16 fans in one PC? There is no way that makes sense unless your case is a 5 foot by 5 foot box. What are you trying to do, make it fly? Simply throwing more fans at a machine doesn't make it run cooler, it's all about controlling the ariflow over the parts that really need it. Not that I'm doubting your solution but what exactly is this 'case' you're putting these fans in? I'd like to see a picture. You're going to get better results with a single larger fan than you will with 4 fans running near each other, the air flow from a single fan will be much more laminar, separate fans will create some pretty chaotic airflow patterns which is not what you want when you're trying to remove heat. Also give DC blowers a shot, they're quieter than normal 'fans' and can deal with back pressure better (they're used in low pressure compressors) so they're ideal for exaust fans. Standard twisted vane fans suck with backpressure (exaust) unless you have fans blowing it and a low point and out at a high point. Even then blowers would likley work better. Most modern Video cards have blowers not fans on them for just this reason.
Generally speaking fan controllers for computer don't control the voltage, they use PWM and adjust the duty cycle to control the speed. What do you need to adjust the speed of the fans? A remote control panel or a thermal management system?