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The blog story of Kalle and Jupp can be downloaded here in PDF or EPUB format, so that you can also read it offline and in case of poor network coverage in Germany, especially in airplanes and trains. I wish you a lot of fun reading, laughing and thinking. With the donations I will finance the translation!

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INTRODUCTION

In 2017, I had the opportunity to attend a seminar myself. 2x 4 days of ‘Calibration & Design Techniques for Modern Sound Systems’. Who is considering NOT to attend the seminar should take my remarks self-critically to mind. If I had to summarize the two-part seminar in one word, I would say ‘impressive’. If I had one sentence, it would read: With almost inexhaustible energy, the lateral thinker Merlijn van Veen inspires his guests and invites them to decipher a previously unconnected correlation of basic knowledge and practical puzzles, he consistently relies on the method of making predictions, verifying them, understanding deviations and constantly equipping his toolbox with new options through inspiration and curiosity, which you can also weigh against each other. 

In the following I allow myself to give a highly subjective summary, which may give the potential interested party information about the expected and at the same time express my thanks to Merlijn for the inspiring days.

Merlijn van Veen is a gifted organist, he plays on the synapses of my mind a mixture of down-to-earth delta blues and experimental 13-tone music. His designs are solid, orderly and self-contained, as in Mississippi Fred McDowell's Shake ‘Em On Down, when he switches between a steam lock that drives firmly in the tracks and then breaks out every 12 bars and dances in the air like the wooden train of a playing child. Another extreme of his designs is the permanent use of all 12 notes, which the common sound technician knows all, but usually only uses half of it. A specialty of Merlijn is the use of another 13. Tone that is completely foreign to the experienced participant at first and then opens the eyes or ears to new options in a mixture of fascination and astonishment. He definitely lives up to his first name!

Merlijn's passionate research and research in all aspects of sound reinforcement technology is astonishing whenever an incomprehensible situation arises, which can be safely explained, however, a few sleepless nights later, the connection is clear.  Here, he relies on his intuition as well as on the valued opinion of many colleagues around the world. We share the passion for sleepless nights and endless discussions about details.

Anyone who believes that "all this is already known" is just as wrong here as in a technical profession itself. Those who get involved in the intense days with Merlijn will experience inspiration and infectious enthusiasm from one of the most passionate coaches I have ever met. Parts 1 and 2 are equally of excellent didactic structure in theory, as well as packed with practical presentations that allow an immediate review for which one rarely finds the time in the hectic working day.

Merlijn van Veen always imparts comprehensible basic knowledge, which he attaches importance to, everything has been known for ages and is not rocket technology but simple natural laws. Following this requires enthusiasm for the topic and requires a high degree of independent thinking. If you are looking for simple recipes that you can cook for, you won't find what you are looking for here. In its place, Merlijn invites you to try it yourself and thus expand his tool case to possible options. Whenever possible, these are presented immediately in a practical way. The methodology is based on the following building blocks. Make predictions based on physical, technical possibilities. Plan, check, verify and understand deviations. ...and if not, keep thinking until you understand!

This seminar is one of the best things you can treat yourself to as a sound person!

I strongly recommend all colleagues who are thinking about joining Part-2 immediately because they already have enough experience not to do that and to visit Part1 beforehand. There are enough aha moments for everyone, even if the agenda feels familiar. Always remember, you are not dealing here with a lecturer who rattles through an agenda, but with an absolutely insane one!

In the following, I would like to add a few core messages of the two-part training to my heartfelt eulogy, which have stuck with me to a special extent and probably look a little different for each participant and are by no means completely listed here. 

So that the whole thing does not seem too dry, I tell you it as a ‘multi-part’ story, which is led by two protagonists in dialogue.

REGISTRATION SEMINAR NEWSLETTER FORM

PROLOG

1. AKT ⁇ LINE ARRAYS

Sunday morning 05:30

Jupp turns on Kalle's phone. ‘The bum has slept again!’ Jupp is standing on the market square with the truck full of material. Daily target: Sonication for a public viewing, and before that Kalle's Top 40 band plays ‘Sax Bomb’. Well Kalle basically does not play a role here and certainly not an instrument. Nevertheless, he does not miss an opportunity to speak of ‘his band’. He mixes the guys since day one and everyone likes his ‘sound’. Where ‘sound’ for Kalle means everything. For the band, ‘sound’ is merely synonymous with ‘there is no way to go without it’. Sax Bomb, whose name never really opens up to outsiders, plays in the cast: Three times saxophone, keyboard, guitar, bass and drums. In addition, the singing changes depending on which of the "chosen ones" has the time. The supporting element are the three saxophones, all of which prefer an alto saxophone. Kalle is left to bend that somehow.

06:30 PA hanging

‘Have you used 0° again?’ asks Kalle when he sees the expression from the prediction software lying around.

“Yes, of course we have 12 modules and just under 35m. Today we can build really cool ‘directivity’, ...ne?’ replies Jupp.

Kalle blushes, but not with shame: “I have told you 100 times that you are destroying the pattern at the front, please go to 1° there must be a bit of curving in! And think of the overshoot, otherwise it frays in the back again. And I want to hear something else. Let's think a little bit about the control”.

Jupp, how shot out of the gun: “What do you want to think about? Always three modules together and ready....ne?’

Kalle shakes his head: “You think from the wrong side, my friend. This is not about the occupancy of the amps, it is about the distribution of sound pressure.”

Jupp rolls his eyes: “Ok, we have a cylinder shaft with 3dB level loss per distance doubling, right...ne?

Kalle slowly but resolutely folds the report together with the clearly wrong calculation: “Yes, only for the frequencies in the near field that really couple. You can easily calculate this: Line length in square times frequency divided by 700! Watch out: We have 3.15m array length here. Let's take something in the lower third and compare it to the upper third. Let's say 500Hz vs. 5kHz. Then the transition to the far field is at 500Hz = 7m and at 5kHz = 70m. And because I'm lazy, I choose the frequencies with a ten-potency difference. Do you understand? Ha, ha, ha. Then I just have to count once. The 3.15m isn't quite right either. Because we have bent the array, we basically have to put on a string and see how long the array is then. Unfortunately, the prediction software does not give us this measure, and manufacturers prefer to torment us with elaborate Fresnel vs. Fraunhofer calculations in order to maintain the voodoo around all the stuff.”

Jupp grins: ‘Brass, that is, at a distance of 7m from the stage, the snare becomes quieter faster than the HiHat...ne?’

