*Today I've got a great question from Itay from Israel about what changes when you move throughout your audience after aligning your system.*
[00:00:22] Listener Question
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Hi Michael, after I, align my system, will it be the same everywhere on, on the field? Like if I move left or right, be the same delay and everything gonna be aligned? Thank you.
*Alright, Itai let me give a few assumptions first and some first principles, then I'm going to jump into seven things to listen for while you are moving throughout your audience because things are going to change, I'll go ahead and give that away, but I want to give you specific things to be listening for to see if your system design and your alignment is a success and where you're going to be willing to give when things maybe aren't.*
*Maybe you didn't get the right speakers, the audience is bigger than you thought, But we need to have a certain set of criteria to look for and listen for as we're moving, or we're just going to walk around blind and not know what we need to be keying in on. So my assumptions are, we're just going to think about a couple of speakers on sticks for this simple exercise, that you've done a good job with the design and the coverage, and that the front of house mix position is within that coverage.*
*So maybe it's lined up with one of the speakers towards the back, or maybe it's right in the middle, whichever. But as you listen to some test tracks, Or maybe the band soundchecking and walkthrough. Let's look at these first principles, and then these things to listen for. So it's our jobs as a systems engineer, and you as the A1, if you're mixing the show and responsible for it, even if you aren't wearing that specific name tag that day, are responsible for minimizing variance and making sure it sounds like the front row in every single seat.*
*We don't just want to minimize the level variance, but also the total variance, but we want to make sure that within a specific bounds, that everything is sounding great. So that's why when we're tuning PAs, you'll see me with four different microphones. That way I can move them around to different seats because things do sound different, but how much different is the question and why?*
*Because putting your microphone in the middle of the audience and hitting the auto button on a DBX processor, isn't going to cut it. We need to be systematic about it. Okay, so let's jump into those six things to listen for. *
[00:02:33] Level Changes
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*The first is level changes front to back. So the inverse square law, which is fancy pants for saying when you're closer to something it's louder, when you move away it gets softer, tells us that for every doubling of distance the SPL is going to be cut in half.*
*So if I'm 10 feet from a speaker and then step back, back another 10 feet, I've doubled that, we're going to see a 6dB level drop. And so that's actually the acceptable tolerance I like in my system. So from the front row in the audience to the back row, when I'm measuring A weighted SPL, I want no more than a 6dB delta.*
*With a couple exceptions, two of them, if I'm in a church or maybe want to specifically provide some seating in the rear of the room for older congregation members. that is where we may want more. And maybe they have the youth group who wants it slamming in the front row. That's, that's up to them.*
*Or sometimes outdoor festivals where there's maybe a lawn chair seating way in the back where people just want to talk and conversate versus the real deal listeners who want to be in the front, that is fine. So again, know your show, know your crowd, but in general, if I'm just designing a normal system, that's the criteria that we meet.*
*So how do I measure that? Well, I put a microphone in the front row of your audience, take a measurement, Put a microphone in the back, you can just have one take another one and look at those traces if they're within 6 dB of each other, within as much of the spectrum as possible, then it's a success.*
[00:03:57] Tonality Changes
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*Which leads into our second thing to listen for is the tonality changes. So not only does the overall level change when you move front to back, it's going to decrease when you move backwards, but the tonality is going to change. And tonality, again, it's a wide word, you know, guitar players are obsessed with tone and some bass players are too, but the tonality If I'm in the front row, things are gonna maybe sound bright and in your face because I'm really close to a speaker.*
*But as I move backward, is there a big drop off in the top end, maybe 1k and above? And so if it sounds, maybe a big 500 Hz bump in the front row and it's not there in the back, or maybe if I move way off to the left, I'm losing some of that. Most of that has to do with moving out of a speaker's coverage, because a, a, the speaker specs we have tell us within a certain coverage, maybe it's a 90 degree by 90 degree speaker, that basically within that 90 degree pizza slice, we can expect it to sound, within reason, the same.*
*So we're going to have some drop off in high frequencies as we move to the edge, but that is going to be a 6 dB drop off at the edge. So as long as we were within that, again, sticking with the 6 dB theme, we're going to be okay. So when I'm listening, as we move left to right, we're going to be moving through the speaker's transition zone of that coverage pattern.*
