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:
- Verification
- Placement
- Aim
- EQ
- 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.
- Set all outputs to unity.
- 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.
- 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.
- Listen. Are there any obvious problems like noise, distortion, or Left and Right sounding different?
- 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.
- Compare Main Left solo at OFFAXL and OFFAXR.
- Adjust aim until OFFAXL = OFFAXR in the HF (high frequencies).
- Repeat for Main Right.
Minutes 8-12: EQ
- Measure Main Left solo at ONAX and set output EQ filters to match your target trace.
- Listen to the filters in and out while playing your reference tracks. Are you going in the right direction?
- Copy the Main Left output EQ to Main Right output EQ.
- Measure Main L+R at ONAX and set EQ filters to return system response to your target trace.
- Listen.
Minutes 12-15: Crossover Alignment
- Measure Sub Left solo at ONAX.
- 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)
- Measure MainL+SubL and check the combined response to make sure you have summation throughout the spectral crossover.
- Apply any necessary combined EQ.
- 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.
that part about gender adaptors flipping the phase, holy shit, I never realized that. pin 2 hot no yummy after adaptor… wow… totally right.
Yeah, it’s kind of frightening when you realize that it could happen anywhere along the audio chain. Luckily, it’s doesn’t happen often (knock on wood).
AHEM!
A CORRECTLY WIRED gender adapter will not flip the polarity. If your gender adapters flip the polarity you’ve got some soldering to do.
And the correct term is POLARITY, not “phase”.
Oh, also, if you were thinking that polarity inversion would occur because of the symmetry of the XLR connector, that is incorrect. What would happen is a juxtaposition of positive and ground, not positive and negative.
That would generally create a condition of no signal.
Good point. But no, I was thinking of improperly wired gender adapters. Again, probably crying wolf over here.
Yeah, you’re right. I did encounter this problem once with a gender adapter, but it’s so rare that I probably didn’t need to bring it up.
Good point about Polartiy/Phase. People get those confused all the time. Other people, of course. Not me. Cough.
Hi,
first of all thanks for great and very informative site, very helpful podcast interviews,and also very helpful articles especially for us that didn’t have opportunity to attend bob mccarthy’s or similar workshops.
Can you please comment article https://www.prosoundweb.com/article/exploring_converving_techniques_for_tuning_line_arrays/ it’s like this “averaging” approach is kind of… i don’t know..
i’m very confused about standard procedure in measurement setup anyway (i have bob’s book but in first edition, so.. you said that in second there is much more examples in field).. there are many articles about theory of sound and measurement, but is there somehow standard approach or standard procedure… like.. draw venue.. draw audience areas… define off-axis, on-axis… put measurement mics in all defined areas… or, what is first position of mic to measure, or what is first loudspeaker group to start measure…
Thanks in advance,
G.
Hi Goran, thanks for commenting.
Yes, I’ve read that article. You are right to be suspicious. Averaging together readings is basically the same as ignoring data. Would you want your doctor to look at your MRI and say, “Well, there’s a tumor in the front, but the middle and back look good, sooooo, average that all together and you’re good!” I don’t think so.
You have to take a critical look at multiple measurements and use all of that data to make decisions moving forward.
I completely understand your confusion. One of the reasons that Bob McCarthy’s book is so long is that he attempts to give us the information to tackle any project. Meanwhile, you have to figure out which pieces actually apply to your project. That’s why I wrote this article, to show you a simple way to plan and strategize. The good news is that I have another interview planned with McCarthy so I’ll put your question to him. Make sure to sign up for my mailing list for the update: https://eepurl.com/dqBtT
I hope I didn’t over promise with the second edition of Sound System Design. There are definitely more examples and step-by-step instructions, but it’s the same basic material. Still, super valuable, but it won’t tell you exactly how to solve your problem. You have to figure out how to apply the material to your personal project.
Hi,
thanks for quick replay, and thanks for keep us informed.. In your review of Bob’s book u said “..The first time I read the book, I was excited to learn that there are areas of audio that can be predicted and measured…”,and i instantly knew that feeling. Same excitement i felt after reading article on Bob’s site https://bobmccarthy.com/sim3-optimization-design-seminar-at-uc-irvine/ cause first reading of book was really hard (well.. to me..) .. I think that this article was very first example really helpful in my understanding of procedure in measurements and data interpretation .. and i wish that there is much much (much.. much….) more.. (…if you can share some similar examples in your work that would be awesome….), also it was kind of “not similar” with John Murray’s approach in article that i mentioned before…
Another interview with Bob is very good news… i’m looking forward..
Regards,
G.
Absolutely, it is not easy stuff to wrap your head around. I was lucky that I had a seminar with Bob right after reading his book and have since had another seminar with Mauricio Ramírez. Reading Bob’s blog will help, too.
I can definitely share more examples. Most of the events I work on are small and simple compared to Bob’s work, but the same principles apply.
I’d like to see more discussion of outdoor system design vs. indoor. Your book is excellent but yes, the more examples the better. It would be nice to see you place designs into architectural drawings, too. Show some actual designs that you think work well in different sized venues. Choose classic size and shapes of various venues and clubs. Perhaps discuss how different styles of music have different needs for bass reinforcement. Enjoyed the book…the best of its kind.
Hi Graham, thanks for writing.
I have a post and design for small rooms coming out soon, but yes, I agree, it would be great to have more comparisons. Send me the architectural drawings for two or three spaces you have access to at your university.
That thing about muting one of the subs while applying high-pass filters to the tops is legen… wait for it… dary! Thank you for the great advice, Nathan!
I’m very sneaky!
Hi Nathan,
This is super interesting – and I’m really just scratching the surface of sound system setup and so have struggled a little bit to fully grasp this article.
Do you know of any videos (or would you be prepared to make one) showing the concepts that you outline here? For example a 15 minute demo showing exactly what you would do with this type of system and what tools you would need.
Thanks,
Michael
I don’t have anything on this site, yet, like that. It’s a great idea. I do, of course, cover all of this in Pro Audio Workshop: Seeing Sound.
That is really nice that these are highly simplified instructions. Sound systems are something I don’t understand though. It would be a good idea to have it done by a professional.
I’m feeling confused on the aiming approach. I (think I) know that Bob’s general approach in this system setup would to have your L & R aim through “the middle of the middle” for each of their respective FAR shapes for their half of the room.
But, I also get how you want the ONAX levels for each side to be as even as possible. That’s why you have them “crossfiring”. So, seems like ONAX being even for each side of the room is more important than hitting “the middle of the middle”? What am I missing here?
Hey Michael, if I am understanding you correctly, the two methods you mentioned are not at odds with each other. In this case, each of the loudspeakers are wide enough to cover the entire audience. Their FAR shape is the entire audience, so the middle of the middle is the center of the entire audience. If they were narrow enough, I might split the audience down the middle and assign each speaker to a side.