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Can you estimate line array splay in the field without software while the riggers are waiting?

By Nathan Lively

I have developed, what seems to be, a lesser known method to find target coverage angle and quickly estimate average splay for a line array in the field in relatively few steps. I discovered it by necessity while creating Pro Audio Workshop: Seeing Sound 3 years ago. Recently a student challenged me on a couple of points and it motivated me to take a closer look to see if I could make it more efficient.

Here’s how I have seen other people do it.

Bottom speaker down angle – Top speaker down angle = Target coverage angle

bottom angle
Bottom speaker angle
top angle
Top speaker angle

17º – 6.78º = 10.22º target coverage angle

Target coverage angle
array splay
Result using auto-splay in MAPP

This works fine when you are using modeling software, but I was looking for a solution for the field with a laser disto and a calculator while I have a team of people waiting on me. After playing around with some right triangles for a bit, I discovered a pretty simple method

In short, if you know the array’s rigging height and where the audience starts and ends, you can find the target coverage angle without software.

Find target coverage angle without software

Here are the steps:

  1. Solve triangle Y. You need the length of two sides or one side and one angle. I would go with two sides since that seems to be more reliable.
  2. Solve triangle Z. You can find the length of the opposite side (6.07′) by subtracting the array height from the from the rigging height. You can estimate the array height by multiplying the number of boxes by a single box height.
triangle1

Then plug those numbers into a triangle solver.

triangle2

16.88º – 7.03º = 9.85º

What about inclined audiences?

But that only works for flat audience planes. What if the audience is at an angle?

inclined audience

The process is a similar. To solve triangle Y, we’ll subtract the the height of the end of the audience plane from the rigging height above the audience.

rectangle2

14.8 – 6 = 8.8ft

Solve for the missing angle. 4.19º

We already have the solution for triangle Z (16.88º).

16.8 – 4.19 = 12.61º target coverage angle

inclined
array splay inclined
Result in MAPP using auto-splay

Now what?

With one more step we can calculate average splay.

tar cov ang / available splay angles = average splay

12.61º / 11 = 1.2º

total splay

My speakers don’t offer a 1.2º splay, so I’ll round down to 1º and make up for the loss with a few of the last speakers. Now I have plan to hand the riggers.

angles 1

What is the result using average splay?

avg splay prediction

It’s not great, but in a pinch I’d rather go with this result rather than leave everything at 0º or just guessing.

0deg splay

The easiest way to improve this result is to use the the automatic solvers built into your modeling software. The best way to refine the result manually for even more control is covered in detail in Pro Audio Workshop: Seeing Sound.

Warning: Software should always be used to double check rigging points and weight distribution. (Thanks Samantha Potter!)

Have you tried calculating line array splay in the field without software? How did you do it? What were your results?

Bob McCarthy: Where do I place my delay towers?

By Nathan Lively

sound-design-live-bob-mccarthy-delay-towers-roskilde-featured

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Support Sound Design Live on Patreon.

In this episode of Sound Design Live I talk with the director of system optimization at Meyer Sound and the author of Sound Systems: Design and Optimization, Bob McCarthy, about how to decide where to place your delay towers and how many boxes they should have.

Notes

  1. Movie: WW1 doc They Shall Not Grow Old
  2. Roskilde Festival
  3. Sub arrays: End-fire, Gradient inverted stack
  4. MAPP XT
  5. Design files for Jockey Plaza
  6. Do I have enough boxes in my delay towers?
    1. Compare the ratio of boxes in your Main array vs your Delay array to the ratio of distances they are covering.
  7. Quotes
    1. One of the big lessons of this experience was how important it was to not just extend 100Hz and above, but to extend the whole show. If you want it to stay impactful, you have to bring it down to 30Hz.
    2. If you’re in an outdoor environment, I prefer over covered to under covered.
Trump Wall at the Roskilde Festival

This Is Why You Are Over EQing

By Nathan Lively

this-is-why-you-are-over-eqing-merlijn-van-veen-featured

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Support Sound Design Live on Patreon.

In this episode of Sound Design Live, I speak with sound consultant and educator Merlijn van Veen while attending his Calibration and Design Techniques for Modern Sound Systems workshop at the Banff Centre for the Arts in Canada. We talk about the way that audio analyzers used in sound system tuning can easily be abused for micromanagement and over EQing, my learnings from the workshop, and your questions on line array vs point source. I ask:

  • What manly songs can I play at soundcheck to make sure everyone knows what a big deal I am?
  • What’s one of the best decisions you made to get more of the work that you really love?
  • What is one concept or idea you wish everyone understood better before attending your workshops?
  • What is the main benefit or transformation you’ve observed for your students?
  • What are some of the biggest mistakes you see people make when they are new to sound system optimization?
  • Describe a loudspeaker crime scene investigation, and how can we try it at home.
  • True or false:
    • A doubling of distance results in a halving of sound pressure level.
    • A doubling of distance results in a 6 dB reduction in SPL.
    • A doubling of distance sounds twice as quiet.
  • What’s in your work bag?
  • Ajax or PSV?
  • Why is the stereo image so much better with point source systems comparing to line array systems?
  • Why are so many people using line array system, when single source system is better, cheaper, and easier to set up?

sound-design-live-touring-foh-sound-engineer-job-Merlijn_van_VeenThe modern line array speaker is 25 years old. It’s been around just as long as the point source, maybe even longer. It’s just another tool. Don’t obsess about it.