*whether it's 90 degrees or not. **So we need to be listening for that and making sure, are we going to stay within that 60 B of Delta, as we move left to right through our speaker coverage patterns and left to right. Cause we were actually looking at the vertical pattern of the speaker on the, the, the bottom half.*
*cause most of the time I'm pointing a point source speaker at the back row of its coverage zone. *
[00:05:38] Direct to Reverb Ratio
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*And, another one linked to tonality, which is thing to listen for number three is our direct to reverb. ratio. So direct sound is a sound that's emanating directly from the speaker. Pretend we are in a, in a, anechoic chamber, aka a chamber without echoes or without any reflections.*
*It's very unsettling. If you've ever been in a recording studio, much like mine, with a bunch of sound treatment that gets you close, it's a very, claustrophobic feeling at first, since we're used to feeling a sense of space. Base around us, even when we're out in nature. and let's say you're in a civil war battlefield.*
*You hear a gunshot going off, it's still gonna echo and move throughout the space, even though there aren't walls. So when we are in a venue and we're at the front row, that means typically we're close to the speakers. 'cause most of the time the speakers are at the front or near the stage. We're gonna be hearing a lot of the speaker versus the surrounding areas and reflections that are bouncing off.*
*And that, that may mean every time you're putting the same rig in a different room, your mixes are going to feel different because you're getting a different ratio of reflections and the reverb times. And that's why there's a thousand different reverb plugins out there because there's a thousand different rooms you could be in.*
*So that ratio of direct to reverberant is going to be more direct the closer you are to the speaker and it's going to be more room as you move farther back. So that's why I put this next to tonality because your perception of reverb and tonality are going to be linked. So if you're mixing, and when you push something backwards in the mix, farther away, taking less of the listener's attention, another way to do that is to lessen the high frequencies.*
*Maybe take a high shelf and bring it down above 1k, because that gives us the perception to our ears of things sounding far away. It's just like if you, you know, Go to the restroom at a concert and all you're hearing is the subwoofers coming through and you open the door and you're washed in top end, that wall is blocking all those mid and high frequencies, so same thing here.*
*So we're used to localizing things far away, having a lack of top end, and we also have more spaciousness or room compared to the direct sound. So in, on the, all the way on the opposite end of the spectrum, if someone who goes right in your ear, that's a lot of high frequencies, very close to your ear, and it gets your attention.*
*So if you want less attention on something, roll off the top end, make it farther, make it seem like it's in a room, more attention, lots of top end, not much reverb, we'll grab it. *
[00:07:56] Floor & Boundary Reflections
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*Moving on to number four is you're gonna notice reflections off the floor and other boundaries happen So this is a little bit different from reverb.*
*We're moving too much earlier So we are used to hearing things from a speaker or anything where it **bounces off the floor in front of us that comes to Our ears so that's that usually the biggest Tonal shift that happens what's happening because a cone filter is happening with that floor bounce So that's usually arriving anywhere from from 3 to 8 or 10 milliseconds later, depending on your positioning, of sound hitting the floor, then bouncing up at your ears and meeting the direct sound late, because it's taking a longer arrival path.*
*So you're going to need to be able to learn and look for that in your data. Huh? You might see this regular cone filter or dip peaks and valleys in the response because of this floor bounce or, you're going to hear it. So as you move forward, that path length is going to change. So you're going to hear it like the airplane flying over sound like that.*
*You're going to hear that when you move forward and backward with that floor bounce changing. And it will be more dramatic if you have less reverb in the room and less dramatic if you're hearing other reflections happening. So this is also true if you maybe move to the edge of your audience and the chairs are very close to walls.*
*So you hear this. thing. So again, it's always critical, to, to have an iPad or similar surface. And we kick off the first song and mixing. You may, it may sound one way at front of house, but always make sure and walk around because *
[00:09:21] Room Modes
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*moving on to number five, you need to listen to room modes. So this plagues small rooms more than bigger rooms because we're getting buildup of what's called standing waves.*
*So that sound moving off the surface, then coming back and, Forming peaks and valleys throughout the room in regular patterns depending on its dimensions and these happen both with the height Width and depth of the room. There's axial modes. There's oblique modes You can get way down the rabbit hole here But all that being said the most uneven it's gonna feel is in the low end So I look at 200 Hertz and below So I would play some low end heavy music and you do a good bit of slow Walking and see if there's any buildups any regular areas So this is also true if you have your subs spread apart and not coming from the same area.*
