We’ve all heard stories of the mystically powerful pro audio engineers who can listen to a mix and happily announce, “the guitars have too much 1k on them.” Or perhaps a nonchalant declaration, “the snare would really come alive with a little boost in the 3k range.” This is great if you have the golden ear or the years of experience to identify specific frequencies by sound. What about the rest of us? If you spend your days at the office and are lucky to get a few hours a week in your home studio then you might never log the hours necessary to develop this skill. Fear not, there is a solution. Sweeping an eq is the process of manipulating a frequency band as a tool to help you identify a sweet spot or problem frequency. All you need is a parametric eq and about thirty seconds of time.
Basic eq concepts
To perform this technique you need nothing more than a fully parametric eq. Most modern DAW software comes with a plugin or has the eq integrated into each track. A graphic eq or semi-parametric eq will not be sufficient. To identify a fully parametric eq band you can verify that it has three parameters: frequency, gain, and bandwidth.
Frequency is the center point of the eq band. This is the frequency that you are boosting or cutting. This parameter is expressed in Hz (and kHz).
Gain is the amount of boost or cut to be applied to the frequency of the eq band. This parameter is expressed in dB.
Bandwidth refers to how wide the boost or cut will be. This parameter could be called Q, width, or bandwidth. We are going to be talking about wide and narrow eq bands. A higher Q is a narrower band while a lower bandwidth (or width) is narrower. Check which name your parameter has and be sure you understand which way to adjust it to make it wide or narrow.
Sweeping the eq
So you’ve identified a track that needs some sweetening to really stand out. If you are going to be using an eq plugin (versus using an integrated track eq) it is time to insert it on the channel. I will be using one of my favorite equalizers, the Waves Rennaissance EQ. I will start the process by setting up an eq filter at 100Hz with 12dB gain and a Q of three (about 1/2 octave bandwidth) as shown below.
We have boosted the frequency by an extreme amount (a 12dB boost is not recommended in most recordings). We have also made the frequency band fairly thin. Many equalizers will allow you to use an even narrow band but don’t get carried away. As the band gets narrower it causes more resonance around the center frequency and more artifacts in the sound. If we make the band too narrow we will hear too much resonance to identify the useful frequencies. The sweeping with a width of 1/2 octave is a nice compromise. Start playback of your mix. You should hear greatly increased bass response on your track (due to the 12dB boost at 100Hz). This is when we get to put the sweep in the eq. Grab the control for adjusting the eq band’s frequency and slowly increase (or sweep) it. Listen carefully to the effect this has on the recording. Close your eyes while you continue to sweep upward. Keep your eyes closed until you no longer hear any effect on the track. Open your eyes and you will find you reached the maximum frequency of your eq (typically around 20kHz) or you have gone above the frequency content of the track (getting up to 10-12kHz on a kick drum track for instance). Close your eyes and sweep back down.
That was fun. Let’s put it to use. Repeat the process of sweeping slowly up and down. Listening carefully, try to identify the frequency (or frequencies) that make the track really stand out. It might not sound great because we have exaggerated the boost at +12dB, but it should help you identify the frequency you are looking for. Here are two examples:
- Listening to your mix you decide the snare just isn’t punching hard enough. Since you’ve read my snare drum guide you know you can probably find the body in the 200-400Hz range. To be safe you search an octave above and below this range, focusing your eq sweep from 100-800Hz. You notice the snare body becomes way too thick around 225Hz.
- That saxophone solo isn’t burning up the middle section of your recording the way you’d like. After looking at the sax eq guide you determine you can add some extra heat around 2kHz. Expanding your search range to include 1-4kHz you start your sweep. You notice the sax becomes obnoxiously hot at about 2.2kHz.
A common theme in both examples is finding what we were looking for but having it take over the track. This is why we use the extreme 12dB boost. It helps us easily identify the frequency by over-accentuating it. Now it is time to tweak the eq to be more pleasing.
Adjusting the eq
Using the saxophone example above, leave the frequency set at 2.2kHz where we found all the heat. Set the gain back to 0dB and the Q to 1.0 (about 1-1/3 octave bandwidth) as shown below.
