Category Archives: Live Audio Tactics

Tips, tricks, and strategies for concert sound in small venues.

In Defense Of Smoothing Your Traces

In the end, you have to be able to read a graph for the graph to be useful.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

There are people out there who insist that, when measuring an audio system, you should never smooth the trace. The argument is that you might miss some weird anomaly that gets filtered out by the averaging – and, in any case, the purpose of graphing a transfer function isn’t for the picture to look nice.

I think that’s an understandable sentiment, especially because it’s a thought uttered by people who I think are knowledgeable, respectable, and worth working alongside. At the same time, though, I can’t fully embrace their thinking. I very regularly apply 1/6th octave smoothing to measurements, and I do it for a very specific reason: I do indeed want to see the anomalies that matter, and I need to be able to clearly contextualize them.

The featured image on this article is an example of why I think the way I do. I’ve got a bit of a science-project going, and part of that project involved measuring a Yamaha DBR12. The traces you see in the picture are the same measurement, with the bottom one being smoothed. The unsmoothed trace is very hard to read for all the visual noise it presents, which makes it difficult to make any sort of decision about what corrections to make. the smoothed trace gives me a lot more to go on. I can see that 90 Hz – 150 Hz could come down a bit, with 2 kHz – 7.5 kHz maybe needing a bit of a bump to achieve maximum flatness.

So, I say, smooth those traces…but don’t oversmooth them! You want to suppress the information overload without losing the ability to find things that stand out. The 1/6th octave option seems to be the right compromise for me, with 1/12th still being more detail than is useful and 1/3rd getting into the area where too much gets lost.

And here’s another wrinkle: I support unsmoothed traces when you’re measuring devices that ignore acoustics, like the transfer function of a mixing console from input to output. In such a case, you should expect a very, very linear transfer function, and so the ability to spot tiny deviations is a must. The difficulty is when you’re in a situation where there a gazillion deviations, and they all appear significant. In such a case, which I’ve found to be the norm for measurements that involve acoustics, filtering to find what’s actually significant to the operation of an audio system is helpful.


Rusty Halos And Screaming Feedback

Your biases can kick your own butt.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

I am sometimes hired to go in and fix things.

Such was the case with a recent event at a small but classy amphitheater. The show promoters had brought me in because of severe problems they had encountered on the previous attempt. A year earlier, the show had been badly marred by persistent feedback issues, and there was a real (entirely founded) concern that the house crew was simply not up to the task.

“The monitors were SO LOUD,” it was said to me, and I was sure I could make things better. Firstly, I would be sure to run things at a reasonable volume – and the rest would surely be academic.

Thus, I got the gig. Then we had a site visit. At the end of the visit, I made a plan: I would take some of the realtime workload off the house FOH engineer by running monitor world. They had all the loudspeaker hardware we needed, so I’d just bring a console and a split. No problem!

The day came, we patched in, and started line checking. Everything was fine, although I felt like I had to be “on the gas” to get a reasonable amount of SPL from the wedges. Nothing truly weird there.

The first act was a couple of tunes in when the trouble started. Feedback started building up, getting progressively worse until a mic on an acoustic guitar blasted off with a shriek that drove the input into clipping. I quietly rolled my eyes at the FOH engineer, thinking that they were winding things up without any necessity. At the same time, the lead performer got on the mic and asked for the gains on everything to be dropped. I did so, not believing that anything was wrong with monitor world, but definitely wanting to make an audible change for the purposes of keeping everybody calm. I mean, hey, FOH was not to be trusted. (This is a general rule. If you’re on monitor duty, FOH is the problem. If you’re on FOH, monitor beach is at fault. If everything is fine for audio, look out! Somebody in lighting is about to screw up.)

Anyway.

Things did indeed settle down, so I thought, “Now we can get monitor world back to where it’s supposed to be. The performers will be happy to hear themselves again.”

*Screeech!*

“Geeze, FOH…” I thought.

