Q:

Reduce bass through wall to neighbour

I like playing loud bass heavy music but I have some problems with a neighbour hearing much of the bass through the wall. I have painted a picture of the situation.
The colors are indentified as:

Orange = Speaker 
Green = Area where a lot of bass gets trapped, I think the correct term for this phenomenon is superposition of the sound waves.
Yellow = Neighbour experiencing the bass through the wall

All the outer walls are about 15 cm (6 inches) thick concrete. I am not very experienced with sound and acoustics but I have gotten the impression that there might be some solutions to my problem, bass traps etc. How would these help me and is it possible to build my own as the cost is very high? The two active speakers stand on a desk.

A:

We have quite a few soundproofing questions over on Music.SE (as obviously people want to practice LOUD!) with useful information like this one:

If you want to prepare a room for practicing drums, there are two things to consider:

The sound inside the room (what you hear): Within the practice room you usually have problems with the high frequencies reflected from the walls. Adding fabric or carpet to the room helps a lot, there are also special acoustic foam absorbers you can buy. Some bands glue empty egg cartons on the walls... These methods will improve the sound inside but will have little effect on the noise outside.
The sound outside (what your neighbours hear): What you hear outside is mostly the low frequencies, coupled through concrete or wooden walls. Unfortunately, these frequencies are much more difficult to dampen. The most effective way would be to build a room-in-room construction, i.e. build a completely closed room out of wooden panels inside your basement room, such that it has as little physical contact with the outer walls/floor as possible.