"Yes, exactly," says Kalle. ‘But only part of the snare, e.g. not the carpet. It is also a saxophone chapel.’

‘However...’, Jupp cannot resist.

Kalle continues unmoved: ‘The said 7m distance from the stage is not correct either. You first have to calculate the b-side with Pythagoras, where the hypotenuse is 7m long. Attention, now it is turned off properly! Most then take the picking point of the PA, but basically you have to take the acoustic center. This, in turn, is slightly behind the PA when curving, but where there is no sound source at all, ha, ha. That's why I move it forward where it cuts the banana and almost simply take the middle of the banana. We also have a small computational problem here: 7m is the hypotenuse, and 7m is the picking point. We can not use this at all, because the transition into the far field is of course somewhere on the flight route in the air. And the sides a and c cannot be the same size, since it is not an equilateral, but a right-angled triangle. We can now subtract half of the array length, so go to 5.5m with the a side, then we land at just under 3.5m distance, but you can also just take the disto and see where you land at 7m from the middle of the array, but enough now! This is not so important, because the consequences are much more important. Back to the saxophone, they all play alto and they have a basic frequency range of about 100Hz to 500Hz. Uh, you know what? You can talk about line array and ominous cylinder waves here a hundred times, but in the end I'm supposed to transport 3 alto saxophones today. It's not a good idea, but it's a different story.”

Jupp scratched his head: “Kalle, what are you trying to tell me...? Can't we just get into the hustle and bustle and pull this thing into the roof...ne?’

Kalle looked puzzled: ‘What do I mean by that? No matter what we do here: The baby will change the tonality over the course, understand? Speaking at the front, the saxophone still sounds fat when I'm done with it, but at the back, the overtones inevitably predominate. Now tell that to the sales fuzzis, which of course my 6 modules are enough, because they all do so, and then believe, I could somehow conjure up at the desk.

Short consensual silence. The moment when even non-smokers want to light a dump out of embarrassment, then Kalle picks up the thread again: “Back to the array! We were still on the left of the modules. I suggest that we look at the array in zones.”

"In zones?" asks Jupp. ‘Why that? They told me during the last training that you should basically look at the thing as a whole...ne. Otherwise the wave front will be destroyed....ne?’

Kalle waved off: ‘Oh, what. It's all panic-mongering. You must always think in phase angles 120°-240° is the area where it destructively adds up. Everything else is positive addition. OK, maybe the directions of the ‘fingers’ in the vertical beam change minimally, but hey: They are there, and the benefits outweigh them. Watch out...you'll see right away.”

Kalle folds up the paper with the angles again and turns the sheet over.

“So, how do we divide the shafts now? If we roughly divide the array into 3 zones and look at how the distances differ, we might come up with a goal-oriented idea. The lowest zone, i.e. modules, is our 0 – distance and we look at how far the middle and upper zones differ in relation to it. This is usually 2:1 in the middle and 3:1 in the back. What does that do in terms of level difference?’

"You mean that with your fingers as a donkey bridge...ne? how was that again?" asks Jupp.

Kalle shines like a Christmas tree: ‘Exactly, look at your left hand: The thumb is on the left. The thumb stands for a 1:1 ratio, you now write 0dB on it. The index finger stands for root 2, i.e. 1.41:1. There you write 3dB on it, we take the approximation for 1.5:1 ratios such as: Two subwoofers get a third. Brother. The middle finger stands for 2:1 or 2 fingers 1 thumb. So ‘Fuck You’ costs 6dB. The ring finger stands for a ratio of 3 fingers to 1 thumb that is 9.5dB. Let's round it up to 10, because most marriages last about 10 years. Ring finger and marriage! Hey, a nested donkey bridge! The little finger is something special, it looks like a one and stands for 10:1, which is 20dB. The whole thing applies to field variables such as sound pressure or voltage. For example, performance sizes are given as an encore, just subtract half. So now I ask you Jupp: If the centre is 2:1 and the rear is 3:1 in relation to the 0 in front, how many modules will shoot best where?’

‘Yes, in the same proportion, best ...ne?’, Jupp suspects.

Kalle nods: “Exactly, let's just take 1,2 and 3 = 6 modules, we have 12 at the start then we can double to 2 for short-throw, 4 for mid-throw and 6 for long-throw. Do you understand how I plan the amps? I don't care if I need one more for the middle and waste a module below. Now explain that to a seller who already gets out of 3 modules per amp channel when BiAmped comes into play.”

“Is everything the same from front to back...ne?” says Jupp.

Kalles grunts disappointed: “NO! It's still three times as far away in the back as it is in the front! And nothing has happened at the transition from the near field to the far field. Let's take the just calculated frequencies again for help. At 500Hz we are at 7m line of sight to the banana in the far field and lose 6dB with each way doubling, if we were inside a higher proportion of diffuse sound level from the room would be added, since this frequency range is a point sound source. But we're out there and we only have the floor. At 5kHz we only go over to the far field at 70m so far we don't want to do so today, i.e. we only lose 3dB with each way doubling and have -3 in the middle and -4.5 in the back. If we measure the zones individually, i.e. switched solo, it is different. There we have -6dB in the middle and -9dB in the back. In this way, you can also check whether the invoice goes up with the near/far field. We can then optimize the overall array by averaging about 6dB level loss from front to back over the entire frequency range. Otherwise, the tonality falls apart. Think of the saxophones. When I work with EQs now, the difference in front to back in tonality becomes too big and it sounds too thin at the back because the LowMid range is a ball source and the higher frequency range by coupling rather a cylinder shaft in the near field. For the frequency range where the woofers couple as a spherical sound source with the array length, I have to work against it via EQ, of course, for the whole banana.

So all that remains is to lower the short-throw and mid-throw range a bit to align the front and middle for the near field in the RF, so that would be -3dB in the front and -1.5dB in the middle. Again in peace: relative level in the RF before: 0, -3, -4,5, HF afterwards: 0, -1,5, -3, i.e. 3dB difference from front to back for all frequencies in the near field. This is today at 35m playing length about 2.5kHz upwards, where everything under it is in the transition, or in the far field, and falls off with 6dB per distance doubling. The counter-calculation for this is simple, namely twice as high as the currently calculated in the RF near field: So 0, -3, -6. Do you now understand why less than 6dB level drop over everything out here does not work without loss of tonality?’

