Improve your stereo speakers

I've had my Harman Kardon speakers for years and they sound great. Nowadays I use them with my Roland A-88 MIDI Keyboard and Logic Pro X to make some tunes. This morning though, the sound from my HK speakers was crackling. A quick look under the hood and I found that the black cone surround had perished. I tried some rubber glue first - didn't work. Then I remembered my emergency packet of Sugru in my First Aid kit. 20 minutes later, Sugru had my speakers working again. I even used a Sharpie to etch Sugru onto my new white Sugru cone surrounds! Thanks Sugru!