Hall, Plate or Church, Please?
by Phil Gates

For this month's topic, I'd like to talk about reverb. Well, more specifically reverb in Digital Audio software programs. As you may have noticed, these are much more involved than the "Reverb" knob on our amps. (One knob for all of our reverb characteristics, how nice.) It's much more involved in software. You have early reflections and room size, delay, diffusion, reverb time, density, and other factors that can make a huge difference in the sound of the reverb, and the track for that matter. Here's a screen shot of a typical reverb control panel from Logic Pro. Use this as a reference for the rest of this column:

Pretty cool looking, but what does it all mean? Let's take a peek at some audio to help prove the examples. Here's a dry rimshot from a record I'm producing right now. It has no effect, or EQ at all:

Example 1

Now here's the same with reverb.

Example 2

Hear the difference? A reverb can bring a nice environment to a sound. This is really what a reverb is; it essentially brings an acoustic environment to a sound. To make it sound (in this case a rimshot) like it's in a different space than it was originally recorded in. This can give it depth, but at the same time it gives the sound anything from a more natural feel, to a way out extreme sound if desired. The settings from the above screen shot are the settings for the 1st wet example.

Now that we've heard the dry/wet difference, let's talk about the different controls a reverb may have.

Initial Delay. This is the delay between when the sound occurs, and when you want the reverb to BEGIN. If I set this pretty high, say 200 milliseconds, this is what it would sound like:

Example 3

As you can already tell, that's an entirely different vibe than example 2, which can be cool in some cases.

Room Size
Now deciding the size of the room you want the rimshot to sound like it's in would be done by adjusting (simply enough) Room Size. Examples 2 and 3 were in a room about 5 meters (measuring the distance between two corners).

Now if I change this, to say 52 meters, you'll actually hear the delay of the sound hitting the other wall, then the reverb of it. Take a listen:

Example 4 Room size

Quite a difference again.

High Cut
You can even EQ a reverb, within the reverb. This can be done by tailoring the characteristics of the reverb. A simple, yet certainly effective tool on a reverb is the High Cut. This can make reverb less harsh and more warm. I use this on vocals. If it's more of a pop song, I may keep this setting at a higher level, like 6kHz. On a ballad, I may bring this setting down to around 3kHz. What this means is that I can control what the highest frequency of the reverb will be. This is useful to simulate whether I want the room to sound like the walls were made from stone or glass:

Example 5 high cut @ 12kHz:

Or a more material like wooden wall sound with the Hi cut at 1200Hz:

Example 6

I made the examples here more extreme, but you'll get the idea. On the first, I had the Hi Cut basically wide open at 12k, then, cut down to 1200Hz on the second example.

Next is reverb time. This is the time it takes the reverb to drop by 60dB. A normal room might be around 1-4 seconds, larger rooms would have larger times.

Here are three different reverb times, a small reverb time:

Example 7

Example 8, a medium reverb time:

And Example 9, a long reverb time:

So these are just the basics of reverb. The entire conversation can be chapters long. In application reverbs are like salt. It's a nice to add a little in that it sounds good to a point, but a little too much can ruin a whole mix. Luckily for us though, we can take the reverb back out if we want.

There are no steadfast rules on reverbs. Just make sure to keep it tasty. Also, to save energy on your DSP, you might want to try using subs for your reverbs. By this I mean if you have a bunch of different back-up vocal tracks, but want them all to sound as if they were in the same environment, don't assign the same reverb to every channel. Send every channel to one reverb. Sub groups are great for this. Use an AUX send to send a much of each track to the reverb. Some voices may need more or less reverb than others. Vary the Aux send level for each track to achieve this.

The terminology for reverbs comes from the origin of that reverb sound. A Hall reverb sounds like a large hall, a Church like a church, and a plate sounds like a dinner plate NOOOOO!!!!, That term comes from one of the original ways to make a reverb, an EMT Plate. Invented in 1957 by EMT of Germany. This is a thin metal plate, suspended in a 4'x8' sound proofed enclosure. A transducer (small speaker) is mounted on the plate to cause it to vibrate. Multiple reflections from the edges of the plate are picked up by two small microphones. You could change the reverb time by using a pad which can be pressed against the plate to dampen the reflection of the plate. You don't really see them around anymore, but the name exists on reverb controls because it is such a desired sound.

At any rate, try out some of these different settings, and see which work for your applications. It may not be just one knob fits all anymore, but that's a good thing when mixing.

Have fun,

Phil Gates

http://www.philgates.com
www.myspace.com/philgatesmusic