Jupp supports: ‘Wait a minute... well, we now have the 8’’ array here, which is 3.15m long at 12 modules, and just calculated that at 35m, which we want to shoot here, it drifts down at 2.5kHz in the far field...ne?. If I now take the 12’’ modules, would the 12 banana be 4.5m long, is the transition frequency lower into the far field in the same situation as here? So at 1250Hz...ne?

Kalle looks proud: “Correct! But try to explain this to the seller, who thinks he just wants to convey a little bit of language. And he thinks that big wood is only for rock 'n' roll. The most important area for speech intelligibility is 800Hz-3kHz.’

Jupp itches slowly in his fingers: ‘Is everything nicely homogeneous from front to back ...?’

Kalle raises her hand: “Unfortunately not quite. With Line Arrays you buy a vertical pattern. And no matter how well the thing is constructed, there is always a frequency range that bundles more closely vertically than others. The French already described this in their first manual in 1992. You can read this on p.152. If you now walk through or measure from front to back, you will identify this area. So it is obvious to work with an EQ against there. Of course, this is completely counterproductive because you do not change the beam. We are not dealing here with a level problem, but with a time problem. So we also have to use the time glue. I'll show you later how to fix this with 3 all-pass filters by building a parametric phase EQ. By the way, the longer the array, the deeper you will find this beaming frequency range. This should not be confused with the LF coupling by array length! These are two parallel problems that need to interact and be repaired separately.”

Jupp laughs: “You're crazy, then we can finally hang up the device and measure it...ne?”

Kalle: “Clearly, don't forget to change the links, 2×3 is up, 2×2 is middle and 2 are down!”

2. AKT ⁇ SUBWOOFER

Sunday morning 07:00 Bass puzzle

Jupp is already shaking his hooves and can't wait to look over Kalle's shoulder again. Like a hungry street dog, he stares at the wooden box with Kalle's hand-picked measuring microphones. ‘Floor or tripod...ne?’ asks Jupp.

"Stative!" says Kalle.

Jupp supports his hands in disbelief in the hips.

‘Why tripod? On the ground you don't have a comb filter through the ground reflection... no?’

Kalle doesn't even look up when he replies: ‘Yes, but on the ground are the feet, not the ears. I'll show you that again with the comb filters, now make the subs ready.”

‘They've been standing for a long time...ne?’, Jupp proclaims, not without pride.

Kalle grins at him: “Let me guess: All evenly distributed and blunt on one feed?’

Jupp him Thumbs up: ‘Yes, log... no?’

"Take care," says Kalle. “We have 24 pieces, 1.35m wide, 57cm high and 70cm deep. The stage is 16m wide. Do you see the house back at 50m behind the stage?

Jupp gives it again Thumbs up: ‘Yes, log... no?’

Kalle nods satisfied: “Good. There is such a spackling of lawyers, whom they bullied so much during their studies that he now deserves a golden nose with warnings. If we throw our bass club into his face, I'd enjoy it, but then we're delivered here. Requirements, you understand?’

Jupp makes the thumb disappear.

“Yes...ne? Then the Melissa comes back and makes the level aunt? She's really cute, isn't she?’

"Yes!" says Kalle.

‘What? Sweet or does she...ne?” asks Jupp.

Kalle laughs: ‘Both, well, uh. Hey, hey!’

Jupp's head is crooked.

‘What's going on? I knew it...ne?

Take care of your age: Never fuck the business, you know...ne?”

Kalle answers: ‘Fuck anglicisms. And can we finally discuss the shitty basses there?”

Jupp puts the forehead in wrinkles. “You want to discuss...ne? I'd be done by now... no? Shall I make piles of three and turn one because of the spack...ne?’

Kalle waved off. “Nee. 2:1 ratio is shit because of the level difference. The guy molds around in the far field, and then he hears two from the front and only one from the back. That doesn't work out. Level-wise. Let's briefly calculate what fits mechanically on the 16m width of the stage. All uprighted is 13,70m. That's not bad. We cross with 12 pieces at 16m, but there are no gaps. And we can't build wider. In addition, the upper edge is only 1.15m instead of 1.35m.’

Jupp seems slowly annoyed: “Age is still possible? Because of 20cm...ne?

What gaps at all? Can we put a fat line without gaps? That's gonna push...ne?

Kalle shakes his head. ‘Yes, exactly. At the back!”

Jupp looks at him with big eyes: “Huh? That's cardio and with 1:1 for the front/rear it has to go all out...ne?’

Kalle: ‘No!’

Jupp: ‘Why?’

Kalle sits down on a case. Jupp knows that it will be followed next by a stupid saying about his intelligence.

‘Ah, Jupp. I could explain it to you, but your brain would explode.

Les mal AES7992 by John Vanderkooy, who described this in 2010 but does not seem to be interested to this day. Otherwise, neither the data sheets nor the sample lists of most manufacturers would be wrong.

Be careful, the question is: Where's in front of such a subwoofer? So acoustically in front, the acoustic center! He described it very precisely. To fully understand this, I'm too stupid, probably should have done Abi, no matter! The acoustic centre is located about one foot (around 33cm) in front of the loudspeaker. The bigger, the further ahead. That's why such a long row presses so horny on the chest, you see?’

Jupp briefly imagines Kalle's head exploding. Then he says: ‘Makes sense! I've always wondered why such large piles push better, even if the sound pressure is the same. But then you can't build any gaps or...ne? What are the gaps for now?’

Kalle nods. “Yes, yes. If it is to push, no gaps. But our goal today is the Spackfilter. Do you know how big the difference is behind the Inverted Stack Gradient Array Is it possible for the whole thing to work?’

“Yes, actually none...ne?” says Jupp.

"Exactly, but you can't do it," says Kalle. ‘The tolerances of the boxes alone are at least one decibel. And what does this mean for the total level after addition at 1dB difference and 180 degrees phase shift?’

“Clearly...ne? That's -20dB instead of -infinitely...ne?’

“Exactly! To be exact -19,3dB, but as I said: We're not that exact. If we stay within 1.5dB and 10degree tolerance we can create -18dB, but even that probably won't work today because things have to get too close to the stage again. I'm glad we don't have to build under it. That's not really possible. But even the metre gap in front of it would have to be, but Ingo, this luden organiser, just doesn't let himself be talked to. Let him deal with this spackling lawyer because it's not quiet enough.’

‘Or with Melissa...ne?’, Jupp suspects.

