Loudspeaker warranties and black market products

Generally agree with @larryi - if a speaker is well designed and not abused, the chances for a warranty need are exceedingly small.

As a buyer, I honestly care very little about warranty. My concern is for out-of-warranty service - whether it’s because the warranty period lapsed, or product was bought 2nd hand, or via gray market. Will the manufacturer make replacement drivers available for purchase at reasonable prices? Because that’s what makes or breaks the long-term viability of a speaker. 

In fact, if I’m buying high-end expensives speakers new, I’ll absolutely want to purchase and stash away some spare drivers. I’ve acquired spare drivers for my Tannoys over the years, but it wasn’t easy nor cheap - even though I was a buyer from a proper authorized dealer. 

Black market indicates stolen or illegal goods (ivory speaker cabinets, opium infused woofers, etc). I think you menat GRAY market ;) 
I generally have no problems buying gray market if the seller doesn’t seem too sleazy and the risk / reward calculation is good.

In my mind, a good manufacturer will service their producs (for "reasonable" fees) no matter the origin or warranty status. VAC is my gold standard of this so far. Rogue Audio is also excellent. Tannoy - oof, they’re a bit rough. Even since before the Behringer / MusicTribe acquisition. 

A leading cause of speaker trauma is inadequate amplification. Most speakers love current and don’t get well with amps that can’t provide it.

Yep, that is a comon cause of trauma to tweeters - when you over-drive with an under-powered amp.

Why? Because normal musical content is comprised of roughly "equal energy per octave", which means when you have a tweeter crossed over at say 2K - 4KHz, it only "sees" a fraction of the overall signal energy. Perhaps around 10 - 20% at most. Tweeters are made to be nimble & lightweight so they can extend into higher frequencies with lower distortion, and this goes hand-in-hand with lower power handling - so the tweeters in most speakers have an actual power handling that is much lower than the speaker’s rated overall power handling - which works OK as long as you feed the speakers a normal music signal. But when you overdrive an amp into hard clipping, those sharp / squared tops are not like normal musical signal. They contain transient energy at very high frequencies (above tweeter crossover) and at a level up to 2x the amp’s maximum continuous power (because a square wave is not a sine wave; it has 2x the area under its "curve"). So basically, the tweeter gets "shocked" with the amp’s full power (and then some), which it was definitely not designed to do. This is why "too little power" gets a reputation for killing tweeters. But at the end of the day, it’s power that kills tweeters, so you could equally kill them by using a kilo-Watt amp at WAY too loud of a volume! It would be an SPL level that runs most people out of the room (if not house), but then some of us are built different :)

And some tweeters are just tougher than others. Compression drivers (like Tannoy "pepperpots") tend to be pretty damn tough, because they have much larger voice coils (2" or so), which can better absorb and disspate heat. 

The ferrofluid in some tweeters (like Tannoy "tulip" waveguides) is meant to absorb the heat energy away from the coils, but it can dry out from too much. And also over time. But this is usually quite serviceable -  clean out the old fluid and add a little new fluid of the right viscosity.

Surrounds should also generally have the ability to be repaired / replaced. Some types are tougher than others. Treated fabric / textile surouns can be VERY tough and long lived. They even stand up really well to cat claws (don’t ask lol). That’s my favorite (again, found on Tannoys). But the driver needs to be designed around that. 

The hardest to fix issues are going to be blown or bashed-up voice coils, and fractured metal cones or domes.