Does anyone know of an active, dsp, phase correct/coherent speaker?
I have seen one claim from the DIY community that was able to produce a perfect step response but I can't personally vouch for it. He claims that he uses DSP to delay the tweeter so that it matches with the mid range (the equivalent of tilting the cabinet as in Thiel design), but other than that, I don't know anything else.
I think using active DSP has its own drawback. It's not all that it claims to be. In someway, it's even more complicated than passive cross over. For example, for a three way, you need six different amplifiers and six different DAC's. I mean one amplifier is expensive enough. In order to have six, you have to use inexpensive amplifier such as digital amplifier, so the quality of the sound is heavily compromised. Likewise, with six DAC, you have to compromise as well. So everything considered, using active DSP is a compromise approach.