Kalle laughs: “Ha, ha! Yeah, that's right. Preferably with the lawyer. He usually reacts to bribery with a luxury hotel including one of Ingo's horses. With Melissa no chance! For this, she wraps the guy from the order office so much around the finger, just because he was here and she drove him crazy with her boobs all the time.

He still dreams of it today when his phone rings in the office.”

Jupp is still shaking his feet. “You're drifting off, I want to have breakfast before the soundcheck...ne? What would the noble gentleman want now, whether the bass gaps...ne?’

Kalle points to the stage. “Please build two pieces each on a euro pallet and pack the roller boards in between. Tension strap, done. Please always turn it right Sub from the front.’

Jupp twists his eyes: "Now don't tell me that turning left or right sounds different! This is not yoghurt...ne?’

Kalle shrugs his shoulders. “I like to reverse rights. What does the mother in Saxony say when she looks at her child?’

Jupp laughs. “Is it clear...ne? I'm going to look at the right... Dude, sooooooo a beard! Why the gap with the roller boards now?’

Kalle seems proud that Jupp inquires about the finesse.

‘Because of the acoustic centre and the resulting distance and symmetry. The overall surface area increases as you place several speakers next to each other. Let's say that the rear subwoofer has its acoustic center at 33cm to the rear and the front correspondingly opposite to the front, since the level of the front speaker without gap has a longer distance to the rear and is accordingly quieter, ergo less extinction. Of course, I can also adjust this, because I still have system limiters at FOH. However, this is even worse if you build a 3:1 ratio because of the overall surface area of the construct without gaps compared to 3 smaller surfaces with gaps. We are building 2 pallets today and we are building 1:1 in the same ratio.”

‘The limiters are in the amps...ne?’ asks Jupp.

Kalle raises his index finger.

“Yes, and what do you think happens when I lower them first via the input gain, and the great limiter that protects the boards normalises that away again? No, I'll do it myself! That's the cool thing about the Lake groups. I do the Threshold Offset in the module and the sweet Melissa gets her juice throttled over a group, ready.”

Jupp scratches his head.

‘Can it be that the subwoofers do -4dB backwards in the prediction software, even though they are spherical spotlights?’

Kalle seems confused.

‘What do you mean?’

Jupp sits next to Kalle on the case.

“Take care! I recently went to a manufacturer and did a factory tour. There was a subwoofer right in the middle of a turntable, but then the acoustic center must be in the middle! And not just the casing...ne?

Otherwise, a relative distance moves around on a varying circular path and the different distance to the fixed measuring micro results in a distance-dependent lowering of the level...ne?’

Kalle nods.

"Yes, but I don't think anyone has the eggs to do it right and Vanderkooy is deliberately ignored. People want backwards dampening. And who wants to build worse loudspeakers than the competition? Suddenly you can't measure it correctly and impute it to the competition, because until yesterday you did it yourself. Classical dilemma. So it's better to ignore it! Speaking of ignoring away, buckle up the pallets and I'll calculate the distance between the piles.”

Jupp bruises his nose. “Do you also work or do you just think...ne?”

“I work exclusively with the brain”, emphasises Kalle. ‘Now get to work!’

Jupp goes to the stage and whistles the melody of 00Schneider in front of him, while Kalle is babbling seemingly senseless stuff: ‘So. 344/80Hz = 4.3m / 3 = 1.43m distance between the acoustic centers of the subwoofers at 80Hz and 1/3 wavelength because at 120 degrees still a clean 0 summation takes place. I want about +10dB for the sublevels to the top! That would have to end, I hope. The half subwoofer is 28cm + 56cm for the whole rotated + 20cm rollboard gap + another 28cm for the next half, makes ...hm...subtotal 1,38m. This then makes 1,43m – 1,38m = 5cm between the pallets. We have 12 piles so 11 gaps, makes 55cm for the gaps plus 12x 1.2m for the pallet piles. Bämm! 15m perfect! If I still want to catch up the meter, I can maybe get the gap in the direction of 15-20cm and get closer to the rollboard gap, I can also make the takeover frequency at 75Hz. 1m remaining space divided by 11 gaps equals 9cm plus the 5 we already have makes 14cm. Short counter-calculation with 75Hz. 344/75Hz = 4,59cm / 3 = 1,53m ... perfect! ...recovered the 10cm, it also benefits the coupling of the tops with the subs. I want to drive it 10dB louder. That's all Melissa accepts anyway.”

"AND...ne?", shouts Jupp.

"14cm between the pallets please!" replies Kalle.

‘Doesn't shed 15cm...ne? Professor!" commented Jupp

– 15 minutes break –

Jupp is done with the subwoofers on pallets.

‘Kaffchen, Kalle? I have to breathe through it, don't I? It's pretty warm for the time.

You're saying that cardio subarrays don't sound really tight anymore?’

Kalle nods briefly as he receives the coffee.

“Yes, that is unfortunately true, the aim is to achieve the highest possible attenuation behind the subwoofer. You can do this if you are really good, with -15 to -18dB. For the -18dB you have to move in a corridor of +/- 1.5dB level difference and +/-10degrees for the ratio front/rear behind the pile. This also works homogeneously over the frequency range behind the sub array. You measure behind the sub array and delay the rear to the front until you are in time and in phase. Remember that the slope of the phases coincides, otherwise you are not in time. And maybe a few integer periods next to it, then you invert the polarity of the rear subwoofer signal. The levels must be as precise as possible on top of each other. For if you have even 1dB difference, the annihilation is gone, and you move about -20dB. Of course, this affects the entire course of the amplitude frequency response. If you need to change levels, you also need access to limiters to change the tresholds in the same ratio!’

Jupp closed his mouth. “Kalle I really wanted to know what was happening at the front. I know how to measure something like that, don’t I?’

Kalle shakes his head.

‘You can buy this homogeneous damping at the rear of the gradient array – whether inverted stack or classic Olsen in a row – with a distortion of the impulse response at the front. Frequency-dependent clubs result from level rises and extinctions. Go to 90 degrees from such a CSA construct and play something impulse-like like a quick kick, then you don't hear one impulse but several. If you now go off the sound field in front, you hear how the timing changes. And also that here and there in the pattern frequencies are missing. Techno DJs see this immediately when people don't react to gimmicks in the sub.

Or set the drummer to 90 degrees, then he suddenly fits like a miracle back to the bass. Hey, hey!’

‘Wow, why do you do that at all...ne?’ asks Jupp.

