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I just completed the fourth presentation of a live webinar training on sound system tuning. The webinars went well, but there just wasn’t enough time to answer all of the question that the 535 attendees sent in. But I don’t want to leave those people out in the cold so I have gathered all of the questions and I am going to answer all of here on the podcast.
I have organized them into sections, so today we are going to continue to part 3 and talk about how to design our sound system for maximum results.
#13 Godswill: What are the factors to consider before designing a sound system?
Godswill, I love that you’re asking this question because there’s a big difference between people who do their work in a purely reactive manner and just wait for people to ask them for things or something to break or something to go wrong before they take action. I was a mostly reactive sound engineer for a long time because I got burned out at the place I was working so I just got lazy and bored. And it was only after working with other sound engineers who were a lot more successful and happier in their work that I noticed how proactive they were with their service. The more you can anticipate the needs of your client and your show, the more time you’ll save and the more taken care of your client will feel.
The answer to this question could take us all day. My suggestion to you is that you sit down and right down all of the factors that you have determined to be most important in the success of a show and its sound system in the past. Turn that into a checklist and use it before every event that you work on.
Probably some of the most important questions to start with are:
- What is the program material?
- What is the size and location of the audience?
- What resources do we have in terms of speakers and power?
#14 Megan: What is the best DIY acoustic treatment for a room?
Hey Megan, so I have worked in two music venues that are small shoe boxes and that were really difficult to work in. Then, due to someone’s suggestion, they covered their ceiling and back wall with absorption panels that just screwed right into the wall and it made a huge difference. I reached out to them to find out exactly what the material was called, but I haven’t heard back. But my guess is that if you reach out to your local building supply store and told them what you were working on they would be able to guide you better than I can.
Obviously this is a permanent solution. It would be great if we could fill a room with temporary free standing movable panels, but you would need a whole lot of them to make a difference in a typical event space. So what most people do is start by trying to control the loudest things on the stage, the drums and amps. So you might try a drum shield or guitar amp isolation box.
#15 Andrey: How to deal with room modes in small rooms?
Similar to the last question, your first line of attack is acoustical. Can we change the architecture of the room? Can we put absorption on the walls? If not, what can we do with speaker positioning? Come up with a bunch of tests to try. Are you using multiple mains? Trying turning one off. Move it around. Use your audio analyzer to record everything you do to help make a decision.
#16 Martin: How do you maintain a clear and cohesive balanced sound throughout a venue?
Martin, you do that by adhering to the principles of minimum variance that we talked about in part 1. Do what you can so that the level and frequency response are as consistent as possible and that the sonic image matches what the eyes see. Who knows, maybe it has nothing to do with you? Maybe, at the end of the day, the noisy HVAC system is the biggest barrier to clear sound, so what can you do to improve that?
#17 David: How to determine where to place speakers in your space and how many speakers to use to get even coverage?
So David, I think one thing you can do is start looking at everything in terms of doubling of distance. Since we know that every doubling of distance cuts our sound level in half, we can look around our room, find which parts of the audience are more than double the distance to a speaker compared the nearest seat to that speaker, and know that we’ll probably need another speaker to start its coverage there.
Another idea that can help you is to start thinking about your speaker’s coverage in terms of length and width. For example, if your main speaker has a horizontal coverage of 100º and is 10ft from the front row, then you can calculate that its coverage of that front row will extend for 16ft. This is something that we discuss in Pro Audio Workshop: Seeing Sound, but you also just open up Bob McCarthy’s book and search for the sections on forward aspect ratio and lateral aspect ratio.
#18 Fernando: How do I choose the right speaker for the space?
So Fernando, in terms of coverage, on a basic level, you should choose narrow coverage loudspeakers for narrow shapes and wide coverage loudspeakers to fill wide shapes. And half the time, that’s the best we can do with a limited inventory. But if you can pick any speaker, then divide the depth by the width of the coverage area, including the speaker. That number is the forward aspect ratio, which you can convert to a coverage angle.
In terms of power, it depends on the program material and you really have to experience it to know if it’s right, but having too much is never a problem.
#19 Jennifer: How to determine how many speakers you may need to fill (x) amount of space?
So Jennifer, of course this depends on what kinds of speakers, what kind of array you are going to deploy, and the idiosyncrasies of the space itself, but let’s take the simple example of a single room covered by a point source array. Since we know that a single speaker can only cover a maximum range ratio of 1:2, then we estimate that a range ratio of 1:2-1:3 will require at least 2 elements in our coupled point source array. And a range ratio of 1:3-:14 will require at least 3 elements, etc. So range ratio can help you quickly estimate how many speakers you will need to fill a space.
#20 Micah: When to use an array versus standard speakers flown?
So Micah, I think the question you’re asking here is when to sub-divide and we need to do that any time we have a distance ratio of more than 1:2, our angular coverage does not match the space, or if we need more power.
#21 Rob: What is the weakest link in most small music venues? Amps, Speakers, poor tuning, Etc?
The weakest link in most small music venues is the architecture. It’s the acoustics. It’s the reflections turning out carefully crafted mix into mush. And as I mentioned earlier, I have worked at two music venues that put up a bunch of absorption, which helped, but this isn’t going to help you on the event that you’re working on today.
So if I had to pick the next most common weakest link in small music venues, it would be speaker position and aim. Since we are in these small reflective rooms it’s very important to position and aim for more control. One of the most common things I see is long narrow rooms with LR mains, which are playing half into the wall because people just default to stereo in most situations when what might work better is a mono main and a relay speaker further down the room. Another thing I have seen a lot is asymmetrical rooms with symmetrical sound systems. You probably know what I’m talking about because you’ve been in a long narrow room that has a bar sticking out of one side, so the speaker on that side is only good for a few feet until it hits the bar, yet we’re playing both speakers as though they are both covering the entire room.
#22 Rune: How to set up endfire sub system?
Here’s what you need:
- 3 or more subs
- Processing channel for each.
Position them in a line, all facing the direction that you want their sound to sum. Then, with your measurement microphone in the front, measure each sub solo, phase aligning it with the sub in the rear. Because what you want is for them to all arrive in time in the front. A couple of verification notes: make sure you are not adding more than 3ms of delay to the speaker closest to the rear, 6ms to the second closest, and so on. If you are, you need to go back and reduce the spacing in between them. Lastly, you’ll want to verify that, with all of them on, summation is maximized in the front.
#23 R: How to maintain frequency and volume/all coverage with budget audio system?
The three things that come to mind when I think about working with cheaper speaker models are:
- The don’t sound the same when you drive them at low level and high level. So I try to get them distributed well so that I don’t need to drive them any harder than necessary.
- The don’t have a very smooth axial response. And what I mean by that is when I stand on-axis with the speaker and then move left or right, it doesn’t just get quieter, the frequency response changes. So I have to keep that in mind during placement, maybe trying to keep the audience within the smoothest coverage area.
- I’ll probably need to spend more time on EQ on a cheaper speaker to tame its response anamolies.