[JohnM]

Well, yes and no. You can determine the delays in the system being measured based on the location of the peak of the impulse response, but the width and risetime of the peak depend on the range of frequencies the system producing it can reproduce. Main speakers, when tested with a full range signal, produce nice sharp peaks and easily measured delays. On a subwoofer the impulse response does not look much like an impulse, it has a slow rise and a broad peak because it cannot reproduce high frequencies, so using the time to the peak of the sub response and trying to compare it with the main speakers is not comparing like with like. You may find that using a sweep that only covers the range both sub and mains can reproduce would give impulse responses from each that are more readily comparable, otherwise it will be interesting to see if Mike can find the article about this topic.