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SPECIAL REPORT: Sound System Design for Small Venues with Bob McCarthy

By Nathan Lively

sound-design-live-sound-system-design-myths-tricks-bob-mccarthy-goran-kset-sketchup

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Are you ready for over an hour of on-the-job training on sound system design for small venues with one of the most experienced sound system technicians in the world? Yeah you are!

In this episode we cover:

  1. How to measure sound systems in heavy wind.
  2. Dealing with highly reverberant spaces.
  3. The precedence effect.
  4. When to subdivide your system.
  5. The advantages and disadvantages to coupling your subs.
  6. How to setup a basic cardioid subwoofer array.
  7. How to aim a pair of L/R mains.
  8. The next update to SIM3.
  9. Combining speakers and microphones with shape and scale in mind.
  10. The best way to potty train your dog.

Details from the podcast:

  1. All music in this podcast by Steve Knots
  2. McCarthy’s book: Sound Systems: Design and Optimization
  3. Sound Design Live eBook
  4. Meyer Sound
  5. USITT
  6. Community hashtag: #XOVR
  7. McCarthy’s blog posts about subwoofer arrays
  8. 6 Smart, Proven Methods To Control Feedback Onstage (Without EQ)
  9. Quotes:
    1. Outdoors you take picture after picture and then lay them over and see where the trends are. You have to throw out certain ones that are not plausible.
    2. Nobody goes into acoustics because they think I’m going to get really good at putting fiberglass on the walls to make dead rooms, but in the world of small spaces that are going to do loud music that is exactly what you need.
    3. The overflow that you have potentially on a wall is no worse than you have, as a certainty, into the other speaker that’s coming from the other side.
    4. The HASS effect or precedence effect (or whatever you want to call it) is vastly over simplified in people’s brains.
    5. System design for small rooms is much more challenging and difficult than large spaces.

Goran O.

Q: What’s the approach in sound design for venues with bad acoustics that are very reverberant? I have mixed in these places and I must say that I’m trying hard to forget the feeling. It is very often the case that the owner of the club has spent money buying a decent sound reinforcement system, but then doesn’t care about acoustics. Or, there are cases when a concert is produced in some kind of multipurpose venue (which is normally a warehouse) and you are expected to create great sound. Would it help to try a more “distributive” approach.

Q: What about using the Haas (or precedence) effect in sound distribution? Bob says that delaying sound systems further then the first arrival of direct sound will mess with the phase, but what about spatial feeling?

Q: I mix a lot of great bands at a student club. Capacity is about 300-400 people. It has a balcony and under-balcony space. It would be great to have Bob’s opinion on how to distribute the speakers because this venue is part of the Faculty of Electrical Engineering and Computing and some students (volunteers) in the club are studying in the Department of Electroacoustocs so they are hungry for knowledge (as I am).

  • Left side of venue is a wall of mirrors
  • One EV bass speaker (tour-x TX2181) per side
  • Four bass speakers in first raw are just barrier for audience.
  • Mid/high boxes (EV XI-1152 – Rotatable 60° x 40°) are 2.4m from floor to bottom of speaker.
  • You’ll see also some JBL speakers behind EV (on middle of stage), but those are not in use.

sound-design-live-sound-system-design-myths-tricks-bob-mccarthy-goran-kset

sound-design-live-sound-system-design-myths-tricks-bob-mccarthy-goran-kset-sketchup

Download Google SketchUp Design

Interactive Panorama
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  1. Goran KSET Venue
  2. Goran KSET Stage
  3. Goran KSET Balcony

Simon E.

Sound system design for a rock show with six actors on close-mic’d wireless, and a band of piano, bass, drums, violin, and sampler in the stage-right wing.

I really wanted to fly speakers over the stage, but in this space it’s not going to happen (no roof infrastructure at all, not even for lighting) so I am resigned to two speakers on tall stands at the sides, angled in and tilted down in an attempt to get an even coverage. Based on the basic rule from Bob (summarized in your earlier article) of “back row on axis at distance 2D, front row at bottom edge of coverage at distance D”, I think it’s close enough. In this case, with 90×60 speakers, it works out to ~9′ up, 15 degrees down, and about 25-30 degrees in to avoid the hard side walls.

