My two Noctua fans can't both be controlled at the same time. =/

I can't find the low-noise adapter. =/

I do have a regular y-splitter in my possession right now. As I said, because one of them is plugged into the 4-pin header, that seems to be the only one that is being controlled in my BIOS. The other one can't because it's a 3-pin CPU fan header, right? So plugging the two fans into the y-splitter and plugging that into the 4-pin CPU header will fix the problem?

It's not a 4-pin splitter; it's a 3-pin y splitter that can have two 3-pin fans into it. Now, someone else told me that there's no point to have both the Noctua fans installed if I'm not gonna be OC'ing. So wouldn't it be better to just have one of them in and have that one controlled by the BIOS?

Yeah, well I intended to OC so that's why I bought the Noctua NH-D14 a while ago, but then decided not to OC so I went and bought the Cooler Master 212 EVO because I wasn't gonna OC and because it's smaller, too. I took that off cause I thought my idle temps were spiking because of the cooler itself so I reinstalled my NH-D14 again. So in that sense, I think it'd be better just to reinstall the Cooler Master 212 EVO I bought cause it has one fan, the fan is great and I don't OC, so it all works out.

UPDATE: So I have my 212 EVO reinstalled and it's running smoothly. It's definitely not as loud as my NH-D14 because it only has the one fan. Plus the fan is running at 900 RPM at level 1 speed in BIOS. Plus my BIOS fan control is set to speed up my fans if my temps exceed 45 degrees. Also it's more quieter simply because the NH-D14 ran two fans at a total of a near 2000 RPM, while the 212 EVO has one fan running at 900 RPM. So that really makes a difference for me. The only thing that I noticed is that my temps stay at 44-46 degrees, in which case my fan speed till go up cause it goes past 45 degrees, and seems to take a very long time to go back down below 45. I ramped up the fan speed to 1200 RPM and it didn't change much. =/ What is the danger temps for a i5-2500k? If my temps aren't anywhere near that, cause they're between 43 - 46 on idle, then should I be worrying so much?

My processor does downclock when I'm not doing CPU intensive tasks, yes. I have my power settings either on "power saver" or "balanced" when I'm not gaming as to save energy. I only have it on "high performance" when I'm gaming. How the heck is downclocking a reason for my temps to be high? I think you mean that if the clock speeds go "up" that it'd raise the temps, right? Are you sure that in the 40 degree range is considered "a little high"? Because I don't think so, but then again you could be right. No, I don't know the ambient temps. How would I even know that? It's a old house so it's hard to know what the ambient temps are. That may sound strange, I know. But it's true; there's nothing in the house to tell me what the temps are. It doesn't feel hot in here so I'm sure that's not the cause of the CPU being in the 40 degree range. I've heard of others online that had that temp range, though. My case has two 140mm blue LED fans on the front, a rear 120mm exhaust fan, and one 120mm on the 212 EVO. Now, every fan besides the rear exhaust is on lowest setting to have the quietest PC I can get. Should I turn up the fans? I should also mention that even with the Noctua NH-D14, which has two heatsink towers and 2 Noctua fans, I still got low 40's temp range. So I'm not sure what is going on. I honestly hate my ASRock Z75 Pro3 BIOS control for my fans. I don't like having to go back and fourth into my BIOS just to change the fan speeds. I'm planning on getting a third-party fan controller, like the Sentry 2 Mix controller. I'm looking to have a quiet, but cool efficient gaming rig. At the moment my front fans and 212 EVO fan are at the lowest setting in my BIOS. Just to get my temps to 42-43 degrees I have to turn my front fans on max settings and my 212 EVO on half. So with the 212 EVO installed I'm getting between 42 degrees and 46 degrees. Slightly higher than when I had the NH-D14 installed, but I assume that's only because the NH-D14 has two heatsink towers and two Noctua fans, where the 212 EVO has only 1 heatsink tower and only 1 fan. Now, while I believe my idle temps are okay, there's some that don't think so. I reallllllly don't want to have to reinstall my NH-D14 for the 4th time because not only am I running out of thermal paste that came with my 212 EVO, it's so tedious to install it and route the cables so it looks clean. Bad enough the installation for the 212 EVO was complete torture when I first installed it. =/ Not only that, but the Noctua fans are hella loud! I can't find the low-noise adapter that came with it so that option is out the window. I do have a simple 3-pin y splitter to hook two fans into and plug that splitter into the CPU header, but I was told that it'd be a bad idea to do. I don't play many CPU intensive games so it's not an issue for me. I'd say the only CPU intensive game I played was Final Fantasy 13 for the PC. Some may not think it takes a powerful CPU to run it, but I believe it does. Like I said, in the house there's no temp monitor or anything to indicate what the ambient temps are here. All I can tell you is that it's not boiling hot here and sometimes it can be cold. I do live in eastern Canada, of course. It's not like I'm in the states where it's hot enough to fry an egg on the sidewalk. lol. I'd like to add a top fan, but I tried putting the spare Noctua fan I had from the cooler and it's loud. I'm gonna have to get a 3rd party fan controller because I honestly hate my BIOS fan control. =/ I want my rig to be as quiet as can be, but I don't want to have to keep my fans on 100% speed just to cool it down by a few degrees.