Let's say we have a room that measures 10'x12x8'. Let's say we put the drums in the dead center. For easy figuring, let's just say the drum set takes up 6'x6' of floorspace. This is just for easy figuring. I realize a drum set isn't usually square. So if this is the case, we have 2 feet of space on 2 sides of the kit and 3 feet of space on the other 2 sides.

So let's say that our floor tom is on the edge on the side with 2 feet of space. When Mr. Drummer smashed the floor tom, you are going to hear some boom, but you are also going to hear the attack. The sound of the attack is going to shoot out in all directions into the room. The problem is the sound of the floor tom is going to hit the wall in about 2 seconds (sound travels roughly 1ms (millisecond) per foot. Depending on the material of the wall, much of the sound will be reflected back (with maybe a little less high end in it). It will 2ms for the sound to travel back. So basically, we'll have the sound of the tom and then (just 4ms behind it) we'll have the sound of the reflection.

Test It Yourself

Take a recorded track. It can be a floor tom, a snare drum, a vocal, or whatever. Use a delay plug-in on the insert of the track. Make sure the feedback is turned to zero and the delay is set for 4ms. Now play with the mix % of delay ranging from 0% to 100%. You'll hear the drum get WEIRD (and NOT a good weird).

Just in case you thought the sound was cool, toss in a cd that you consider to have great drum sounds. Now listen back to the track you just dicked with. You'll find that you probably don't like it anymore.

This is the sound that this one single wall is adding to your single floor tom assuming you are recording the drums with a single mic. Now let's add another wall.

• Take off the 4ms delay insert.

• Create a new aux send with that same 4ms delay

• Create a second aux send with a 16 ms delay

• Create a third aux send with a 14 ms delay

• Create a fourth aux send with a 18 ms delay

In this case we haven't figured in the sound of the floor or the ceiling. This setup here should get the point across. No experiment with sending your track to all of these aux sends. Make sure all the delays are set to be 100% wet with none of the original signal. Now play around with levels. The longer the delay, the lower I would set it's level. So I would have the 4ms delay much louder than the 18 ms delay. You'll want to knock a little high end off of each of the delays since I hope you are not recording in room that reflects everything back 100% (I'm not sure if this physically possible).

While this certainly isn't 100% realistic, it will clearly illustrate the crappy tone we'll hear in a small room. This “crappy” tone is commonly called “boxiness” by engineers. It has a “smearing” effect on any instruments. It makes your tracks sound dull, but also somehow harsh at the same time.

If you recorded your track in a room like this, you probably already have this boxy effect, but it's probably a little more subtle.