SB Acoustics 12” SB34NRXL75-8

Those are pretty big speakers you're running now if they aren't giving you the bass you're looking for have you messed around with positioning? Looks like they are rated down to 23hz and look like they have the volume to get that low in room.

Please, forgive my lack of comprehension(Oldtimer's Disease strikes again).

#rodman99999: not a problem at all, actually I had to mention the system info.
#jond: the listening room is 180m2, I tried many different positions and I positioned them to complete to 2 corners of a triangle, 3.corner(peak) is listening point. Room is my office sametime, usually I listen classical music 24bit records, or some SACD. I really like to have some deep and low bass. Therefore, I will try to build a custom cabinet for SB Woofers.

*Also, do you have any idea what kind of wood has to be used.

Come over to the DIY forum. You'll find lots of speaker builders there, and it's easier to communicate with the images in your posts.

http://www.diyaudio.com/forums/multi-way/

or here:

http://www.diyaudio.com/forums/subwoofers/

Thank You !