Low end frequency problems can plague a mix if they aren’t identified and addressed. In episode 39, I discuss how the low end frequencies can work both positively and negatively. I also discuss how you can control excess low end both on stage and in the sound booth.
Update: Just to be clear, when I talk about mixing the bass and kick drum together around the 80 and 100Hz areas, I’m not talking about rolling off frequencies of one of the instruments. I’m talking about cutting a narrow area so one instrument can dominate that spot in the mix.
Transcript
(Here’s a rough transcript)
Welcome episode 39 of the behind the mixer podcast, I’m your host, Chris Huff. If you’re a member of behindthemixer.com and get the regular newsletter, you’ll remember last week I posted up a huge article on strategies for people who were serious about learning church audio production – same can be true, really, for live audio production in general.
In that article, I covered everything from vocal mixing to critiquing your mix to how to keep your ego in check. What we do has a lot to do with technical matters, creativity, and working with people.
Today, I want to hit a topic that often plagues new audio techs and it’s that of low end frequencies. There are great sounds created in the low end but we don’t always want them. In some cases, we only want them in some channels. Already this might seem a little confusing.
Here in Indiana, if you dig deep enough, you hit a layer of the earth we call Indiana clay. It’s red, firm, and if you add just a bit of water, it becomes pliable enough to make beautiful pottery. Seems like a great medium for pottery work, right?
However, if you’re trying to plant a garden or put in a tree, that same red clay can be a royal pain as we have to remove it and replace it with fresh top soil, or what most people think of as dirt.
Low end frequencies are like that clay, both useful and annoying.
Low end frequencies tend to run below 250 Hz. There isn’t a hard and fast rule on where it begins but that’s a good place to start.
Let’s start with what low end frequencies can provide in a mix. I’d say warmth, energy, and a solid foundation to the music because without enough low end, the mix sounds thin. But as mentioned, low end frequencies can be equally problematic when it’s someplace we don’t want it.
Now imagine a singer with the drums bleeding through into his microphone.
There’s your good and bad.
When we are mixing audio, we want low end in some channels and not in others. How we can control that comes in a few areas.
First, let’s look at stage setup.
What enables a good grab of low end frequencies?
We want the low end of drums, bass, and electric guitars. Even acoustic guitars can provide a nice bit of low end energy as the open string of the low E of an acoustic guitar runs around 82 Hz. For that matter, even the open B string is around 246Hz.
You could be getting sounds from these instruments in a variety of ways, such as on-board pickups, amps, and direct sends.
If you aren’t getting the sound direct into the system, then you want to use a close-miking setup. For example, with a kick drum, you’d want a kick drum mic inside the drum. Or, with an upright bass, I’d place an instrument condenser mic on a stand, close to the strings around the bridge, assuming I can’t use a proper mic like a dpa d:vote 4099.
In the case of stage amps, like guitar and bass amps, you’ve got options. You could run a line out from the amp if the amp has that functionality and get the sound that way. Or, you could mic the amplifier up close – the method I prefer.
You want up close miking because you want to capture the low end at the source so you don’t have to have it so loud that it’s broadcasting out for other channels to pick up. In some cases like guitar amps, you’re still going to get some volume direct from the amp.
The next part of stage setup is musician placement. I don’t want my singer to be right by the drums. I need to watch for proximity to other microphones meant for other instruments or vocals.
Finally, on the stage, I don’t want my singer to use a microphone that’s going to pick up everything on the stage. Therefore, I’m going to tend toward a cardioid vocal mic that the singer will have right up to their lips. I don’t want to get into drum shields and the such but I hope you can now see how the stage work can go a long way to keeping the low end frequencies where you want them.
Now that takes us to the work in the sound booth and, at least in the interest of this podcast, I’m going to focus on removing or reducing the low end where necessary.
Remember how i said the vocal microphone needed to have the low end removed when you’ve got the drums in the background.
We want to remove that low end from the vocal channel. However, it’s not the ONLY low end we want to remove.
When it comes to low end control, we have a few options. The first might seem the obvious but it’s NOT the first place we want to go. And I’m talking about the EQ control for the low frequencies.
This control creates an EQ shelf. That is to say everything below a certain frequency is reduced by the same about. Commonly, we say everything below that point is rolled off but in reality, it’s not. With the EQ control for the low EQ, we can control how much the low end frequencies are cut. For example, 3dB or 12dB or more. Therefore, if you want to reduce, the key word being reduce the low end, you use the EQ control.
However, if you want to remove it completely, you turn to the High pass filter, commonly abbreviated online as HPF. This applies a significant cut and what I’d call a true rolloff of frequencies below a certain point.
Back to the low end in our singers mic.
By using the high pass filter, I can remove everything below a value, such as 100Hz. In the case of analog vs digital mixers, analog mixers are usually using a fixed point HPF such as 80 or 100 and digital mixers give you full control. I have seen analog mixers with a variable HPF but those are rare.
But we’re not done. Just because the drums are gone, it doesn’t mean I’m done with my low end work.
This is where we get into the other way low end can mess up your mix. It can remove clarity, cause it to sound muddy, make instruments hard to tell apart. You get the idea. It’s like a fog settling in over a town – it makes it hard to pick out one building form another.
I might want to reduce some vocal low end or even pick a point in which I only want to cut a thin amount of low end, such as somewhere between the 250 and 350 mark for male vocals to improve clarity.
