11. Room & Boundary Effects for Playback Systems

The recording of music is only one side of the coin when it comes to completing the chain of events to observe our work. We can make the most wonderful recordings, but without proper playback we may never know their true content. Having great playback equipment does not mean we will get good results any more than throwing a stunning pair of microphones in a room will give us good results on the recording side. Understanding how to position speakers in a given space is the inverse of our true stereo recording. Like different stereo recordings techniques dispersion patterns and bandwidth of speakers will dictate where they should be placed in a particular space. The inherent qualities of the room which they reside will be our main limitation in their final result. Selecting a space and how it is treated will as in selecting a recording site greatly affect our results. The setup of a quality playback system is just as critical as the recordings themselves. 

Selecting a room

Finding the ideal space to place a playback system in will depend on the equipment at hand. The more extended the bandwidth and informational qualities of a given system the greater potential risk for problems may occur. Taking advantage of a more critical system will always require more effort but the rewards will be equally as great as in getting the recording space to work with the given material. Placement of speakers is often the most difficult aspect to achieve but other components as well need to be considered. To handle a large full range speaker will most often require a larger space; putting them into small rooms will often limit the frequency range obtainable and restrict their dynamic capabilities. Small monitors of high quality will generally suffer from the opposite not being able to fill a larger space and losing there capabilities with their more restricted output. Avoiding rooms with the same multiple dimensions especially square rooms is best if possible.

Room Surfaces

Next to the dimensions of the room the surfaces it is comprised of will have dramatic effects to consider. Concrete floors are a good place to start especially when full range speakers are employed. Wood floors can have good results for smaller monitors but with a great deal of bass output solid foundations are defiantly preferred. Wood floors over a concrete bass could be even better deriving a nice ambient quality to the solidity. Wall surfaces of brick will increase bass output as low frequencies can not escape, Plaster walls can have a good solid effect while allowing some unwanted bass energy to transmit out of space. Drywall construction is not usually as good at energy storage, but there are exceptions. Ceiling heights and shapes will be next to considered, too high and a great deal of output is lost, too low and reflections can become a problem. A rough or uneven surface would be preferred, vaulted; rising or cathedral ceiling can have interesting qualities as long as the height is not too drastic.

Tonal qualities of the Room

The ideal room would have high energy transfer with as little ring as possible. When ever damping is used to silence problem areas efficiency is lost. Using minimal amounts of treatment is suggested unless there are serious tonal problems. Low frequency problems are very difficult and sometimes impossible to correct the use of speakers with less bandwidth may be the only compromise for such spaces. Mid and upper frequencies are much more easily treated breaking up slap echoes is important the use of pictures and other wall hanging are all that may be needed although there are several treatments available such as room tunes. Carpeted floors are ok but thick carpeting can suck out large amounts of energy. Wood floors with area carpets often sound the most natural making sure that there is a carpet between the listener and the loudspeakers.

Careful set up of a quality sound system will derive great benefits choosing the correct speaker for the given space is essential and when things are properly assessed playback of better recording will be able to give us the closest approach to the original sound.

Ken Christianson, Pro Musica, Chicago

posted on: 2011/09/14
* 12. True Stereo in Perspective
* 11. Room & Boundary Effects for Playback Systems
* 10. Instrument Positioning & Room Manipulations
* 9. Choosing a Space-Acoustical Considerations
* 8. Troubleshooting True Stereo Sound
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