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How To Tune A Sound System In 15 Minutes

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Even professionals often skip sound system setup and go straight to mixing because there just isn’t enough time. Unfortunately, you can’t go directly to your artistic place without first passing through science. The good news is that even the smallest amounts of time can be put to good use. 

How? With a plan.

Simple Sound System Goals

The goal for tuning a sound system is very simple: manage interactions to reduce variance across the listening plane. Put another way: provide the same sound in every seat. Setting the master EQ for perfect sound at the mix position does not meet this goal. Instead, we need an order of operations to help us make changes that will benefit the entire listening area, or at least mitigate damage. The order of operations is:

  1. Verification
  2. Placement
  3. Aim
  4. EQ
  5. Crossover alignment

It might seem like you don’t have 15 minutes to spare to check all of this, but the most important items are listed first. Completing a few is better than nothing.

You will need a dual channel analyzer like Smaart, SATlive, SysTune, Tuning Capture, RiTA, Open Sound Meter, etc..

Here are the speakers we need to set up: (2) CQ-1 (wide coverage main), (2) 650-P (2x 18-inch sub) in an uncoupled symmetrical point destination array. It’s your standard left/right mains situation (see diagram below). This is the most common professional sound system setup that I run into; it is not good or bad, just common. 

Our job as a waveform delivery service is to minimize phase distortion that causes comb filtering. Comb filtering makes a swooshing sound in the high frequencies as you move your head and should never be fed after midnight. Unfortunately, any array with speakers facing in towards a destination will produce some amount of combing. We would prefer a single CQ-1 and 650-P flown above downstage center to match the room. This design often doesn’t happen because of hardware and time limitations. I could complain about it and waste your time, but those speakers will still be sitting there, bored as hell.

Download the MAPP XT project if you would like to follow along with each step.

Disclaimer: This is a highly simplified example with minimum microphone positions to give you an idea of the structure for verifying and calibrating a professional sound system. There are many factors at play and details that I do not cover, like how to operate an analyzer. For a more in-depth analysis of this subject listen to my interview with Bob McCarthy.

Minutes 0-4: Verification

Do you think a lighting technician starts running a show without making sure that each instrument responds at the correct address? No! Better make sure all of your speakers play what they are supposed to play.

  1. Set all outputs to unity.
  2. Play pink noise and isolate one speaker at a time. In this setup we are unable to solo individual drivers, but do it if you can.
  3. Is the left output playing from the left speaker? If not, track it down. Many times it’s just a case of faulty patching. If you’ve got lines wrong inside of a closed box, you’re going to need more than 15 minutes, so I hope you have a backup. Repeat for each speaker/driver.
  4. Listen. Are there any obvious problems like noise, distortion, or Left and Right sounding different?
  5. Measure phase response on your audio analyzer at on-axis of each speaker/driver. Confirm matching relative phase. A phase offset of 180° indicates a polarity inversion. Any point in the signal chain could cause a polarity inversion so either track it down or simply invert phase anywhere else so that they all match in the end.

This step is the most important. It will be a sad dance party if your subs aren’t working.

Placement

In this situation there’s not much we can do with placement. We would like to move each speaker closer to the center of its coverage area, but we have a stage in the way and no rigging hardware or points.

Minutes 4-8: Aim

We only have a single measurement microphone, so we’ll need more time on this step to move it between positions. If I were running late and needed to cut one step from this process, I would cut this one and instead estimate the aim with a laser.

  1. Compare Main Left solo at OFFAXL and OFFAXR.
  2. Adjust aim until OFFAXL = OFFAXR in the HF (high frequencies).
  3. Repeat for Main Right.

Minutes 8-12: EQ

  1. Measure Main Left solo at ONAX and set output EQ filters to match your target trace.
  2. Listen to the filters in and out while playing your reference tracks. Are you going in the right direction?
  3. Copy the Main Left output EQ to Main Right output EQ.
  4. Measure Main L+R at ONAX and set EQ filters to return system response to your target trace. 
  5. Listen.