The stage manager asked me if there was anything I wanted to relay up to the FOH mix position. “Yeah, let’s pull the whole mix back 6 dB.” Everything seemed okay. I tried to get things back to normal in monitor world, and *Screech!*

Holy crap. The problem was on MY SIDE of the equation! As realization dawned, my brain actually started to work. There was no way that FOH would feed back in that frequency range, unless they were running at a ludicrous volume. It was monitor world. It couldn’t be anything else than monitor world. FOH was just fine…I was the idiot for the day! I had given FOH a “rusty halo,” which is the assumption of continuing inadequacy after a bad experience. Sometimes people deserve a rusty halo, and sometimes not. This was a definite case of “not.”

I’m still not sure quite what happened. The only explanation that seems at all reasonable to me is that the powered wedges we were using somehow underwent an unexpected increase in onboard gain. How that was precipitated, I can’t really guess, though the monitors that seemed to be giving me trouble were exposed to heat and sun until shortly before the trouble began. (A general cooldown of the components in the boxes seems like a farfetched reason to me, but that variable does correlate with the problem appearing. Correlation is not necessarily causation, but still.)

It was revealed later that the monitor wedges we used almost always seem to do something strange to the house crew. We say that it’s a poor craftsman who blames their tools, but if your tool is inadequate or dangerous then you can’t possibly do your best work. My guess is that the personnel at the venue are perfectly adequate to their tasks, and faulty equipment is their downfall. The same thing happened to me as what I imagine happened to them: They had things working perfectly well at soundcheck time, and then the wedges launched themselves into orbit. “The monitors were SO LOUD” had just become part of my own reality, which leads me to believe that I encountered the same issue as they did the previous year.

In the end, though, the important lesson was that I didn’t take the appropriate actions at an appropriate speed, because I was assuming that my side of the mix could not possibly be at fault. No! Your side of the show can ALWAYS be the problem. Look. Listen. Consider. Act.


Delayed Response

My plan worked – and much more smoothly than I was anticipating.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

This past Saturday, I implemented my plan for delay speakers at IAMA’s Bluegrass Night. I can report the following:

1) The plan basically worked as expected, with a few caveats. I ended up setting the delays at around the 70-foot mark rather than 80, because 80 felt like it was a little too far back. (There were also some handy trees at 70 feet that worked as natural barricades for the delay stands.) I just “eyeballed” (ear-canaled?) the delay-speaker sound level.

2) Switching out the time-correction on the delays had a very interesting effect. They were loud enough, and close enough to the main PA that de-aligning them didn’t sound like a total mess. The extra volume tended to mask some of the “slap” from the propagation delay. However, when all was time-aligned with the main rig it seemed that the two setups blended into one another nicely. With the correction bypassed, my brain instantly “localized” the delay speakers as a sound source. In some cases the effect was fairly subtle, but when listening to playback that had strong timing cues the result was very noticeable.

3) I’m not sure if it was really the fault of the delays, or if it was more to do with my mix position overall, but I did get the sensation that achieving clarity/ intelligibility in the mix was a touch challenging.

4) I must have guessed right about the level for the delay speakers, because nobody complained at me about the overall mix being too hot or too quiet.

5) What I might do differently on my next attempt would be to set up the delays as another full PA with subwoofers. My decision to cluster all of my subs at the front of the stage seemed basically okay, but I also got a bit of a sense that it would have been better to have more bottom-end support for the crowd sitting further back.

Not bad for a first try, I’d say.


A Plan For Delays

I think this should probably work. Maybe.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

Last year, I did a show at Gallivan Plaza that really ought to have had delays, but didn’t. As a result, the folks sitting on the upper tiers of lawn didn’t get quite as much volume as they would have liked. This year, I intend to try to fix that problem. Of course, deploying delays is NOT as simple as saying “we’ll just deploy delays.” There’s a bit of doing involved, and I figured I would set out my mental process here, before actually having a go.

Then, after all is said and done, we can review. Exciting, no?

So, here’s the idea:

A) Set primary FOH as a “double-hung” system. Cluster the subs down center, prep to put vocals through the inner pair of full-range boxes, and prep to send everything else to the outer pair. Drive the main PA with L/R output.

B) Have the FOH tent sit on the concrete pad about 60 feet from the stage.

C) At roughly an 80 foot distance, place the delays. The PA SPL in full-space at that point is expected to be down about 28 dB from the close-range (3 feet/ 1 meter) SPL.

