265. Busting Subwoofer Myths

There are a lot of myths and misunderstandings when it comes to subwoofers and sub arrays, but the reality is that there’s no reason to be afraid of them. In Episode 265, Sean and Andy huddle up with two very smart folks when it comes to low end — Phil Graham and Merlijn van Veen — to bust subwoofer myths and help us all understand them better for our next gig.

Phil Graham started building hi-fi loudspeakers with his grandfather as a teenager in the 1990s and joined the B&C Group five years ago. Today, he’s the chief operating officer (COO) of Eminence Speaker, acquired by B&C in 2023. Based in Germany, Merlijn van Veen is a noted audio educator and he also serves as senior technical support and education specialist for Meyer Sound.

Episode Links:
The Cheese Grater (Horizontal Sub Arrays) by Merlijn van Veen
Redistributing The Error (Sub Power Alleys) by Merlijn Van Veen
5 Finger Rule (Calculating Decibals Without A Calculator) by Merlijn van Veen
Signal To Noise Episode 38 with Merlijn van Veen
Signal To Noise Episode 206 with Bennett Prescott of B&C Speakers
Eminence Speakers
B&C Speakers
Meyer Sound
Episode 265 Transcript

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Transcript

Episode 265 - Substravaganza, featuring Merlijn van Veen and Phil Graham

Note: This is an automatically generated transcript, so there might be mistakes--if you have any notes or feedback on it, please send them to us at signal2noise@prosoundweb.com so we can improve the transcripts for those who use them!

Voiceover: You’re listening to Signal to Noise, part of the ProSoundWeb podcast network, proudly brought to you this week by the following sponsors:

Allen & Heath, introducing their new CQ series, a trio of compact digital mixers for musicians, bands, audio engineers, home producers, small venues, and installers that puts ease of use and speed of setup at the heart of the user experience.

RCF, who has just unveiled their new TT+ Audio brand, including the high performance GTX series line arrays and the GTS29 subwoofer. Be sure to check it out at rcf-usa.com. That's rcf-usa.com.

Music: “Break Free” by Mike Green



Andy Leviss: Hey, welcome to another episode of Signal to Noise. I'm your host, Andy Leviss, and with me, the brat to my summer, Mr. Sean Walker. What's up, Sean? 

Sean Walker: Uh, home sick today, buddy. Just, uh, you know, logging in with a pair of AirPods and, or whatever this thing is, the old ones that you plug in, and, uh, you know, a little stuffy nose, but we'll get it done today, which is the beauty of remote podcasting, rather than having to come to a studio someplace 

Andy Leviss: Right? Technically that's a vintage microphone, so like that's the that's the hip thing, right? 

Sean Walker: Uh, absolutely, it's 

Andy Leviss: Heh heh  

Sean Walker: the thing, because there's no Bluetooth noise in this thing, and it's like, $Free.99 dawg. 

Andy Leviss: Yep. 

Sean Walker: But I finally got a brand new laptop for the first time in 10 decades or whatever that thing was. I've been rocking a 2012 MacBook Pro for, I don't know, since 2012 probably. And last Wednesday, I went and bought a new MacBook Pro finally, because I was like, okay, cool. 

The battery's toast, and it's literally just like right up in the corner there going, you need to maintenance this thing. And it just said some pinwheels for everything, and I was like, alright, stop being a cheap son of a bitch and go get yourself a new laptop. 

Andy Leviss: so so everybody on the Discord should be looking out for all the, oh god, why isn't this working because I'm on Apple Silicon for the like week or so? 

Sean Walker: Totally. Yeah, as you start downloading things, you're like, what the fuck is that, dude? Why doesn't it just work, you know? It's been out for years. It should just 

Andy Leviss: You'll you'll spend the next three weeks updating Waves and 

Sean Walker: Oh, dude, that reminds me, speaking of waves, I haven't really been a plug in guy for For a very long time. But I got a, um, I got a call from a, from a client that was like, Hey man, do you guys have that new waves live box VST plugin server Dante? And I was like, click buy. Yes, of course we do have one of those that can rent to you for a week for corporate gig. 

And so we just got one of those. And so I'm kind of excited to try it and see if it, you know, see how, see how it do as it were and, uh, 

Andy Leviss: Heh heh 

Sean Walker: see, you know, see what's up. So if you've got any. Waves plugins that you need, that I need to use, or actually to do anything, I'll do any plugins, so I'm excited to like, start downloading some other shit to try, and not, not to like, load up my show file, but like, what are the few key pieces, like, what's the one that you use that's just like, Money, cash money on a corporate vocal, that, that iZotope thing, you know? 

Andy Leviss: Oh, yeah, the voice denoise. 

Sean Walker: Yeah, dude! I'm stoked to try that, 

Andy Leviss: Yep, everybody doesn't hear them on every episode of the podcast, 

Sean Walker: that's what I'm saying, dude. That's what I'm saying. You're about to turn these little 5 headphones into a gorgeous podcasting mic someplace. 

Andy Leviss: Well, and, 

Sean Walker: uh, you know, we're coming to the end of summer season here and getting ready for corporate season, so it's going to be a whole lot more like, you know, listen to CEOs talk about EBITDA and taking over the world and all the other stuff they're doing, and a whole lot less kick drums and sub dudes screaming Big guitars hitting down beats making everybody happy. 

Andy Leviss: yep, I closed out the summer yesterday with a last minute rooftop beach hotel gig, so that was, that was the way to close up the summer. That's um, our good friend of the podcast, frequent visitor to the Discord, uh, Leo Pysak is, uh, he'd been covering for, I can't remember Dave's last name, but he was covering somebody else's seat doing monitors for the band R. 

I. P. E. And they were gonna be like an hour from me, so I texted him last week and was like, Oh, hey, you're out with Ripe, aren't you? Like, Kate and I were thinking of coming to see the show. And he was like, that's actually the one show I'm not gonna be at of this leg. You know, that's the first show after I leave. 

And I was like, ah, well, maybe we'll still go see the show. We'll see, you know, whatever. But like, good to chat with you. And like, two days later, he texted and was like, Hey, the guy who was supposed to be covering monitors for Sunday's show can't do it anymore. You still around? 

Sean Walker: Ha ha ha 

Andy Leviss: So the day started with me thinking I was buying two tickets to the show and ended with me mixing monitors for the guys And the, you know, Leo was graying and sent me a pile of videos walking me through the whole setup You know nice little like, uh, Allen and Heath, D Live, CTI, 1500 

Sean Walker: Oh sweet. 

Andy Leviss: Yeah, um, 

Sean Walker: little compact guy that flies in a pelican, 

Andy Leviss: yeah, that thing is, 

Sean Walker: ATA weight and everything. 

Andy Leviss: is insanely light. 

Like you can like, you can pop it on your shoulder like an old school boombox. It's wild. 

Sean Walker: And the band were stoked when you did that. Started walking around with your gold chains and your 

Andy Leviss: right? 

Sean Walker: on your right neck. Yeah, 

Andy Leviss: Yeah, it was, it was pretty great. I will say it's, it's cool. Like when the band does like intros at the end of the show and they go around and like, you know, they get to, they, you know, gave Cassidy a shout out at front of house and like, he's fucking awesome. 

And then they came and they looked over at me and pointed at me and they're like, guys, and let's give a big thank you to this guy. Cause he jumped in like on 48 hours notice to save our ass tonight over there on monitors and like had the crowd like, you know, screaming for me, which was pretty fun. 

Sean Walker: Nothing like being the most famous this guy 

Andy Leviss: yeah. 

Sean Walker: night that's ever been this guide. 

Andy Leviss: Yeah, no, they did. They were very, they remembered my name every single time. It's the, the tricky bit on like subbing in on monitors is like they're used to people who know their voices and don't need to know who's calling on the talk back. 

Sean Walker: Totally 

Andy Leviss: So, like, one of the dudes would be like, yo, it's so and so, like, I need a little of this. 

And everybody else would be like, hey, Andy, can I get a little more of that? And I'm like diving for, like, talkback meters to see which talkback meter is bouncing. 

Sean Walker: Totally, 

Andy Leviss: But it was, it was pretty all right and, and Dave, who's, I'm sure by the end of the episode I'll remember Dave's last name, but, like, he, he set up a, a really smart rig on that console. 

