Sonos Sub 4 + Arc ultra + Era 300s

The bass from a Sub should be subtle, not room shaking. Could your expectations be wrong?

What sources are you using?  Music or video?  If video, are you playing sources that are at least Dolby Digital 5.1 (Note - 99% of YouTube videos, even the ones marked as surround sound or DD 5.1 are downgraded to stereo 2.0).  Try an action movie that has explosions and is definitely in DD 5.1, DD+, or Atmos.

In addition to the source you may be listening to a sub requires the correct positioning in the room. Try playing a source (preferably a movie you know that has good low-end) and moving the sub to different positions in the room.  Some find positioning the sub at an angle in a room corner or behind furniture such as cabinet or sofa work best. Of course placing the sub along a wall can’t be ruled out. Be sure to mark the spots where low-end gives the best response to your ear. 

Also , know that the topography of the room also influences low-end response. A room with carpet, plush furniture and drapes can affect low-end (dampen) response. Rooms with all hard surfaces can have a negative effect as well (too booming). The ideal room has a balance of soft and hard surfaces without leaning to the extreme in either direction.

Last comment… TruePlay isn’t a silver bullet. It can have a positive, negative or no effect at all; again depending upon the topography of the room.

Good luck to get the low-end tuned to your liking!

EDIT:

If your space is open concept (or cathedral like) you may need two subs to achieve the desired effect. After all is done (whether using one or two subs) you should not be able to pin-point the location of the sub when watching a movie or listening to music as low-end sound should be non-directional.

I prefer my Sub be unnoticed, adding to the other speakers but not making itself known.

In a smaller room (Beam Ones) I have the levels backed off from flat and on a track that contains low frequency content the difference is quite noticeable when  toggling on and off. Tracks that contain little low frequency energy don't sound different. The Sub is positioned center-wall to reduce the impact.

In a larger room (Arc Ultra Era-100) that is an open plan I have my Sub levels up several steps, it is alao in a corner to increase the output. The Sub on/off is pretty subtle for most sources as the Ultra picks up a good bit ot the low end my previous Arc did not. Still with the proper source the Sub adds a great deal to the overall sound, quite unobtrusive as you never notice the Sub, just the richer low end sound.

In my 2.5 car garage I have a Play 3 Pair and Sub. Spouse banished them and I'm resistant to selling them so why not? They are in a corner for maximum impact and the Sub contribution is truly amazing. To keep the neighbors happy it is necessary to either keep the car-door closed or the Sub off for evening listening.

I no longer have an Apple device so I use the internal tuning where available or just the level controls when it is not.

Pick your content to have a lot of low frequency sound and fool with your settings. I'd suggest subtle and balanced  ut if you prefer to rattle the room that certainly should be doable. With nothing coming from the source in the Sub's range it isn't going to do much, if anything, content is key for initial setup.