It made a low throbbing/buzzing noise with the LED turning red and the woofer cone visibly moving back and forth. Then it got worse and the woofer cone just lurches violently back and forward again with the red light. I'm happy buying components and replacing them and also measuring voltages across various points. I'm not sure what version of the speaker this is and where I might start. I've seen similar threads to this but the speaker insides look different. I have some photos. Thanks Andy

Audio Players & Recorders - Alesis