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HOW TO: Record Any Room Sound

May 5, 2016

Back in days of yore, when the term “digital” referred to a caveman’s fingers, the only way to add a sense of space to one’s recordings was by, well… recording in the space. Spring and plate reverbs were still a few thousand years off and homo-Neanderthal musicians could barely dream of hardware digital room simulators, let alone their software counterparts. Audio engineers eventually developed methods for generating a sense of space in a recording—some of which are not only still used, but still sound great.

Converting an empty room into a reverb “chamber” was one of the earliest methods of creating ambient effects. Audio pioneers like Les Paul and Bill Putnam designed reverb chambers for Capitol Studios and Universal Recording (respectively), the sound quality of which remains legendary today. You can emulate their efforts with surprisingly good results by using a room at home as a chamber. You’ll need two microphones (for stereo), an amplifier, and at least one speaker (or powered speaker). Using two speakers will dramatically increase the sense of stereo but the size of the speakers is really not critical. Bookshelf-type speakers work very well.

Fig. 1. Speaker and mic placement in the room.
Start by choosing a room, preferably one that is relatively empty and does not have a lot of absorptive material in it. The room doesn’t need to be large; it’s more about how lively it is. The more reflective the room’s surfaces, the more dramatic the results. Place a pair of speakers at one end of the room. Aim them toward the side walls to generate tangential reflections, as opposed to facing them directly toward the opposite wall. At the other end of the room, set up a pair of microphones. The mics can face the speakers, but pointing them away from the speakers will allow them to capture more reflected sound and less direct sound. Facing the mics away from the speakers lengthens the path that sound waves travel from speaker to microphone, enabling you to vary the perceived room size (see Figure 1).

Next patch an aux send (stereo if possible) from your DAW or mixer to the amp or powered speakers. Use a post-fader send so that the room effect stays proportionate to the level of the “dry” sound. For example, if you are treating a vocal, you want the amount of effect applied to follow the fader level when you raise or lower it. The mics are patched back into your DAW or mixer, providing you with a “return” from your reverb chamber. You can return the mics to an aux track in the DAW, or record them to audio tracks so that the effect becomes part of your session. (I recommend the latter.) If you are using a hardware mixer, return the mics to a pair of input channels so you can use the mic preamp. You probably can’t use the effect return on a hardware mixer for this purpose because effect return inputs are almost always line level and never provide phantom power. (I’m sure somewhere there’s an exception…)

The nice thing about generating room sound in this manner is that you don’t need high-ticket mics and speakers. Room sound isn’t necessarily about having a frequency response from 20 Hz to 20 kHz, and I’d argue that room sound shouldn’t be full bandwidth. I typically roll off the high frequency response of a reverb around 4 or 5 kHz to prevent it from getting splashy. A lot of low end in your ’verb muddies the mix, so cut the bottom end around 100 to 200 Hz using a highpass filter.

To capture a solid stereo image, use cardioid microphones; omni mics make the image more diffuse. Most engineers use condenser mics for this purpose but you can try dynamics as well. I’ve used everything from AKG C414s to Shure SM57s. Experimentation is key. Some rooms sound better when the speakers are played louder to excite more of the room resonance, other rooms not so much. You can also compress the “return” from your chamber or—if you’re looking for that ’80s snare sound—gate the return.

A typical living room probably won’t work very well as a live chamber because stuffed furniture and carpets don’t create a lot of nice reflections. A tiled bathroom, on the other hand, is a much more interesting space. Try placing the speakers on the floor facing up, and put the mics near the ceiling to increase the path between speaker and mic. A garage can be an interesting place to record, though you may hear noise from the outside world.

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