Spiral bevel and double helical gear reduction mixers enable the most efficient transformation of horsepower into torque. The more torque available, the greater the ability to mix the contents of a tank. Torque is horsepower divided by speed, so the higher the agitator shaft speed, at constant horsepower, the lower the available torque, the lower the mixing capability. The purpose of a double reduction gearbox is to lower the agitator shaft output speed and increase torque. Think of a double reduction gearbox as a magic black box or a large lever arm to leverage your work load.
The concept of mixer speed is counter-intuitive, in that most think that a higher speed mixer is what they need. It is for this reason, for flow controlled applications, that you will mostly see slow speed mixers being applied to larger tanks and the highest speed mixers are applied to the smallest tanks.
Double reduction drives typically provide agitator shaft speeds between 24 to 175 RPM's. Triple gear reductions are available but are not as common. Due to the numerous number of speed options, vertical versus right angle drives, mounting options, and gearbox torque capacities (case sizes) available, these designs do not lend itself to insertion into a price matrix. Therefore, we'd rather handle these applications by referring them to the factory.