The Birdy Rohloff is supplied with 52T / 13T which gives gearing of 19.9" to 104.4"and I'm planning to change the sprocket to 14T which drops the gearing to 18.4" - 97" which is very close to the gearing on my main bicycle. However, a double chainring with 11-32 casette will never give the gearing range of the Rohloff so theere has to be a compromise somewhere. My aborted project to put a double chainring (54 + 38) on a Birdy City (8 speed hub gear) would have given gearing of 22.3" to 97" with a 16T sprocket. 22.3" would be just OK for my worst local hill but it would have been easy to lower the gearing by fitting a bigger sprocket.