D) Place a mic directly in front of one side of the main PA, and another mic in the center of the audience space, at the 80-foot line. (The propagation time to the delays will be slightly different depending on where people sit, so a center position should be a decent compromise.) Using both mics, record an impulse being reproduced only by the main PA. Analyze the recording to find the delay between the mics.

E) Send L/R to Matrix 1, assign Matrix 1 to an output, then apply the measured delay to that output. Connect the output to the delays. Also, consider blending the subwoofer feed into Matrix 1 if necessary.

F) Set an initial drive level to the delays so that their SPL level is +6 dB when compared to the output of the main PA. The added volume should help mask phase errors with the delays for listeners in front of the delay speakers, due to the contribution from the main PA being of much reduced significance…but it may also be possible that the added volume will be a problem for people sitting between the delays and the main PA. “Seasoning to taste” will be necessary. (For people sitting between the main PA and the delays, the time correction actually makes the delays seem to be MORE out of alignment than less, so the delays being more audible is a problem.)

So, there you go! I’ll let everybody know how this works. Or how it doesn’t.


Start From The Top

When working on mixing a “bass” instrument, don’t necessarily start with the low frequency information.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

Whenever I have a problem (that is genuinely my problem and not because of the instrument or player) where a bass guitar, kick drum, or other “LF” instrument is just a pile of boom or indistinct rumble, it’s often because I failed to “start from the top.”

Or, the middle at least.

You see, it’s not really all about that bass. I’ve said many times that low-frequency information IS important and part of “the fun,” and that hasn’t changed for me. In truth, though, a mix stands or falls on the absolutely critical midrange (where almost all the musical information actually sits). It’s my very strong opinion that the midrange information, then, should be what you start with whenever possible. The “impact” of a kick drum? The sound that makes that giant percussion instrument sound like it’s aggressive and smashed against your nose? That’s almost always high-mid information and up. The definition and character of a bass guitar that really gives it the ability to speak in a musical way? Low-mids and up.

So, I say to you, get those areas right first. Yank down your aux-fed-sub drive sends and roll those channel HPF filters up. Use a low-shelf EQ as a sledgehammer if necessary. Especially do this, and do it more aggressively if you’re starting from what sounds like a muddy mess. Then, start pushing that fader upwards. You may need to run your preamp or trim level a bit hotter than you’re used to, but eventually, you should find a place where what’s still passing through ends up dropping into place with the rest of the band. If you’re just listening to one channel at a time, then you can ballpark yourself by finding a satisfying blend with the wash coming off the deck.

After that’s done, THEN start letting some bass frequencies through. You may find that you need a lot less LF than you first thought, especially if you were driving the deep-down sound hard in an effort to hear the instrument in question. I find it quite trivial to create a whole maelstrom of booming slop if I’m using the subwoofers to push something like a kick drum into the right place against everything else, but I find it much harder to make a mess if I park the “click” in a handy place, and then gently move the bottom into alignment afterwards.

It’s a bit counter intuitive, I know, but I can’t remember a time where I put the mids and highs under a microscope first and ended up with a result I disliked. At the same time, I can easily remember all kinds of situations where I didn’t, and subsequently backed myself into a terrible-sounding corner by starting with a bunch of unreadable low end.

Oh, and here’s a postscript bombshell for you: I have a sneaky suspicion that, for many engineers, the subwoofers they end up saying are the punchiest are actually very similar to other offerings in the general class. My guess is that the REAL difference was how the full-range PA mated with those subs, and that’s what got their attention.


Tuning A VerTec System

You can do a lot by simply treating it like everything else you’ve worked on.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

I’m sorry that I haven’t been around much lately – I’ve been busy. Very busy. So busy that I’ve been saying “No” to things a lot.

One element of my busyness has been being turned loose on a VERY classy room in Park City. For the moment, I won’t name it here, although you may have heard of it. (Not naming it here might be a little ridiculous, actually. Anybody can get on my Facebook page and see what I’m doing. Well, anyway…) It’s a little too big to classify as a small venue in my own personal taxonomy, but hey, as we’re all learning, many of the lessons in this business scale up and down.