It is time to start your mix playing back again and adjust the gain. Listen very closely during this step. It can help when first learning effective eq to always close your eyes while adjusting. Grab the gain control and slowly ease it upward until it hits that sweet spot. Upon opening your eyes you may be surprised to see it was no more than a 2-3dB boost. If you got a 6-9dB boost don’t be ashamed. If that is what your mix needs then that is what you give it. Now do the same with the Q (or bandwidth) control. This time nudge it wider and narrower listening for that sweet spot. You will find the wider settings give you a more natural transition into the boost but will also appear less focused (which could be exactly what you want). The narrower settings will have more of a slick, produced effect (which could also be what you want) while also accentuating only the element you were after and leaving nearby frequencies untouched. The fictitous sax track in our example could end up looking something like this:
Using eq to eliminate problems
So far we have only discussed how to use this technique to enhance tracks. Sweeping an eq can also be effective as a corrective measure. The process is very similar but you still want to set up your eq band for sweeping with a 12dB boost (rather than cut). This may seem counter intuitive. After all, we are trying to get rid of the problem not draw attention to it. Here are two examples to explain the boost vs. cut philosophy:
- The snare drum in your recording has a terrible buzz. Set up an eq band as discussed above and start sweeping. At some point you will hear the buzz go from annoying to downright intolerable. This is your target frequency.
- Your lead singer sounds just a bit too nasally. Get that eq going with a nice boost and sweep away. Listen for the point at which the vocals go from nasally to sounding like a bad sinus infection. This is your target frequency.
In both cases we found the frequency we were looking for by identifying the point at which the problem got worse. In the context of a mix it can be much easier to identify boosting the problem than cutting it. Try it both ways to convince yourself. Sweeping to identify a problem while you have cut the swept band will often leave you guessing across a very large range.
Once you have identified your problem frequency it is time to tweak it in. The settings you use for fixing a problem can tend to be a bit more extreme than the subtle tweaks for accenting a flattering frequency. Set your gain to 0dB but leave the Q at 3.0 (about 1/2 octave bandwidth). Play your mix while starting to lower the gain, cutting the offending frequency. Do a bit of adjusting the Q and gain controls to find the spot where you can eliminate the problem with the least amount of effect on neighboring frequencies. You can get away with deeper gain cuts when your bandwidth is narrow. If a wide bandwidth is required to doctor a stubborn area then you probably won’t be able to cut a lot of gain without adversely affecting the sound of the track. Do what works for your mix though.
Recommended eq plugins
|Waves Musicians Bundle 2
This is my most recommended way for home recording engineers to get into the quality of Waves plugins. The bundle includes three of my most used plugins: Renaissance EQ, Renaissance Compressor, and Renaissance Vox. Coupled with the Musician’s Bundle 1 you would have just about all the plugins you will ever need in your home studio.
|Waves SSL 4000 Collection
This package from Waves is a bit more expensive and only includes three plugins. Since the eq is the exact same eq in the included channel strip it is actually more like getting only two plugins. I’m not a big fan of the bus compressor which brings it down to just one cool plugin, the channel strip. Oh what a plugin it is though. The higher price and one recommended plugin might make it seem like less bang for the buck, but if I could justify spending the cash on this I would be using the SSL eq on everything instead of the Renaissance Eq. These are very cool sounding plugins.
|Wave Arts Power Suite
Wave Arts are making some great plugins. This bundle does not include a standalone eq but an integrated channel strip. Though the channel strip may be overkill for simple eq tasks the plugin makes up for this shortcoming by including the excellent Wave Arts MasterVerb. This is the only bundle listed here to include a reverb. It would be a good choice if you want to upgrade your general plugin library but have a limited budget.
|Sonalksis SV-517 Equalizer
This is a basic package that includes only the equalizer. It is kind of pricey to get just and equalizer but Sonalkiss make great products and have their die hard fans. If you have expensive tastes this could be your eq.
Sweep your eq
A word of caution: it is not necessary to eq every track in your recording. After learning a new technique it is not uncommon to be tempted to try it on every piece of audio you can get your hands on. Use a little bit of judgment before even considering putting an eq on a track. There is no need to eq your hi-hat if it sounds great and sits in the mix perfectly. Sweeping for eq bands is a technique to turn to when a track is less than stellar or is having a hard time cutting through the mix. Your eq will never let you down if you remember to use your head, your ears, and your heart (but mostly your ears).
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