You know, like, dude, pulling some tricks to, like, Matrix stuff so, like, the cue bus gets Matrixed in with talkbacks so, like, you can always hear it. 

Sean Walker: Oh, that's super smart. 

Andy Leviss: Yeah, it was pretty, um, it was, it was only like the second or third time I've like dug deep into a D Live and it was, it was a pretty tight. It's like, it's definitely getting more comfortable and it's a, it's a surprisingly capable console, especially in that small form factor that the CTI is. 

Sean Walker: Dude, that's awesome. It's always tricky to try to do like monitors in general, but like those quick throw and go when you didn't build the file on a small surface where you're like, and what did I need? Let me just tap, tap, tap, tap, tap, tap, tap through the pages and the layers, trying to find what you went and then it inputs to outputs, inputs to outputs. 

And you're just like, Oh my God, with the dance, with the finger dance, trying to make it happen. You know what I mean? 

Andy Leviss: Yep, absolutely. And then, and one of the guys had been on cause they're on like a grab bag of different in ear brands, just depending on what each guy wants, what each guy needs. And one of them, his sE535s had, uh, I guess had been busted. So he was on, they have like a floating pair of the KZ ZS10, like inexpensive ones that, Like, they're just kind of there back up or if they need for a guest. 

And he'd been on that for a little bit and got his 535s in like right before the show. So we swapped them out and it took me like halfway into the show to be like, he's at like, I need more hi hat. I need more of this. And like after a few, it started dawning on me. He's been using the KZs for two weeks. 

The Shure sound dull compared to how insanely bright those KZs are. He doesn't need all these changes. He just needs like about a 3k, you know, boost. And I slowly did that and I saw him look up at me and lock eyes and just nod and slowly started cheating back all the other notes we had done. 

Sean Walker: There you go. 

Andy Leviss: that was pretty, but yeah, it was a good reminder in like modern world about like Think about what they're asking and think about what that actually means they need because they're not always going to be the same thing. 

Sean Walker: You mean like he's not asking for more kick drum, he's just like, I need more overheads, I need more hi hats, I need more, you know, like all the bright stuff? You're like, okay, it'll be just Shelf up is send or something. Yeah, that makes sense. I'm into that. 

Andy Leviss: yeah, well, speaking of, speaking of kick drums and low end though, we should, we've got two lovely guests here sitting here patiently while we banter on like the clowns we are. 

Sean Walker: Yeah. 

Andy Leviss: we should introduce them. I'm going to, I'm going to introduce the, the one who's a returning guest first. We've got the one, the only Merlijn van Veen 

Merlijn van Veen: Hi, everybody! 

Sean Walker: Sup dawg.  

Merlijn van Veen: It's a, it's a pleasure. It's been a minute and I'm happy to be back on the show. Thank you for the invite. 

Andy Leviss: Yeah, absolutely, and happy to hang with you, because like, I, you came on the show before we were a part of it, and so we've like, we've had the pleasure of hanging with you in the Discord, which, if folks aren't in the Discord, they should hit the link in the show notes and join. But, uh, it's, it's good to actually put a, put a face with the, with the voice and the, and the words. 

Merlijn van Veen: Uh, I couldn't agree more. 

Andy Leviss: Um, that being said, why don't you, just for folks who, who may not know who you are, you want to give us the quick, like, you know, two or three sentence? 

Merlijn van Veen: yeah, I think, um, for the people that do know me, um, I, you know, I, I, I basically wear two hats, um, in, in my private life, I, I 

Sean Walker: Whoa, whoa, whoa, whoa, whoa. Easy, killer, careful with the hats. 

Merlijn van Veen: in my private, 

Sean Walker: Let's keep it pro. Let's keep it pro. 

Merlijn van Veen: in my, in my private life, I tend to present myself as an audio educator and I think that's how most people know me. Um, but I also have a daytime job, obviously. Um, and I'm very proud of that. Um, I'm a senior technical support and education specialist at Meyersound. And so, um, most audio professionals are aware of me, um, one in, you know, in one role or another. 

Andy Leviss: Cool, cool. And yeah, I mean, I will, it's funny, you were actually responsible for the weirdest reaction I've ever had when Kate came home from work one day and saw me in front of the TV watching the, the decibel math, the, the five finger rule 

video. And she just walks out and says like, what the hell are you watching? 

Merlijn van Veen: Yeah, the, the, the, it can be a little bit of a shock to the uninitiated. Um, 

Andy Leviss: she's a sound engineer too, she just wasn't expecting it. 

Sean Walker: No, what's the five finger rule? 

Merlijn van Veen: Oh, it's, it's, it's, it's a, it's a, it's a, it's a little, um, approach that, um, I came up with that basically enables you to calculate decibels on the back of an envelope if you need, need to, without having to resort to a calculator. And it's, it's mostly as a sanity check. It's like, does this make sense? And then you can always pull out a calculator and double check. 

Um, 

Andy Leviss: And I'm scribbling a note to link in, to link that in the show notes for folks, cause it'll be useful to folks, and also just that way since we talked about it, they know where to find it. So, uh, yeah, I mean, one of the things you're well known for is lots of, uh, SAA's blog posts on subprocessing. So, uh, we wanted to get you on because we're going to kind of do a little bit of like a sort of substravaganza, a little bit of subwoofer myth busting on that. 

So, uh, the way we're kind of figuring it is, uh, you are here as our what happens when we put subwoofers together kind of expert. And our other guest who I'm about to introduce is kind of here to, to talk about. Putting a subwoofer together and how, how single boxes work, how boxes go together. Uh, and that is, uh, Phil Graham. 

Phil, why don't you tell us a little bit about yourself? 

Phil Graham: Sure, I guess, technically I am, I am, uh, Sean's corporate season guy, since I'm more likely to talk about EBADA these days than anything else. Uh, my grandfather, uh, which is how I'm even standing here talking to y'all, uh, he, he ran a, an integration company back before that was a thing. He did paging and telecom and automation and early, even early fiber optics in, in Detroit for the automotive industry. 

And he was the guy that introduced me to building speakers when I was a kid. So I started building hi fi speakers in the 90s and realized that the hi fi guys didn't really know what they were talking about, especially back then. And then sort of came over to the pro side, worked for a regional sound company and In college, went to graduate school, uh, my, my background is in materials chemistry, it has nothing to do with audio at all. 

Uh, and then after a career in the lighting industry, and I, not stage lighting, but just working for companies that built light fixtures for outdoor applications and software for those kind of applications. Uh, five years ago, almost, almost five years ago, I got recruited to work for BNC. Uh, the large speaker manufacturer in the world, uh, largest speaker driver manufacturer in the world, headquartered in, in Italy. 

And so, uh, I wanted an opportunity to be in a role that was more business minded and a little less engineering minded, and, uh, that, that has me here today as Chief Operating Officer of Eminence Speaker. Eminence is one of the last remaining, uh, Speaker driver manufacturers in the United States and the BNC Group purchased the company a year ago and it's my day to day to supervise that facility and bring it into the fold and help do all the things that are necessary to combine operations of two companies that You know, were separate and had their own ways of doing things for the better part of half a century. 

And so, that's never boring. There's plenty to do every day. And I suppose I come here knowing something about speaker drivers, though working for BNC has definitely proven to me that I'm not a driver designer. Uh, but also having some practical experience of designing boxes over the years. And then also, long, long ago, uh, doing some of the stuff that's now common. 

Uh, things like Cardioid Arrays and Fire Arrays, um, doing all pass alignment, stuff like that. I was doing that stuff circa 2000. Uh, when I worked for a regional, because I was an engineer, and these are things that seemed like they would make sense and should work for audio, because they work just fine for antennas. 

And, uh, I was not old enough to know that no one did things that way back then, and I remember definitely having some conversations where people told me on no uncertain terms that we would not be turning that speaker around backwards, and what are you doing, and those kinds of things. So, it's kind of fun to poke your head back into the industry two decades later and see People have actually decided to educate themselves in physics a lot more than they used to, and now some of that stuff that I was told would never work and you should not be doing is commonplace. 

So that's, that's fun. 

Merlijn van Veen: I love that you bring up educate yourself. Because, uh, my colleague, uh, Mauricio Ramirez, also known as Magoo, uh, he just did an interview for a Spanish speaking country. And he said, you have to realize that there's no flight simulator for audio engineers. Nobody in their right mind would ever put a pilot in the plane without having spent ample time in the flight simulator. 

