[Introduction to PA] Basic Knowledge of Stage Monitor Speakers

favorite_borderLast updated:2024/8/4

[Introduction to PA] Basic Knowledge of Stage Monitor Speakers

• PA / sound (audio)Aida Takashi
  Born in 1972, male. Living near the west coast of Kagoshima Prefecture. I sometimes do PA (sound engineering) for live houses and outdoor events.

Put a monitor on the stage

Once you get a little used to it, anyone can connect things like microphones and CDs to a mixer and play the sound through speakers.

Meanwhile, in a sense, the speakers that require even more care than the front-of-house (audience-facing) speakers are the monitor speakers.

We don’t send the exact same sound as the front-of-house to the stage.

A karaoke contest and the like can be handled with that, though.

First, let's use a simple setup diagram to get an idea.

Assuming two floor monitors (wedges) at the musician’s feet.

The word “AUX” suddenly appeared in the diagram.

For now, please keep the word “AUX” in mind as you read on.

I really simplified it for the sake of understanding, so I didn’t include things like GEQ.

First off—sorry to jump right in like this, but...The monitor is sent from the mixer’s AUX output.Please be aware of this.

I stated that the monitor is from AUX, but in reality it depends on the case.

As I’ll explain later, if the AUX output is pre-fader, it’s inconvenient when sending karaoke tracks from a CD or MD to the monitors, and for something like a small karaoke contest, you can just split the stereo output as is.

There’s also a way to make good use of the MATRIX output that comes with the slightly pricier table.

In live situations, we usually send from the pre-fader AUX.

So then, what is this AUX, anyway? It’s short for “Auxiliary.”

If you’re used to home audio, it’s probably a term you’ve seen before.

It apparently means something like “assistance” or “support.”

In short, it’s an output section on the mixer that isn’t locked to a specific use like the main out (stereo output). It’s an output you can use however you like.

But I’ve never seen anyone on-site call it “auxiliary.”

I call it 'A U X,' but there are people around me who pronounce it 'ox.'

So, with that in mind, let’s look at the signal flow of the mixer and figure out how we should connect things to send monitors to the stage.

Pre-fader and post-fader

The figure below shows a hypothetical 4-input/mono-output mixer.

In a 2-AUX configuration, we designed AUX1 to be pre-fader and AUX2 to be post-fader.

Here, two new terms have appeared: “pre-fader” and “post-fader.”

Including the meaning of that term, let’s examine it while following the flow of the signal indicated by the curve.

It’s shown with a red dotted line how the signal flows to the main out, so if you use that as your reference, it’ll be easy to follow.

Just to confirm, as you can see from the red dotted line, the flow to the main out is as follows:Gain trim >> Tone control >> Fader >> Master faderIt's okay up to this point, right?

Pre-fader

In live PA, sending to the monitors is done in most cases using an AUX bus configured as pre-fader.

"Puri" refers to the "pre" in "preamplifier."

People say “pre-event” for doing something ahead of an event, but it means the same thing as “before [something],” i.e., “before ○○.”

In other words, “pre-fader” means that it adjusts the signal before it passes through the fader.

Due to the specifications of the virtual mixer, the pre-fader AUX is designated as “AUX1.”

As shown by the solid blue line in the figure on the left, the signal flow passes through the gain trim, then branches off along the red dotted line and runs to another system.

[Gain Trim >> AUX1 Trim >> AUX1 Master Trim]

In other words, it controls the AUX output while skipping both the tone controls and the fader.

What I mean is that the output is fixed regardless of whether the fader is all the way down or all the way up.

To put it more simply,It feels like they brought another simple mixer.It is.

In the explanation above, I said to bypass both the tone controls and the fader, but be careful: depending on the model, there are pre-fader paths that still pass through the tone controls.

There should be something called a “block diagram” toward the end of the manual, so please take a close look at it.

In that case, the signal flow is:Gain Trim >> Tone Control >> AUX1 Trim >> AUX1 Master Trimwill be

Post Fader

While I’m at it, I’ll write about post-fader sends, which are often used for sending to effects.

About how to connect effect pedalsThis pagePlease look at it.

