How old is the TV?
Consumer law isn't governed by warranty durations per se (which is why you see 'this does not affect your statutory rights' on warrantees and guarantees etc)
An item sold has to last a "reasonable" length of time. If, say, it was only 2 years old you can easily argue that isn't a "reasonable" length of time for the speakers to survive. You may even find it can be traced back to a design fault at time of purchase.