‘If you want the stage to be quiet or if you are not allowed to stimulate the room so much, because the hall radius in the sub is otherwise too small, you have no choice,’ explains Kalle. ‘In the far field behind the stage, the whole thing is a bullet again anyway. And if the front/rear ratio is not 1:1, the sooner.

"Why don't we make Endfired today...ne?" asks Jupp.

Now Kalle turns his eyes.

‘Because of the Spakenanwalt! The tactical goal today is that he has as much peace as possible. We buy this with worse sound for the listeners. At Endfired, we don't make the reverse damping to that extent. With Endfired, it's the other way around: Front homogeneous and maximum addition. At the back a polar pattern of side lobes with addition and extinctions. Salop said: Gradient or CSA is shit at the front, at the back it clears out nicely homogeneous. Endfired makes homogeneous addition up to the critical frequency at the front, but it sucks at the back.”

Jupp crosses his arms: ‘What do you mean by Critical frequency... no?’

Kalle gets up and reclines. ‘It's nice that you ask. Let's start first to understand this. You select the frequency to which the Endfired Setup is tuned. This is the frequency at which a maximum extinction is achieved at the rear. The octaves above and below do not reach this attenuation, we come back to it right away. Now you place the subwoofers at a distance of 1/4 of the wavelength of this frequency. The distance calculated from acoustic center to acoustic center. Then you place your measuring microphone forward into the sound field at 0 degrees and measure the rear sub. The delay locator you set free snout and then no longer tackle it. Then you measure the front sub and delay it until you are in time and in phase. Uh... we already had the subject. Hopefully you'll end up at 1/4 of the wavelength or 90 degrees of the tuning frequency expressed in runtime. Let's take 50Hz, wavelength 6.86m, 1/4 lambda is then 1.715m. First of all, this is the distance zw. Front grill to front grill and secondly, the sound for 1.75m needs about 5.1ms. So if you land at 10ms and wonder why the slope is uneven in phase, you now know why. Or not?’

‘Because I'm not in time, but half a period, or a quarter next to it, right?’ suggests Jupp.

Kalle nods. “Correct, but it is best to discuss this again when we measure. First, a line check. Polarity Check, please.

Gottfried reconed last week. You know his red/black vision.’

Jupp froze in motion.

‘Moment...ne? But now you have skilfully circumnavigated the critical frequency. You should become a politician...ne?’

"That was not intentional," Kalle apologizes.

‘The tuning frequency gives the phase difference of 180 degrees and the maximum achievable extinction behind the array.’

‘180 degrees means complete extinction...ne?’

Kalle raises her hand.

‘Only if the levels are exactly the same. At 0.1dB difference only -38dB and at 1dB difference -19.2dB. We had already discussed that. It is now about the critical frequency, at which there is a full summation behind the array, and thus an 8er characteristic. This is the frequency that is twice as high as the tuning frequency. Fully stupid, if you actually have something like a kidney characteristic as your goal. You can easily remember that if frequency A has 180 degrees difference, then a frequency B twice as high by half the wavelength has 360 degrees phase difference. And 360 degrees means full 6dB addition, where level differences are much more accommodating than differences due to extinctions. Where we are at levels: The first row Endfired brings +6dB in front, each more only +3. With the annihilations at the back, it is similar. They increase with the amount of rows.’

Jupp looks desperate. ‘And nu...ne?’

“Yes, then you can't play the frequency”, says Kalle. ‘The cut-off frequency and the slope of the crossover filter shall be selected appropriately. And sometimes, but only sometimes, a notch filter also helps. Then we take the 1.7m distance front grill to front grill for a 50Hz endfired arrangement, which we have just calculated. Then what is the critical frequency with full beam to the rear?’

Jupp as if shot from the pistol: “Clearly...ne? 100Hz, right? But that's outside our 80Hz...ne cut-off frequency?’

Kalle nods. ‘If the filter has 12dB/octave slope and is at 80Hz, the 100Hz at 0.25 octaves is only at -3dB below. For critical frequency 2. Order, which is at 720 degrees phase difference – i.e. 200Hz in our example - we have 1.25 octaves, and thus -15dB at 200Hz compared to all frequencies below 80Hz XOver. With this level, our 200Hz are now blowing forwards and backwards as a characteristic of 8".

‘Uh...ne?’

“Exactly. So, and now I want to raise the subwoofers by 10dB in relation to the tops so that it sounds nice. Equal Loudness Curves and all that. Yes, have fun with the comb filter between top and subs! 100Hz is then +7dB and 200Hz -5dB in the subwoofer signal in relation to the top.’

‘And now...ne?’ asks Jupp.

Kalle:

Either we take a steeper filter with 4th order, but it costs too long a group runtime, or we work with a notch filter in the subwoofer path to dampen these frequencies specifically. Of course, they must not be too steep, as frequencies between 360 and 240 degrees also add up constructively. A compromise of filter 2.order, steep notch at 1. or 2. critical frequency and a PEQ below 1. Notch could be interesting. In the delay time you also have a bit of negotiating mass, it does not necessarily have to be 180 degrees, if it is only about the level distribution forward. You can also give yourself 30 degrees of leeway to compromise between the rear as much as possible in the tuning frequency, but less problems with the tuning frequency forward. In addition, the comb filter with the tops. But we're not doing an endfired thing today because of the spacking lawyer.”

Jupp nods. ‘Well, then...ne? Can an inverted stack arrangement also be operated as an endfired?’

Kalle laughs briefly. ‘Ha. Of course, so do the French.

Then you have to delay the front speakers to the rear ones.

However, the predetermined housing size also results in a predetermined tuning frequency. Let's say the subwoofer is 70cm deep and has its acoustic center 33cm in front of the front grill. This corresponds to a quarter wavelength of the tuning frequency, i.e. 1.36 times 4 equals 5.44m. That's about 63Hz, not a badly chosen tuning frequency, I think. Depending on where you now set the separation frequency, you have to pay hellish attention to the critical frequency. And think of the notch filters!’

Jupp is not satisfied yet. ‘Is there really a difference between stacked and flown subwoofers when working with such inverted stacks?’

Kalle raises her eyebrows. “Oh yes! On the ground, everything is basically vertically symmetrical, since the ground coupling is added as a mirror sound source. For example, if you rotate the upper one, it will be delayed in the gradient array. That always pulls the beam up a bit, but there's no one there. If you now pull it up into the roof, then with unbalanced designs immediately results in a directing effect. So I would always be in favour of building something like this symmetrically. If you want to direct flown subwoofers, please do it purposefully.