A task I was allowed to undertake was re-tuning the installed VerTec system. Some big complaints about it were an overabundance of “honk” and “boom,” and the hope was that I could do something to alleviate those problems. I believe I have mostly succeeded in making the rig better, and it was most definitely not an exotic process. I slapped a measurement mic in front of the FOH mix position, ran Room EQ Wizard, and got to work. The measurement traces confirmed what could be heard: The system was very heavy on the midrange, with some troublesome peaks in the subwoofer zone. After a bit of doing, we are where we are now, which is a much flatter place.

The main key, I can say, was to get over my own intimidation. VerTec, or really any similar system, looks hairy because of all the boxes involved. The thing to remember, though, is that for any given coverage zone the boxes are meant to combine into one big source. If you’re going to fret over something, fret over each overall zone of coverage, not the individual array elements. Pick your battles. As Bob McCarthy might say, decide what to tune for and ignore the rest. In my case, I had it pretty easy, because I chose to tune for the main room and not worry specifically about the boxes angled to hit people standing near the hangs. I didn’t have any outfills, infills, or other such coverage areas to consider.

A barrier that I encountered was that we’re locked out of part of the system management processor. With that being the case, I didn’t have the ability to adjust individual bandpass input or output levels. I did have EQ access, though, so that’s what I did all my work with. Was that an ideal situation? No, but what I’ve discovered over the years is that getting the basic magnitude response of a system to behave is the primary battle. I’m not saying other things don’t matter here. I’m not saying that adjusting bandpass gain by way of an EQ isn’t a kludge. I’m not recommending that, but I am saying that you might have to do it sometime, and it won’t ruin your life. Do what you can with the tools you have.

In the end, even with an imperfect approach, the system’s listenability has improved. We seem to be getting compliments on the sound in the room at a regular pace now. I’m certainly looking forward to next spring, when I plan to do another tuning that will start with tweaking amplifier gains first, but for now we seem to be in business.


An Open Letter To Event Planners

We need to be more clear with each other about what it takes to do things the right way.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

Dear Event Planners,

My name is Danny Maland, and I’m what would commonly be called “a sound guy.” A/V. An audio human. Show crew. That kind of thing. I’d like to take a moment to address an issue that has caused me some problems over the years. I don’t know if it’s trending towards worse or better, but as a person with an engineering mindset, I usually pick “assume the worst” and go with it.

Now, before you mentally check out, please be assured that I’m going to stay away from snarky finger-pointing here. We’re all on the same team, and actually, I think that production has not always been good at being on the same team with you. My feeling is that we spend lots of time failing to explain our needs to you, and so assumptions get built that lead to poor outcomes. With that on the table, let me lay out the crux or nexus of this whole thing:

When it comes to the spacetime continuum, production needs a lot of it. A lot of all of it – both space and time.

There’s a significant amount of pressure out there to compress both schedules and square footage. Time is money, space is money, and both together are a lot more money. Clients like to save money, and so do I, but value-engineering live music is not something I can recommend. Any show, even one that is a repeat performance, is itself a singular event that can never be repeated. All of us have exactly one chance to get it right, and squeezing anything that supplies the endeavor (space, time, electrical power, etc.) increases the chance of a trainwreck.

You don’t want that, and neither do we.

As an event planner, I’m going to guess that you like specifics. So here are some for you to consider about space and time.

1) If you’re going to have a full band with pro-production at an event, please consider a 20 foot wide by 20 foot deep area (or about 37 square meters total) to be the bare minimum space for it all to happen inside. I know that some people will say, “That’s overkill!” but I really do mean this. Bands that are forced to be right on top of each other don’t perform to their full potential, and close quarters makes for mic-to-mic bleed that hampers a good mix. Feedback also becomes a real pain when the performers are in very close proximity to the PA system. Yes, some permanent venues have a smaller area to work with, but remember that we may be bringing everything with us. We don’t have the ability to do a fully maximized and tweaked install at the drop of a hat. We need cushion, especially when we’ve just loaded in and everything is spread out.

2) For scheduling, please have any production that’s self-contained with the music set to arrive a minimum of four hours prior to soundcheck. If you’re in a situation with no real loading dock, add another hour or two. We need lots of time to set and tune, especially when the space is one we’ve never been in before. You might think you want us to “throw and go,” but that’s not going to get you great results. I’ve gotten lucky on plenty of throw and goes, but not so lucky on others. I don’t think you want your event to be a luck-based mission. That’s too much uncertainty with too much money and reputation on the line.