Minutes 12-15: Crossover Alignment

  1. Measure Sub Left solo at ONAX.
  2. Compare to Main Left solo. Are phase measurements within 60º through the crossover region? If so, move to step 7. If not, fix it. (for more, see How to verify main+sub alignment in Smaart)
  3. Measure MainL+SubL and check the combined response to make sure you have summation throughout the spectral crossover.
  4. Apply any necessary combined EQ.
  5. Listen to the result with your changes in and out. 

This is a stripped-down example of one of the most common sound system setups that I have encountered in the field. It skips steps and makes assumptions, so use it at your own risk. There is a lot more to do to be thorough, but I wanted to demonstrate that even a small amount of time can be put to good use.

If Poor Speaker Choice and Placement Were a Crime, We’d All Go to Jail

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Support Sound Design Live on Patreon.

In this episode of Sound Design Live I talk with principle teacher at Synergetic Audio Concepts and a co-author of Sound System Engineering, Pat Brown. We discuss the motivation of mistakes, finding clients through retail work, investing in high quality tools, practicing at home, and the biggest mistakes in sound system design and optimization.

I ask:

  • What was the first record you ever bought with your own money?
  • How did you get your first job in audio?
  • Looking back on your career so far, what’s one of the best decisions you made to get more of the work that you really love?
  • What are some of the biggest mistakes you see people making who are new to sound system design?
  • If you could wave a magic wand and make it so, what is one concept that you wish all sound system designers understood better?
  • Tell us about the biggest or maybe most painful mistake you’ve made on the job and how you recovered.
  • What software do you us in your seminars?
  • What’s in your work bag?
  • What is one book that has been immensely helpful to you?

If the FCC prosecuted sound system designers for poor array design, like you would for a for RF antenna design, they’d be putting us in jail for how we spew energy into rooms.

Pat Brown

Notes

  1. All music in this podcast by Nataly.
  2. Course 50: How Sound Systems Work
  3. Software: GratisVolver, CATT-Acoustic, ReflPhinder, SketchUp, FIR Capture
  4. Books: Handbook for Sound Engineers, Sound Systems: Design and Optimization
  5. Workbag: impedance meter, polarity tester
  6. Quotes
    1. I had just screwed up a system really bad. I wanted to know what I did wrong and was glad to find out I had done everything wrong.
    2. The key is to do it enough times to where you don’t have to think about the steps each time.
    3. Everyone should have to do retail for a while.
    4. The music store makes a great front end for a contracting business.
    5. I get that call all the time: OK Pat, I’m out in the room, I’m got my mic up, I’ve got my USB card hooked up. Now what? And I always say, “Pack it all back up. Go home. Lock yourself in your living room. Get a couple of little sound speakers and learn how to drive the thing.”
    6. If the FCC prosecuted sound system designers for poor array design, like you would for a for RF antenna design, they’d be putting us in jail for how we spew energy into rooms.
    7. You have to minimize the excitation of the room because you are creating your own interference if you are not thinking about that.
    8. I’ve never been impressed by market share. Just because something is the most popular thing out there for doing something; that’s never been a good enough reason for me to use it.
    9. The thing about acoustic modeling programs is that you can be way off. It’s always necessary, if possible, as a sanity check, to compare it to measured data in the room.

What’s the difference between Broadway and Rock ‘n’ Roll to a system tech?

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Support Sound Design Live on Patreon.

In this episode of Sound Design Live I talk with touring system technician and Master Sound Engineer at the Guthrie Theatre, Alex Ritter.

I ask:

  • How did you get the system tech job on the Lady Antebellum tour?
  • How did you get the job at the Guthrie?
  • What is a system tech?
  • Walk me through a day in your life while you were working on the Lady Antebellum tour.
  • One of your responsibilities at the Guthrie is to prepare the sound system for new shows and sound designers. System optimization is all about managing interactions and you are managing many interactions in these rooms. How do you keep it all straight?
  • What’s in your work bag?
sound-design-live-alex-ritter

You get the work you get because of the people you know and what they think of you.

