There's a known issue where the grille foam is missing.

Using this D&B Audiotechnik subwoofer is easy. Just connect it to your audio system as you would with any other subwoofer. Make sure the connection is secure for the best sound. As for the missing grille foam, it doesn't affect the basic function, but you might want to be a bit more careful around the grille. For maintenance, keep it in a dry place away from direct sunlight and moisture. Regularly check the connections to ensure they're still tight. That way, you can enjoy great bass from this subwoofer for a long time.