The client may push on these things. The event space may try to get you to cut down. Please stand firm! We need your help to get this right.

So, that’s it. Let’s be sure to uncompress everything and work towards better results. Like I said, we’re all in this together. Our success is your success, so let’s work as a team to produce amazing things.

Best regards,

Danny


The POTH Commentaries – Monitor Engineers Are An FOH Engineer’s Best Friends

A good monitor engineer makes life so much easier.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

Let me tell you about a sound craftsperson called Jason Knoell. Jason Knoell runs H2 Audio out of Provo Utah, and he was the monitor engineer on Pigs Over The Horizon. He made my life so much easier, it was almost too easy.

Jason works with Advent Horizon (the core of the POTH lineup) on a regular basis. With that being the case, he was a natural choice for me to bend my rule that monitor world is not a junior-level position. Let’s be honest, I was also being selfish; I wanted to SEE THE SHOW, DANGIT! In any case, Jason knows what he’s doing. While he’s technically junior to me, industry-wise, he’s not “the new guy” by any means. He’s built a reputation with Advent by doing good work, and I knew that I needed an extra pair of hands on the gig. If I was going to pull off both an FOH mix and the run of the lighting computer, someone else would have to be on point with taking care of the band and FX cues.

Thus, Jason.

(I should also clarify, if I haven’t already, that the only way for junior-level audio humans to become senior-level is for them to take on additional responsibility. At some point, a newer engineer has to run monitor world, or they will never learn how.)

Anyway…

The first major consequence of having someone else running monitors is that my role shifted. For Jason, my job was to be his system tech until everyone was settled in on deck. This meant that, as much as possible, everything was set up, tuned, and “pre-dialed.” The functional goal was that Jason would be able to walk up to the console and get the players what they wanted in a fast, frictionless manner. You better believe that, long before Jason arrived, I spent time trying to get the monitors to have a laser-flat magnitude curve, and also that I wound up the vocals in those wedges to find and correct any problem areas – if the engineer is fighting with the system, the system tech hasn’t executed properly.

The second outcome was that my life at FOH was bliss. I barely had to think about the sound on deck at all. I didn’t have to keep an eye out for players with mix changes. I just had to get the FOH PA to comport with what monitor world was doing. Being able to pour my entire attention into that task was a dream come true. In fact, I might go so far as to say it was one of the easiest, “full production” rock-band mixes I’ve ever done. Sharing the mental workload with another person meant that the “struggle factor” I usually associate with a complex gig simply wasn’t there.

The experience also highlighted that I need to make sure to remember to spend significant time in monitor world myself. I also need to keep some “both sides at once” experience in my toolbox. Mixing for the folks on stage is a perishable skill, and it’s imperative that I maintain a good grasp on it. When life gets too easy, an audio human is liable to get soft – and I don’t want that.

But anytime Jason wants to mix monitors for me, he’ll be very welcome.


The POTH Commentaries – Turbo Surround Reverb

It was actually a “mistake,” but I kept it.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

Many things are discovered by accident. The glue for Post-It notes, for instance, was apparently an unintentional result of trying to create a much stronger adhesive. Gated reverb for 80’s-era drum tracks was also a case of “we didn’t intend to do this, but we liked it.” In the same way, Pigs Over The Horizon featured a vocal reverb with nifty characteristics that I didn’t plan out at all. In fact, at the time of the show I was a little surprised by its behavior, only realizing what I had done at a later time.

I had made the decision that any time-based FX processing for the show would be heard from the surround loudspeakers I briefly mentioned earlier. So, into the surrounds went my delay and reverb returns. What I noticed during the show was that, when Rylee, Grant, or Lisa “got on the gas” with a powerful vocal part, the surround reverb would launch like a rocket and punctuate that phrase. When they backed off, the reverb was much more tame. It was a cool bit of drama, so I kept it.

But what was really happening?

A habit that I’ve gotten into as an FOH mix human is to aggressively limit my main outputs. I don’t necessarily recommend my craziness to other people, but for me, the setup operates as a sort of automatic vocal rider, plus a method for keeping a mix in a bit of a box. I can, essentially, decide precisely how much the FOH PA gets to contribute to the overall volume of the show, and then set a “do not exceed” point. With the right settings in place (and a really excellent band on deck, of course) I can smack the limiter with the vocals – which helps to keep the lyrics on top without ripping people’s heads off. (Or, more precisely, it doesn’t rip people’s heads off any more than is necessary.)

