I know you have to change the voltage for the fans to change speeds but how. i only have 2 headers (1 3pin 1 4pin) do i need a controller? can i use bios or software?
What motherboard do you have? Its been a long time since I've seen a motherboard with a 3 pin fan header, they are all 4pin PWM nowadays
But yes in the BIOS you should be able to set the fan curve for each header.
Make sure the other fan is in DC/ Voltage mode and not Auto or PWM. That should allow you to change the fan curve then.
Did some research it appears your mobo doesnt support 3pin fan control. You will either need to get a fan controller, or more simple and cheaper get something like this https://www.amazon.com/Noctua-NA-SRC10-Accessory-Low-Noise-Adaptors/dp/B00KG3KELQ
You can look around but basically those cables are either called low noise or resister cable adapters.
Only two I know of and I don't know how 3 pin fan control works with them. Personally I only have 2 fans ( 200mm on the front and 140mm on the back) on my case, and it provides more then enough air flow.
https://www.amazon.com/Phanteks-Uni...ords=cpu+fan+controller&qid=1580159161&sr=8-8
https://www.amazon.com/SilverStone-...ords=cpu+fan+controller&qid=1580159161&sr=8-5