The example by Erin's complex load is a mild one with a 20 ohm peak. It can easily get to 60 ohm for some speakers and high ° of phase. This exaggerates the issue even more. For 3 or 4 way crossovers it could also be present at even lower frequencies. You can see from the trace that even the mild 20 ohm peak has ripple effects much below its actual peak frequency.
Also; if you'd be so kind to combine your responses into less posts if you respond to many different ones at the same time. You can make several quotes into one post. This make the thread look a bit cleaner.
I'm sure, as I said, that there may be some cases where a particular speaker may be more susceptible to this. And there are undoubtedly people who are more sensitive to this.
In my case, I looked at the impedance load of the driver from 175hz-7khz that the amp would be driving. I was not concerned about the amp that would drive >7khz because I don't think I'd notice it, and besides, I knew I'd be able to adjust the crossover pot when using my pink noise generator and spectrum analyzer to adjust the volume of the four separate drivers in each channel.
And then, there's the reality that what happens on the recording end has so much influence on what you're hearing on the playback end, that these still relatively small differences may help in some cases, hurt in others, and not matter at all sometimes.
Re posting answers to different questions in the same post, I actually find it's a bit disjointed. And I think what you're seeing is a flurry of posts from me, because I started reading this thread from its inception, and had comments to the earliest posts.
doug s.