Small Rooms Defined
Small rooms that have a volume of less than 100 cu.ft. are rooms in transition. They have all the acoustical issues of larger rooms, with a greater emphasize on low and middle frequencies. In these sized rooms, people become part of the room acoustic. Each human has the absorption coefficient of around 10 sq. ft. of carpeting. That amount has an impact on small room sound.
Make a Big Deal Out Of Everything
Everything is exaggerated within a small room. Even the surface material of the room boundary surfaces can have an impact. One must make sure all the individuals that will be involved in the recording process within the room must be calculated in during the sound check phase prior to recording anything. A single person’s room position change in a small room can be noticed in the recording.
Variable Acoustics/Low Frequencies
The only way to achieve some sonic sense to a small room is to have moveable panels. Small rooms have no space for low frequencies to go. They must be made smaller to sound larger. Low frequency management must be attempted to be dealt with. Only a diaphragmatic absorber can provide the necessary rate and level of absorption for a small room. It must also be mobile, so it can adapt to different sound recording requirements. Resonances will move around more easily within a smaller room depending on the pressure created by the source instrument.
Movable panels or variable acoustics help change the direct to reflected energy stream or direction. If our small room has close in proximity room boundary surfaces then we need to be able to redirect the reflections along different energy pathways. Close, parallel surfaces, give rise to flutter echo which is never wanted in any size room. Anything that has the word echo in its name can not be good.
Mids and Highs
Middle and high frequencies can be managed using absorption and maybe diffusion depending on the room’s use. Diffusion requires certain distances in order for the diffused waveform to expand fully, so a small room may lack the space requirements for diffusion. Sound absorption technologies can be readily employed. Care must be taken not to over absorb at all frequencies.
Reflections within our small room takes on a new meaning. How do we separate the direct sound from the reflected sound within our small room. We need to hear the direct sound first, but with close room boundaries we are always competing to find the direct sound. Trying to find that balance between direct and reflected energy at the microphone position is critical in a small room. The musicians must also be able to hear each other or all is lost.
Small room coloration can be used to one’s benefit especially with today’s modern music. Everyone is always looking for a different sound to record with this instrument or that vocal. A small room can add numerous effects if you will to your sound. Care must be taken not to be to taken with new and seemingly unique sounds for they can tire quickly if overused.
Their Own Sound
All small rooms have a characteristic sound to them. In fact, if one goes in enough of them, one can tell which sound absorbent technology is being employed. One can even tell who the manufacturer is. Small rooms receive large amounts of absorbent technologies because reflections are competing with direct sound from sources.
Time Domain, Not Frequency
This unique sound we hear in small rooms is attributed to time not frequency response. The frequency response does fill the room with sound, but it is the push and pull of the pressure areas of room modes and the abundant reflections from the close in proximity room boundary surfaces. EQ can not even compensate for these deficiencies.
Care must always be taken from the very beginning of the recording process. It must be monitored closely and the purest waveform recorded. It can not be fixed later in the mix. All of this is hypercritical when it comes to small rooms because the reflections and room modes will leak into everything and do it quickly. Do not assume mic position # 1 will work with all instrument and vocal amplitudes.
Small rooms should have small uses. By that we mean that one should find the two uses for the room that sound the best and stay with those uses. Small rooms can not and should not do everything. They can do some things well, things that have less energy associated with them. Small rooms are energy sensitive at all room locations.
Small rooms have special acoustical needs. Their use needs to be limited to the uses that produce the best sound. Resonances and reflections abound, so care must be taken to try and address these issues along with finding the proper microphone position for optimal sound recording. Variable acoustics will help us but there is still no substitute for cubic volume.