[Q] Change boot logo in CM12.1

Hi everyone.

Two days ago I installed AK kernel v306 and my boot logo was changed to a 2-part logo: the oneplus logo followed by a small ak logo.
Today, after flashing the new kernel version (307) the logo was changed again (now only a big ak logo).

Can anyone point me out (if there is) a way to change the boot logo back to the original one?

Thanks in advance.