If all goes well, I will be borrowing a pair of Nexo PS15s (original version – 100ºx55°) and a pair of PS8s (100ºx55°) which will go on the floor in the middle as front-fill.

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Mark N.

I am in the process of redoing a PA in a 650 seat worship room and have been trying to find the best placement for the subs and mains. The stage is in one corner with mains directly above the steps currently aiming at each aisle.

The center speaker has moved slightly off center and the x-over between the mains is in the middle of seats. I have stressed the concern of rearranging the seats so the x-over is in the aisles.

I can rehang, reposition, and the speakers can be visible. My thought was to flip the mains over so the horn is at bottom to get past the projectors. EV has seen the room and suggested that, too.

Here is the info of our current set up, along with photos and drawings of the room.

Room Info:

  • 70’x70′ square, ceiling height is 20′ from floor, 18′ from stage.
  • Walls are just drywall, 2 being outside walls with brick veneer on outside.
  • The ceiling is gypsum, suspended. Above it is empty with metal roof. This part of the building is actually shaped like a pyramid so roof peaks near center of audience about 45′.

PA:

  • Main Cluster- (3x) EV 1122s/66 (60ºx60º)
  • Amps: (1x) 2ch EV cps2.9
  • Subs: (2x)

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Thorsten B.

Q: When is the next update to SIM III coming out? It’s been a while.

Q: I have a theory that if I use the same model of microphone on every input and the same model of loudspeaker on every output, the sound will be more even and smooth because in the interaction between microphone and speaker there is only one frequency response instead of 12 or more if I use the typical 4-6 types of microphones and speakers. Do you agree? Does this work in the real world?

Frequency Coordination and Antenna Placement for a Rock-Solid Wireless Microphone System

By Nathan Lively

sound-design-live-wireless-microphone-frequency-coordination-antenna-placement-karl-winkler-singer

Subscribe on iTunes, SoundCloud, or Stitcher.

Support Sound Design Live on Patreon.

 

In this episode of Sound Design Live I interview Karl Winkler from Lectrosonics. We discuss the basics of frequency coordination, wireless microphone myths, and how the Super Bowl manages 1,000 channels of wireless devices. Karl also explains what a backup frequency is, whether bluetooth devices, microwaves and cell phones will cause interference, and how to prepare for rogue wireless devices.

sound-design-live-wireless-microphone-frequency-coordination-antenna-placement-karl-winklerNotes:

  1. Music in this episode by The Giovanni Quartet, Brodsky Quartet, The Bartok Quartet, and Brentano String Quartet.
  2. USC Recording Arts
  3. Karl’s principles for success in audio
    1. Have a good attitude. If your job is to roll tires from the back of the store to the front, you should be so good that people will pay to see you do it. Don’t be afraid of the work or think of it as being beneath you.
    2. The basics always matter. Every art and science requires you to know the fundamentals.
    3. Really listen. Learn to use use your ears as a troubleshooting tool. See Trouble-Shooting Audio Systems tutorial.
  4. SynAudCon – Making Wireless Work
  5. Wireless Workbench
  6. Myths
    1. Wireless mics are voodoo.
    2. A directional antenna is always better.
    3. I can get more range with boosted antennas.
    4. Lectrosonics is too expensive.
  7. Interview with Jim Venable from the Wireless Speaker Association
  8. Axient system from Shure
  9. Spectra Pulse from Audio Technica
  10. Lectrosonics Facebook Group and FAQ page
  11. Words
    1. sound-design-live-wireless-microphone-setupCavity Filter = Pass band filter. Blocks out bands of frequencies to focus only on the ones you want.
    2. Shark Fins = Directional antennas = LPDA (log periodic dipol arrays)
    3. Intermodulation distortion = Occurs when two or more signals mix within an active device and create phantom frequencies.
    4. Backup/spare frequencies = Pre-coordinated channels that you don’t need at the moment, but are already calculated to fit into your system design, preventing guess work.
  12. Big Mistakes
    1. Not separating your IEMs, comms, and mics into different bands.
    2. Bad antenna placement.
    3. Not calculating signal loss for long antenna cable.
  13. Quotes
    1. “Audio is a guilded career. You start as an apprentice. That’s how most people get their start.”
    2. “Your attitude is irreplaceable.”
    3. “There is something to learn from everything you do in life.”
    4. “Any time you add an active component, you are potentially raising the noise floor and increasing distortion. It can mix signals and create intermodulation products. You always want a net zero gain between antenna and receiver.”

