🚀 go-pugleaf

I use Audition mostly to create digital archives of vinyl LPs. While I have a very good turntable, preamp and cartridge, there is still enough residual low-frequency information (25Hz and below) that I would like to eliminate it. I do NOT want to lose what LF info is present, only eliminate the residual rumble. I understand there are several ways of going about this in Audition:
- equalizer / parametric equalizer reducing low frequencies
- noise reduction, getting noise profile from silent passage (lead-out groove)
- other (see below)

The EQ option seems too heavy-handed and I can't seem to find any indication of the phase impact.

FFT filtering can also work but again, I'm concerned about phase.

Right now, the simplest way seems to be to use the Noise Reduction feature but my question then becomes one of optimal settings. I understand the smaller the FFT size, the less granular the filtering. It seems with smaller numbers (less than 4096) portions of the midbass (above 50Hz) are also impacted. Larger FFT sizes are said to introduce phase anomalies, which I also want to avoid.

I would also like to try an old analogue audiophile trick. Turntable rumble is actually 180 degrees out of phase from right channel to left. I would love to find a way to sum frequencies below 25Hz as (at least) a first step in this process. So far, I haven't found any simple filter that does this.

I'm open to ideas - please contribute!