*They're going to have cone filtering. So this is not room modes, but it's going to feel like a similar phenomenon. So both those things are working against you. Either how the reflections are coming off a wall and coming back with one another, or the two direct sources are interacting with one another.*
*So both of them are going to make this regular movement and basically have this sensation.*
*That's why I like to advocate for having a single subarray in the center, because it eliminates that path differences of things interacting with each other, and it has one discreet place for you to localize to. *
[00:10:41] Seam Alignment
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*Number six is seam alignment. So a seam, you know in a baseball, the lace is moving around, that is two pieces of cowhide coming together, being sewn together by that neat little red yarn or.*
*Nylon, whatever it is. so it seems when you have two zones that are handing off coverage to each other, so I, I don't like have having systems, lots of overlap, you know, here in the studio I'm perfectly, in between the center of my speakers and it's designed for this one unique listening position.*
*But in live sound, we have speakers covering audience members everywhere. So I want to subdivide the audience into zones and have them. each speaker covering that zone, but we're going to have to have a transition period where one speaker is handing off to another. Maybe have a really wide room, which I've done before, a convention center that's almost a football field length, but the state was so it's going a long way.*
*So it's about, you know, a hundred yards or a hundred meters by 50 meters. And so I had four different arrays spread out across the room. And so, they have to be handed off to one another, so I needed to make sure they were in time, which Eteh, you asked about the alignment, that's making sure that where these zones are equal and level is where I want to time align them.*
*So these zones were in particular on the same lateral and vertical planes, so I didn't have to really do much to align them with each other, but I did have some front fill speakers that I had to, have then aligned with the where the front fills met the main speakers to take care of the rest of the audience.*
*So seam alignment, again, it's most seam less or smooth when you are able to choose and level set each zone first. So I put a microphone in the middle of its custody, solo it, Get it's level set, and do that for each zone, and then you're going to turn on those zones and find where they meet at equal levels.*
*So that's getting a measurement microphone, looking at the impulse responses, and seeing we're at the same height, or just do it by ear, or listen to where they interact the most. So it's going to have that shoooo sound as you walk through those zones, so walk back and forth and find it, and then time align them right there.*
*So whichever speaker arrives earliest, earlier is the one you're going to need add delay to to align right there and that makes seams most seamless. So we've talked about level changes, tonality changes, direct to reverb ratio, floor and other boundary reflections, room modes, seam alignment, *
[00:12:57] Imaging
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*and now let's end with imaging to tie it all up.*
*So we as humans, We have a really, we have two ears, so we're able to localize sounds to specific spaces. And it's still crazy to me that we can still listen in 3D, we know an airplane sounds like it's coming from above us, and, you know, a frog is croaking on the ground, even with just two ears. We're best at localizing horizontally, but we still can do some up and down.*
*So if I'm listening for imaging, does it feel awkward if I'm in the front row if there's not a front fill there, even though my PA is able to cover all the way down there because I'm basically listening 90 degree tilt above me. So sometimes I may need to put a front fill there not to have intelligibility, but to bring the listener's attention down to where the stage is.*
*And so, Even though I like having my audience very neatly subdivided and having zones covered, sometimes I will push speakers closer to the stage and angle them out so people are listening towards the stage. So in general, that's a rule of thumb I like to have, is how can I make sure the listener's attention is going towards what they're looking at as much as possible.*
*So I want to know, hey, are the listeners going to be looking at this huge room and these delay screens, or they're going to be looking at the actual stage? I want to push my audience towards what imaging, and where I place my speakers and how I align them and the levels I set them to promote that. One last thing about imaging is that, again, I want to reduce the amount of variance in, both tonally and level wise throughout the audience, but sometimes I may need to soften the top end and the rear rows to make it sound like the, the, the sound is far away and it's not the pss pss in your ear.*
*All right, we covered a lot there. I hope those seven principles will help for you as you have this list of things to listen for as you're moving. Bottom line, yes, things are going to move, but we want to have them within a specific parameters that are acceptable to us. And if they're not, know how to fix it or know maybe to encourage people not to sit there where it's less.*
*Or if you're not in an ideal front of house mix position, know what you're trading off. Things are going to change. I'll Again, I'm Michael Curtis. Thank you so much for submitting the question, Atay. If you would like to do that, you can go to my website, producedbymkc. com slash question. You can submit it via voice or text.*
*Thank you so much. Catch you next time.*