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The Five Most Popular Posts of 2013

By Nathan Lively

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eBook Cover 1400px2013 was a big year around these parts. Besides publishing the Sound Design Live eBook, I created a Google+ page, a YouTube channel, and even made the podcast available as a BitTorrent! I also expanded the site to include reviews of pro audio books and hardware, as well as sound engineering tutorials and articles. Wonder what topics people were most interested in this year? Ladies and gentlemen, I give you Sound Design Live’s most popular podcast interviews and pro audio tutorials and articles of 2013:

  1. Sound System Design & Optimization with Bob McCarthy: Bob McCarthy told us why graphic EQs are useless, common misconceptions about stereo, and why we must optimize our sound system design before we mix.
  2. How Much Do Live Sound Engineers Make?: Salary information for four sound engineers in the U.S., Czech Republic, Slovak Republic, Greece, and Sweden.
  3. Condenser vs. Dynamic Microphones For Live Sound: Philip Graham of Ear Trumpet Labs compares condenser microphone and dynamic microphones for live sound, and discusses close miking and stage monitor feedback.
  4. From Highschool Dropout To Head Of Audio: An interview with the late Steve Brown about his journey from high-school drop out to head of audio at the Royal Exchange Theatre in Manchester.
  5. Condenser Microphones For Live Sound: Why are condenser microphones less common in live sound? What are the advantages and drawbacks? Listen & learn.

I hope your year was as great as mine, and that you have many fun projects lined up for 2014. I’m looking forward to another great year on Sound Design Live, so if you’d like to hear an interview with a specific individual or read about a particular subject, let me know in the comments below and I’ll make your dreams come true.

High-fives,

Nathan Lively

How To Find Speaker Coverage In One Step

By Nathan Lively

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Subscribe on iTunes or SoundCloud.

Please send me a message if the embedded calculator above is not working.

In sound system design, step one is to define speaker coverage. Lucky for you, Daniel Lundberg and I have created a great new speaker coverage calculator that makes this initial step quick and easy. The calculator will give you a consistent coverage result for any scenario, but unfortunately it’s not very smart. It doesn’t know about walls and other speakers, so it works best for single-speaker applications like balconies, side fills, and smaller venues.

Consistent coverage means that SPL will not vary more than 6dB. So if the highest measured level in the audience is 100dB SPL, then no part of the audience may be lower than 94dB SPL. This calculator is designed to give you the least amount of level variation across the listening area, but there are many more variables at play here. With that in mind, let’s proceed.

Step 1 And Done

Put your measurements into the Speaker Coverage Calculator above. That’s it! Listen to my conversation with Lundberg for a more details on how it works.

Example 1 – Balcony

Let’s take the room from How To Tune A Sound System In 15 Minutes, add a balcony, and raise the ceiling. I used visual aids to show a four-foot seated audience height covered by four speakers: Main, Balcony, Sidefill, and Under Balcony. Download my MAPP Online Pro project to follow along.

sound-design-live-speaker-coverage-calculator-example1

Put your measurements into the speaker coverage calculator above. It recommends a nominal vertical coverage of 51° and a UPQ-1P aimed 25.3° above the front. You can manually work out the angle in MAPP, or use the speaker coverage calculator. Input the angle of your architectural guide (the one showing distance to front) and the calculator will tell you exactly what to put into the Rotation About CDRM box in MAPP. I put in a 139° front angle and got -15.7° for the speaker aiming angle.

sound-design-live-speaker-coverage-calculator-example-balcony1

Here’s a prediction at 8kHz. Did we meet our criteria for consistent coverage? Just looking at the graph I would say there’s no more than a 3dB difference from on-axis to off-axis, and consulting the virtual SIM I see there is no difference in average SPL and only about a 4dB difference in the high end. Great success!