‘Yes, and how does that...ne?’ asks Jupp.

Kalle waved off. “Quite simply: Either simply hang bluntly among each other and start and delay individually. Only here the problem always arises that delays from different directions are relative, and you also build up nasty clubs.

Or you build e.g. 4x4 Endfired, which mechanically point downwards around the desired angle. Or you can combine Inverted Stack Gradient with this Endfired arrangement. But then please build symmetrically, otherwise you won't be able to see where you're beaming. In the case of the French variant, you have to think carefully about what happens when you fly. If you build 3:1 and turn the bottom, the top three are delayed, and you pull the beam back up. I would build it symmetrically and with a 2:1 ratio. Then it just shoots. If I want to beam somewhere else, I'd rather do the whole thing than classic endfired. When it comes to hall radius in an arena, where you work with a Monster Mono Center, the following is interesting:  8 subwoofers each, half symmetrically rotated and manually set up as a real inverted stack gradient. The whole 4x in a row as a classic endfired. If you still want to pull the beam down, you can work with different pickpoint heights. It is best to use 2 d8+ motors. Then your calculation is not set in stone, because there should be hall plans that are not so exact.”

Jupp nods in agreement. Then he asks: “Where we are at Sub Arrays...ne?

With such a long horizontal line, there is a rather narrow opening angle and a fat hotspot in the middle...ne?’

"Yes, that's right," says Kalle. “Are we still philosophising about ‘Arcen’ before we get to the pods? You know that this is a stimulus issue for me.”

Jupp is grinning. "Come back, I can remember that. What's more, you're so upset about...ne?’

“All right, let's take our subarray of 24 boxes. Now let's imagine they're all just blunt forward in a straight line. In the middle forward, a hotspot results for all frequencies, because all frequencies meet at the same phase angle due to the symmetry. The horizontal opening angle results from the array length, i.e. in our case 16m. We simply look at it as a wavelength and convert it into a frequency, i.e. 21.5Hz...and tada! This is our horizontal opening angle in degrees, i.e. 21.5 degrees at the -6dB point. This is of course much too tight to meet the side VIP grandstand here, but we take care of it when measuring. There are two ways to get there now. Firstly mechanical, secondly electronic. Mechanical means that we simply define a circular path with the required radius. If you are in Southern Germany, you have to take an ellipse. Otherwise, they're all spinning the wheel, he, he. This is now nicely homogeneous and does not destroy the impulse response. However, you buy this with hotspots backwards, because the same summation as just forwards also results in backwards. That's stupid, of course, if you shoot the drummer with it.”

“Why? He is happy if he has a lot of rums in his bag, then I save myself the Drumfill – Sub...ne?’

Kalle looks mild. ‘Well, Jupp, and when does the projectile arrive?

First, it's about 6m away. That's the first 18ms. Then we have to adjust the baby to the tops in phase position. So you can easily add another 6ms, plus converter, plus console, plus processing. It's like 6ms again. You can only do this if you want to get out of the band. Hey, hey, I know what I'm talking about, I used to be young too.”

"OK, OK, understood," says Jupp. “What about the electronic version, let's take the...ne?”

“Well. Unfortunately, that's not going to be perfect either," says Kalle. “Now you buy the silence at the back with a smeared impulse response at the front. Similar to what we have already discussed with the gradient array. Take two speakers, place them next to each other, and delay one. Now you stand to the right of the pile. One arrives earlier than the other. But if you stand on the other side, it's exactly the other way around, and the delayed speaker arrives even later. Of course, this is not good for impulse fidelity! It doesn't happen mechanically. It's best to take a piece of paper and paint it twice with each other. Once for each viewing position, it clicks.’

‘Can't you do anything...?’

Kalle crosses her arms and buzzes: ‘Mmh. Ah, yes. It can be repaired a bit, but the problem remains.”

Both are silent.

Then Jupp gets up. “I wasn't so excited about the torture, is it still early today...ne?”

Kalle crooks his head. “How can I explain this to you in two minutes?

First of all, the basic requirement: We segment the array into individual zones with their own control and delay option. We calculate delay times for the individual zones by circular trajectory or ellipse. Then exactly the problem of the smeared impulse response arises. Especially in the middle, where it should be the best. Here's how to optimize: Do you know the window functions from digital signal processing? Rectangle, Hann, Hamming, Blackman-Harris, Raised-Cosine and so on?”

"Yes, I've heard it before, but I don't know what it is," says Jupp. ‘You know: Pierre Littbarski Realschule Köln Kalk...No?’

“How could I forget that. OK, you have a sample value.

The window function describes with which weight it flows into the subsequent calculation, all higher mathematics. Not my thing either.

Of course, the value is the same over the entire period, i.e. 1 and outside the period 0. It's a rectangle window. Spectral side lobes are formed around the multiples of the sampling frequency. These clubs basically describe the same problem we had with the subwoofers in the last hour. Only in antenna technology with much higher frequencies. But, hey! We Tonfuzzis always think we've discovered a new universe with line arrays and beamsteering. In antenna technology, this is an old hat. So why not try something that is done there: To lay precisely these window functions over the level ratios with which we assign the individual time-delayed subsignals? By: Try and Error With different window functions, the process leads to the same horizontal opening angles as possible at all frequencies of our subarray. Now you!’

Jupp is visibly impressed. ‘Big old age! You're insane...ne?

Don't say you built that Excel calculator again?’

Kalle waved off. ‘No, that has already been done by such an insane Dutchman. You can download it on his website. So S.A.D so S.A.D, The incumbent President of the United States would tweet.”

‘Can we finally measure...?’

“Yes! You've been building. I just have to take some coffee away.”

3. AKT ⁇ INCLUDE

Sunday morning 08:30 Measuring

Kalle set out 10 minutes ago to ‘bring some coffee away’. Jupp, who has used the time to build up a few measuring microphones, now passes himself out of pure impatience to Kalle's measuring computer with a few test shots, then Kalle with red head finally appears again.

“Human being, where are you staying, were you still having breakfast without me, no?” he greets him.

Kalle bursts out: ‘Just stop, I've been looking for one here to leave some water for a moment. There I stand at the church behind the tree, the priest opens the door of the church for Mass which starts immediately and whistles me together, I drunken piece of shit should look for another front garden, this is a church. I can't interrupt it, so I try to de-escalate the scene with a bit of small talk. I say: I'm sorry, but I couldn't help it. It's kind of my front yard, too. I am baptized here and pay my church tax diligently. I'll be right back. He replies: How, away again? You come in and listen to my sermon.”

