One notable issue is that the grille foam is missing from both speakers.

To use these D&B Audiotechnik Ci90 loudspeakers, first find a stable and suitable location for them. Place them at an appropriate height and angle to get the best sound coverage. When connecting, make sure to use the right cables to connect to your audio source. As for the missing grille foam, be extra careful not to let dust or small objects enter the speakers. To maintain them, regularly clean the exterior with a soft, dry cloth. Don't expose them to extreme temperatures or humidity. Also, check the connections from time to time to ensure they are secure.