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Example 2 – Side Fill

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The speaker coverage calculator recommends a UPA-1P aimed 21.2° above the front. Virtual SIM tells me that there is about a 8dB difference from on-axis to off-axis. This doesn’t meet our requirements, but I found that if I aim it lower I can can get more even coverage and meet the crossover point with the main speaker.

sound-design-live-speaker-coverage-calculator-example-side-fill

Example 3 – Under Balcony

sound-design-live-speaker-coverage-calculator-example-under-balcony1

With limited height, it’s going to be hard to cover this listening area with one speaker. The speaker coverage calculator recommends subdivision, but it also keeps recommending a giant JM-1P (see prediction below).  Now I know how Dr. Frankenstein feels: I asked for consistent coverage and I got it, but I also got a mob of angry townspeople. I tried a UPM-2P here aimed at the last row and that worked a lot better.

sound-design-live-speaker-coverage-calculator-example-under-balcony

Example 4 – Small Venue

Let’s take a look at Ashkenaz, one of the first music venues I worked at when I moved to Berkeley. When I first put the triangle lengths into my speaker coverage calculator (9.5′, 28.5′, 25′), it gives me some crazy results and recommends that I subdivide the array. Let’s assume that I use a down fill to cover the first ten feet of the audience. With new results, I try a UPQ-1P and see that it provides even coverage. I also observe that aiming it further down will get me less consistent coverage, but will let me send more of those expensive decibels into the audience, providing more bang for the buck.

sound-design-live-speaker-coverage-calculator-example-ashkenaz

To Subdivide or Not To Subdivide

How do we determine when we need to subdivide our coverage into more than one segment? Here’s a nice rule of thumb that I learned from Bob McCarthy’s seminar: measuring from the speaker, take the ratio of the distance from the first row to the last and subtract one. So in our example the first row is 9.4ft from the speaker array and the last row is 28.5ft from the same array. That’s a ratio of 1:3. 3 – 1 = 2. So a two-segment array would probably work better for this coverage area. How many speakers in each segment? That’s up to you and your budget.  For a much better explanation of this topic, read McCarthy’s article, Array Or Not To Array.

Finding Speaker Coverage When Front And Back Are Equal

The horizontal coverage plane of a sound system often looks like an isosceles triangle (two equal sides and angles) and the loudspeaker nominal coverage can be found with basic trigonometry. Remember soh cah toa from trigonometry? No?! Me neither. Lets watch this video! To find speaker coverage angles in the field, find the lengths of the triangle for the area you are trying to cover and solve for the inside angles. There are also plenty of free triangle solvers online and iPhone apps.

Please test this out the speaker coverage calculator and send me your results! If you have suggestions for a better calculator, let me know in the comments below. After I get some more comments and suggestions I’ll publish a second version and Daniel and I will do another podcast with a better explanation and more case studies.

BOOK REVIEW: Sound Systems: Design And Optimization by Bob McCarthy

By Nathan Lively

sound-design-live-review-sound-systems-design-and-optimization-bob-mccarthy-book-featured

sound-design-live-review-sound-systems-design-and-optimization-bob-mccarthy-bookI freely admit that I love this book. I’ve read Sound Systems: Design & Optimization cover to cover and use it as a reference on an ongoing basis. The first time I read the book, I was excited to learn that there are areas of audio that can be predicted and measured. It felt like all of a sudden invisible audio could be visualized and altered. Since then, I’ve felt a strong affinity for system tuning and have tried to bring it into my work whenever possible.

The upside of reading this book is that you learn a lot about topics you never knew existed but have been affecting your audio work this entire time. The downside is that you will want to change everything, and be frustrated when you can’t. All of a sudden you will want to move speakers around and fly mono point-source clusters. You’ll want to measure everything and play a lot of pink noise. You’ll want to throw out your graphic EQ and RTA, but you will encounter resistance from producers, managers, owners, colleagues, and the clock. It is really hard to be so excited about this stuff and not be able to get your hands on it. Keep your eyes open and trust me, opportunities will start to present themselves.

Sound reinforcement is far from perfect. Speakers are “mechanical devices attempting to produce wavelengths that vary in size by a factor of over 600:1.” Luckily measurement systems are affordable and we can set goals to get the most out of our imperfect systems. McCarthy is a realist, and his book is all about triage. Your patients will never be 100% injury-free, but you can apply pressure and stop bleeding from the major arteries.