Notes

  1. All music in this episode by Young Link.
  2. Check Merlijn’s FB page for the most up-to-date information on seminars.
  3. My first interview with Merlijn – Understandable Misunderstandings
  4. Merlijn’s calculators, including Subwoofer Array Designer.
  5. Crime scene investigation:
    • Measure On-axis
    • Move off-axis (while keeping the delay locator unchanged so that you are equidistant) until you observe 6 dB of angular attenuation.
  6. Merlijn’s box of toys: Genelec Acoustic Tape, iSEMcon EMX7150, piston calibrator, protractor, laser range finder, Ampro humidistat hydrometer, transformer-based DI to handle up to 200V.
  7. The popularity of line array loudspeakers: less real estate, better range ratio.
  8. Quotes
    1. The FOH position is self-calibrating. If you don’t like what you hear, your brain will instruct your hands to start pushing buttons until you like what you hear. But there’s no guarantee that what you perceive in that square foot is the same art that the rest of the audience is perceiving.
    2. As much as I like to do art, ultimately, it’s a physics class.
    3. Luck is what happens when preparation meets opportunity. -Seneca
    4. Acknowledging that there is room for improvement is half the battle.
    5. You have this X-ray photo of your sound system, and it’s very tempting to start addressing every minor deviation. I did this in the beginning. It sets the table for micromanagement.
    6. Every new technological development, by definition, in the beginning, is used too often and in the wrong way. -George Lucas.
    7. If what we hear does not correlate with what we measure, we lose confidence in the measurement platform. And then most people will rely on their ears. But if you can connect the two, then you gain confidence in the things you are doing and you will feel more secure in approaching a new situation.
    8. The modern line array speaker is 25 years old. It’s been around just as long as the point source, maybe even longer. It’s just another tool. Don’t obsess about it.
    9. What I like about point source [speakers] is that afterward, I suffer less from listening fatigue.

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sound-design-live-podcast-episode-98-this-is-why-you-are-over-eqing-merlijn-van-veen-main-sub-alignment

sound-design-live-podcast-episode-98-this-is-why-you-are-over-eqing-merlijn-van-veen-nathan-lively

 

Honestly, Live Audio Is Not Based On Science

By Nathan Lively

book-review-live-audio-dave-swallow-featured-image

book-review-live-audio-dave-swallowDid you hear my interview with Dave Swallow? You should. In our conversation it was obvious that he has a ton of valuable information to share, but that information is kind of hidden in his book. Let’s dig around in the dirt and pull out the gems.

Your job as an engineer is to get the best out of what you are given, even when you are given the worst.

Bored.

Swallow spends a lot of time covering information that you can find in the user manuals for mixing consoles and outboard gear. It overshadows his personal experiences with mixing, which were the parts that I found interesting AND that I couldn’t find somewhere else. If I were to edit this book, I would cut everything but the personal experience.

I found the summary of audio basics to be too brief, and disconnected from the practical goals of the book. It would probably be better served with footnotes and a glossary.

WTF Bro?

Some parts of Live Audio are just plain misleading.

For example, the section on hearing loss prevention is misleading because he says, “You can’t wear earplugs while you are mixing because then you won’t be able to hear what you are doing,” then later mentions that molded earplugs are “worth the money.” The truth is that many artists and engineers work with molded ear plugs and IEMs and enjoy slower hearing loss and a longer career because of it.

I do really appreciate this point, though: “Don’t put anything down your ear.” It reminds me of a story I heard from a friend about new military recruits that had access to medical facilities for the first time and would excessively clean their ear canals, leaving them dry and irritated. Ear wax is normal.

book-review-live-audio-dave-swallow-line-arraySome of Dave’s comparisons of point source and line arrays are also misleading.

