Hi Pavan Kumar,
Dell XPS 14 L401X supports both 1066 and 13333MHz memory types. However, the speed will be considered based on lowest memory module as mentioned in my previous response. Request you send me the system service tag via private message. I will check and see the reason you are unable to detect the tag. Also let me know if the sound is working fine now
To send a private message, click on my user name and select start conversation.