Um, but we audio professionals, we don't get to do that. We learn while doing and with all the fallout that comes with it. And, and so, um, sorry, I digress. It's just, I couldn't help, couldn't help myself when he said, you know, learn, learning while doing on the job. 

Sean Walker: I thought bar gigs were flight simulators. Isn't that how that goes? Just a horrible pa with a super loud, mediocre band, and you're just questioning your life choices for like a, a year is what you're trying to figure it out. And then pretty soon you get to a real rig, you're like, oh man, I'm not nearly as awful at this as I thought I was 

Andy Leviss: that's always that catch 22 of like, we say it's not about the tools, but sometimes it is about the tools. 

Phil Graham: Yeah, Sean, I mean, when I was, when I was in college, that was, University of Florida at the end of the 90s, so the height of new metal. And so doing shows for me back then was like a vocal mic and maybe some kick drum and hoping that the PA wouldn't explode because everything else was coming off the stage from ridiculous Mesa half stacks. 

And so, uh, I, I didn't learn a lot about mixing in those first few years, uh, of, uh, of working for a regional in a college town. 

Merlijn van Veen: Yeah. It's called combat audio 

or guerrilla audio. 

Phil Graham: Yeah, it was not, it was not an act of subtlety. 

Sean Walker: I am familiar with eminence from their guitar cab speakers. 

Phil Graham: Yep. 

Sean Walker: They also make. Every other kind of speaker for pro audio ish or 

Phil Graham: Yeah, I mean, it's funny because everybody, I think everybody at the company, uh, before our arrival, and I think everybody in the world, kind of thinks of the, the, the MI application first. But if you look at the, uh, if you look at the book of business, uh, while MI is definitely one of the pillars, it's by no means the only pillar. 

Uh, there's a lot of OEM. Manufacturer for, for brands you've heard of that, you know, don't get talked about, but same as being, same as being, you know, that doesn't work that way. Um, and then also, uh, there's a lot of distribution. There's a lot of guitar amps out in the world. And so people end up, uh, uh, over the years, uh, needing new speakers. 

And so there's a steady undercurrent of that kind of work. There's also a meaningful work for sirens and notification systems and, and, uh, All kinds of, all kinds of things that have walked through the door, which is true with BNC also. One of the reasons that BNC bought Eminence is that about 75 percent of the revenue of the two companies was from different customer sets. 

So there wasn't actually a lot of overlap between who they were selling to. 

Sean Walker: that's a good synergistic partnership or marriage together. If you've got two, two big income streams from two different things that aren't trying to fight for the same thing. 

Phil Graham: Yeah, I want to also, you think about like COVID, right? So it's like, MI did well during COVID and BNC was pretty sleepy though for a couple years. So you can Yeah, yeah, yeah, trying to find some uncorrelated revenue is 

Merlijn van Veen: Don't put all your acts in one basket. 

Phil Graham: So, 

Andy Leviss: It's 

Phil Graham: but, but that's a, that is a, most people know MNIST for the MI stuff, but they actually have a pretty broad catalog of, of, of OEM. 

And if you look at, revenue, OEM is, dominates revenue. It's more than 50%, so. 

Andy Leviss: right? Not. And. And before we dive in a little further, I feel like I should just mention for folks listening, cause I know it's a thing we talked about before we started that, well, Phil works for Eminence normally, and while Merlain works for Meyer, we are, they're here as themselves today. They're not here as representatives of those manufacturers. 

So we're gonna, we're gonna not pull punches and, and, and not be too, we'll be fairly brand agnostic, I guess is the, is the word I was going for there. 

Merlijn van Veen: Just fellow audio professionals hanging out. 

Andy Leviss: just a bunch of nerds. 

Phil Graham: I like working for a company where I don't have to come in and be a corporate robot all the time. It's pretty nice. Normally in a senior role, you would have to kind of always tow the company line, but I can just be here with my head. It's nice. 

Andy Leviss: great. 

Sean Walker: sweet. 

Andy Leviss: so, I mean, I know we had, and we'll go through, and, and, if, like I said, one of the things I want to touch on is, is anybody here on the chat, like, can throw in, like, you know, comment, like, this is a myth that I hear all the time that, like, needs to get, needs to go away, and we can help spread some of that gospel, but I've certainly got a bunch of, like, hit lists for some topics on Subwoofer stuff I'd love to ask you two about, because Every time I think I understand, I realize like, I'm not actually sure about that. 

So I feel like you, you two will either know the answers or at least, uh, be able to make them up with much more confidence than I would. Um, 

Sean Walker: I start? 

Andy Leviss: go for it. 

Sean Walker: How much does size matter? Wait, we're talking about speakers still, right? 

Andy Leviss: Yes. I know you got confused with the five finger rule, but, 

Phil Graham: Wow. Yeah. 

Sean Walker: Let's talk about size. 

Phil Graham: Well, I think, I think, 

Sean Walker: it's been 18 inch subwoofers for as long as I can remember, and now they're going like 19, 19 and a half, 21. Why, why the size change? What, what makes that? Why am I giving up all my truck pack for more speaker size? Because it makes me want to blow my frickin brains out that they don't truck pack as easily as they used to. 

What's up, fellas? 

Phil Graham: well, so I'll put the manufacturer hat on here for a second. Um, and I'll prove my point about being, being brand friendly. Both RCF. and Adamson have done a good job of coming out with a speaker that is larger than 18 inches. Um, and in fact, former guest of the podcast, Bennett Prescott and I have talked at length about how we would do well in the BNC group to have a, about a 19 inch speaker, call it 500 millimeters, give or take. 

The reason for that is, is that like, if you actually design a real box out of wood that you can buy, uh, and make it stiff enough and put handles on it and stuff, 19 inches is about the biggest driver that you can put in a box with a good size port that performs well, that you can truck pack all over the world. 

So, 21s are too big, and an 18 arguably leaves some output on the table. Um, there's a lot of physics to that, Sean, but one of the most basic things is that, um, diameter, It goes by the square of area, right? So if you take, you take the radius of a, it's pi r squared. So if you increase the radius a little bit, you get a pretty substantial increase in the surface area of the cone. 

And, uh, there's also a slight improvement, slightly larger cones actually couple with the air slightly better, but ultimately you're getting, you're getting more cone area to couple. And the motors, the motor structures are pretty strong. So, um, there's enough motor structure now. with Neo, uh, NeoMotors in particular, to be able to, uh, to move a bigger cone. 

So, uh, I, oh. 

Andy Leviss: and say Merlijn's itching with the face 

Phil Graham: Yeah, 

Merlijn van Veen: no, no, no.  

Andy Leviss: makes a 21 inch driver. 

Merlijn van Veen: I was about to say, I hope my boss, John Meyer is not listening to this podcast because we just launched 21 inch subwoofer. So, uh, 

Phil Graham: but I think that, I mean, I think that the Meijer product points out that point. Like, it's a single 21, right? A very good 21. Uh, but there, there are, there are limitations on, on that. You could go even bigger. I mean, there's, there would be no hesitation From, from a physics standpoint, to go as big as like, you have like the Powersoft M Force, which is like 24, um, you could, you could continue to go bigger. 

There, there are some practical realities of what you can run down a production line, and then, yeah, and truck pack. Ultimately, it's truck pack. 

Sean Walker: Truck pack. 

Phil Graham: Yeah, 

Sean Walker: The most important thing in any audio gear is truck pack. I don't care how it sounds, I don't care if it's reliable, it must truck pack or it's not even going to get onto the truck. 

Andy Leviss: So, and, and like, purely speaking driver wise, like there's, I assume there's like, there's kind of continuums of like, the larger the driver, the lower it can go, but the larger the driver, it's also gonna be a little slower, like is that a balancing 

Phil Graham: that, that's, that's all hokum, so, doesn't, doesn't, have any, any, that's all hokum. 

Sean Walker: Hook'em. 

Andy Leviss: I said we were gonna buff some mists. Busts, I just said busts, some mifts. SubWoofer 

Phil Graham: is, is that the two major things that matter for a bass speaker are kind of the linearity of the motor and the behavior of the cone, right? And so, the linear of the motor is a, could be an entire separate podcast, but the behavior of the cone is a little more simple. 

