EQ tips for desk, monitoring and PA

[Al Krow]

@EBS_freak recently posted a very helpful note for setting up the EQ and, in particular, applying HPF for kick drum, as an incidental comment on his IEM thread in response to me commenting that "our desk hpf kicks in at 100Hz and up till now the view has been to leave the 50Hz+ region for the kick and just hpf everything else including my bass".

 

I thought it would be very useful to repost it on here as an OP so that it remains easily accessible to anyone interested.

 

I'm sure there is plenty of expertise on this the wider topic of EQ when setting up the PA and I suspect plenty of us have EQ related questions, which we can maybe explore further on this thread.

 

Analogue desk settings suggestions when applying HPF to the kick drum (by @EBS_freak)

There is an easy response to this. For each venue, try and listen for what works best. If you are running an analogue desk without outboard, your options are more limited in terms of processing (compression, gates etc) but it worth remembering a HPF, at say 100Hz, is not literally cutting everything (e.g. hard cutting) below 100Hz. There will be a slope associated with that drop off and that drop off may not be behaving as you think. Let me try and explain how even with an analogue desk, and without the flash toys, you can make your kick drum thud at that fundamental.

 

For the benefit of this example I'll tell you that kick drum fundamentals (depending upon kick drum) are typically somewhere in the 50, 60, 70 Hz zone. (Depends upon type and size of drum, tightness of skins etc)

 

So... I've googled generic analogue desk and the Allen and Heath ZED something or other came up. Quite a common mixer the ZED... so I downloaded the manual to find out what the channel strip looks like -

 

 

So we've got (at the top) a HPF which is 100 Hz. I've looked at the specs of the roll off and it's 12dB/Octave. I'm not sure of the Q on the HPF as it's not stated in the manual - but I'll show that for the roll off, it's not that important anyway, especially when we're using the eq in the manner in which I'm going to show you.

 

So... here's our EQ with no gains applied on any of the EQ filters and no HPF applied.

 

As you can see, totally flat. If you feed in anything in the lows, it will get pushed to your output bus. First things first, let's push in the HPF button and see what that does to our frequency curve.

 

As you can see, with a 12db/Oct cut, it actually starts cutting above 100Hz and tapers down as the frequency lowers in accordance with that 12db/Octave gradient. Now let me show you what is actually happening at that 100Hz point on the HPF...

 

Before we move on too much, lets come back to the Q. In the above example, the Q (shape) is at 0.71... is we lessen it to 0.1, we can see how it impacts the roll off -

 

And if we boost the Q we can influence the eq quite dramatically...

 

But... it's worth noting, the last thing you want on a PA, is a huge bump like this when putting on a HPF (I'm just showing you for your understanding). In reality I would wager Q is probably around 0.75 or 0.71 so there is cut only (e.g. nothing going above the horizontal line in our graphs).

 

So just to get us back on path, as stated before, with the HPF button depressed, your EQ is going to look something like this.

 

OK. Now lets look at the LF filter on the channel strip...

 

As you can see, this is at 80Hz and is a low shelving filter (as shown by the logo under LF)

 

So lets whack that up to +15dB and see what we get...

 

You can see that shelf curve in action (curves upwards and then flattens out (the orange section). Our resulting EQ curve shows we are still getting a boost of low end from around 50Hz and above. So thats our target kick drum zone right there... however... it's also probably including a lot of unwanted mush because of the breadth of frequencies being boosted.

 

So what can we do...?

 

Lets set the LF back to 0 to get back to just our HPF being applied.

 

... and now lets draw our attention to those lower mids on the channel strip.

 

 

So bearing in mind I told you a kick drum fundamental could be typically found around 60Hz, lets apply a boost of 15dB with a Q of say, 2. (Obviously you'd be using your ears to determine how much you want to boost that frequency so it sounds right - and remember, the volume of kick controlled via this channel (for the overall mix) would be controlled via the fader)

 

Well, would you look at that! A kick drum fundamental which is poking out like mad but with some significant cut between 70 and 100 where all your mush resides. And on the other side of the equation, you have mega cut from just above 50 which is getting rid of all the sub mush and unwanted energy sapping, speaker punishing frequencies.

