Performance Testing

Please refer to the dedicated test setup page as it applies to this review as well and I did not want to go over it separately to save on review space.


There is a standard and a power version of the Alphacool Apex Stealth with the former going up to 2000 RPM and the latter, which we have here, having a rated RPM range of 400 to 3000 RPM (+/- 10%). The provided two samples went from an average 2968 RPM at 100% PWM down to 301 RPM at 10%, following which the fans remained at 301 RPM until they turned off when no PWM signal (0%) was provided. I will mention here that Alphacool advertises a zero RPM mode with these fans but a lot of fan controllers simply can't get lower than 10% PWM duty cycle, let alone as low as 10%. So there is a good chance you may not see the fans turn off at all but, if you do, they do turn back on at 450 RPM or so. So there is an effective control range of 0-100% here even if most of you will see the 10-100% duty cycle in your PC and this is still excellent! Indeed, the ~300-3000 RPM range is also quite massive so I will give major props to Alphacool here. Needless to say, this is plenty for PC cooling applications be it for someone who prioritizes noise or those who want better cooling. The RPM response curve is quite linear until ~2000 RPM following which there is a slight plateau; I can see why Alphacool sells the 2000 RPM version of this fan now too. Likewise sample variation is minimal when it comes to the spinning speed although I did notice a slightly larger discrepancy at higher fan speeds when it comes to the fan airflow and noise. Context is needed to talk more about the fan's relative performance and noise, so I have comparison charts below for some fans tested at set RPM values, or as near as they can get to those.


The charts above help compare the Alphacool Apex Stealth with other fans at different chosen RPM values reflecting usage scenarios most popular with watercooling, although some fans go higher as is the case here. The charts are to be considered for comparison within this result set only and are not to be compared with results from another test elsewhere owing to different testing conditions. Note that these are average values for all samples of each fan and do not reflect any sample variation, and I also suggest looking at RGB fans separately from the others given they tend to sacrifice some performance by having LEDs take up space where the rotor blades could have been pushing more air through. The interesting takeaway here is the Apex Stealth is among the quietest fans on the market, often on par or even quieter than many RGB fans. It does so while also having a frequency response that is tilted towards the lower frequencies meaning there is less of an annoying pitch even at faster fan speeds. This ends up making the Apex Stealth sound even quieter than it measures to most people to the point of being fairly inaudible inside a PC case a couple of feet away at typical operating speeds. You can push the fans faster than most others thus, which can be helpful since this isn't the most powerful fan when mounted on a radiator of average airflow restriction. Indeed, the relative performance seems to dip the faster the Apex Stealth spins so perhaps the sweet spot is 1500-2000 RPM here. I will also confirm there was no perceived vibration or bearing noise during testing, including at the lower fan speeds, so the decoupling mechanism and HDB bearings worked as promised.


Instead of having CFM/dBA charts that can potentially be taken for more than they really offer, I am going to show three other fans as a comparison for further context. These include the subject of this review—the Alphacool Apex Stealth—in addition to three other high performance fans that the Apex Stealth's marketing made me want to compare against. These include the Thermaltake TOUGHFAN 12 Pro, the Lian Li UNI FAN P28, and the Phanteks T30-120, all of which use LCP rotors and are excellent performers. The Noctua NF-A12x25 also merits consideration here but it is the oldest here by far to where I had to skip it to keep the graph useful. The Power version of the Apex Stealth offers the longest RPM range to where we see it extending on either side of the other three fans here. It also fares favorably at lower fan speeds but then loses to the others from a performance/noise basis the faster they spin. Keep in mind that you can spin this fan faster and still have it sound not as loud as these numbers suggest, so the difference between the fans is not as prominent, but it still ultimately pushes less air than the others at the same fan speeds and that in turn means less heat dissipated through a radiator. Perhaps things might be different with something less restrictive such as an air cooler where static pressure is less of a bottleneck. Either way, it would be fair to say the Alphacool Apex Stealth is better seen as a quiet fan with decent performance rather than a performance-driven fan besting other such entries in the market.