I'm trying to create a wideband specrogram app for Android, but I don't seem to get the right set-up for the patch. Everything I get from the rfft object looks narrowband at first sight (seen in a PD canvas).
PS: I'm just a language teacher so I'm way beyond my dephth here, but I have managed to do it with javascript in the past.

For the frequency/amplitude data mapping, [sigmund~] is probably your best bet, as you can set how many bands (-npeaks) to measure up to what frequency (-maxfreq) at what time intervals (-hop). It's quite well documented in the help files.