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 quiet 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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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

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Loudspeaker Buying Guide Pt. 2

Photo courtesy of Tim Geers

Photo courtesy of Tim Geers

This is part 2 in our series on selecting speakers. As I said last time, deciding which speakers to buy for your church can be a daunting task. It’s typically an expensive decision, and a really expensive one if you choose poorly. It’s important to not simply buy the first set you year, or decide on a system based on a magazine review. Even hearing them in another building may not be a good indicator of how they’ll do in your building. So here are some more questions to consider. 

What is the Vibe?

This goes along with the source; are we looking for quiet and contemplative or loud and energetic? Do we simply want to reinforce some acoustic sounds so they can be heard in the back of the room, or do we want to put the sound right in your face? Even in the extremes, we have options. For example, if we’re going for more of a concert feel, what genre do we wish to emulate? Some PA’s will deliver a very edgy, rock ’n’ roll sound, while others are more hi-fi. Knowing what vibe you want to create will begin to dictate the system you ultimately install. 

What is the Environment?

Churches run the gamut from acoustically live, highly reflective cathedral type rooms, to dampened and treated theatrical venues. Like everything else, the environment will effect the choice of speakers. Highly reverberant rooms will require speakers that have excellent pattern control to keep sound from bouncing off the walls, ceilings and floors. Very dead rooms will require more speakers to energize the space and overcome all the absorption.

There is also the issue of aesthetics. Many congregants would object to a modern, black flown line array in a historic cathedral. In such a room, a smaller, less visually intrusive system is required. Even in modern churches, sight lines, trim heights and other architectural features will dictate one speaker type or another. Make sure your integrator is asking these questions. 

Can We Hang ‘em High?

Some rooms make it easy to hang—or fly—speakers. In others, it’s impossible. In still others, it’s impractical or not necessary. Before you get your heart set on 600 pounds of beautiful, flown, line array, make sure the roof structure can actually support it. And yes, it’s possible your roof cannot support that much weight. In more traditional venues, wall or column mounted speakers are often the best choice as they can blend into the architecture rather easily (especially if they can be custom painted). In some smaller, multi-purpose rooms, portable speakers on sticks might be the best option. 

Can We Afford Them?

Speaker systems can range from a few hundred to a few thousand dollars for small rooms; from ten- to fifty-thousand for medium rooms and upwards of a hundred thousand to almost a million dollars for very large rooms. In those vast categories are all kinds of variations. Some well-known manufacturers are very good, and rather expensive. Other lesser-known companies can be almost as good and considerably more affordable. Not everyone needs or can afford a Mercedes; quite often, we can get by quite nicely with an Infinity or even a Nissan. 

Just be sure to buy enough PA for your room. Too many churches buy on budget and end up unhappy with the results. Build in some headroom; make sure the system can go louder than you need it to so you’re not pushing it to the edge every weekend. 

Those are some general questions and parameters you should be considering before beginning to hone in on your speaker selection. Now that we have that established, next time, we’ll consider some of the categories and sub-categories of speaker systems. 

Roland

Loudspeaker Buying Guide Pt. 1

Photo courtesy of Larry Jacobsen

Photo courtesy of Larry Jacobsen

Buying loudspeakers is perhaps the most daunting task a church tech will face. Today we have powered and unpowered speakers; line arrays and point source boxes; flown and ground stacked; cheap and eye-watering expensive. In each of those categories, we have dozens of manufacturers with hundreds of models to choose from. While it’s not possible in the space of this article to tell you what to buy, we will attempt to guide you through the process of selecting the proper speakers for your space.

The Perfect Speaker

First, there is no perfect speaker. All speaker designs make compromises in deference to the laws of physics. The right speaker for one room might well be entirely the wrong speaker for another room. Don’t get sucked into the trap of thinking that the speakers in the church that put on that big conference are the right speakers for you. They may be, but they also may not be. 

Second, once you get beyond putting up one or two speakers in a small room, I believe there needs to be some design involved. A competent integrator should be able to model the room and show you some options based on prediction software and help narrow down your choices. Far too many churches make the mistake of just hanging some boxes in the room, pointing them wherever and hoping it sounds good. From experience, I can tell you that most of the time it doesn’t. Plan on spending at least some of your speaker budget on an actual design. You can thank me later. 

As I said, there is no “best” speaker. What you want is the right speakers for your environment. To get to that right speaker, we have to ask some questions, and determine what we are trying to accomplish. Once we know the intended result, we can begin selecting speakers that will effectively deliver the results. It’s much like buying a vehicle; you wouldn’t buy a two-seater convertible if you intend to haul around a lot of mulch. Then again, a pickup would probably not be the best choice to drive a large family to baseball practice. With that in mind, let’s ask some questions.

What is the Source?

Believe it or not, the requirements for a speaker system that will deliver primarily the spoken word and one that will engage the audience with concert-level sound are quite different. Different churches have vastly different programming styles, and the PA needs change as we consider those styles. 

In a very traditional, liturgical setting, the speaker system really just needs to deliver the frequency spectrum of the human voice evenly throughout the room and with great clarity. The volume levels don’t need to be that high (relatively speaking), so we don’t need a bunch of drivers in the air. Don’t be fooled, however; getting a system like this to sound good requires some careful design. It’s just not likely to be as expensive as a full-on modern service system.

As amplified music becomes more and more of a priority, the system needs to adjust. Some churches want concert-level audio, and the only way to get that is with a big PA. Even in smaller rooms, you’ll need to move a lot of air, and that requires a good number of full-range speakers, as well as low frequency drivers (sub woofers) to deliver the goods. Most churches fall somewhere in between those extremes and will need a system designed accordingly.

This is the first in a series of questions we have to ask when it comes to selecting speakers for a venue. Next time, we’ll delve into a little more detail.

“Gear