Ignoring Jupp's outrageous look, Kalle Fort continues: “In no way will I enter your church again after the shit you delivered at Theo's funeral! Theo was my best friend since kindergarten! Until an insane motorcyclist shot him down on his bike!’

Jupp wags his hand at the next words as if he had scalded.

"He's always been committed to your fucking church - which I never understood - and you're rattling down an 0815 show at his funeral? No, my friend! We are both through!”

Jupp scurries in and interrupts Kalle, because he knows that the monologue will continue for at least an hour.

‘Drink, I understand. Let's just keep working, it's distracting. I'm sorry the story came back up. I've started before and a little LF Contour on the left array, ne.’

Kalle grins like a shark: ‘Wrong order jupp, you can delete directly. First the work, then the pleasure.”

‘Not the lyre again...’, Jupp pleads

Kalle raises her eyebrows. “However, as long as you have finally seen it. The primary task is to deliver evenly wherever sound is to be sounded. We are the waveform delivery service. That's what I call tuning. When we're done, we're talking about taste. This How should it sound. By the way... are you at the desk today or me? And how did you think of the order in which we now measure?’

“I was thinking about LF correction because of the line length of the line arrays. The preset is good. And then the professor will do whatever he wants anyway", Jupp justified his strategy.

“Let's put our goals together”, Kalle suggests and starts:

‘The subwoofers shall be: Inverted stack gradient be measured. I always say: A stacked Nierchen brings peace to the neighbour while he is drinking beer.’

Kalle giggles lonely about himself and realizes that he is not funny. With a more serious voice, he continues: "Then we want to try to supply the VIP grandstand, where the 12 customs officers hang, a little more with subs by a Arcing, and then adjust the levels by means of a window function from digital technology so that the coverage over all frequencies is as equal as possible. Then we reached the first sub-target, the subwoofers as a whole are ready. Let's look at the line arrays. We want a uniform level drop from front to back, we want to correct the air absorption of the high frequencies in the rear area. And if we have enough time, I wanted to show you the story with the beaming correction and the all-pass filters. Then we finished the arrays as such. Then we bring the subwoofers with the tops into phase and finally the front fills. We then check the whole package later in time with the band and adjust it halfway. Before we start measuring, however, we should align the arrays and secure them against the wind with aluminium pipes.”

Jupp proudly announces: ‘Kalle, please, I've been doing that for a long time, no.’

Kalle pulls the forehead in wrinkles: ‘Aha?’

Jupp crosses his arms. ‘What do you not like? They hang 1a, 100% straight ahead, huh?’

Kalle shakes his head.

“I don’t like that. I don't want to do dual mono today. I would like to use a stereo sound system. Otherwise I won't get my 3 saxophone friends under control. This means that we need an overlapping area as large as possible, where the left and right bananas can be heard in the same voice. The arrays are about 18m apart and the width for the audience is also not much larger. I have already measured with the laserdisto. It is about 25m, which go as a hose to the back and at 35-40m to the back is end. All Line Array modules have a horizontal opening angle of 110 degrees. I now place two measuring microphones at about half the depth. One at the left edge of the sound reinforcement surface and the other at the right edge. Now I turn on the left banana and turn it on until the levels of the two positions are the same. I repeat the same for the other side. The cover in the back area I take to check. Let's go, grab the ratchet and pinch yourself to the pipe and let's start Stage Right. I quickly set my Smaart generator to band limited from 800Hz – 20KHz.”

"Clearly boss, why do you limit the noise, no?" replies Jupp.

Kalle seems to have been waiting for the question. Radiantly he answers: "So that I can understand it better with my ears, because down there the thing is more of a spherical sound source, and we are interested in the area where the directivity also works. If the manufacturer were to publish an isobar chart, I could also briefly show you this, but correct and complete technical data does not really correspond to the zeitgeist of marketing-focused customers. Before you climb up, I'll make you both bananas, and you go horizontally through the audience area and pay attention to the level differences, OK?’

Jupp grins: Sure, great, then I'll hear on the way back whether you messed up or not, huh?’

He runs trembling through the sound field, climbs to the Stage Right Banana and shouts: ‘Sach Stopp Kalle and do hinne ne?’

Kalle compares the levels of the two measuring microphones and the amplitude frequency responses, calls ‘Stop’, goes backwards and runs across the field.

‘Come on, fix this thing’

After the other side is also set up, Jupp climbs out of the traverse and runs like a shot chicken across the square to the FOH, where Kalle is already waiting.

‘And? did you hear what happened?’, Kalle would like to know.

‘Yes, it was quieter in the middle than in front of the bananas. Now it's almost everywhere the same loudness between the bananas, isn't that what you always do?’

‘No.’

‘Aha.’

“Good. Then we can start measuring now. Why did you put the Magnitude Smoothing back on subterranean 1 octave and hide the coherence? I want you to stop fumbling on my box! Buy your own measuring system!”

‘On 1/48 octave I see only zapping and strokes, no one understands that, right?’ complains Jupp.

“However, if you set smoothing so high, you make the wrong decisions. Don't get used to it! Wait a minute, I'll show you. You look here at the amplitude frequency response at 1 octave smoothing and I'll do something at the desk. Then you tell me a parametric EQ to correct," says Kalle.

Kalle goes to the console and builds in the PA feed two parametric EQs with low bandwidth at 750Hz and 1500Hz with each +6dB and Q=5 and asks Jupp: ‘So now tell me a filter to correct that.’

‘1kHz, -6dB, Q=0.3, ne?’

“OK, is that right for you?”

‘Yes, that looks flat again, doesn’t it?’

‘Well, then please set the magnitude smoothing to 1/48 octave.’

"Huh, what is that? Batman? no?’

“You've broken it! Because you didn't recognize the problem because of the smoothing.

Wait a minute, I'll take the filters out again, and we'll finally be able to move on," Kalle buzzes.

“Well, I understand that, but the zapping makes me mad, doesn't it?

What is it anyway?" asks Jupp.

‘The result of comb filter effects. We see here not only direct sound but also all reflections. For example, look down here at the 110Hz extinction. What could that be?”

‘The ground reflection from the PA to the measuring micro, eh?’ suggests Jupp

“Yes, but that sounded a bit strange now, and I know that you prefer to measure on the ground. Can you explain why?” Kalle wants to know.

