Equalization before compression?
I am often asked the question whether or not the EQ should be placed before the compressor. The answer, as is most often in post-production, is “it depends.” I have developed a set of simple guidelines that I generally follow to help answer the question of where to place the EQ in the signal chain.
1) If the mix requires a large amount of corrective equalization in the low-end, say 400hz or lower, then I almost always place an EQ before the compressor. The reason being is that the low-end of a song has the potential to “eat up” a large amount of headroom in a mix. For instance, if there is a huge low-end to a song, clearly more than is desired, then it would be unwise to place a compressor first in the signal chain because the low-end would over-manipulate the compression threshold. In this case, it would be smart to place some corrective EQ on the mix, roll of some of the lows to a desired level, and then run the mix through a compressor.
2) If the mix is lacking low-end then I usually place an EQ prior to the compressor. Again, the amplitude of the low-end of the music will play a very big roll with the compression threshold, therefore getting the bass-end close to desired levels is recommended. In this example, if you decide to compress the song first then you run a risk of over manipulating the mid-range and creating a situation where the compression is not transparent. This can be a desired result in some cases but usually not.
3) In the event the EQ is placed prior to the compressor for corrective purposes then please remember there is no rule that says one cannot place another EQ after the compressor. In most cases I will use several EQs on a mastering project. There are certain EQs that are great for the low-end of music (i.e. API), and there are great EQs for just the high-end (i.e. Manley Massive Passive) and others that are great for transparent correction.
Again, there is no right or wrong here, just practice and experimentation.