwoofer to that of the main speakers. In my own experience I have found measuring and setting this properly to have significant sonic benefits. In reality, this is somewhat like a different form of a phase control, yet the phase control on your subwoofer delays the signal further, where setting the distance longer than your mains in the processor will actually delay your mains speakers to "wait" for your subwoofer to catch up. Now I'm not saying your system can't sound great without carefully measuring and adjusting this parameter. There are many compounding factors which could make the real distance for the subwoofer an appropriate setting. That said, if you want to play with this as a sort of phase control and can't measure energy vs. time, you have a good bet by counting on the subwoofer being later than the mains, so start investigating by making the virtual distance of the subwoofer longer, not shorter. Enough for one post... Cheers,
