This subwoofer suffered some shipping damage on the top rear corner. A claim was filed, but I will be keeping the sub and get parially reimbursed by insurance. I'm no DIY, but just want to patch this up and paint it black so it blends in better. I was thinking maybe a black dyed polyester resin.
Really blurry pic. Sand it out so the edges of the damaged area are smooth. If it is MDF, you will then want to seal the grain, you can use resin like you said, but wood glue diluted with a little water works too. Then you will need to build the corner back up, bondo works very well for this. Apply bondo/sand/apply/sand until it's flush and level, then paint black.