The best solution would be a high pass filter; but, of course, the Prophet '08 doesn't have one. There are two other possible methods for trimming back the lower frequencies. If you're not using filter modulation modulated by the envelope generator, then you could try raising the Resonance just a tad. The other method is to switch to the 2-Pole Filter setting. Both options reduce the lower frequences, but they also affect the overall sound, so you'd have to adjust a number of parameters.