Element 2 - Drum Machine, ambient

Now that we've got the mics, stereo configuration and delay down, we need to figure out where to put the microphones.

If you've never spent time playing around with this, you might be surprised at how big a difference moving a microphone has on the sound that it produces, even if the change is a matter of inches (or smaller). In a room like the one we're recording in, some of this has to do with how the dimensions of the room interact with the sound.

This is an involved subject and I'm skimming over it for the purposes of providing some explanation. But think of this - sound travels in waves. The length of the waves is determined by the pitch (frequency) of the sound. Since the sounds we're present a complex wave that's the result of many interacting pitches, you can think that there are a bunch of different size waves bouncing around the room. When the length between the walls is the same length as a sound wave, that particular tone will be emphasized.

We've tried to deal with some of this by making the distances between the floor/ceiling, north/south walls and east/west walls different enough that each dimension emphasizes different tones. (See the [ Acoustics ] section for more on this.) But this means that you will hear different tones emphasized from the same sound source depending on where in the room you're listening to it.

Hopefully you're still with me. We've got three dimensions to consider of where to put our m/s microphone system - how far away from the speakers (back/forth), how off-center (left/right) and how far away from the floow (up/down). The first two are easy. On the last record, we did a long experiment and ended up figuring out that about 9 feet away from the speakers sounds good. There's not a lot farther back we can go, so this is convenient. As for left/right, we want to capture the stereo sound in as balanced a way as possible, so we'll put the mics right in the middle of the room.

This leaves us at our question - how high to place the mic from the ground?

Mic Placement


1. 0 feet, rug - This places the mid mic as close to the ground as possible without touching. The rug is beneath it. Keeping the ambient mic close to one of the reflective surfaces (in this case, the floor), should minimize any delay interactions between the direct sound and the first reflection off the floor, since they'll both reach the mic at almost the same time.

2. 1 foot off the floor.

3. 4.25 feet off the floor - I'm including the graph I used to figure this out on the right. In a nutshell, I figured where any of the most simple fractional divisions (1/2, 1/3, 2/3 all the way up to 9/10) were along the imaginary line from the floor to the ceiling. These should be the places where the most apparent "wave emphasis" takes place. (Boy am I ever dumbing down a very complex topic here.) I then picked a spot that was not on any of those divisions - in this case 4.25 feet.

4. At the ceiling - The theory here is the same behind point 1 above - minimize the delay interactions at the ceiling level.

5. 0 feet, no rug - Since the rug eats up some of the higher pitches, taking it away should create a brighter sound.

This is all building on what we've learned so far. The direct drum machine is sent through the RNP, the ambient mics are in an M/S pair with the e22s as the mid mic and the ambient mics are delayed 20 seconds from the direct sound. As with before, the relative level of the ambient mics to the direct sound is exaggerated to make the comparison easier.


The sound clips here are again "labeled" with the computer voice. They follow the order presented above.

Drum machine - ambient mic placement comparison.

It's surprising how much different it sounds as a result of changing only the height of the mic stand. The 0 feet mics present a stable image that sounds even across all of the sounds; as expected, peeling the rug back brightens it up a bit. The 1 foot mic sounds hollow in some spots and boomy in others. The 4.25 foot mic seems to provide the widest sounding image - perhaps because it's closest to the level where the HF drivers on the speakers are. The ceiling mic is a mess. I'm glad it didn't work as it would be a real pain to get the mics up on that 11 foot ladder for the whole time.


It's obvious that the 0 foot is the best sounding of these. I like the less bright sound on the rug version, so we'll stick with that. Final part on the drums is simply picking the preamp.

Mics will be placed about 9 feet back from where the speakers are in the room, and the heavy doors on the shelves mean we can center between those doors and the oppostie wall.

You end up using a ruler a lot when you're doing this stuff.

Things get silly. Fortunately, the tape on the ceiling mics tells the tale: no.

The somewhat confusing graph that gave the idea of where to put one of the mic testing places. See "Choice 3" over there to the left for some idea of what's going on here. Basically, put the mic at a height (on the Y axis) where there isn't a dot.


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