Do speakers have to "warm-up" too?

Good question. I've never seen or heard of a speaker manufacturer talk about "warm up time." It makes sense to me, but I tend to agree with Beavis that the amps, and possibly the pre (provided your using a pre)(and even with standby mode), are still warming up.
Especially if your running large monoblocks.
Of course, I only listen to music whilst sipping my favorite beverage.
And the more I sip, the better it sounds (usually). ;-)

Beavis, perhaps, but remember, in the post french_fries says he lets his amps run for 30 minutes before putting any signal through them. Now Perfectionist has the right idea when it comes to listening enjoyment!

I doubt that there is much warmup for speakers. Conceivably, the suspension parts (surround, the spider, etc.) could be warmed by friction, but I have never heard of that making an appreciable difference. The voice coil itself is NOT a moving part in that it should not be rubbing against anything so there is no issue of a change in friction coefficient.

If anything, the resistive heating of the voice coil from usage should detract from sound quality by causing compression. As the coil warms up resistance increases and the output of the driver will fall. I would expect hard usage to temporarily adversely affect the sound quality, not improve the sound.

Sure, speaker probably do have a warm up time. Many contain capacitors, resistors and inductors that change as signal passes through them.

My Sound-Labs were very slow to warm up in spite the amount of time the electronics had been on. Sound-Labs back plates contain two large transformers, (one EI and one Toroidal). Also, 8 or more resistors (depending on which version you have), a brilliance control, switches for mid and bass EQ and several caps. All these are in the signal path.

No doubt there are other examples of speakers with similar parts, even if much fewer that this example.

As for the voice coil improving or suspension freeing up too? Could be, I would not argue with anyone who says it does.

If you have a hummm in your system the speakers will worm up before you start listening...:-)