So, for POTH, I definitely had that limiter in place. Here’s the key, though: It was NOT applied to the surround speakers. I had completely glossed over setting output dynamics for them. So, a big vocal part would happen, and go into the reverb send at full throttle. The dry signal would continue on to the main bus, where it got brickwalled…and the wet signal would blast through the unlimited surrounds. This “ex post facto” level adjustment to the dry vocal meant that my dry/ wet mix was suddenly tilted more in favor of “wet.” On the other hand, if a vocal part wasn’t smashed into the limiter, then my set proportionality was mostly untouched.

In a way, what I effectively had was an upward expander on the reverb send. A totally accidental one. Was it, technically speaking, “wrong?” Yes. Am I going to keep the basic idea around if we get to do the show again? Also, YES! It was cool! (Well, I thought it was…)


The POTH Commentaries – VCAs/DCAs

VCA/ DCA control is very handy, especially for “non-homogenous” routing situations.

Please Remember:

The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

Want to use this image for something else? Great! Click it for the link to a high-res or resolution-independent version.

Author’s Note: This article is the first in a short series that addresses concepts and happenings related to Pigs Over The Horizon, a Pink Floyd tribute starring Advent Horizon and Friends.

When you start working with more full-featured consoles, you’ll likely run across something you might not have seen before. It’s a control feature called the VCA, or sometimes DCA on digital desks. What is this strange creature? What is it good for?

First off: A VCA is a Voltage Controlled Amplifier. The “D” comes in as a way to say that the same concept is being applied in the digital realm. (In my opinion, a digital system has it much easier, because you don’t have to work with analog circuit logic and the complexities of components or circuit layouts that come with that whole business.) The whole notion rests squarely on how it’s possible to build gain stages that modify the applied change to an audio signal in proportion to a separately applied control signal. If you have a number of control signal generators available, and can choose which control signal to apply to other gain stages, then you end up with a number of VCA/ DCA assignments. Connect a fader to the control signal generator such that the control signal is modified by that fader, and you have a VCA that’s intuitive to manage.

The VCA/ DCA concept, then, is that of a control group. When you assign faders to a control group, you are directing the console to maintain the relative balance that you set amongst those faders, while also giving you an overall level control for all of those channels at once.

“Like routing all those channels through a bus?” you ask.

Yes and no. The magic of the VCA/ DCA is that you get bus-like level management, but your routing is unaffected. In other words, VCA/ DCA groups are control groups independent of audio signal considerations. This was a big deal for me with Pigs Over The Horizon, because of how we did the playback FX.

The playback FX were in surround. Two channels were routed up front (in mono, actually), with two more channels that were sent directly to surround left and surround right, respectively. Once the surround channels were “lined up” with respect to each other and the feeds to the front, I didn’t want to change that relationship – but I DID want to be able to ride the overall FX cue volume if I had to.

I couldn’t achieve what I wanted by busing the four FX channels together; They would all have ended up going to a single destination, with no way to separate them back out to get surround again. By assigning them to a DCA group, though, it was a cinch. The routing didn’t change at all, but my ability to grab one control and regulate the overall volume of the unchanged balance was established.

Of course, busing is still a very important tool. You need it whenever you DO want to get a bunch of sources to flow to a single destination. This might not just be for simple combining. You might want to process a whole bunch of channels with exactly the same EQ and compression, for example, and then send them off to the main output. If that’s not what you’re after, though, a VCA/ DCA group is a great choice. You don’t chew up a bus just for the simple task of grouped volume control, and if you change your mind on the routing later it’s not a big deal. Your grouped controls stay grouped, no matter where you send them, again, because of that “independence” factor. The VCA/ DCA has nothing to do with where signals are coming from or where they’re going – it only changes the gain applied.

I personally am not as heavy a user of VCA/ DCA groups as some other audio humans, but I see them as a handy tool that I may end up leveraging more in the future. I’m glad I know what they are, because they’re a great problem solver. If your console has them, I definitely recommend becoming familiar with their usage. The day may come when you need ’em!