I own a pair of Avance Signature mk II, the bass speaker of one speaker is broken and I need to replace it. Anyone of you could help me where I can find spare parts for Avance speakers?
I would first contact a retailer for the line. If the company is still doing business somewhere in the world, they are obligated to carry replacement parts for at least five years. If the speaker was prone to damage, it's possible a dealer has a spare woofer in stock. If not, then I would make an educated guess that the driver is a fairly generic unit supplied by a larger manufacturer such as SEAS or VIFA. Contact a driver retailer such as Madisound or PartsExpress and discuss the possibility of finding a replacement driver in their stock. If the driver was built by a larger supplier such as VIFA, then you may or may not be lucky enough to find they used a driver which is easily replaced. On occasion a speaker manufacturer will have a company like VIFA take an off the shelf driver and hand tool it to their specs. In that case you'll need to replace the bass driver in both channels.
It might come down to buying a pair off eBay or the like and having spare parts available since small speakers can be fairly easily damaged by large amps. There is the final possibility that a local rebuilder could fix your current system though experience says the repaired speaker systems are never exactly like what you had. Check with any local pro sound shops for a source for speaker rebuilds.