 

So there you go, you have EQed your fundamental on your kick drum channel... and you still have the upper mid to address any 200-400 boxiness. You've also freed up a bit of space in your mix for your bass guitar to reside! (although you may want to be EQing your bass channel with a different approach based on what you've just learned - e.g. still using the HPF albeit with maybe some LF and LM with different frequency centre points and Q.

 

Granted, it all depends upon how feature rich your filters are on your analogue desk... but hopefully this has demystified HPF somewhat!

[Phil Starr]

Well I for one found that very interesting, though I still didn't get the "sine wave" bit. That was in the second part of @EBS_freak's answer, Thanks Russ

 

Posted Friday at 13:14 (edited)

  On 11/04/2024 at 12:34, Al Krow said:

Can you talk us through your thinking and how you would go about applying "a sine wave on a gate" please? I'm not familiar with what you have in mind here! 

This one will need a quite feature rich digital desk or outboard (however, I will drop in an easy alternative once I've talked you through it)

 

Basically, kick drums on mics can be quite a pita in the live environment because they tend to pick up not only the kick drum but all the low end rumble crap on stage.

 

So theres a number of things you can do to address this. The common one, is to use two mics. One which is getting the all the beater frequencies and the other which is getting the lows - but the gain can be a lot lower as you don't need to boost the gain on that mic to capture the beater frequencies. Lower the gain and closer proximity to the drum means higher signal to noise ratio without all the bleed.

 

OK what else? You can also apply a gate. The gate stops any signal from the mic getting onto your mix bus. Once a threshold is exceeded (e.g. a kick drum is kicked), the gate opens and lets the sound of the drum through... before closing again. All this means is that you get the sound of the drum but the ambient mush which is present whilst the drum isn't being kicked doesn't go into your mix. However, the low end you are getting may be that fundamental plus still quite a lot of mush. So how can you get all the low end fundamental without the mush?

 

Answer? Fake it.

 

So you use a mic to capture the beater and roll off all the low end and associated mush. So how do you get that low end thump of the kick? Easy - that's where the sine wave comes in. So lets choose say 60Hz. Set up a sine wave (some desks have sine generators (usually labelled oscillators) - other desks without the functionality, you'll need to plug in a sine generator onto another channel - however, if you haven't got an oscillator, it's unlikely it will support the next bit).

 

Of course, what you have now is a permanent sine wave present on your mix bus. What you need to do is configure it to be side chained and triggered when the gate on the kick drum channel opens. When you've done that, you'll end up with the kick drum with the inferior low end being augmented with the pure sine wave. That will give you purest bottom end - and with some big subs, you'll be pinning people to the wall with the most precise sounding kick drum you've ever heard.

 

BUT>>>>> as I said, not every desk can support this. Whats the alternative?

 

Drum trigger. I always carry around a Roland TM-2 with a RT30K trigger. This gives you the opportunity trigger a sine... but if you are going to do that... you may want to trigger the complete kick drum sound completely. Whats not to like about a lovingly crafted studio quality kick drum sample in a live setting?

 

And that's it!

 

PS this is a cheat which is also used on more studio recordings than you would think. Gives you that low end precision which a mic simply can't deliver.

Edited Friday at 16:51 by EBS_freak

Edited April 17 by Phil Starr

[EBS_freak]

11 hours ago, Phil Starr said:

... though I still didn't get the "sine wave" bit. That was in the second part of @EBS_freak's answer...

 

Especially for you @Phil Starr - https://www.basschat.co.uk/topic/389429-the-iem-in-ear-monitors-bible-thread/?do=findComment&comment=5173832

 

 

Edited April 17 by EBS_freak

[Phil Starr]

10 hours ago, EBS_freak said:

Especially for you @Phil Starr - https://www.basschat.co.uk/topic/389429-the-iem-in-ear-monitors-bible-thread/?do=findComment&comment=5173832

 

 

And for anyone else interested. Follow the link people, there are a series of sound clips showing the sound before and after the technique. Really interesting even if your desk doesn't have that facility. If nothing else it'll make you think about your drum mic placement to get that mix of the 'click' and resonance.