It's not a bug, the program is limited to 20K for several reasons. One, I matched it to the original PCD spreadsheet. Two, going higher provides no benefit. As a crossover program, anything above 20K is not likely to be of much importance, if any, given audibility or lack thereof. Three, adding additional sample points increases the calculations in the program that tends to reduce responsiveness. I saw no need to go beyond 20K.