Chamber Reverb

Echo Chamber

The first reverb effects created for recordings used real physical space as a natural echo chamber. A loudspeaker would play the sound, and then a microphone would pick it up again, including the reverb effects. Echo Chambers has been integral to recording history – from EMI's Abbey Road to Capitol Studios in Hollywood. Like most natural reverbs, the idea is to set up a mic in a room. Then, you need to direct a signal to it and record that signal with the room's color in full effect. The obvious issue is you need a fully isolated space for the chamber to shine. That's why people will still rent specific studios just for their chamber. It is hard to find that perfect sound.

What Makes a Reverberation Chamber?

The typical reverberation chamber is made of brick, stone, concrete, or other dense material. The walls are usually covered with several coats of plaster. This results in a highly effective surface, allowing the midrange frequencies to decay for several seconds. Studies from the 1960's showed that reverberation time at echo chambers would increase over the years. This is because the plaster is becoming less absorbent as it dries out. The size of most echo chambers is relatively small, ranging from 1000 to 2000 cubic meters.

This will result in a rapid onset of reverberation and high echo density since the sound doesn't have that far to go before it reflects off other surfaces. Reverb chambers are usually full of air, and air isn't a dispersive medium. The time delay between the channels will be based on the time delay between the speaker's output and the first reflection received by each microphone. There will be all sorts of phase complexity after some time (given how signals mix), but you won't have the phase weirdness you find in a dispersive plate.  

Reverb Chamber Size

The size of the reverb chamber is sometimes seen as an issue. Furthermore, larger rooms have better acoustics characteristics in comparison to smaller ones. A small reverb chamber can produce a reverb with a broken frequency response and reflections that can color the sound. On the other hand, a large reverb chamber is very expensive to build, and only big studios can afford it.