Alex Ritter

Notes

  1. All music in this podcast by Sulagna Handique.
  2. Alex on LinkedIn and FB.
  3. The Guthrie Theater
  4. Master sound engineer = production sound engineer = top of the union ladder
  5. If you want to work in theatre, build relationships with sound designers and general managers. If you want to work in concert sound, build relationships with production managers, FOH engineers, monitor engineers, and artists.
  6. Shows: Wicked, Noises Off, West Side Story
  7. Software: AutoCAD, OmniGraffle, VectorWorks
  8. Hardware: Stagetec Nexus, Outline Newton
  9. Workbag: Q-box, M30 RTA mic, Leica disto/range finder, Nikon forestry pro, Sound Devices USB Pre 2, Motu 18i2, iSemCon 7150, Lectrosonics R400 wireless transmitters
  10. Books: Sound Systems: Design and Optimization, Yamaha Sound Reinforcement Handbook
  11. Resources including an empty delay tracking spreadsheet, an example delay tracking spreadsheet, and CAD blocks.
  12. Quotes
    1. You get the work you get because of the people you know and what they think of you. I made the decision to be nice to people and create contacts and cultivate those as best I can.
    2. We’re in a service industry. The day you realize that is the day that you get more jobs.
    3. I want to make sure that what I do will reflect a show condition. It makes no since to just tune a front-fill by itself and say “Hey, it looks flat.”
    4. Part of my job is to make sure that what the engineer hears at FOH is replicated for the other 16,000 people that are there.
    5. I feel like if I did six EQ cuts in a system, I did something wrong.
    6. If you’re going to change the system on an engineer. They should should know about it before you do it and don’t do it in the middle of a song.

Create a sound system tuning checklist and map before your next show

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One thing I do to prepare for every show is to create a sound system tuning checklist and map. That way I know what to do and where to do it.

Make a plan. Work the plan.

Pat Brown

Why?

First, it allows you to think through your actions. What system tuning procedures must you complete and in what order? How can you arrange those actions for maximum efficiency? (aka minimum number of microphone moves)

Second, it allows you to be more creative and flexile in the field. We all know once we arrive on site tomorrow, many things will change. Speakers will get moved and timelines will adjust. But, since you thought through your process the day before, you’ll be able to respond to challenges and adapt to changes more quickly.

What?

There are hundreds of potential sound system tuning procedures you could choose from, but you have a limited amount of time. You need to choose the ones that will create the most significant results.

sound-design-live-system-tuning-roadmap-web-660px

Here’s an overview. (download the roadmap here)

First, I label all of the speakers. For a very small system I like to use easy to identify letters:

  • L = Left Main
  • R = Right Main
  • S = Sub
  • FF = Front-fill
  • D = Delay
  • R = Relay

For larger systems I’ll use Bob McCarthy’s lettering system:

  • A, B, C, D for asymmetrical elements like Main, Sub, and Front-fill.
  • A1, A2, A3 for symmetrical elements like Main Left and Main Right.

Second, I write out every action I might want to take. Then I edit and rearrange the list so that the most important steps (like verification) come first.

Priorities:

  1. What order will make me feel confident that the client could walk in the room at any moment and I would be ready for soundcheck?
  2. What order will allow for the minimum number of microphone moves?

Lastly, I draw in my microphone positions with labels to identify their location in relationship to the audience shape I am attempting to cover. Since the audience is the thing I can’t change, I want to work backwards and adjust my speaker placement and aim to match.

Example

Here’s a small show I worked on recently in a hotel ballroom. As you can see, I’m expecting left and right mains with subs underneath. I investigated a center position for the subs, but found it unlikely.

Now that I have the outputs labeled, I’ll write out a big list of everything I want to do during system tuning, starting with verification steps and usually ending with a measurement of combined systems at FOH so that I can continue measuring during the soundcheck and show. Then I edit and rearrange the list based on the priorities listed above. The more detailed the better. You can see that mine is very sparse, but I still include some reminders like copying the EQ from Left Main to Right Main.