Generally, it's linear. Since you're only reproducing bass, you want the cone to be pretty stiff. You don't want it to have, you don't want it to be folding up on itself and tacoing when it moves in and out. And then also you want the, uh, you want the sound in the box to stay in the box. I don't think people appreciate just how much The leakage through the cone is like one of the dominant, undesirable effects from, from speakers. 

Anybody who's played with tube amps knows this, because cones for guitar speakers are like nothing. They're as wispy as possible, and the box they're in hugely affects the sound, and a lot of that has to do with not just the closed box versus ported box versus open back or whatever, but it's a lot of it has to do with the sound in the box bouncing around inside the box and having the box's own resonances and then just passing straight through the cone because the cone isn't damping the sound. 

So for subs. The motors are a big topic, but cones, generally stiffer cones, cones that are treated or designed to be stiffer and are thicker, generally give you the cleanliness of response. And also, um, A thicker, heavier cone tends to stop its own movement faster. But the reason that the, the, the other part of it, Andy, is a myth is that the total phase shift for, for the bass is dominated by the high pass, low pass in the box. 

So your typical box has second, third or fourth order low pass, second, third or fourth order high pass, and then if it's ported, it has about four poles more, so another four orders of magnitude. of, uh, of Rohloff, and the phase shift from all of that dominates. And in fact, you have, you end up in this weird circumstance where the motor parameters affect the phase too. 

So for a lot of actual physical speaker drivers, the, the, the acoustic center of the driver is not actually where the cone is. So, that, that tends to blow people's minds, but that has to do with the, with the, with the phase of the current in the motor. So the motor has its own electromechanical behavior, and then when the cone moves is not necessarily correlated with when the, when the audio came out of the amplifier. 

Merlijn van Veen: it's, uh, it's, I can second that it never ceases to amaze me when students are offended about the phase shift that they see in a main loudspeaker. And then I'm like, well, if that's offensive to you, buckle up, 

Phil Graham: Right. 

Merlijn van Veen: right? Cause, cause a subwoofer, at least the ones that I encounter, a subwoofer isn't capable of delivering more than one frequency at a time. 

Um, and you know, for our well behaved full range loudspeakers nowadays, at least everything typically above 250 is delivered as one package. Yeah. But Subwoofer is all over the place. 

Phil Graham: But also like 

Andy Leviss: is one package, but it's a package like the way the UPS driver kicks it to my porch from the street. 

Phil Graham: also 

Merlijn van Veen: And that's assuming no Porch Pirates. 

Andy Leviss: Yeah. Oof. 

Phil Graham: have a decay too. So the human mind is naturally triggered to think that bass should last longer. But we 

Sean Walker: I've been triggered for years. 

Phil Graham: But we definitely take bass and make it longer just by the nature of the filtering that we do. So, um, that's a system design philosophy in terms of overlap and filter order and stuff is a totally different discussion. 

And also there's some work that was done a couple decades ago on group delay, which is a way of sort of wrapping up all the phase behavior and kind of trying to put a bow on it. And it seems like Above a couple hundred hertz, people are pretty sensitive to that, and below a couple hundred hertz, people are less sensitive. 

So we can get away with a little bit more, um, ugliness in the low frequencies. 

Sean Walker: All right. So if I'm, if I'm going to summarize the answer to my question, the reason that they're going to 19 or 21 inch is because you get for a little bit extra cone area or a little inches around, you get a lot more area. And because now they have the motors to drive those effectively, you can have quite a bit more output then. 

The other size, is that 

Phil Graham: Yeah, that's, that's right. Yeah. 

Sean Walker: And, and not a terribly much larger package that still will fit in a truck, so I don't have to throw a hissy fit like a six year old girl? 

Phil Graham: Yeah. Also, 

Sean Walker: do it, dude. I'll throw a fit. I don't care. 

Phil Graham: cones are cheap, and, and, and magnets are, and, and steel are expensive. So. 

Sean Walker: Copy that. 

Phil Graham: So, it's like, if you get a motor that's strong enough, you lose very little by trying to put a, a, a, the biggest cone you can get away with. I just am of the opinion that, for a truck pack, that my, a 19 is a really good size, and I wish that we, we had one. 

So, and hopefully we will. 

Merlijn van Veen: And I'll have Phil correct me if I'm wrong. Um, but it's, it's, uh, you know, for me, and I'm, I am not, I am not, uh, I'm not trained in the black art of doing what you do, but ultimately it's my understanding that you know, for when it comes to SPL, the, the, the balancing act is still cone area versus excursion, because what you're ultimately trying to do is displace an air volume. 

I'm talking about liters. And so, so to display more https: otter. ai 

Sean Walker: Or both. 

Phil Graham: Yep. Absolutely. Yeah, and I'm just trying to not, I mean, I'm trying to do the 21s a favor. There's nothing inherent about a 21 that makes it slow or bad transient response or whatever. All that stuff is just not physics. Um, but, but, there is a world in which a 21 doesn't truckpack as nicely. Um, it depends on the kind of truck, right? 

I mean, if you're in semis all day, sure. 21s make a lot of sense. Uh, but like, if you're in a box truck, or if you're trying to do one box that truck packs globally, I mean, BNC Group, China is a major market for, for us, right? Much, much bigger than you'd think. And these are, you know, product that stays in China. 

Their trucks are different sizes. So trying to figure out what a lorry is globally is, is its own thing too. 

Merlijn van Veen: Well, here's what I'm going to say. Let's follow up in one year from now and then we'll have the final verdict on whether 21 inch trackpacks are not. 

Phil Graham: No, I'm for sure. Uh, I think, I think that, uh, that, that, uh, it, it just depends on what you're trying to do. If, if I was only doing arena shows, it's kind of hard to argue with a 21. It's got a lot of grunt and it'll fit in the truck and you get more bang for your buck for sure from the motor. But if I was like in a U Haul or something with a lift on the back of it all the time 

Sean Walker: Now I'm really triggered. 

Phil Graham: I mean the audience runs the gamut, right? So 

Sean Walker: your point. We're, we're in 16 foot Isusus, right? And 

Phil Graham: Right. Yeah. Cab 

Sean Walker: 26 foot, you know, straight trucks or 

Phil Graham: Yep. 

Sean Walker: And that's super, like it has to, it has to pack. It's super specific for 

Phil Graham: and heaven help you with the double 21 in the Sprinter, right? So, alright, so enough of that. I'm not trying The physics takeaway is the size of the speaker does not matter. Cost, cost matters, and that has to do with the design of the motor, and if you can put more cone on the same motor and it gives you good performance, that's a good, that's a good thing to do, that gives more value to the customer, and, uh, but none of the, none of the other stuff about whatever people think the phase response is, or transient response, that, that, that's not real. 

Merlijn van Veen: It's all about circumference. 

Sean Walker: still talking about speakers, right? 

Phil Graham: That's right, 

Sean Walker: Yeah. Okay. And so, so then it's each manufacturer's idea. Or R& D, or marketing, or the combination of the three that decide whether they're going to release an 18, a 19, a 19. 5, a 21, or whatever, on how they think they're going to accomplish that same goal of, you know, the largest, most powerful, best motor truck pack, what the customers are asking for, that whole package is how then you decide whether you're making a single 21, or a dual 19, or a dual 18, or whatever, 

Phil Graham: yep, I think 

Sean Walker: and what your market is probably. 

Merlijn van Veen: Well, and I'm happy you're bringing up the word dual because, you know, right now we're, we're talking about driver against driver, but you know, last thing I'd like to say about the truck pack is that it becomes an entirely different conversation if you're talking about a dual 18 inch versus a single 21. 

Sean Walker: Sure. Totally. 

Merlijn van Veen: And, and so, uh, That's, that's also an aspect to, 

Phil Graham: Yeah, it's worth pointing out if you sit down and do a little napkin math, a middle of the road 18, And a really good 21. Two 18s, two middle of the road 18s, and a really good 21 are about the same in terms of total displacement. So, the difference is not small. Like, 

Sean Walker: It's not even, even in, um, the same manufacturer's product line. Sometimes if you move up one level of like, when you go from maybe their MI line to their pro line, you get a shit ton more 

Phil Graham: extra. Yeah, absolutely. 

Sean Walker: appears to be. A similar box, you know, the grill's the same. Like from the, from the, uh, Lehman, right? 

