What is the norm? How many of you use the subsonic filter with your turntable?

I also have a Hegel V10 phono preamp and don't use the subsonic filter.  My SOTA turntable (with vacuum holddown platter) sits on a special heavy shelf in my Target stand, so there's no need for a subsonic filter.

I use a subsonic filter, -3dB at 8 Hz., 24dB/octave. I use it when I listen at loud volumes. It can be switched in or out through a tape monitor type circuit.

I do not use one or needed one. Haven't had that problem in about 40 years. As the quality of my turntable went up. Typically it is a resonance problem with your turntable or compliance mismatch between tone arm and cartridge. Perhaps there are some other possibilities. But look at your turntable and setup to find the problem. 

@dwette I agree with others about using rumble filters. If there isn’t a problem with warps or bad mastering, woofer pumping is a sign of setup issues. In that case a rumble filter is a band-aide that does nothing but – maybe – mask the problem

@ghdprentice But look at your turntable and setup to find the problem. 

+1 best to chase down to eliminate the feedback than to try to filter it out

Most "audiophile" phono pres don’t make this a switchable option, or really even make clear what they’re doing. The original RIAA spec is flat to 0Hz. Some stages probably use this. RIAA IEC modified this to add a high pass at 20Hz. Other stages probably use this. The IEC spec is not a very steep filter - definitely helps a bit, but it’s not going to save a bad configurations on its own (bouncy floors, crappy racks, subwoofers nearby etc).

The KAB Rumble filter is a different beast and much much steeper than IEC or anything I’ve had built-in to a phono stage - it can in fact save bad configurations. The question is whether you find it sonically transparent or not for audible frequencies. That said if your woofers are flapping wildly, no question it’s better to use a KAB until you get the mechanical issues under control - which ideally you would do anyways. Electronic fixes are more of a band-aid.