Low Volume Output ddj-400 on speakers

i connected my ddj400 to harman kardon speakers (max volume on speakers already) , and the speakers won't go loud. i trim all the channel level meter to 0db (2green - 1st blinking orange), also the master level is set to 2 o' clock (0db). *my speakers gets loud 100% as it should be on bluetooth connection with phone but when connected to ddj400 it can be loud for only 50%. is it because of the soundcard on ddj400 is weak so the signal strenght is weak too. do i have to switch to ddj800 or ddj1000? will it make any different? i want my speakers to get loud as it nomally does.