I am planning ahead for getting an A88X chipset motherboard and have only a couple of options to get but they both have two fan connectors. I am currently using a Xigmatek Dark Knight Night Hawk Edition Heatsink fan in one header, two CF-V12HP Cougar Fans with a Y splitter at the top and back of my case in another, and a Noctua NF-A14 at the front of my case for the third header.
Can I use another Y splitter for the Noctua and and Xigmatek fan to let me use the two headers that will be available or will this decrease the speed of the Xigmatek fan which runs 700 RPM faster than the Noctua 140mm fan?
If they are both PWM (4 pin) fans, then they would be controlled by the PWM signal and should run at their respective rated speeds depending on that signal. What you would need is a splitter that has one fan connector with all 4 pins and another with only 3 pins (the RPM or sense signal needs to be disabled on the second fan or the controller will get confused). PWM uses a constant supply voltage and varies speed based on the 25KHz PWM signal. My AIO cooler uses this setup to control 2 or more fans on one header.
If one of them is a DC (3 pin fan) then you wouldn't be able to mix them since the supply voltage is what is varied on a DC fan to control speed and at best you may be able to get the PWM fan to adjust speed, but the DC fan would be maxed out due to the constant voltage needed by the PWM fan.
This may be what you are looking for: Silverstone CPF01.
You should also check what the max rated current draw is on the fan header for your mobo and make sure that the comibined current draw of the 2 fans does not execeed it.