If you wish a wide range but not extremly low or high gears, speed-drive is your choice.
speed-drive "type 08" allows to mount chainrings with 27 t. or bigger. This equals chainrings of 45 t. or bigger in high gear mode.
A chainring with 30t. equals 50t. in high gear mode
speed-drive "type BCD110" can be equipped with chainrings of 34 t. or more. Such a chainring in high gear equals a 56t. chainring.

Biggest chainring available with BCD110 is 53 t. Equals one with 87 t.

Black bars in the diagram on the right show additional gears in combination of speed-drive with a wide spread 8-speed-hub.

Please find a gear range calculator (for meters per revolution) here:
-> in combination with derailleurs
-> in combination with internal hubs

Please find a gear range calculator (for gear inches) here:
-> in combination with derailleurs
-> in combination with internal hubs