Pro tip: Print out your list and map so you can access it quickly and take notes.

Bonus

If you want to be a badass, you’ll open up MAPP XT, and go through every step on your list. This is not in an effort to predict the data, but to practice the moves so that they will feel more natural in the field tomorrow.

The only step you can’t practice in MAPP XT’s Measurement Viewer is averaging, but you can export your traces and do the averaging in Smaart. Here’s how.

The results

I got into the room the next day and guess what happened…

Everything changed. 🙃

The audience shape changed, which meant that I not only had to reposition the mains, but also had to add front-fills and work that into my system tuning checklist. But, I didn’t stress about it at all because I had planned it out the day before and I knew I could be flexible.

Are there any of these procedures that you’d like me to go over in more detail? Let me know in the comments below.

What do I need to know about my speakers?

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Do you know everything you should about your speakers?

Maybe you know the model number and power requirements, but do you know the coverage angle and forward aspect ratio?

How long will it take you to find this information in the field? How many people will wait while you look it up?

I spend a lot of time on every show getting to know all of the speakers I’ll be using. I want to be as informed as possible for quick decision making on site. It’s frustrating and embarrassing to take my phone and try to look up some facts that my colleagues on site may not even understand or think is important.

For a lot of people, the answer to this problem is an app like the PA Bible. My problem with this solution is that you are still spending precious time getting your phone out to go through a database. At least it’s faster than Googling around for the data sheet, but it still takes time.

What if every speaker came with all of the most important information printed on itself, like the tag in your shirt with care and washing instructions? Except this tag would include:

  • Angle, order, forward aspect ratio, and lateral aspect ratio for both vertical and horizontal coverage.
  • Voltage, current, and resistance.
  • Operating frequency range.
  • Peak SPL and class.
  • Spectral divider (crossover) specification.
  • Impedance and power handling capability for each driver.

Now multiply that list by every speaker in your inventory and it’s a lot of information to try to memorize.

But do we really need to know all of this? Will it help us in the field? Let’s look at some example questions we might need to answer.

Where do I put my speakers?

For speaker placement decisions I rely heavily on forward aspect ratio (FAR) and lateral aspect ratio (LAR). FAR will tell me how well my current design matches the audience. LAR will help me space my front-fills for a solid unity line across the front row.

To calculate the FAR and LAR for your speakers use the following math, which you can find on my aiming triangles business card:

  • FAR = 1 / sin (coverage angle / 2)
  • LAR = 2 / FAR

Where do I cross over my speakers?

The speaker manufacturer will include information in their documentation about how to combine match pairs of speakers. If you are combining two un-matched speakers, their operating range is important to know so you can expect a big area of overlap or a gap.

How many speakers can I put on a circuit?

To answer this question you’ll need to know the rating of your circuit and each of the speakers you want to put on it. The circuit will be rated in amps so if your speaker only has information in watts, you’ll need to do some quick math. Another reason to get that information ahead of time.

Where do I set the limiter for these speakers?

The more separate components you combine in the chain, the more complicated the calculation. I have little experience in this area, but I know that you’ll need to know about the power handling and resistance of every driver in every box you plan to use.

How many speakers do I need in my delay towers?

If you are using unmatched speaker models between main and delay, you’ll need to know the power scaling relationship. Look up Peak SPL on the data sheet.

As you can see, there’s a lot of information we need to know about our speakers. With enough time in pre-production we can gather all the information and make a spreadsheet, but what about when you just show up in the field and are handed a pile of speakers?

Have you ever seen a sound engineer stop to look up the data sheet for every one? I haven’t. And you can’t expect anyone to know every spec of every loudspeaker.

Speaker Stickers

What about a label on every speaker with the most important details that will help us with quick decision making in the field?

It might look like this.

And I might make them.

So what do you think. Would this be useful to you?

Yes, I want them!