So, the pfft~ reference reads:
"full-spectrum-flag (0 or nonzero)
A non-zero fifth argument may be used to specify "full-spectrum mode". In this mode, the pfft~ object will internally compute a complex FFT and process full DC to SR mirrored spectra (instead of simply eliminating the redundant half of the spectrum). This takes up extra computing power, but may be potentially useful in some of the more esoteric spectral processing applications."
Fine, now I -am- on the more esoteric spectral processing side and use fft~ for a complex fourier transformation at the moment. Since it's limited to frame sizes of up to 4096 I ask myself how would I use pfft~ instead? I see no second input for the imaginary part popping up when I set the spectral flag...?!