You can adjust the sub level up or down as much as you wish.  If you aren’t listening at high levels and your room isn’t too big, it should be fine.  Especially if you’ve never heard a sub in that room before.  

Thanks jgatie 

The room is medium size but not completely square. Its partially open from one side

honestly even without the sub I am happy with the bass but I can use a hint more especially if it will also make the arc sound even better

I have an Arc with two Era 300s and a Sub Mini.  My room is about 4x4 metres.  The Mini is more than enough.  

Easier to turn a big Sub down that get a Mini to play louder than it is designed to.

I have a big Sub and Beam/One setup in a 10x10 foot (3x3 Meter) room and it is easy to get just the level of sound I like.

The Mini wasn’t available when I bought so I might have tried one in here to save some money if buying today but I do not regret the full Sub at all.

Thanks guys for sharing your thoughts and experience. Joffy, do you feel a big difference in sound quality when you turn the sub mini off? 
 

You’re right Stanley but in my scenario I live in an appartement hopefully without direct share walls with neighbours but still I find myself not turning that much the sound level up. I am more into overall quality of sound than loudness just need the little bass feeling that a subwoofer offers

I reckon Subs always make a substantial difference, no matter what your set up is.

As a follow up to this conversation I finally pull the trigger for a sub gen 3 will receive it tomorrow ! I tested the arc in the showroom of my local dealer with the sub mini and with the sub both with music and top gun movie. In both cases the soundbar freed from the bass sounds better. The mini make the bass sound better, definitely bit there was still too much arc for the sub. With the sub gen 3 you can see that’s the right fit. Even at low volume you feel a stronger more deep base than with the mini. Both are great but the regular sub is much more impressive tbh.

Also they had the setup coupled with the era 300 and it was damn good. I really heard the atmos effect. with the arc I can hear it bit it’s more on the soft side. 

I received the big sub find a place for it next to the bar on the left and it sounds great. I can finally hear all the frequencies. I watched Tetris on apple tv and the atmos soundtrack sounds unreal I really get the home theater experience even if my room is not the best for acoustics.  I don’t regret my choice. Now am pushing more sound level I hope neighbours will not complain

here is my setup and the room if you have any suggestions on placement (am taking the photo frim the big opening to the hall)

How about this system with 2 mini subs so that you can have evenly distributed bass but not overkill