I can’t hear the Difference in the change the low pass filter or the volume on my SVS subs

I think it's more a matter of VERY attentive listening, and after really learning what you are listening for. I run one SB-3000 and two SB-2000 subs and subtle setting differences can also be very subtle to discern by ear as well, especially when buried under other music, usually louder.

I'll sometimes run just the SB-3000 and go between pre-sets to A-B the differences and learn a bit more while critically listening (which is not too often these days...  :-)

I use measurements and feel they are very important in getting the best clean match and overall sound. A DSPeaker Anti-Mode 2.0 tames the room and speaker bass and the subs are dialed in later for a flat, measured in-room response.

I'm not sure if my positioning is unique or not but I'll describe it:

I'm set up in my living room.  My couch and love seat are in an 'L' configuration and the couch is the focal point.

An end table sits between the couch and the love seat.  I have the sub under the end table and it points away from the listening area making it a source for background and filling in.  There's a caveat however.

For the sub to sound its best and to 'disappear', you have to be at the focal point of my listening area.  I have the speakers tilted a slight amount.  If you leave the listening area, then the sub no longer disappears.  As a matter of fact, its presence  is very evident.

I mentioned the sub points away from the listening area so behind the love seat, you have a birds eye view of the sub's grill and it is very noisy back there.  The only one that does not seem to mind is my dog lol

Thanks, everyone.