  1. Hardly anyone uses a pure line array with all speakers parallel anymore. So the arrays he refers to are really two different versions of a coupled point source array, with different speaker types.
  2. You can aim any speaker array poorly. Swallow writes, “Line arrays tend to create strong sound reflections off the rear wall, which muddies the sound in shallow rooms.” That doesn’t make sense. You can point a point source array at the back wall and make problems just as easily as you can with a line array.
  3. When Swallow writes, “Line arrays require a very high ceiling because they must be tall to work properly,” I think, wow, that’s way too general. Firstly, most line arrays have hardware available so that they can be ground stacked. Secondly, he is really discussing the physics of array length versus frequency response, so his offhand reference to “tall” is useless. Lastly, Swallow suggests avoiding line arrays for outdoor events because, “As much as they have the ability to not lose many decibels over a long distance, the actual power of the wavefront that is formed seems to be fairly weak, rendering the sound pretty useless in anything over a slight breeze.” Is it just me, or is that confusing? If it’s not losing decibels then why would the wavefront be weak?
  4. In another example Swallow writes, “…with the point source system, you get more volume down at the front”; why? I want more explanation!

I understand that Swallow is introducing these concepts in a way that won’t be overwhelming, but you can’t just skip to the end and lead the reader to think there is nothing more to know, that things are always one way. My advice is to take his rules of thumb with a grain of salt.

book-review-live-audio-dave-swallow-humidity-hf-absorptionAnother confusing subject is the environmental effects of humidity and temperature. Swallow’s comments on directional transmission are helpful, but he makes a big deal about temperature increasing the speed of sound and having some effect on high frequencies. I read it several times and didn’t understand what he was trying to say. Here are three important things to remember about temperature and humidity from Sound Systems: Design And Optimization:

  1. The speed of sound in air is only slightly temperature dependent. A 1% change in the speed of sound occurs with either a 5°C or 10°F change in temperature.
  2. As humidity rises, high frequency transmission improves.
  3. The high frequency loss rate is highest around room temperature and increases as temperature either rises or falls around this standard.

And one more thing that is just plain wrong: “To measure a room’s frequency response, you use a real-time analyzer (RTA).” Why is this wrong? Please read this.

Meeting Ear To Ear

And then, a saving grace! Remember in my article on controlling feedback onstage when I condemned “ringing out” stage monitors? Swallow totally agrees! See? I’m not crazy. The world is crazy!

This procedure…is extremely annoying for anyone else trying to work in the room and is considered by most industry professionals to be extremely amateurish. Instead, you should understand what the frequencies do in terms of how boosting and cutting each frequency on the graphic affects the overall sound…Do not sacrifice the sound of the system just for a little more volume.

Also, Swallow’s explanation of why graphic EQs are pretty much useless is right on the money. I’ve already beaten that subject to death on Sound Design Live.

Hey, remember in my interview with Philip Graham when he challenged my assumption that dynamic mics are more forgiving than condenser microphones on vocals? Well, read it and weep Philip:

A dynamic mic can be much more sympathetic, more forgiving to a bad mic technique…

There are some sections that a good editor should have just cut. For example, in the section on using an SPL meter Swallow describes the fast and slow response settings: “If you have a fast reading, you’ll see the numbers changing very quickly on the display, whereas with a slow reading, the numbers change much more slowly.” Really? You just wasted seven seconds of my life. I can’t get those back now.

Awesome!

So where are the good parts in this book?

book-review-live-audio-dave-swallow-la-rouxThe value of Live Audio is Swallow’s personal experience. For an example in this section on how he uses Pitch Shift:

With La Roux, I use +4 on the left side and a delay of 14ms; on the right side I use -14 and a delay of 4ms. When combined with the vocal, it gives a very unique sound and sinks the vocal into the music while still keeping it loud enough to be heard.

This is gold! I had never thought about using pitch shifting in live sound before! Why can’t the entire book be like this?

When we get into the chapter on mixing is when Live Audio starts reading like great advice and less like a bad user manual. His suggestions for  equalization, dynamics, and effects processing are very helpful. Also, the section on microphone technique is useful and gave me a lot of god ideas to try. Especially his five-mic array for piano.

I really appreciate Swallow’s suggestions for critical listening. I generally try to work really fast and have been guilty of trying to fix everything with EQ. Swallow reminds us throughout the book to walk around the venue and stage when there is a problem we cannot identify.

His best tip on soundchecks is to finish the soundcheck on the first song of the set so that everything will be set to go right out of the gate. Brilliant.

I’m glad Swallow talks about panning and stereo because I’ve long wondered why anyone would ever setup a stereo sound system when only a small portion of those people in the center will hear in stereo (see What’s wrong with stereo?). Swallow answers this question by explaining that while yes, stereo panning will produce a different result in each seat of the audience, it also produces a sense of spaciousness that everyone enjoys. And now I remember that Bob McCarthy said pretty much the same thing in our interview. Basically, stereo is here to stay because people like it and there are ways to accomplish it without sabotaging your system optimization.

Conclusions

I can see how this book might be good for a stage manager or technical director who doesn’t have experience in pro audio and may want an overview of how it all works. But if you are a sound engineer, skip to the sections with personal experience and definitely read the mixing chapter. Because honestly, Live Audio is not based on science. Swallow has toured the world making music, so when he says that something works or doesn’t, it’s because he’s been there and done that.

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