I just used Elemer's sticky-puddy (same idea as Blu Tak) to fasten down my kid's train track and it would be good alternative to Blu Tak. It's soft, the color of an eraser, and can be reused. Noel from Skylan Stands recommends an alternative you can buy at Home Depot made by 3M that isn't quite as sticky but also won't rip the vinyl veneer from your speaker box, something Blu Tak has been known to do if you don't twist it off the stand correctly. Bottom line, there are other options than Blu Tak.

Good luck