NF-A9
We consider the 92mm NF-A9 to be a heat sink fan, we have seen this size used a bit by Noctua in the NH-U9S, NH-D9L and NH-L12 (NF-B9 is used in the L12) coolers. Whilst you could use a 92mm fan as a case fan, after looking recently, we could only find a few cases that actually have 90mm fan mounts. 80mm, 120mm, 140mm and up seems to be the focus of chassis manufacturers now.
If you are using a small form factor case and can’t fit a 120mm cooler, you have 3 options, a water loop (AIO or custom), the stock cooler (no thanks) or a 90-92mm aftermarket cooler. If you decide on the latter, you are accepting that the fin stack and heatpipes are going to be smaller with less surface area than the larger heat sink coolers and airflow is more important. Accepting physics doesn’t mean that you want a leaf blower in your rig to keep the CPU cool. This is where the NF-A9 comes into play. We have seen the NF-A9 4-PIN variable speed (PWM) used on the newer NH-D9L and NH-U9S and it’s a ripper – it even handles overclocking.
The NF-A9 replaces the older NF-B9 which is also still available in a Redux version. Noctua provided 2 versions of the NF-A9 for review, the flexible fixed speed (FLX) and the 4-PIN variable speed (PWM) that can be controlled via a motherboard header.
NF-A9 FLX
The NF-A9 FLX can operate at 1600, 1250 or 1050rpm with the assistance of the included LNA and ULNA accessories.
In our testing, the decibel meter struggled to give us a consistent reading above 18.5dB(A) at 30cm with the fan running at 12V/1600rpm. Although we could hear a slight hum at this speed in open air testing, the pitch wasn’t annoying nor noticeable. The airflow at full tilt was strong and steady at 60cm.
Then we attached the LNA and ULNA – what noise? the NF-A9 FLX became almost silent except for the very soft sound of the air passing through the fan frame and fan grill at less than 30cm. Inside a chassis, it was inaudible to me with either the LNA or ULNA fitted and borderline audible at 12v but your experience will vary depending on your case selection.
NF-A9 PWM
The NF-A9 PWM has a 4 pin fan header and operates at up to 2000rpm or 1550 rpm with the LNA fitted. This fan is suitable for the NH-U9S, NH-L12 or NH-D9L CPU coolers.
We added the NF-A9 PWM fan to our 92mm coolers to run them in dual fan mode. We found that at 12v, the temperature difference was about 4 degrees cooler on the dual tower NH-D9L and about 3 degrees on the NH-U9S single stack heat sink. Where dual PWM fans were used in a system controlled scenario where the software manages the fan speeds to maintain a temperature curve, the fans maxed out at about 50rpm lower than when a single fan was fitted.
Which one to use?
For lower power TDP CPUs like the i3 or a low power i5, the FLX version could be just what you need for that silent running media PC that never breaks a sweat. The safe bet is the PWM version if you have a motherboard with fan control functionality. Whilst you can pair the PWM version up with an NH-D9L or NH-U9S for a dual fan setup, the gains are minimal but they are there if you need that extra 4 degree drop in temps.
