Matt- Offset tweeters are to randomize the distances of the edges to the tweeter and reduce the diffraction ripple in the response. BSC is a compensation of the baffle-step loss below the point where the wavelength equals the width of the baffle of the speaker. Baffle step loss is mainly a low frequency issue loss due to the cancellation of waves wrapping the perimeter of the cabinet. There is a peak before rolloff as well that sometimes has to be dealt with.
Thanks Ben. I definitely need to read more on BSC and just exactly what that is and how it's corrected. After I posted my original response, I started reading. Signals below 750 Hz will move around the cabinet's baffle, while signals above that will play forward (the higher you go in the FR, the more forward they play I'm guessing?). So if you have no BSC to compensate in the loss of frequency from the waves moving around the baffle, you'll have a bright or thin sounding speaker. Correct?
Most of this^^ was taken from here... http://www.salksound.com/wp/?p=42
I actually read Salk's explanation a while ago, and I've had Jeff's blog printed about this for a long time now. It's funny how the further you go in speaker design, the more this stuff starts to make sense
I do understand diffraction as it relates to flush vs top mounting a tweeter or centered vs offset, I've actually played with it and can't hear the difference between offset vs centered tweeters in a standard baffle. I had BSC and diffraction confused with each other