This Electro - Voice ELX200 - 18S passive subwoofer offers great audio performance. However, there's a small stain on the grille as shown in the pictures.

To use this subwoofer, first connect it to your audio system using the appropriate cables. Make sure the connections are secure. Place the subwoofer in a suitable location in your room, as its position can affect the sound quality. When it comes to volume, start at a low level and gradually increase it to your desired setting. As for maintenance, keep the subwoofer clean by gently dusting it regularly. Avoid exposing it to moisture or extreme temperatures. If you notice any further issues or the stain on the grille gets worse, it's best to consult a professional technician.