Can you hear the crossover point of a speaker with a well-designed crossover?

[catapult]

with a well-designed crossover?

The definition of a "well-designed" crossover is one where you can't hear the transition. So, by definition, the answer to your question is no.

[Shaun]

Firstly, the drivers need to be of similar technology, so that the radiation pattern can be similar. For instance, it's not easy to integrate a monopole configured driver with a dipole configured driver, because of the different power fall-off rate as the distance from the source is increased. But it's not impossible to achieve good result this way.

Then, the correct crossover point and driver sizes should be chosen, or you'll get a poor off-axis response (1" dome tweeter with 10" woofer is good example of a bad combination), as the radiation pattern of a dynamic driver narrows with increased signal frequency. A driver typically has good dispersion at the lower frequencies, but starts to beem at the upper end. So you need to cross over to the next driver before the off-axis response of the driver in question falls off too much. And the next driver has to have sufficient power handling capacity, or it will result in distortion. (When I say "next", I'm progressing from lower frequency to higher).

Good off-axis response is essential in a reverberant/"live" environment. Now, it is acceptible for the system response to roll off when observed from off-axis, but the transition must be smooth, with minimal dips or peaks.

Look up some nice papers from Harman Kardon on this subject. I don't have the urls, sorry.

Hope this helps...