Why are is my memory running at 2400 MHz when both the sticks are 2666 MHz models?

[Fimmt]

So, I just installed a second 8 gb ddr4 memory module (HyperX Impact) in addition to the default one ( Samsung M471A1K43CB1-CTD). Both have a standard speed of 2666 MHz (and so it confirms the HP diagnostics tool, too) but for some reason, after installing the newly purchased one they run together at a speed of 2400 MHz, which honestly confuses me since even my chipset has a standard speed of 2666 as well. Would really appreciate some help with this.

[Riddle_Decipher]

@Fimmt Here's a list of parts tested and approved to work on your device:

For details on how to replace the same: click here & visit page. 44 Chapter 5 Removal and replacement procedures for authorized service provider parts

P.S: Welcome to HP Community 😉

Let me know how that pans out,

If you feel I was helpful, simply click on Accept as Solution to help the community grow,

That said, I will have someone follow-up on this to ensure you've been helped,

Just in case you don't get back to us, 

have a good day, ahead.