I'm about to post some video entries on processing drums that include my use of equalization (EQ). I have a love/hate relationship with EQ (extreme on both sides), and I thought that is might be a good time (before I post those videos) to ramble briefly about my overall approach to EQ. With regard to EQ while tracking, please see my earlier post on the subject.
Regarding EQ in general, I take a subtractive approach first. This is pretty much what it sounds like -- subtracting (removing) frequencies that I don't want, rather than adding (boosting) the ones I do want.
Acoustic energy (anything you'd use a microphone to capture) is often very complex, formed from multiple fundamental and harmonic frequencies that interact dynamically to create each voice's unique timbre. Almost no instrument can be radically shaped by manipulating a few frequencies -- that is, by tweaking a few bands on an EQ, even a very nice and expensive EQ, you're not going to convince a listener that an acoustic guitar is really an electric guitar. It will just sound like an acoustic guitar with some EQ (even if the curve is so dramatic that it now sounds like a weird acoustic guitar). You're not likely to affect enough harmonic content and interaction of the multiple, complex frequencies of the instrument to betray the fact that it is, indeed, an acoustic guitar.
Similarly, if an instrument is a bad-sounding instrument, you're not going to be able to manipulate a few frequencies with a quality EQ and convince people that it is a nice sounding instrument. In this respect EQ is quite limited in its ability to 'fix' things in a mix. This is why it is so important to record the best instruments you can, well maintained and tuned, and hopefully played by a competent musician. Then, using a good-quality microphone that is an appropriate choice for the instrument, along with careful mic placement, capture the sound of the instrument as best you can. Then, when you reach for EQ it will be to massage the frequency spectrum to better place the instrument within its spot in the overall soundscape of the mix -- not to 'fix it.'
If you ever hear an engineer say, "we'll fix it in the mix," it might be time to rethink things...
So the overall character of a signal is captured with proper instrument selection, tuning, mic selection and mic placement (yes, gain staging is uber critical too, but I'm this is a blurb on EQ, so I'll save my lecture on gain staging for a future post). EQ will not change the overall character of the sound, but rather just the tonal balance of the instrument (remember, an acoustic guitar stills sounds like an acoustic even with EQ). Therefore.... subtractive EQ makes a great deal of sense as a primary EQ approach.
EQ's main strength is in helping you blend multiple signals together into a cohesive, balanced final mix -- featuring the frequency spectrums (spectra?) you desire in a given signal and attenuating others. Since the basic character (timbre and 'quality') of an instrument is captured apart from EQ, an additive approach to EQ only serves to accentuate a portion of the signal you like.... but there is so much more spectrum information critical to the signal than that one section you wish to emphasize! With a primarily additive approach, boosting frequencies ranges of signals throughout your mix, you will notice that while you 'hear' everything (once you've balanced the faders), you're not really getting the full timbre of the tracks, leaving the final mix feeling somehow incomplete or hollow. Unfortunately, this trait is often blamed on bad converters or plug-ins, or 'recording to digital' in general (often stated by twenty-somethings who have, themselves, never spooled a single reel on an analogue multi-track! But I digress...). This isn't something to blame on digital. Rather, it is squarely the result of poor engineering.
Subtractive EQ processing, however, tames the frequency ranges you don't want, leaving the whole of the rest of the signal, timbre and all, translating naturally within the balance of the mix.
Another benefit of subtractive EQ is that while it leaves the timbre of a given signal relatively intact, it is actually removing amplitude from the signal, increasing that track's headroom. When mixing I find that I remove LOTS of low and low-mid content from tracks that simply don't benefit from it. These lower frequencies have a lot of power in them. Removing them not only makes room for the tracks that are intended to own the bottom of the frequency spectrum (kick drum, bass, etc.), it also drops the power of all signals that are so processed. After awhile I find that I can push up the levels of everything much more to use up the newly available headroom, which makes the mix 'feel' louder, even though it may be hitting the same level on your meters as a version of the mix done with an additive approach.
The 'subtractive' mix will feel louder and more natural.
So I recommend subtractive EQ highly. It's not as obviously sexy as pushing up the frequencies you want to hear, but in the end your mixes will sound more balanced, more complete, more natural, and LOUDER (without resorting to any dynamics processing). That's a win, win, win, WIN!
Thanks for reading.