What makes the Seasonic PRIME TX-1600 Noctua Edition so quiet and how much quieter is it compared to the regular version?

The Seasonic PRIME TX-1600 Noctua Edition is around 8-10dB(A) quieter than the regular model across the entire fan speed range. This massive improvement is mainly due to the superior performance-to-noise efficiency of the award-winning Noctua NF-A12x25 120mm fan as compared to the regular model’s 135mm unit. However, the Noctua Edition’s custom-designed, highly optimised fan grill also contributes to its superior acoustic performance.

Semi-passive operation at typical ambient temperatures and medium loads

The Seasonic PRIME-TX platform automatically regulates fan speeds depending on the electrical load and ambient temperature levels, ensuring that internal components are kept within safe thermal limits. Thanks to the semi-passive control setup, the fan will stay off at typical ambient temperatures up to 25°C and up to 50% electrical load (800W). Once the load increases, the fan will start at 17% PWM and slowly ramp up to around 45% PWM. For the Noctua Edition, this translates into an active fan speed range from ~540 to 1200rpm. It’s only at higher ambient temperatures that the fan speed range will be expanded to access higher speeds. In particular, the maximum speed range of 80-100% (2000-2400rpm) is reserved for worst-case scenarios where the PSU has to provide its maximum electrical output at 50°C ambient temperature.

Noise reductions throughout the entire fan speed range

Throughout the entire range of 17% to 100% fan speed, the Noctua Edition is around 8-10dB(A) quieter than the regular version:

Interpreting the measurement data, it must be noted that while the improvements are consistent over the entire speed range, the sound pressure levels at the lowest speed settings are so small that differences will be difficult to perceive in most situations. Simply put, both versions are so quiet that improvements can be measured from close distances in extremely quiet environments yet may not be noticeable in listening and cannot be measured in situations with higher ambient noise levels due to the fact that the noise emission from both units will be below the ambient noise floor. In order to ensure consistent and reliable measurements, the values below 20dB(A) have been recorded at 10cm distance and then extrapolated to 1m. Whereas the two units may appear to perform similar at their lowest speeds when measured from larger distances, measuring at such a short range makes it possible to demonstrate that the Noctua Edition is significantly quieter all the way down to the lowest fan speed setting, before the fan will be switched off completely.

While the differences at low fan speeds may only be noticeable in very quiet environments, the Noctua Edition provides a consistent ~8-10dB(A) noise reduction across the entire fan speed range, which gives it a decisive edge when building quiet systems. For example, at 45% PWM, the maximum fan speed that the PSU will reach at typical ambient temperatures (up to 25°C), the difference between the Noctua Edition’s ~24 and the regular model’s 34dB(A) noise emission is massive and will be highly relevant for noise-optimised builds.

The role of the fan grill and how we measure its benefits

When it comes to the contribution of the Noctua Edition’s fan grill, it must be noted that its purpose is not only to reduce noise levels but also to increase airflow. Therefore, comparisons against the grill of the standard model must be made on an airflow-normalised basis to properly assess the acoustic benefit. If noise levels are tested without taking flow performance into account, it may actually appear as if the standard grill was performing better because noise levels are slightly lower than with the Noctua Edition grill at the same fan speed setting, especially if the Noctua fan is simply mounted to the standard 135mm grill and the openings around the fan are not sealed. This is because the openings around the fan let air flow back towards the intake side, which reduces overall flow impedance, aerodynamic load and noise levels, but would also lead to significantly worse component cooling performance. When the openings around the fan are sealed, it will still run very slightly quieter with the standard grill than with the Noctua Edition grill, when compared at the same RPM and without taking airflow performance into account:

However, airflow and cooling performance are significantly higher with the Noctua Edition cover, as can be seen when plotting intake airflow versus fan speed (PWM %):

This means that the NF-A12x25 fan can run at lower speeds and noise levels using the Noctua Edition grill to achieve the same component cooling performance. To tell which grill is quieter at the same flow performance, the flow and acoustic measurements need to be combined into a chart that plots sound pressure levels (dB(A)) against volumetric flow (m³/h):

From the airflow vs. dB(A) chart, it can be seen that the contribution of the Noctua Edition’s fan grill is significant with around 2dB(A) lower noise levels at the same flow performance.

Fan grill engineering background: Optimising pressure gradients

The fan grill of the Noctua Edition has been engineered and optimised to ensure as smooth as possible pressure gradients when the blades of the NF-A12x25 fan pass the struts of the grill. To this end, the grill’s radial struts are angled and swept against the sense of rotation of the fan and the sweep of its blades, which helps to avoid situations where the leading edges of the fan blades are parallel or almost parallel to the grill struts, which would cause a high pressure pulse followed by a sudden drop in pressure when the blade moves out of the overlapping position. These pressure fluctuations not only result in audible noises but also lead to uneven aerodynamic loading that can cause flow separation and lower flow performance due to varying impedance. By contrast, the smooth transitions enabled by the Noctua Edition’s grill allow for minimum pressure fluctuations, stable blade loading, even flow resistance and low tonal noise levels.

Conclusion: It’s both the fan and the grill!

In sum, it’s the award-winning NF-A12x25 that is the key factor enabling the Seasonic PRIME TX-1600 Noctua Edition to run significantly quieter than the already quiet standard version, but the custom-designed fan grill also contributes ~2dB(A) to the total ~8-10dB(A) reduction in noise levels.