Building Proper Gain Structure Pt. 1

Image courtesy of El Gran Dee, used under Creative Commons.

Image courtesy of El Gran Dee, used under Creative Commons.

While I’ve written about gain structure before, I continue to run across people who don’t fully understand it. And that means one thing; I need to keep writing about it. I actually understand why many people have a limited understanding of proper gain structure. It’s not glamorous like plug-ins or digital consoles, and there is really nothing new to discuss. However, if you’ve never gotten a good handle on how to properly set gains on your console, there is no time like the present to learn.

If your gain structure is whack, no amount of EQ, plug-ins or compression will fix it. For this post, I will focus primarily on input channel gain structure (overall system gain structure is another post, but I’ll mention it briefly). 

 To Hit the Pre's Hard Or Not?

It has often been debated whether it is better to hit the pre-amps hard then turn down at the main output, or run the mains up around unity and dial back input gain to get the SPL you want out of the system. As a general rule (there is an exception, which I’ll detail in a minute), I would argue the former is the correct (or at least better) method, and here’s why. Most pre-amps sound best when you hit them pretty hard—at least up to the point of clipping, which is too hard. By running your pre-amps hard—and by hard I mean within 6-12 dB below full-scale on a digital board, or within 6-12 dB of clipping on an analog board—you are maximizing your signal to noise ratio. Typically, preamps  just sound better when you keep the levels up. Keep in mind, that’s a general rule, your mileage may vary. Now, it’s quite possible that if you dial your input gains up so that all your pre-amps are running high, your overall system level will be too high. That’s when you would lower your main level to compensate. This method will keep the signal to noise ratio high throughout the mixing chain, and will attenuate the signal at the last possible moment. 

Goals of Proper Input Gain Structure

Before we get to setting up the gain structure, let me lay out my goals in for the process. First, I want to maximize S/N ratio. Keeping the input level high means I won’t be boosting it later, which adds noise. Second, I like to mix with my faders around unity. Mixing with faders at unity is another key ingredient to good mixing. 

The fader resolution is highest right around unity, so you can easily make small adjustments. If you try to mix with your faders at -20, a slight change in fader position might yield a 3-5 dB change rather than the 1-2 you actually desire. Finally, I want to be sending a very solid signal out of my mixer to the processors to again maximize signal to noise. 

Using All the Bits?

At one point, I believed that if we were mixing in the digital world, we wanted to try to use up as many bits as possible to keep S/N high. And that may have been true at one point, but now that even inexpensive consoles are using 24, 36, 40 and higher floating point resolution internally, we effectively have unlimited dynamic range and high S/N ratios. Modern digital consoles are very quite and have great dynamic range. So the point of running the input gain high is really to extract the best tone out of the pre’s. 

So now that we have some understanding of the goals of the process, we need to consider how to properly set up the gain on the console. And that will be the focus of the next post.

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Don't Skip These 3 Steps in a New Building

There are some conversations that I have over and over. Of late, conversations about building a new building have been popping back up. Of course, hundreds of things need to be considered when building a new building, but there are few themes that seem to get missed more often that not. Skipping these things ensures two things: First, you and your congregation will not be happy with the performance of the sound, lighting and/or video in the room. Second, there will remain a healthy market for companies that specialize in fixing churches that were designed and built poorly. 

With that said, here are three things you cannot skimp on when entering a building project.

Fix the Acoustics Before You Build

First, the overall acoustic signature of the room has to be correct. This is where most churches take short cuts. They let the architect design the building; which is fine except most architects really don’t understand how acoustics work. Now that I work with architects, I understand why. They don’t look at buildings the same way we do as production folks. A few are getting better at it, but they're the ones who design churches for a living and have AVL guys on staff. 

The problem is most architects want the room to look nice and be easy to build. They never consider standing waves, comb filtering, reverberation time, reflections, and other nasty acoustical anomalies that will make it hard to get decent sound. Some argue that it can be fixed with electronics. It can't. There is no magic black box that will suddenly cancel out the bounce off the back wall that makes it really hard for everyone in the room to hear what the pastor is saying. 

So I strongly suggest all churches have an acoustician look at the plans before they are finalized. Most of the time, it only takes a few tweaks here and there to make a huge difference in how intelligible the room will be, and most of the time the cost to build is the same or only marginally higher. Very few churches get this part right, and it's why there's a huge market for acoustical study and retrofit of existing buildings. Given the acoustic treatment budgets in some of our remodel projects, I can guarantee you it’s a lot more expensive to fix it later. 

Don’t Skimp on Infrastructure

The second thing to consider is infrastructure. Again, most churches don't think of this. Audio, video, and lighting take a lot of wiring. If you leave it to the electrician to do it, you will be fighting the building forever. Especially if you are on a concrete slab. You need an easy way to get cabling from the tech booth to the stage; to speakers, to video projectors and to the dimmers. That means conduit. Conduit is cheap and easy to put in as the shell is going up. Afterward, not so much. Once you determine your needs for right now, lay out the conduits you need and make double-dog sure they get put in. Then add a few more empties just in case. And go big on the empties. Nothing is quite as frustrating as trying to figure out how to get a VGA cable down a 3/4" conduit (unless you enjoy making up Mini-15 connectors...). Having a couple of empty 2" conduits will make your life (or someone who comes after you) a lot easier in a year or three.

