@audiokinesis can you expand on how low, or how much of the phase curve that's low inductance, at low impedance is acceptable for most tube gear? I don't want to hijack the thread but isn't this the crux of amp/speaker "synergy" save perhaps efficiency? Also, every XO has a resistor value on at least one driver so the designer is making an "eq" choice for us (other parameters notwithstanding) whether we know it or not. Lots of speaker DIY sites will show final responses with different R values for the builder to mull over. Not all ears and rooms are equal.