[quote picture=”https://sounddesignlive.com/wp-content/uploads/2013/07/sound-design-live-bob-mccarthy-headshot.jpg” name=”Bob McCarthy” align=”left”]If the system is always operated safely within its linear range, there is no need for limiting. This could happen in our lifetime, as could world peace. But unfortunately, we have to assume the worst-case scenario: that the sytem will be subjected to the maximum level of abuse fathomable, plus 6 dB.[/quote]

Introductory chapters walk you through terminology with a minimal amount of math and a constant connection to their necessity for the job at hand. This is not a simple read. There were many ideas and terms I had never heard before, as well as lots of tables and diagrams to interpret. This complexity is also what made the book so captivating. I couldn’t beleive that there was so much about audio that I didn’t know! McCarthy makes sure to keep you motivated by providing real-world applications like a carrot at the end of a stick.

[quote name=”Bob McCarthy”]The premise of this text is minimal theoretical math and maximum field applicability.[/quote]

Pro Tip number one: This book is best read from start to finish. Later on you can use it as a reference manual, but if you try to start in the middle of a chapter without understanding the context you may be disappointed and confused. This isn’t because you’re dumb or the material is obtuse! Rather, our brains like to preserve energy, and when you present too many new ideas (including vocabulary) at once, they fight back and try to dissuade us from attempting to understand the material. That’s why you don’t always understand everything the first time you read it, but when you go back read it again the concepts become more clear. Pro Tip number two: also check out McCarthy’s website for more real-life examples.

One thing that I love about McCarthy’s style is that he crushes audio myths left and right, but does so gently and with good humor. It is kind of annoying to find out that I’ve been doing it wrong for the past ten years, but I don’t feel attacked, just well-informed. For example, graphic EQs are really no good for system optimization because of their fixed bands, but I’ve used them for years because they were…available (see interview below at 24m24s). Also, designing a stereo system is usually a futile effort because only a small triangle of the audience will hear in stereo, but I did that for years because that’s how recording studio systems are set up (see interview below at 28m54s).

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[quote name=”Bob McCarthy”]The real-time analyzer (RTA) has a number of applications in which it is the best tool for system optimization: zero.[/quote]

Speaking of doing it wrong…back when I was starting out in theatre at the National Theatre of Portugal, they had a rack-mounted 32-band RTA. No one really knew how to use it, but look at those pretty LEDs bounce up and down! Later I bought my own handheld RTA. Man, it was cool. No one had ever seen one. I felt like a god over sound. I could take measurements in different locations of the room, average them together, and set my graphic EQ by the numbers. Solved. Why did I think this was the best tool for system optimization? From the manual and marketing materials for the RTA of course! Another win for marketing over science.

Back to the book! The section summaries and best-practice recommendations in the newest edition are super helpful. McCarthy makes a point to be unbiased and very specific in his writing, which is a breath of fresh air after audio literature that is full of useless generalizations that pander to quick answers. With the first edition of Sound Systems I would sometimes finish an entire chapter having learned many details on a subject and still not know where to start. Imagine a whole book about making pancakes that focuses on the food chemistry of eggs and flour. In contrast, the second edition of McCarthy’s book includes some recipes at the end to get you started.

Pro Tip three: Take notes! This book contains a wealth of knowledge. As you read it, you will find specific pieces of information that pertain to your work. Write those down. I refer back to mine often, except I lost it in a move a few years ago. I’m going digital this time!

One of the reasons that this book is so long is that McCarthy is genuinely trying to prepare us for any situation we might possibly encounter. I mean, it’s 106 pages before “We are now ready to apply our study of summation and the acoustic crossover to the practical construction of speaker arrays.” It does not provide solutions for specific scenarios; instead you’ll have “a road map with milestones of what we should expect to find, and where.” This is one of the rare occasions in life when stereotypes are good. Without them, the possibilities for design and optimization would be endless and nauseating. Armed with a set of geometrical tools, we can look at a design or a space and begin to narrow down our possible outcomes. No matter how complex the speaker array, it is still built on the basic foundations of physics.

I never thought that I was a geometry lover, but my favorite parts of this book are the sections on speaker coverage. No one speaker is a perfect fit for a room, so there is always opportunity for system design. Looking for help finding speaker coverage in a room? Check out my article Finding Speaker Coverage In One Step.

This is a challenging read, but completely worth the effort. McCarthy eases you into difficult physics concepts with great care and humor. Before you know it, you’re swimming in the deepest waters of professional sound system design.

Really, though, you don’t have to read this book to get great sound. You could just hire me to do it for you. 😉

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