Due to the virtual mixer’s specifications, the post-fader AUX is designated as “AUX2.”

The flow of this signal is shown with a solid blue line in the diagram on the right.

You can take “post” to mean something like “next” or “after.”

That phrase in the political world where people say, “Who’s going to be the post-Nakasone…?”

A fader refers to the vertical fader located at the very front of the mixer.

In other words,Adjust the signal after it passes through the faderIt means trim.

As you can see from the signal flow, you adjust the signal of the channel you’re operating separately from the main out, but when you raise or lower the fader, the AUX output will automatically follow and get louder or quieter.

The signal flow branches from the point where the red dotted line passes through the fader and runs along a separate path.

Gain Trim >> Tone Control >> Fader >> AUX2 Trim >> AUX2 Master Trim

You get it now, right?

This output is often used for sending to an effector.

At things like cabaret shows, if you’ve got some headroom on the post-fader AUX, it’s often more convenient to use this for the foldback (monitor).

[Practical] Sending a monitor mix via pre-fader AUX

Alright, let’s put it into practice right away.

I tried simulating a live venue with only two vocalists.

What I want you to understand once again is that the red solid line represents the signal flow to the main out, and the blue solid line represents the signal flow to the pre-fader AUX 1 output.

If you send the monitor via a pre-fader AUX like this, you can adjust the monitor without affecting the front-of-house sound at all.

Conversely, it also means you can adjust the surface without affecting the monitor at all.

In other words, you can adjust the balance of the sound heard in the audience and the balance of the monitor sound that the performers want completely independently.

If this were a post-fader output linked to the front-of-house mix, then when it’s showtime and you think, “The person on the left is quite a bit louder than during rehearsal—let’s turn them down a bit,” lowering the left person to balance the FOH would simultaneously lower that person’s voice in the monitors as well, which would be problematic.

In recent consoles (as of early 2012), it has become common for each channel’s AUX trim to have a switch that lets you choose whether it is pre-fader or post-fader.

I don’t have that kind of console, but if I did, when turning a CD into karaoke for something like a music show, I would switch the CD’s channel to post-fader.

By doing this, when you fade out the backing track, the monitor sound can also fade out in sync with the fader operation.

Conversely, if even this backing track is set to pre-fader, the front-of-house sound will fade out, but the monitor (foldback) will keep sounding live and continue outputting until you stop the CD.

Then what should we do at tables where we can’t switch between pre and post?

I’d like to send it back from a post-fader AUX since there’s no other way, but those are all used up by the effects unit.

I'm in trouble.

There are ways to do it, but I'll leave it as homework for now.

If you can accurately grasp the specs of the console you have and the on-site requirements, and instantly complete the wiring in your head, then you’re a full-fledged pro… I guess??

Aside: A live show is a collaborative creation between the musicians and the PA (sound engineer).

Especially for live shows, I don’t recommend staying put in front of the console during rehearsals.

to some extentmidrangeWhen you think things have settled, go up on stage yourself and listen to the monitor sound near the performers’ ears.

It’s a different story if you listen to it once during the preparation stage and can unquestionably imagine how it will turn out from there, but even then it often ends up quite different from what you had in mind.

I’m in my early forties (as of when I’m writing this page), but with younger musicians, when I ask, “Is the midrange okay?” I often get a quick reply like, “Oh, yeah, it’s fine. Thank you.”

But just to be safe, when we actually get up on stage, it often turns out the sound pressure isn’t enough or there’s some other issue.

In such situations, I always propose the following move to the musician.

“If we add a bit more low end to the whole return, won’t it feel more like we’re really doing it?” “Yeah, when it howled earlier, we cut too much. We shaved it down to the point where there’s almost too much headroom, so should we roll a little back for now?” and so on.

A live performance isn’t just about sending the musician’s voice and sound to the audience.

It’s something we create together through communication with the musicians.

In that sense, if you usually make an effort to join the after-parties and, during breaks in rehearsals, maybe share a smoke together (or a coffee), having that kind of relationship makes it easier for both sides to make and receive requests about the sound without holding back too much.

Of course, there are times when the only person I can communicate with is the manager, but it is what it is.

Because managers know performers and singers inside out, try to extract as much information as possible.