Can you help remove my tweeters?

My replacement tweeters have turned up for my credos but I am having difficulty getting the old ones out. Are they glued in? if not they seem very tight. Yes I have removed the 3 screws. I did post a while ago about a problem I had where I had plugged stuff in wrong and had blown the tweeters but the thread has vanished. Any particular reason why?

Sorry, just realised i've posted in the wrong section.