Room acoustics & treatment

Date:17&18th march 2010
Duration: 6 hours


Having recently changed the layout inside my project studio, I decided to consider about the acoustics of the room to achieve better results in mixing.
Limitations on space means extra care must be taken on the layout, practicality and the final result. I knew compromise had to be made because of the less than ideal space but I needed to learn the theory in acoustics more so I could improve the acoustics of the room using treatment.

 Above is the layout of the room as of now. There is a fixed bookshelf on the bottom right of the room which is acting as a diffuser at the moment (with different depths of books and general uneven surface) which if necessary could be moved.
There is drumkit inside the room which cannot be placed anywhere else other than this particular room. Although far from ideal to have the drums in the same room as control room, no other alternative exists at the moment.
All the rack mounted gear is tucked under the table to save space so that's not an issue. Two guitar amps are placed in front of the table in the top centre of the diagram above. One of those are usually tucked under the table when not in use. There is also a Bass guitar cabinet which is stored in another room and only is brought in when tracking so its not included in the plan.
There is a sofa which is used for artists to sit on for tracking purposes (bottom left)

Background Research

After spending several hours browsing through websites and articles in Sound on sound magazine I got a basic grasp of the fundamentals of acoustics.
Here are some areas I need to consider to improve the acoustics in my room:

• The listener position has to be symmetrical in proportion to the dimensions of the room. So currently I am tucked away in top left hand side of the room and I'm going to have to find a more symmetrical position inside the room.
• Try to reduce reverberations inside the room. The room has carpeting and thick curtains and there is very little reverberation inside the room. Not enough to for it to be a problem and just enough for critical listening and mixing.
• Prevent standing waves & acoustic interference. Because of the bare wall behind the listening position, in all likelihood there are waves reflected from the wall and interfering with the sounds coming from the monitors. This causes peaks and dips in the frequency response of the room and this must be sorted.
• Reduce modal ringing. This is more difficult to deal with and I'll probably look further into it on another occasion.
• Prevent flutter echoes. This is usually treated using absorption and diffusers. Dealing with echoes can improve stereo imaging.

Recently I was donated 20~ panels of acoustic foam from a friend who had acoustically treated his vocal booth for recording. After doing research online and reading articles in magazines, it became apparent that acoustic foam panels are not very effective compared with other materials such as rigid fiberglass. These foam panels and okay at absorbing high frequencies but do next to nothing for bass frequencies.
What I decided to do in the end was to source other products that are more effective in lower frequencies such as bass traps and use them in conjunction with the donated acoustic panels. I will also attempt to find creative ways in which to use existing furniture etc to further improve the acoustics of the room.

Here is plan for the room showing new positions for furniture and absorption placement:

The red indicates a bass trap, blue indicates acoustic panels and the green indicates diffuser.
The bass traps are going to have to be purchased and the diffuser I'll attempt to construct myself. The foam acoustic panels will be placed on the walls not only as a single panel but two layers on top of each other. This will increase the thickness of the foam and increase its absorption coefficient, extending its absorption frequency range to mids as well.
After everything is done I should end up with a room more suitable to do critical listening and mixing in and less coloured by the room and enhanced stereo imaging.