Get Your Systems Integrator Involved Early

The final thing (well, I could think of a dozen more, but these are the biggies) is to get your A/V/L systems integrator involved in the project now. Again, most churches wait until the building is up and drywall is being taped before considering who they'll use for the A/V. Bad idea. As with the acoustician, the earlier you get the A/V guys involved, the easier, cheaper and better the final product will be. They will be able to tell you what kind of wire to have pulled while the building is open. They can work with the acoustician to get the speaker fly points set correctly. They will be on the watch to make sure a duct run doesn't end up where you need to put a screen or projector. 

Choose your vendors carefully of course; make sure they have a proven track record of getting church design & install correct. Don't skimp on the design and planning phase. Cut out equipment if you have to. You can always re-purpose your existing mixer and upgrade to digital later. It's a lot harder to acoustically retrofit a poorly designed building. It's better to start with just a few lights and add as you go than to be fighting too low of a trim height because the building wasn't designed properly.

There is a lot to do when starting a building project. Sadly, the systems that churches rely on every single week to create powerful and engaging worship experiences are often afterthoughts at best. Don’t make that mistake. Your congregation will thank you later.

Roland

Loudspeaker Buying Guide Pt. 3

In the previous two posts, we considered some questions that we need to ask and answer before selecting a PA. Once we have an idea of what we’re trying to accomplish, what our design criteria are and how we can implement that design, we still have a few more choices to make. I told you this wasn’t an easy process!

Powered or Unpowered?

A decade ago, an audio amplifier was big, heavy and required a lot of current to work well. Today, even powerful amplifiers can fit into small spaces and don’t weigh nearly as much. As a result, more manufacturers are opting to include them in their speaker systems. There are some significant benefits to this approach. First, the amplifiers can be exactly matched to the speakers. Since the amp is in the box, cable runs are incredibly short, which means nearly 100% of the amp’s power is deliver to the speaker, not turned into heat in the cable. Crossover points between drivers can be optimally set, and often DSP included in the box, which makes for a far more predictable system. 

The downside is that if an amp goes on a speaker that is 50 feet in the air, someone has to go up and change it. You also have to supply power to your powered speakers, which means double the number of cables running to each box. And the inclusion of amps also means the powered speakers will be slightly heavier than their unpowered brethren. This is not typically a problem, but it has to be considered. 

Which is better? Like all things in audio, that depends. Often times, powered speakers are an excellent choice as many of the tuning decisions have been optimized at the factory, which means it should take less time getting them sounding great in the field. On the other hand, if your installer wants to do something rather custom to accommodate a specific situation, sometimes the added control of separate components is better. The availability of power and space for amps also factor into the decision. 

Thankfully, there are excellent choices in both powered and unpowered varieties and it’s not uncommon to see the same speaker available in both powered and unpowered versions.

Line Array or Point Source?

Line arrays—multiple identical boxes hung close together in a vertical line—are all the rage right now. And to be sure, they solve a lot of problems in certain situations. They typically boast good pattern control, are very efficient and are easy to rig; characteristics that make them excellent choices for large venues. Nearly every large tour is using line arrays right now for those (and other) reasons. They are not the right choice for every venue, however. 

Smaller rooms (under 500) will often be better served with a more traditional point source box. In small rooms, it’s difficult to hang a long enough array to achieve good pattern control, and they get very expensive very quickly when compared to a point source system. Don’t fall into the trap of thinking that since line arrays are “new technology” they are inherently better. There has been a lot of development going on in both types, and modern point source systems can be incredibly effective when designed well.

A relatively new type of system is emerging as a great problem solver for certain rooms; the digitally steerable array. Using a larger number of small drivers and a bunch of digital signal processing (DSP), these systems can be life-savers for problematic rooms. A digitally steerable array can vary it’s coverage both vertically and horizontally to keep sound going where the people are and away from where they are not. Because they typically use a bunch of small drivers, their footprint is small making them ideal for very traditional rooms where aesthetics are a big deal.

Get a Listen

If it’s at all possible, you want to listen to the speakers before buying. Ideally, you would be able to hear them in your space. This may not always be possible, or it may not be free. You may have to spend some money to rent the speakers, or at least pay for a demo. If you’re looking at a smaller system, the local rep may have some boxes he can bring by. You may not get a whole system, but you’ll get a good idea of whether these speakers will work for you or not. Having a set of tracks of your band using virtual soundcheck is a terrific way to audition the speakers. If you can’t arrange for the speakers in your room, try to visit a venue that has them. This is less ideal, but will give you a good idea of what they sound like.

Conclusion

Which type of speaker to buy comes down not to selecting the “best” speaker, but rather the best speaker system for the room. Thankfully, the science of speaker design has evolved to a point where we can accurately predict performance before hanging boxes. Being able to try out different models inside the computer is a great aid to developing a great sounding system. What speakers you select will vary depending on the room, style of service and what environment you are trying to create. There are plenty of options out there, so with proper research and a good design, the end result will be a system that meets the needs for your church.

“Gear

Today's post is brought to you by DiGiCo. DiGiCo audio mixing consoles deliver solutions that provide extreme flexibility, are easy to use and have an expandable infrastructure, while still providing the best possible audio quality. Visit their website to learn more.

Church Tech Weekly Episode 215: I'm a Tech Director Not a Theologian

Live from SALT 14! Where does art come from? Usually from pain. We unpack that thought and start a discussion about how our worship services may change.

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