Reverb
As another tip, watch your reverbs. When you add reverb to anything, you’re performing an additive process and that could mean even more low end and more muddiness. With digital consoles, you can EQ your effects busses. We do this at my church by rolling off much of the lows and the highs because they aren’t what we want reverbed, especially the low end.
I also mentioned different instruments that provide low end, such as bass and kick and guitars. When it comes to mixing these, you need to decide what amount of the low end you want each to have. For example, you might give the bass 80Hz, the kick 100Hz and the upper areas to the guitar. In doing so, you can cut frequencies from these channels so the others come out or you can boost. You might even do a little of both.
There is no simple answer to how you should do this as it depends on what frequency signature you’re getting from those instruments.
Consider today’s podcast as a basic low end primer. There’s a lot you can do to improve the low end, such as I just mentioned with the bass and whatnot but the most important work starts with eliminating it form where you don’t want it.
Thanks for joining me on today’s podcast and if you’d like to learn more about mixing, check out my guide, audio essentials for church sound.
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Very informative… Thanks
If I had to sum up the article, it would be this: it is necessary to have plenty of the right frequencies in the low end of the spectrum for bottom end and warmth, but it is imperative to not have what I call “mud”. Bump guitars in the low mids, but consider putting a high pass filter on them. Bump the bass below 100 Hz (depending upon the bass and how well the system is tuned), but cut the bass in the low mids (to get out of the way of the guitars). Emphasize the fundamental of the kick and low toms, but seriously tame their first harmonic with an appropriate low mid cut. High pass filters on all vocals, and I usually reduce their low mids as well. And know what your system can handle. If you have 12” speakers for mains, you will need to be a lot more creative to get a good clean bottom end of your mix because of the limitations of your system.
Good…, GREAT advice!
One of the very first things I do,(and teach) is to high-pass everything except the kick and bass.
It is amazing how quickly it kills so much rumble and annoying noise.
Downward mixing and subtractive E.Q. …, I am a real proponent of both. :)
Hi Chris, Thank you for all of your insight and guidance.
Just a quick question about reverb. If you have hpf-ed out offensive low-end (bleed etc.) in vocal channel(s), doesn’t that eliminate those frequencies from being reverbed when the signal gets to the effects portion of the board, and so no need to adjust reverb bus (for too much low end)?
God Bless y’all
Yes, you are right on that. I didn’t mean what I said. :) I meant those as two different things…as in good things to do. I didn’t meant to cut it twice. :)
May I suggest that you update the Bass Guitar cutoff frequencies since I personally use all the way down to 15hz in my playing at church. Many 5 or 6 string bass players do the same and would be very shocked to hear no solid bottom in the house mix if our low notes were wiped out of the system. I do understand that most house subwoofers only go to 30hz cleanly so most systems will not play down to 15hz well at all but we can at least let it try. My Bass Cab reproduces cleanly to about 12hz so when our church needs thunder I supply it. Sorry for the Geekiness, I am a retired Electronics Engineer and have been in this type of work for over 50 years.
I wasn’t saying to cut them off there but those are areas where you might want to emphasize them in the mix.
Excellent idea since most Subs do not go much lower than normal woofers in home systems. I was referring mainly to problems like I have had in public performance where the Bass Drum is passing way too low frequencies and it totally muddies up the Bass Guitar sound. My first instrument was drums and the Bass drum in real life is never a THUD as the electronic drums make it. lol
In live sound, there is no usable audible low end below 40hz….
And again, those really low frequencies below 40hz are the major cause of ‘mud’ .
Cut them off and see how the system sounds clean and defined.
Really wipe out the lows from the Synth, Bass Guitar, Organ, and Piano? Not really a good idea. The Mud you may be hearing could be distortion from the PA system not able to reproduce that low so in that case, an investment in true Sub Woofers is called for. Too much boost on the Sub Woofer Channel is often the issue so make sure the PA is not tuned up for ThudMUD instead of clean music. A really good distortion analyzer can come in handy when you are hearing mud even at low levels from the mixer. In my church, when we need clean lows we use my Bass Guitar Cabinet because it reproduces cleanly down to 12Hz. Not all Cabs can but mine is a Discontinued Ampeg model designed to reproduce Extreme lows at high volume cleanly. It sounds much better than most PA systems I have played through. A balanced system is a Happy system in my 50 years of experience.
I agree, I have been using a single 15” bass cabinet as a sub for years. It may be larger than the “compact” units being sold lately, but it really carries the bass!
Sound dept. head, and regular bass player.
Enjoy that warm bass. :)
Bassman.
Thanks for the info Chris. I heard somewhere not to use a high pass filter on drums and bass. I know I need a decent amount of low end in the bass and drums. My goal is to start out by cutting out the excessive, unneeded low end where applicable with a high pass filter on everything except drums and bass. In most cases a low shelf, along with a peak filter reduction or two will help me to rein in that low end on the drums and bass. But there may be times from what I hear in my samples. It may be necessary to add a high pass filter, low shelf and a low peak cut to a drum or bass track. It may be necessary for me to do all of that with some of the none bass and drum tracks. I know I gotta watch those problematic low and high mid frequencies too. Just my two sense. I’m still learning and I think that I may be able to mix some master ready songs this year.
I wouldn’t use a HPF on the bass or the drums but I would apply a cut to one area, like 80 to the kick drum if that’s an area where I want the bass to dominate. You should be able to close your eyes and distinguish the instruments in the mix.
Excellent plan.