Features:
Although the Silent 12 and the Silent 12 PWM fans look seemingly alike on the outside, there is quite a difference in their performance on the inside. Since the PWM model is designed to likely be mounted on a CPU cooler (since few motherboards support PWM case fans), it has a higher RPM to it. By spinning faster, it allows this fan to move more air and thus help cool a CPU properly. Mounting the lower RPM Silent 12 on a CPU could be dangerous because it may not provide nearly the required cooling abilities that some CPUs demand. To concentrate on the similarities first; both Silent 12 models use a hydro-dynamic bearing design. Built to replace the standard ball and sleeve bearing designs, this is not only a quiet alternative but also a long lasting one. With a MTBF rating of 50000+ hours and a five year manufacturer warranty on the fans, they are designed to last. All the fans in the 'Silent' series have a black body with white blades and are certainly eye catching inside a windowed case.

  
(Click any box to see it enlarged)

We will focus a little more on each model, starting with the regular Silent 12. As mentioned earlier, we're looking at the 120mm size of all these fans because that is the most common size used for PC cooling today. The non-pwm Silent 12 runs at 1000RPM which moves approximately 37CFM of air at around 20.2dBA. I was surprised to see honest decibel ratings here, 20 may seem "loud" to some, but in reality this fan was the exact definition of completely silent. Since this model of the Silent 12 is not PWM controlled, it simply uses a standard 3-pin fan connector for power. I did think about making a mention on how no 3-pin to molex adapter was included but I realized it wasn't worth it because so many new computers now have many 3-pin connectors available and the die-hards will likely have a fan controller anyway's.

The PWM version of the Silent 12 is essentially the previous one on steroids. Since it needs extra cooling abilities to keep today's hot CPUs running safely, this fan can run from 750 to 1000RPM. It can move a maximum airflow of 58CFM and sound levels will vary from about 12-25.5 decibels. Other than those minor spec changes, there are no other differences between the two silent models.

I will also make mention that GELID Solutions does make a temperature controlled version of the Silent fan series (not reviewed here today). For those who don't have PWM available and want to run a silent computer without having to manage a fan controller, the temperature controlled series may be worth looking into.