Motherboard I have is https://www.asus.com/Motherboards/Z97DELUXE/specifications/Might work with motherboard adjusting timings to suit the slowest, but it's a might. Might being, mixing is a gamble.
What motherboard do you have? I suggest going 2x 8GB 1.5v Gskill or Corsair DDR3 ram to keep things simple.
It just works, not sure how to check at what voltage and speed?Ok cool so what's the situation now?