If you're just looking at the thing, you're like, I don't know, man, they're both black boxes, you get a whole lot more when you get, like you guys were just saying, better motors, better cones, better DSP in it, and a lot stiffer, better box or port or whatever. It's pretty astounding as we, you know, as we run out of PA and then we have to go rent things around town, not, not all of them are created equal, even though they kind of all look the same. 

It's been pretty interesting to, To physically run the gamut, not just in theory, but just going like, well, that's not the same replacement I thought it was. Holy moly. You know what I mean? Like, it's pretty, it's pretty crazy. 

Merlijn van Veen: Also, the number, also the number of coils, you know, um, we're now doing, uh, we're now doing four coils as opposed to two or one. And so there's a lot of innovation, fortunately, still going on. 

Sean Walker: When you say coils, you mean the voice coils and the, is that what you're talking about? Instead of like a dual voice coil, you're doing a triple or quad or whatever? What does that do for us? I'm not, I'm not super hip to the like, manufacturing of that. What do the extra voice coils do for 

Merlijn van Veen: It's, it's ultimately, it all ties to the, to the motor. 

Sean Walker: Got it. Just a stronger, 

Phil Graham: gives you a stronger motor and better, better thermal handling, both. 

Sean Walker: Got it. 

Phil Graham: You only have so much, steel can only hold so much magnetic energy, and so the only way to get more, more push is to have more coil with the magnetic energy that you have. And like, if Merlijn made a, a double 18 and a, and with, let's say, ferrite drivers, right, versus then, like a Neo 21 like they're gonna use in something that's a high end touring box, the, the double 18 is probably 30 or 40 pounds heavier, 15 kilos heavier than the, than the 21. 

Because of the extra frame and the ferrite magnets. So, there is a, there's a, there's for sure, it's not just how much it weighs, I mean, how big it is, but also how much it weighs for the truck, too. 

Sean Walker: Absolutely. And how, and for rigging and for whatever, if it flies, right? Like it's a, I, I am, I'm seeing it's quite a, quite a number of compromises and balances and trying to get the right performance out of the thing. And that's, that's pretty cool, dude. It's, it's pretty sweet  

Merlijn van Veen: Well,  

Sean Walker: I got this much money to make a speaker. 

You know what I mean? 

Merlijn van Veen: I, I only want to say I'm happy that Phil and I are in agreement and I just, I'm sorry that I got a little bit defensive over there. It's just, uh, you know, just be, just, just being mindful, mindful of the, of the, um, of the community and whatnot. 

Phil Graham: Yeah, I mean, I think it's worth, let's just be plain for people, okay? A speaker With a ferrite magnet, the thing that determines how much it costs is the steel and the motor and the basket. Those are the two most expensive components. For a neodymium speaker, the neodymium motor, the magnet itself, and the steel dominate the cost. 

The rest of the components, they're not, they're not free. Uh, the coil is like kind of the next most expensive. But in terms of like, if you're trying to do bang for buck, uh, in terms of total, total cost, uh, in a ferrite speaker, Uh, speaker, because the ferrite magnets are fairly cheap, uh, the steel ends up being the most of the cost, and in a NEO speaker, the NEO's the first cost line, and the, and the, uh, steel is the second cost line. 

So, if you have a speaker that's NEO or ferrite, you can weigh it, almost, and figure out about how much it costs. 

Sean Walker: What about the CEO's boat? Isn't that a line item on like where you got to put it in the speaker? 

Phil Graham: Well, Lorenzo doesn't have a boat, so, uh, Ha 

Andy Leviss: I say, John does not strike me as the yacht type, although that's a great image to have in our heads now. 

Merlijn van Veen: John on, John on a boat. 

Andy Leviss: Yeah, John on a, on a super yacht. 

Sean Walker: That's awesome. Okay. Now that we got our nerd on about how the speakers are actually made. Let's get our nerd on about how we're gonna use them and if a ding dong like myself is gonna throw these things into a field someplace and pretend to do a rock show, what are some of the like, biggest faux pas that you guys see in, in pictures or, or people asking around the world, and then what are some of the like, sim either simplest ways to fix that, or things where you're like, yo man, I wish everybody knew these like, couple things that just would save everybody's subwoofer life. 

You know what I mean? 

Merlijn van Veen: Okay. Well, I'm happy to go first. 

Phil Graham: go first. 

Merlijn van Veen: uh, it's, you know, just the first thing that comes to mind, like literally the other day, I just published an article on this, um, is, you know, when, and we're talking about horizontal subwoofer arrays, which is, is one way to attack power valleys that are associated with left, right deployments. 

Uh, there are people that don't like that. And so a horizontal subwoofer array in front of the stage is one way to work. You know, to go about that, um, typically spreading the beam using some form of delay tapering or even more fancy old pass filters and whatnot. Um, but a critical ingredient is of course, the spacing between the loudspeakers. 

And um, one of the honest mistakes that I see in the field is that, um, if you ask any audio professional, what is the maximum spacing that I can afford? You're likely to going to get one of two answers, which is either half a wavelength or two thirds of a wavelength for the crossover frequency. And the honest mistake that I see in the field is that people assume the electrical crossover while failing to realize that the acoustical crossover is ultimately determined by the size of one's haystack, right? 

How much your low frequencies are emphasized with respect to your mid highs. And since the haystack I think is still the rule rather than the exception, um, people end up with the spacing that is too sparse. And then they, then they lift the subwoofers an 18 dB tall haystack. And suddenly we all become aware of the part of the spectrum, the out of band frequency, which, which have not been optimized for which the spacing is too large and those frequencies, nobody, including myself, nobody likes hearing those frequencies. 

So it's, it's, uh, it's something of our own making. It's, it's, uh, 

Sean Walker: So, since I love a good roll in the hay, uh, are you saying that when, when we have a bunch of loud subs, and, and when I measure in smart, I've got a, let's say a 60 Hz crossover low pass on the subs, that's the preset for the subs, but when I measure it in smart, it's really more like 125 where it meets with the, with the mains ish? 

Merlijn van Veen: exactly. 

Phil Graham: Right. 

Sean Walker: and if I take that haystack out and I stop rolling in the hay like a little kid, then that starts to come back down closer to 60. 

Merlijn van Veen: It's concealed by the main PA. Main PA conceals those frequencies, but, but by, by elevating those subwoofers and basically lifting them out of the swamp, you just added a whole octave to the subwoofer pass band, which otherwise would have remained inaudible. And if you don't take that into consideration for your spacing. 

Then you're going to get a spacing, which is, is too sparse for those frequencies. And you're going to get all the nasty effects that nobody likes, the time smearing and, and the, and the, and what I call the cheese grater, read the article, uh, you're going to get the, you know, the interference pattern over space and whatnot. 

Sean Walker: So then I need to actually not be thinking about spacing my subwoofers at a 60 hertz crossover but at a 125 crossover if I'm going to roll in the hay like that is what you're saying. 

Merlijn van Veen: Exactly. Which is gonna, which is gonna end up with spacings that are twice as, you know, twice as small as your typical, you know, anywhere from two to three meters, or let's say 69 feet, uh, it's going to be twice, twice less. And, um, and that's, and it's an, it's an, uh, 

Sean Walker: basically. 

Merlijn van Veen: yeah, well, uh, for, for, for, for dual 18 inch, you know, if it goes up to 80, I tend to go with six feet, but with a, we have the 21 inch that we talked about just now, which goes up to 125, that's the closest third octave. 

I go with, with one and a half meters. So that's, uh, it's like four and a half feet. And that's center to center, not the distance between the walls of the enclosures. 

Sean Walker: Got it. Center to center. Okay. All right. 

Phil Graham: Yep. 

Andy Leviss: So, 

Merlijn van Veen: honest mistake. Go Except that users forget that ultimately, it's the size of your haystack which determines where the acoustical crossover happens at what frequency, regardless of where the electrical low pass filter lives. And that's an honest mistake. I'm not judging, just that's something that I see. 

Andy Leviss: so, 

Sean Walker: okay. Andy's been judging me for years. 

Andy Leviss: uh, it's cold in Seattle, it's okay. Um, 

Phil Graham: I think, I think when you think about boxes, it's worth mentioning, too, that almost all modern boxes, and this is largely obscured in the processing, do a bunch of EQ. on subwoofers. A lot of times there's a, there's a, uh, some extra, uh, boosts in the lows to flatten the response to the box, and then there's, there's going to be a high pass filter, and you know, depending on the manufacturer, there's three or four choices for low passes in front of that, and some people, uh, you can, you can overlap the boxes pretty heavily, and then do some EQ in front of both to keep the response how you want it. 

