OK Grandmaster. Compression is a tool, and you may already have one. I'm not familiar with Adobe audition, but compression is often an available plugin in recording software packages. It is a really useful tool. Do you need one? Possibly. Do you want one? Yes. Remember that for many years, perfectly good recordings were made without compression, but now, very few people would consider recording much of anything without one. The most commonly used cheap hardware compressors are FMR audio's RNC (really nice compressor- no kidding) and DBX166, and one by Joemeek. High end compressors include the Distressor, and offerings by Avalon and TC Electronics.
Some compressors are called "optical", and it's really just a different electronic path to compression. Some compressors are "clean" and others "colored". The RNC is on the clean side, Joemeek on the colored side.
So what is it? Simply put, compression reduces the difference between the loudest and quietest part of a recorded signal, to improve control over the dynamics of a recording. This allows you to increase the loudness of the soft parts without having components in the signal chain (or your ears) being overwhelmed by the loud parts.
It works like this- First, there is an adjustable threshold. Let's say we set it for 100db. Until the signal reaches 100db, the compressor does *nothing*. Then we have an adjustable ratio. Let's say 3:1. For every 3 db above the threshold, the compressor will allow 1. So at 103db, you get 101, at 106, you get 102, and so on. The 2 other parameters are attack and release. Attack determines how fast the compressor acts when the threshold is reached, and release determines how long the compression effect will remain once the signal drops back down. When we have a fairly high threshold and a fairly low ratio, we call it "soft" compression. When we have low threshold and a high ratio, we call it "hard" compression. When the ratio becomes very high, about 20:1, we now call the compressor a "limiter". The soft ceiling has become a brick wall. Most compressors have "make up gain", to replace gain that the whole signal has lossed due to compression.
So- what do we use it for? There are 2 basic schools of thought here. The first group says that compression is a kind of necessary evil that we use sparingly, only when we have to. These guys avoid compressing as much as possible when actually recording, using it only on very dynamic sources that go from quiet to loud and back again, like drums, and vocalists with less than stellar mic technique. This group will add compression later to an individual track, or even to the finished mix, as desired.
The other group uses quite a bit of compression going in, in order to gain punch and help a signal to stand out in the mix. This is a standard on funk bass and pop vocals. Note this- once you compress something, it is almost impossible to uncompress it. Expanders try to do this, but basically don't. So- if you use a lot of compression when tracking, you need to get it right. Note that "colored" compressors can act as sound filters, and actually change the tone shape of a recording, whether they are acting to control dynamics or not. This is often desired, and can be one of the attractive features of certain compressors, such as Joemeek and Avalon. Cheap compressors often can be heard when they kick in and out, called "pumping", and generally suck. They can also dull the higher frequencies of recordings. The few cheap compressors you find that are popular are appreciated because they don't do that (much).
My advice is to first find out if your software contains a compression plugin. If it does, play around with the settings for practice. For a cheap start, like many people, I like the RNC. It is pretty clean, and has very few of the bad habits of most cheap compressors. It is under $200. Note that it is a stereo compressor, not a 2 channel compressor. Therefore, it can compress one or two channels, but only with the same settings on both channels.
My personal opinion? I'm a group one. I will use soft compression, say 3:1 on some vocalists going in, but I'll usually save compression for post-production processing. If you are recording the 1812 overture, and they roll out those damn cannons, I suggest 12:1. Hope that helps.-Richie
