Zalman ZM850-HP and ZM1000-HP

Fan Speed and Acoustics

The fans of both units stay at a just below 1000RPM for most of our load levels. The fans stays at these very low rotations under room temperature throughout our loading, only spinning faster when full load is reached. We have not seen anything like this before and need to congratulate Zalman for this approach. The heatpipes and 140mm fan are doing their job and cooling the unit very well, so there is no need for faster wind speeds. 1400RPM is the fan's maximum speed, but as we will see in the next graphic it is not perfectly silent.

Even though the previous graphic doesn't show how the fan accelerates before full load too well, the acoustic noise levels show the results. The fan spins just a bit faster as load increases, but it produces more noise than expected. There is absolutely no noise up to 600W of load; the PSU stays at a constant 17dB(A), which is quite low and not audible running in our acoustic chamber. If the unit is installed in a PC, users will not be able to hear it at all even with higher loads.

Now all you would need is to find two or three really quiet graphics cards and a CPU cooler and your silent system would be ready for this high-power, relatively quiet PSU. Without water cooling this will prove very difficult, since the coolers for today's graphics cards have to dissipate so much heat. Overall, however, both Zalman units deliver a very good performance from the silent point of view.