So that's how I used to, to like to do things when I was doing system tech work, is use a lot of overlap. So, uh, So, I mean, there's lots of different ways to skin the cat, and some of that stuff has been obscured, uh, from the customer, and I think that's probably good for consistency, but it definitely hides Merlijn's point on what, what, what's really happening in terms of the physical boxes in the world. 

Merlijn van Veen: And that voice, that, um, that haystack will also bite you in the behind in another way because, uh, another popular configuration where, where it shows up is the gradient configuration, which goes by many names. Uh, it also is known as Cardioid Subwoofer Array or CSA. And then in certain countries, it's even known as the Augsburger array. 

Um, but, um, let me set the record straight. We, you know, we have these configurations thanks to Harry Olson, to the best of my knowledge, the gradient array, unlike AntFire changes the voicing of your subwoofer. And, and that means that a gradient array or cardioid has a, has only has a two octave wide interval where you have summation. 

in the front of the stack. And then you're going to get an octave wide suck out in the front of a gradient array. Again, if that's concealed by the main PA, no problem. But if you do your, your, your haystack once more, then that null in front of the array is, is, is is, uh, revealed, we become aware of that, and now we feel that there is a lack of certain frequencies that we're expected to hear coming out of the subwoofers, because for any other configuration other than gradient, uh, where the voicing isn't changed, we're, we're accustomed to hearing those frequencies coming out of the subwoofers. 

So that's another instance. Of, of the haystack being the root cause for an alleged deficiency that is associated with gradient when there's nothing wrong with the gradient, you just need to realize that it changes the voicing of your subwoofer. 

Sean Walker: are you saying that gradient array has giant frequency gap at the top end of it someplace, and when you raise the haystack up that gap becomes audible? Is that what you're saying? 

Merlijn van Veen: That, okay. 

Sean Walker: layman's terms? 

Merlijn van Veen: in layman's terms, yes. Let's do an A B comparison. You're, you take two subwoofers, you deploy them in an end fire. Well, then anything in the front adds up, right? And so the sonic signature of your subwoofer is preserved with or without a haystack. But if you take the very two same subwoofers and you deploy them in a gradient, you're only going to get band limited summation in the front with a null for the higher frequencies. 

Again, if that's concealed by the main PA because you don't have a low frequency haystack, you're not, you're not emphasizing those low frequencies. You're just doing a low frequency extension. You're just continuing where the main PA runs out of gas. That null is concealed. But if you do your haystack once more, suddenly you're confronted with frequencies that normally are there in the end fire example, but suddenly are no longer there, and that then is an alleged deficiency of end fire and time smearing and whatnot, when it's a direct result of you shifting the acoustical crossover and raising our awareness of what are technically out of band frequencies. 

Sean Walker: Okay. 

Andy Leviss: so, since we have a wide range of folks listening, obviously it's a much larger thing to really dig super deep into, but can we give a quick, just for folks who may not know, what EnFyre versus Gradient is? The kind of quick, you know, 20, 000 overview of what EnFyre is and what Gradient is? 

Merlijn van Veen: Well, I think for starters, you know, what we're talking about is what Bob McCarthy likes to call, we're trying to achieve directivity by committee. We have a bunch of omni directional subwoofers and we're going to rate them in a clever ways just to become directional and whatnot. And so, you know, in our, in our classes that we teach, uh, I, you know, as, as taught by Magoo, one of my other mentors, you know, we like to say and fire and gradient are basically mirror images of each other. 

N Fire is no compromise in the front, no time smearing, no transient distortion, and all the compromises in the back. And with Gradient, it's exactly the other way around. Gradient is zero compromise in the back, broadband cancellation, and the compromises in the front. And there is no wrong, there is no right, it depends on where you are. 

You know, what, what, what, what is mission critical? If you want a perfect solution in the front with zero compromise, go for end fire at the expense of what happens in the back. But if you want to have a perfect solution in the back, well, you may want to consider gradient at the expense of a little bit of compromise in the front. 

And it depends. 

Sean Walker: And it also depends on more than just that. It depends on how much space you've got, right? If you've got, A limited space, you may not have the space to do an end fire, which is for those that may or may not be hip when the speakers are one in front of the other, rather than stacked on top, right? So like, if you're on a small stage, you may not have the ability to get into the crowd. 

With an extra layer of speakers, right? Or is there another way to do N FYRD that I'm not hip to? 

Merlijn van Veen: Well, speaking of myths, right? There's this assumption that, you know, and, and, and so. We basically have two flavors. We have the inline configurations, like an inline skate, 

where the loudspeakers are sitting in front of each other. And then we have what we call the inverted stacks, where you put the bricks on top of each other. 

And some of them may be facing in the opposite direction. And of course, that has the smallest footprint because it only has the footprint of a single subwoofer. And one of the things that's poorly understood is that it is always assumed that end fire can only be done inline. 

Sean Walker: Yep. That was what I understood. I'm excited to get, I'm excited to get learnt. 

Merlijn van Veen: And with Gradient, right? 

We know that you can do it both inline as well as in an inverted stack. But I got news for you. You can do EndFire in an inverted stack as well. 

Sean Walker: Hit me. I want to know now. 

Merlijn van Veen: Oh, 

Sean Walker: do I, how do I, how do I do N FYRD in an inverted stack? 

Merlijn van Veen: it's the same principle. It's the same principle. So with an EndFire array, you know, the recipe is you take a subwoofer, the rear one, and we call that T0. 

And then we have a number of subwoofers in front of it. And we're going to time delay those all back to the rear subwoofer. And so in my mind, it's like a magnetic rail gun, everything fires and propels in one direction. So that's the recipe, T0 and then the number of loudspeakers in front of it, all going to get time delayed through that rear subwoofer. 

So now let's do a thought experiment. We're going to take the bottom loudspeaker and we're going to turn it 180 degrees around. And all the loudspeakers that are sitting on top of it are just facing forward. Who is now T0? Well, that's going to be the bottom subwoofer whose motor is sitting in the back of the array as opposed to the front of the array. 

And all the loudspeakers that are sitting on top of it, you're going to push those back just in accordance with the recipe to the rear facing element. And that's EndFire. The million dollar question is, is that enclosure deep enough to give me the quarter wavelength displacement? Because with the inline configurations, you get to tweak that. 

You get to play with the spacing between the elements, but once you go inverted stack, especially if it's flown or rigged, then the spacing is predetermined by the depth of the enclosure. 

Sean Walker: That makes sense. And then, so if they are in an inverted stack, to make the difference between gradient and endfire, are you saying basically where you time that is what makes that happen, whether you time from the back or time from the front is how you determine that, or is there more to it than that? 

Merlijn van Veen: Well, great. 

Phil Graham: there's a polarity inversion for 

Merlijn van Veen: Yeah. 

Phil Graham: So, Sean, I think, I mean, we've been super technical, and I'm first one to blame for this in this conversation today, 

Merlijn van Veen: Well, I didn't bring up the word nerd. So, so 

Sean Walker: Damn it, Andy! 

Phil Graham: I think, I think we've, I think we've proven our nerdery. I would say, especially for the bulk of the audience, you should use whichever one your manufacturer helps you support, especially if you don't understand what we're talking about. 

Because the reality is, is they will both give you cancellation behind the array, and that will be good for most of your events. And if you can just hit a preset on the back of the box and it does it, and you don't totally understand, then that's fine. Just use it. It's, don't, don't be afraid of it. And then, uh, if you, uh, if you do want to go in deeper, then, um, I mean, even, even for the, uh, even for something like, Sean, like, your pretty well integrated system that's all from RCF, they're going to have opinions on how to do either type of array, uh, when you put it together. 

So, um, 

Sean Walker: They do, and I've, and I've done both, and I'm, I'm asking questions not only for myself, but for the zillion other people that, I have not had the pleasure to do that, right? I, I have had the, the blessing and luxury to learn how to do smart and learn how to try to do it myself. And I've also had the blessing and luxury of having world class systems engineer come go, Oh, you're so pretty and show me how it's done on my own rig in my own shows and go, Oh man, that is way better. 

So, uh, some of it is me trying to understand it. Some of it is. Hey man, here's the, the word around the water cooler, let's, let's sort out some of that as well, right? Because, uh, we, specifically, are almost always in a limited space where a stack is what I can do. I cannot always make them in line, right? 

