Hello,
Pink noise has a very, very high continuous level across the entire audio spectrum with virtually no dynamics at all. Whereas music is quite the opposite. Pink noise is basically every frequency at full volume at once, not even today's pop music has the same high continuous level across the entire spectrum as pink noise. It's rare to see recorded music with a continuous level above 50% of the peak level (whereas pink is 90%+ continuous of the peak level). The older rock recordings from the tape days are 20-30% continuous.
Mechanically there are a few potential issues using pink noise, especially if used incorrectly. The first is heat. Pink noise generates heat in the voice coils far faster than music; because of the continuous level/nature of pink noise compared to the dynamic nature of music. If you run pink noise at or above the coils rated continuous wattage for too long you will blow the coil and need to get the driver reconed. My towers are rated at 130 watts rms and are a 6 ohm box. My bryston has been measured at over 260 watts at 8ohms, which is going to deliver well over 300 watts at 6 ohms. I can listen to music at the full capabilities of the bryston without damage to the coils because the peaks can't be more than what the amp can cleanly deliver. The peaks are high but the continuous level is within the rated ability of the coil.
I've seen several cones folded when they are new because they haven't been broken in properly. New speakers tend to have very stiff surrounds, especially if they have the accordion type surround. Listening to pink noise at a given volume works the speakers harder than the same perceived volume of music. The surround is typically stiffer than the spider. When the pink noise is turned up too high the coil pushes the cone forward into the stiff surround. If the surround doesn't give in the cone begins to flex, if it flexes too far it snaps and becomes a fold in the cone. Using music which has the dynamics will repeatedly lightly push into the surround slowly breaking it in giving the cone more and more room to freely move until it has full range of motion. Think of it like a muscle. After a 30 minute stretching can you keep your legs straight and touch your toes, or do you need to stretch for 30 minutes for weeks to be able to touch your toes without ripping muscles in your legs...
As the speaker components are used they do wear out. The surround and spider become less resilient. As this happens the speaker becomes less and less efficient at it's specified upper frequency limit. As an example, if you have a bass/mid driver running from 20hz to 2kHz and the tweeter taking over from that; the xover is limiting the bass driver to 2k. As the parts wear out it will have issues producing the 2k because it's not stiff enough to move fast enough. It develops a mechanical type cross over of 1.9k then eventually 1.8k, 1.7k and so on. The tweeter will have the same issue over time starting at its upper limit and working down. With the bass driver the xover may let 2k through to the driver but mechanically it just can't do it.
Playing pink noise speeds this wearing out process. 10 hours of pink noise is like playing music at a higher volume for 40 hours.
The music you listen to will change how fast the components of your system wear out. If you listen to heavy metal your tweeter will wear out far faster than somebody who listens to jazz or classical because the metal music has a lot of aggressive top end compared to jazz. They both have the same instrumentation but the mixing is handled very differently. If you use pink noise too much and or too hard to break in your system and you like classical music you could wear out the tweeter more than intended and miss some of the nice twinkley highs. And if you like classic rock you may wear out the bass driver too much reducing is ability to punch out the drums and bass the way you like to hear it.
Just remember that pink noise generates full throttle noise across the entire spectrum, where as music doesn't. If music did the same it would sound like pink noise.
