room space


I have a living room in apartment with listening space of 4m (from listening coach to front wall where speaker stands) x 6m wide with the height of 3m.  I am planning to purchase a 2nd hand Dynaudio Contour 3.3. But I am afraid that such kind of not so large space, the bass might cause standing waves which make bass unclear or vibrating the floor which cause down floor inhabitants complain.  Do you have any idea for my condition? Or should  I buy a smaller one such as Contour 1.8 MK II? Tks. in advance.  
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There is no point is buying a "smaller" speaker. It is about how low the speaker plays. That is the sad truth of it. A smaller driver just moves more than a larger one and will have more distortion (generally) than the larger one at the same volume.  

Now a speaker that does not go as deep would help. 

"Maybe you should consider 2 or 2.5 way speakers to reduce potential overhang bass."

How do you come up with that? Unless you are referring to a specific speaker? A well designed 3 or 4 way speaker can easily deal with bass issues that a typical 2 or 2.5 way can't. The overall design is far more important than generic features.

Assuming that your walls are 4m apart room will amplify 42.875Hz  - (about the lowest sound of the bass guitar).

   343/4/2=42.875

where 343m/s is the speed of the sound in dry air, 4m is the distance between the walls and 2 - because sound has to go forth (reflect from back wall) and back to add to sound produced by the speaker.  There would be peaks and valleys at different distances, since it is standing wave, but you can play 40Hz and walk around.  You can always attempt to decouple the speakers from the floor.  I used Vibrapods directly under speaker, but it made my narrow speakers very unstable.  You might want to use something like Vibrapods with large granit or marble plate and then speakers on the spikes.  Vibrapods have weight rating, but there are many others similar.  I placed pods with higher rating in the front (front of the speaker is heavier).  It is easy to measure with weight scale.  Vibration is also a function of speaker construction.  My new speakers are standing on the spikes directly on the floor and I cannot feel or hear any floor vibration (basement underneath).

"We have Focal here which might be the another sister brand of JM Labs. The new Focal costs a lot for the high End models. In now days, you can't image why the hi-end is so expensive."

I think Focal is the right name. It used to be JM Labs made the finished speakers you go buy in an audio store and Focal just made raw drivers. I believe the 2 companies merged and they now call everything Focal. In the US they have some very expensive speakers, but they also have models that are very reasonable, and you can often find them on sale and get even better prices. But if you don't have any of these brands available to you, try the Dynaudio as long as you can sell them and not lose much money if they don't work. I would get the bigger of the 2 pairs (the 3.3's). You're less likely to have an issue with them. 

some one else may be able to answer this better but would a speaker designed for corner placement be better suited for your room.