The UE 4 Pro and UE 5 Pro are both dual driver monitors. The low frequency driver in the UE 5 Pro is larger and capable of a higher volume output. It is a step up in the product line because it can go louder and can be used for various applications. The UE 4 Pro, is more effective for those who don't need the extra low end that the UE 5 Pro offers or who play on quieter stages. The UE 4 Pro has a flatter and more “reference like” response, making it very suitable for producers and audiophiles. Visit these links to learn more about the UE 4 and the UE 5.