A magnetic assembly (x00) for producing an optical effect layer (OEL) on a substrate (x20), said magnetic assembly (x00) being configured for receiving the substrate (x20) in an orientation substantially parallel to a first plane (P) and above the first plane (P), and further comprising: a) a first magnetic-field generating device (x30) comprising three or more first dipole magnets x31 ai (x31 a1 , x31 a2 , ...), each of said first dipole magnets having its center C x31-ai (C x31-a1 , C x31-a2 ,...) disposed on a loop (x32) in the first plane (P), wherein said first dipole magnets x31 ai (x31 a1 , x31 a2 , ...) have their magnetic axes oriented to be substantially parallel to the first plane (P), wherein said first dipole magnets x31 ai (x31 a1 , x31 a2 , ...) are at least partially embedded in a supporting matrix (x33); and b) a second magnetic-field generating device (x40) comprising a second dipole magnet x41 having its magnetic axis oriented to be substantially perpendicular to the first plane (P) and being arranged to have a projection of its center on the first plane (P) be located at a projection point C x41 within the loop (x32), wherein the second magnetic-field generating device (x40) is disposed above the first magnetic-field generating device (x30), characterized in that angles α i are formed between each of the vectors C x 41 C x 31-al ( C x 41 C x 31- a 1 , . , ...) and the vector h x 31- al ( h x 31- a 1 , h x 31- a 2 , ...) of the magnetic axis of the respective first dipole magnet x31 ai (x31 a1 , x31 a2 , ...) wherein all of the angles α i , when measured in a counterclockwise direction, are in the range from about 20° to about 160° or in the range from about 200° to about 340°, and wherein each of the first dipole magnets x31 ai (x31 a1 , x31 a2 , ...) is disposed at a first distance (Y i ), said first distance (Y i ) being on the first plane (P) between the projection point C x41 and the center C x31-ai (C x31-a1 , C x31-a2 ,...) of the first dipole magnet x31 ai (x31 a1 , x31 a2 , ...). a) a first magnetic-field generating device (x30) comprising three or more first dipole magnets x31 ai (x31 a1 , x31 a2 , ...), each of said first dipole magnets having its center C x31-ai (C x31-a1 , C x31-a2 ,...) disposed on a loop (x32) in the first plane (P), wherein said first dipole magnets x31 ai (x31 a1 , x31 a2 , ...) have their magnetic axes oriented to be substantially parallel to the first plane (P), wherein said first dipole magnets x31 ai (x31 a1 , x31 a2 , ...) are at least partially embedded in a supporting matrix (x33); and b) a second magnetic-field generating device (x40) comprising a second dipole magnet x41 having its magnetic axis oriented to be substantially perpendicular to the first plane (P) and being arranged to have a projection of its center on the first plane (P) be located at a projection point C x41 within the loop (x32), wherein the second magnetic-field generating device (x40) is disposed above the first magnetic-field generating device (x30), characterized in that angles α i are formed between each of the vectors C x 41 C x 31-al ( C x 41 C x 31- a 1 , . , ...) and the vector h x 31- al ( h x 31- a 1 , h x 31- a 2 , ...) of the magnetic axis of the respective first dipole magnet x31 ai (x31 a1 , x31 a2 , ...) wherein all of the angles α i , when measured in a counterclockwise direction, are in the range from about 20° to about 160° or in the range from about 200° to about 340°, and wherein each of the first dipole magnets x31 ai (x31 a1 , x31 a2 , ...) is disposed at a first distance (Y i ), said first distance (Y i ) being on the first plane (P) between the projection point C x41 and the center C x31-ai (C x31-a1 , C x31-a2 ,...) of the first dipole magnet x31 ai (x31 a1 , x31 a2 , ...). <EOS>