Montis vs. Summit X

Is it 5k€ worth to upgrade from Montis to Summit X?

in a word ............maybe.

IMO though, as I've stated before, for the price difference one can buy a great sub, locate it ideally and perform on par with the Summit X and probably have a few $$ for music !

At the moment I've paired the Montis with a Descent i. But I think the Summit X needs less space

Tough choice. If you already own a pair of Montis speakers, then adding a sub is the correct option. But if money and space aren't issues and you're choosing to buy either speaker from new, buy the Summit X.

The ears adapt so quick to better sound...
When I listen to the Montis alone the bass is good and sufficient.
But listening for a while together with the Descent i and then switch off the subwoofer you think you listen to a bookshelf speaker ;-)

My question: Is the bass of the Summit X as good as the bass of Montis together with Descent i (4*10" vs. 5*10" bass drivers / 2 in Montis +3 in Descent)

I own Summits and a Descent, so can provide some insight. I would say the bass of the Summit X is going to be better than that of Montis + Descent I, meaning much more accurate and seamless with the panels. But it will never have that bottom octave impact that only a subwoofer can provide. I don't think you will miss the added slam though. I only use my Descent for movies. The Summits provide more than adequate bass for music. My advice is to get the Summit X if you can afford it.

So you mean Summit X is the right choise. And adding a sub later (BalanedForce 210?)

I am of the camp that says that a Montis + two subs correctly placed and EQ'd is going to beat a single Pair of Summits any day.

Here's why:

The Montis has a very good active crossover for the bass portion that yields very good panel to woofer integration. The single powered woofer, focused on frequencies >80Hz can perform much better and cleaner if not charged with trying to do low bass. The panel is the same as the Summit, so zero diff there.

Two subs, strategically placed in the room (best would be middle of front wall and middle of back wall) individually adjusted with PBK (so minimum a Dynamo 1500X, ideally BalancedForce models), allows for balancing out room modes in the bass region, which when done correctly, opens up the entire frequency spectrum.

The Montis has possibly the best panel woofer intergration of any hybrid Martin Logan speaker - some would argue that it's even better than the Summit X. I will bite the bullet and say that it's not worth the extra 5K euros for the Summit X