We're on, in my particular case, we're on, you know, small to large mobile stages and, uh, you know, and structures. I don't have ginormous festival stages where I can have, you know, 10, 20, 30 feet of barricade in front of the stage. I get, like, Six feet, right? Just enough that I can get some stuff in there. And then sometimes security can walk by. 

But, uh, if I said, Hey man, I need three subwoofers deep of this spacing in front, promotion would go, not a chance, dog, sort it out some other way. You know what I mean? So, uh, what, what are some of your best solutions other than what you just said, which is, you know, Follow the manufacturer's preset, which is excellent advice, and I've done that, and it works great. 

Merlijn van Veen: I, I, 

Sean Walker: a step in between, absolutely. 

Phil Graham: your shop. Doing it in the field is a lot. 

Merlijn van Veen: Oh yeah, I completely 1000 on the same page, uh, with Phil, especially if you do not, if you're not familiar to the point that you feel confident that you have mastered the technique, uh, sure. Stick to the manufacturer preset. Um, but as an educator, it should not come as a surprise that. You know, a big part of my career is also about emancipating users and teaching them these techniques. 

But like Phil said, if you want to play with it, I'm, I'm, you know, nine out of 10 times during class, I say, when in doubt, let's try it out. Okay. But as Phil points out, do it in the warehouse when you're not on the clock, right? Do it in the warehouse, do it in the loading dock until you feel confident that you, that you grasp the fundamentals of it. 

Before you deploy it in the field, because if it goes wrong, you know, it's like, yeah, well, I did my best. Well, huh, we paid you to do your best. Right. So, so 

Phil Graham: Also, we're 

Sean Walker: give me your best. Yeah. 

Phil Graham: We're glossing over a little bit about how the sound bends around the box. And so, the total distance around the box is part of it. There's also small changes that are due to the actual physics of the air and the diffraction around the box itself. So, it's one of those things where the numbers in the textbook formula are not usually typically exactly right, if you're trying to find the maximum cancellation, for instance. 

Merlijn van Veen: there is even, there's even a name for it. It's called the fudge factor. 

Sean Walker: That's highly technical. I like it. That's super technical. That's, that's going in the memory books, for sure, because you got to fudge it a little times, because fudging it comes right before fuck it. I give up. Yeah. 

Merlijn van Veen: No, but it's what, what, what, what Phil said is like the discrepancy between what the formulas give you and the values you end up finding in the field. There's a name for that. I didn't come up with that. It's the fudge factor. 

Sean Walker: I like it. Okay. Question. So if we're going to go one step further, And, uh, and we're going to say, okay, we've used the manufacturer's presets, they're working great. Everything's fine. Nothing is broken. Nothing's fucked here, dude. What's the next step of like things to try in the shop before you go to a show that you're like, Hey man, I want to make some improvements on the manufacturer's presets. 

I've got a measurement rig of some kind, and I would like to see if I can't squeak the last few ounces or feet or decibels or whatever performance out of this. Array. But I've still got the limited thing of whatever the manufacturers are. I still have to stack these subs. I can't, I can't do a classic or, or what we would see in pictures of an end fire, which is speakers in front of each other, right? 

They still have to be stacked. How do I do that without manufacturers presets and have it in end fire stacked up rather than in gradient. I'm still going to flip the subwoofer around, but I'm going to time it. I'm not going to polarity invert. Is that what you're saying? 

Merlijn van Veen: I do want to backtrack. Sorry for doing this 

Sean Walker: No, no problem. 

Merlijn van Veen: You know, it's like, this is not rehearsed. So we're having, we're having this conversation. You said like, what is a, what is a typical faux pas when it comes to deploying subwoofers? Well, here's one that is like really a red flag. These frequencies or specific, these wavelengths are claustrophobic as fuck. Don't fence them in. So don't put it under the stage. Okay. And I cannot evangelize that enough. And that's, that's, you know, you, you brought up the topic of real estate. That is really a challenge because Ant Fire hogs real estate, right? Especially if you go deeper, you're in the process of making a graveyard. 

And, and so where are you going to put it? So it ends up next to the stage. Uh, whereas with your inverted stacks, you know, if you like have an egress area in front of the stage, you still have a fighting chance of putting something in front of the stage, but forget, forget inline configuration from the stage. 

And, and so, uh, if people yield. To, to lack of real estate, you know, they might be tempted to put it on the stage and that's just where I put my feet in the, in the, in the ground and say, don't do it. 

Sean Walker: totally. 

Andy Leviss: And that actually brings me, brings me back to a question I had earlier that we didn't get to that was a question somebody else gave me to, to ask today is we were talking about spacing and as we're talking about them getting claustrophobic, like, where's the diminishing returns? Like, what, like, if, if I'm worried about spacing them too far, like, I also am worried about, I don't want to smack them right up against each other in multiple dimensions either, correct? 

Ha, 

Merlijn van Veen: Yeah. I mean, there's, there's, there's some manufacturers have an outspoken opinion. Um, my safety clearance recommendation is one meter or three feet between the walls of all enclosures and, you know, their surroundings. And yeah, and somebody said earlier, size matters. I mean, if you, if you, if you'd like have a road case, that's the size of a shoe box, that's, that's not a, that's a, that's a pretender object, that's not a contender object. 

But if you have like big objects, uh, that are, you know, significant in size and, and boundaries and whatnot. No, that's, you need to stay clear of that. And I, my, I typically recommend, you know, at least a one meter case. Clearance Corridor between the walls of the enclosures and, and their surroundings. But I'm eager to find out what Phil has, has to say on that. 

Phil Graham: I don't, I don't, unfortunately don't have the deep knowledge I'm going to have to, to, uh, to, uh, defer. Sean, I can tell you what I used to do, cause there was a season where I would went around and kind of cleaned up installs for people where we would try to either rehang the PA or just process differently rather than buying a new one, uh, which was always fairly easy to sell. 

And one of the first things that I would do is I would sit down and I would take the high pass and low pass off of a sub and just measure it directly. And. Before I put a high pass back on, I would try to figure out using a, you can buy for a hundred bucks a device from Parts Express. They'll tell you the impedance, show you the impedance curve and show you the tuning frequency of the box. 

You figure out the tuning frequency of the boxes using this thing called the woofer tester. And then I would use smart in the ground plane and I would, uh, Uh, flatten the response of the boxes out to about 500 hertz, trying to knock down any resonances that we observe from the ports, because the ports have resonances themselves, and those resonances don't, are not harmonic, they're not related to the musical content in any way, they're a function of geometry. 

And then also, sometimes, sometimes the boxes will have weird resonances, or the room they're in will, the stage, the stage will vibrate, or the stairs. Try to knock all that stuff down, and try to get a pretty flat sound. Ground plane transfer function of just the sub with essentially no processing. Then add back in the high pass and the low pass. 

And then the other thing that I would do is, especially for installs, a lot of the subwoofers they put in installs kind of have small ports and they tend to compress pretty quickly. So if I could figure out where the crossover frequency, I mean not the crossover, but the tuning frequency of the box was, sometimes I put a little EQ there, cut like 2 3 dB, which is inaudible in the world, if you don't know any better, and would make sure that, that, that you're like 3dB less output right on, on the port, and the ports generally for, for lots of boxes that was enough to quiet the ports down, so that when you're really, boxes really go and it wasn't all just fart, fart, fart, it was still something that sounded like music, quite a little bit quieter, but enough to keep the boxes from, from making these ugly noises that don't relate to, to the music that's being played. 

And then I think another thing, Merlijn's jumping 

Merlijn van Veen: no, I just, I just, for 40 minutes, I resisted the intention to use that one verb that you just used. 

Sean Walker: Come on, let's fart, dawg. Let's get it on. 

Merlijn van Veen: I was like, I'm not going to use that. I'm not going to use it. Thank you, 

Andy Leviss: It's a much more translatable word than chuff, 

Phil Graham: Yeah, Chuff, Chuff, I mean, but Chuff is like closer to the actual sound, right? 

Sean Walker: mean, let's be honest. Farts are always funny. 

Phil Graham: So yeah, true. So uh, those are, those are two things that I would consistently do having to make sense of what was in the room. Um, and the other thing that I would always try to do if it made sense for the stereo images is use lower order filters. 

