Modulator PAL B/G 6.5 MHZ sound spacing to B/G 5.5 or 6 Mhz s. spacing

I have a small broadcast CABLE tv system. Using 12 Modulators which accept 12 Audio /Video signals and output composite RF signal. Each RF output of each Modulator will then feed a signal mixer. So there are 12 channels. The system is PAL B/G with 6.5 sound spacing. The problem is that most of the users have only PAL B/G 6 mhz Televisions. So the users can get the video picture but no sound OR SOUND WITH TERRIBLE HUMMING Question is how I can tune the modulator with 6.5 mhz of sound spacing TO SOUND SPACING 5.5 OR 6 MHZ.

PETER