Open box means: the product is still in brand new condition but has a damaged packaging.
The product is still under the 1 year limited warranty.
Warranty doesn’t cover:
Damage due to misuse of product
Damage due to using the product outside of the recommended specifications.
Damage due to negligence or abuse
Improper installation (including professional installation)
Damage due to clipping, overpowering and/or distortion (improper tuning)