Um, I, I tend to prefer second order low pass and second order high pass on the top boxes and try to overlap them quite a bit. And if you're going to use a lower order filter, then you need the, especially the subwoofer to sound cleaner and closer to what you actually want in terms of a flat transfer function out quite a bit farther, especially with the Haystack, you know, you've got, 

Sean Walker: And for those listeners in the audience that have no idea how many orders are in things and they can only read the DSP that says 6, 

Phil Graham: yeah, yeah, sorry. It's one order per six. So if the order is four, six times four is dB per octave. If it's second order, that's, that's, uh, uh, that's a two, that's 12 dB per octave. And unfortunately that comes from some math you use to define the filters, but yes. 

Sean Walker: My brain already hurts if you gotta do math. Sorry, dude. 

Phil Graham: So, it's, it's, it's 6, 6 is 1, 12 4, et cetera, et cetera. 

Um. 

Sean Walker: And, and why, why do you prefer the, the, uh, shallower slopes on the, or the less orders? Oop, oop, he's got a hand up. Yes, yes. 

Phil Graham: I'm curious to 

Merlijn van Veen: I just, I, I, I think I, I don't want to steal Phil's thunder. So I'll let him go first. 

Phil Graham: Well, for me it was, I, I, you know, I very early started playing around with all passes. Uh, cause I read some papers about how they used all passes in, in, in the cutting lathes for vinyl. Cause it turns out that, you know, voice is not very symmetric, so you can use an all pass filter to shift the phase of the voice frequencies. 

And therefore you can make the, uh, the top and the bottom of the wave more symmetric. And therefore you can get a slightly louder signal in the, in the constraints of vinyl or tape. And so almost all these old vinyl lathes and tape machines had an all pass in them, and their old radio processors, the radios use this forever too, where they shift the phase in the mid range to improve the symmetry of voice. 

And people love vinyl, and people, you know, like, talk about how great it is, so I figured that like, okay, if I can slap a giant all pass filter right in the middle of the band, probably I can get away with a lot. And it seemed like you can get away with a lot as long as the group delay is short. You know, if the group delay is a couple milliseconds or less, you can probably get away with murder. 

But like, as the group delay gets longer, it gets more audible and, you know, everybody's heard that subwoofer that's still going three days after the kick drum hits it, right? And so, it seemed like to me that we probably couldn't hear phase, but you probably could hear the total group delay, and so, using a lower order filter, is an immediate cheat to give you less group delay in the low end. 

I 

Sean Walker: And for those in the audience that don't know what group delay is, how is that different from just like milliseconds delay between tops and subs? What, what is the group delay? Is that the total delay of things or is that 

Phil Graham: technically it's the negative first derivative of the phase response, but it's a, it's a way of showing sort of what the overall, uh, arrival time is of a collection of sound, not just a single frequency. That's how to think of it. And so, so, so here, here, let me, let me explain the math. Like, so at, At, let's say, 100 Hz, 360 degrees of phase, that's one wavelength, okay? 

So at 100 Hz, that's 10 milliseconds. At a thousand hertz, 360 degrees, or one wavelength, is, is one millisecond. So it's the same amount of phase shift, but the amount of time involved is totally different. And the idea is, is that your brain is pretty sensitive, uh, to, pretty insensitive, especially in high frequencies to the phase, uh, but pretty sensitive to the group delay. 

At least that's what people seem to think from the papers that I read. And I was not an acoustic, I was not an acoustician and I wasn't a researcher. So I just went by what I read in the literature by bringing the order of the filter down. So if you go from a fourth order filter to a second order filter, you cut the inherent phase shift of the filter in half. 

So that's half the group delay back for free. And the trade off is, is that you have to make sure that the, the low, the low box and the, and the top box. are, are happening together through a wider range of frequencies. And then a lot of times, because you got two band passes overlapping each other now, you got too much low mid, so you have to cut that. 

But you can cut that for the whole array, you don't have to cut that for the individual boxes. The other thing that it does is by sharing the, sharing the mid range between the boxes, um, the most difficult region for For speakers to reproduce, people think it's the bass. It's not. It's actually the lower mid range. 

If you look at the impedance curve of a, of a, of a speaker driver, the lower mid range is where most of the energy goes, like, because low mids are really loud, right? Chugging away guitars are super loud in that 100, 100 to 300 hertz range. And if you look at the impedance curve, that's the region where the most power comes into the speaker driver. 

So if I got two speaker drivers and I can share some of that, that, that input between them, then the overall heat input in each driver goes down. So by sharing some mids with the subs and vice versa, you reduce the excursion of both drivers for the same amount of output and you, you have less heat into the drivers and overall that makes the sound system better behaved and more consistent. 

So I am, I am not on team Haystack. I've tried to simulate Haystacks in my, in my life, usually by using shelving filters on the input and output of the signal as needed. But I try to overlap. Now, sometimes it doesn't work, right? If the PA is way up in the air and the subs are on the ground, hearing 300 hertz, even a little bit out of the subs is super weird for the people in the front. 

So sometimes you just can't do it. But like, if the PA and the subs are reasonably, like, In the same plane, and uh, you have a, and the PAs, especially if you have some front fills, so the main PA is not having to cover the nearest area, you can get away with a lot, and you can overlap them a lot, and it's better for the drivers, and it's better for the boxes, and it gets you less group delay to start with, so it already gives you an easier path to cleaner phase response. 

Merlijn van Veen: Now, I'm going to add to that, um, there's, there's another, there's a third or fourth, I lost count. There's a fourth or fifth advantage and that is it prevents acoustic shock. Now what do I mean by that? Um, the last use case that Phil gave is like PA up in the air, subwoofers on the ground. If you use very steep filters, then you're going to get a transition range. 

Think about the keys on a keyboard. You're going to get a transition range that maybe occupies three white keys on the keyboard. So think what that does if a bass guitar player plays a chromatic A chromatic, uh, uh, uh, melody on the bass guitar. He goes through an octave. Okay. Then you're going to get a split in the sonic image because most of the notes are coming out of the air and everything else is coming off of the ground. 

And so using filters that are inherently less steep means that you're going to get a gradual transition that maybe doesn't occupy three keys on the keyboard, but maybe an entire octave. So that, you know, you don't get the jumping up and down in the vertical between notes coming out of the air and notes coming off of the ground. 

And that's another reason. And then, and then finally is that you also have to bear in mind that depending on the design of your loudspeaker, and again, we're assuming that for whatever reason, which is very unlikely in today's industry, we are assuming that for whatever reason, the filters that load the high pass filters that are baked in the product don't suffice. 

That's what we're talking around now. And I think that's becoming less and less of an issue because, you know, manufacturers got their cut. Stuff in order, but even if you feel the need to apply additional filtering, you have to bear in mind that these products already have a natural roll off baked into them. 

So if you look for a 20, 20, 40 B per octave slope, and you're going to use a fourth or low pass filter without acknowledging that there's already a natural role of building to the loudspeaker, you may end up with an effective slope that is in the order of sixth or eighth order in the order of 36 to four, you know, to, uh, what is it? 

Uh, I don't do math life. There you go. Thank you. 48 to be proactive when you intended to do only half of that. So that's another common, uh, honest mistake. Cause again, really, these are honest mistakes, 

Phil Graham: a ported box, a typical vented box, which is most common by far, has a fourth order roll off built in, so that means that like, if you do a fourth order, Uh, uh, uh, uh, high pass filter to protect the box from excursion. You're, you know, that's an eighth order roll off at the bottom of the, of the spectrum. 

Merlijn van Veen: which tends to be the rule and not the exception. 

Phil Graham: Yeah. So yeah, a lot of people do that. Um, and I know some of that comes from the old days where people didn't have PEQs around, so they couldn't like juice the corner. So you'd have to, typically it's a, then a box gives up real quick after the, after the tuning frequency, you don't want to go too much below that. 

So people, you. 

Sean Walker: sorry, I'm sorry to interrupt. 

Phil Graham: No, go ahead. 

Andy Leviss: Actually, I'm going to interrupt the interruption, and pause us here for this week, so we can give everybody's brain a break for a bit, and pick back up with this on next week's episode. In the meantime, thanks to everybody for listening, and thanks as always to Allen & Heath and RCF for sponsoring the show, and we'll see you right back here where we left off next week on another episode of Signal to Noise!

Music: “Break Free” by Mike Green