I have not looked at mine, but looking at many other oem speaker systems - the door gets full range and there is a simple high pass filter at the tweeter.
This is true.
I don't know it is a true full range, I'm betting the stereo has a highpass that will filter out all the extremely low notes that they don't want to ruin the speakers with.
I'm not *positive* on that, but I do know that I can get a bit of bass distortion from my front speakers with the upgraded DSP amp.