Jupp scratches the back of his head.

‘How was that again, huh? The first peak is divided by the wavelength at the speed of sound and the first notch is half of it, right? I see at the Smaart the frequency of the first notch at 110Hz and also the wavelength is displayed directly 3.13m. If I halve this now because at twice as high frequency the wavelength is only half as long, then a reflection with about 1.55m distance difference would have to be the cause, ne. Where is the disto?’

Jupp goes to the measuring microphone and uses the laser distance meter to measure the distance to the banana.

Then he targets a point on the ground, then goes to that point and measures from the ground again to the banana, calculates briefly and calls: ‘1,52m GEIL!’

"Very good, and why is there a hole now?"

‘Yes, because the phase angle between the direct signal and the reflection at 110Hz is exactly 180 degrees, right?’

Kalle nods appreciatively and says: "Runs, and why doesn't it erase completely, but only with -15dB?"

Jupp thinks briefly: ‘Because the level of reflection is lower than that of the direct signal, but now don't ask me how much, no?’

‘Hey, yes! Let's briefly consider what we have discussed about the combining, transition and isolation zones. In the combining zone, the level difference is less than 5dB and our notch is greater than 12dB. The level difference must therefore be less than 5dB. What was the distance from the micro to the array?’

‘Approximately 17m, huh?’

‘Super, the difference was 1.5m. That is, we are looking for the level difference of 17 to 18.5, which is -14dB.’

‘How did you calculate that so quickly without a calculator, eh?’

"You remember what we tattooed on your fingers?" asks Kalle.

Jupp is babbling: ‘Outside 1 and 10:1, two basses get a little brother are 1.5:1, 1:2 because of finger and thumb, 10 years of marriage holds the ring finger.’

He points to his hand and counts from thumb to little finger: ‘1dB, 3dB, 6dB, 10dB and 20dB!’

“Exactly! But let's move on now, I'm happy to be finished when Melissa shows up.”

‘That's right, Jupp. We're not in vocational school, are we? Are we going to continue with the line arrays?”

“No, let's start with the subs. Distribute the micros behind the pile.’

‘You don't want to put one in front, do you?’

“No, what does that mean? We want maximum extinction in the back. We pay for this with side legs and distorted impulse response. Let's do the basic setup first. Later arcene Let's do something else for the grandstand seats", explains Kalle.

Jupp has been holding the four measuring microphones with the NF lines like a bunch of carrots in his hand for 5 minutes and makes an outraged face.

“What is the basic setup? That's already done in the cardio preset, isn't it?’

Kalle waved off. ‘Yes, this is a hybrid preset, an endfired setting in stacked configuration.’

‘What?’ asks Jupp. ‘It's sausage anyway. The main thing is cardioid and you're done, aren't you?’

“No! We need proper reverse damping today. The factory setup has the advantage that in the direction of 0 degrees to the front all frequencies are summed in equal phases, but with the disadvantage that there is no complete extinction to the rear. As with a classic Endfired setup, The tuning frequency is a bit high. There is no classic Gradient Inverted Stack Cardioid Preset, "So let's do it ourselves quickly", Kalle decides and sets in motion.

‘OK, I'll set up the microphones and then you'll show me what you're doing, right?’

Jupp places the bundle of microphones routinely behind the subwoofers and goes back to Kalle inspired by curiosity.

‘So Jupp, watch out!’

“OK, right?”

‘This is the front subwoofer at the rear measuring position on 180 degree axis. I save it now and no longer tackle the reference delay in the measuring system. Then I take the subwoofer pointing backwards and delay it until the phase frequency responses are exactly on top of each other. Then I invert the polarity and Zack erase the two babies.” 

Jupp is grinning. ‘Well, not really, they've just gotten so 6dB quieter now, haven’t they?’

‘Yes, of course, I also have to make the rear subwoofer even quieter so that the two are exactly the same loudness and then optimize something on the frequency response. In terms of diffraction, a bit of what you see above is also happening here," explains Kalle.

"Ah, that's right! If the difference between the two levels at 180 degrees phase angle at approx. plus/minus 10 degrees tolerance is 6dB, then this does not erase completely, but only to -6dB, right, no?’

“Correct Jupp! At the measuring position, the front is twice as far away, so I make the rear quieter. One more tick, one more... Too much! Back again. Just short two EQs and we made minus 15dB out of it. Check all measuring positions and you're done. Then let's delay a little bit towards the outside of the grandstand.”

Kalle pats Jupp on the shoulder. “But I quickly calculate this, dear Jupp, in the Excel list, so I can then calculate the level offsets directly. Do some coffee.’

Jupp returns with a cup of black magic. He preferred tea.

‘What level offsets? We have made everything the same, haven't we?’

Kalle sips his coffee and explains: "Yes, that's why we also have to be careful to always adjust such a whole cardioid block. By delaying the outer subwoofers, we pull the cover slightly wider towards the grandstand. Unfortunately, however, we pay for this with a smearing of the impulse response, and this is exactly what you can still optimize a bit if you apply a window function to the levels of the delayed subwoofers. So let's try it with one.  Hanning window and see what happens. I haven't tried that yet, but it should work in theory.”

Kalle types numbers into an Excel spreadsheet that looks like that of a dubious investment banker on a lecture tour and transfers the calculation results to the system controllers.

‘So, Jupp, let's go to the grandstand and see if this is better than before.’

Kalle and Jupp stroll to the VIP stand, switch things back and forth on the system controller, grin like two full honks and find themselves quite horny.

Kalle: ‘Fits!’

Jupp: ‘Krass, huh?’

Kalle says in a tone of voice, as if he is just walking over water: “Subwoofers are ready, then let's do the line arrays. Set up the 3 Mikros StageRight.’

Jupp grabs 3 tripods and places them on the zero-degree axis of the left line array. The first in the front third, the second in the middle and the third in the back third. He then pulls out the microphones behind the subwoofers, clips them into the microphone holders and connects the cables.

‘Stands’ he yells towards Kalle.

Kalle takes the lower modules of the banana and takes the first shot.

Jupp panics: “Ey wait for me! I want to see what you do, don’t I?’

‘Hurry up. We don't have forever, although if you keep learning like this, I'll have a lot of time soon. Look here Jupp, these are the lower modules at the front measuring position. Now the middle one in the middle and the upper one in the back. So, here are three measurements, what do you notice?’

Jupp looks at the measurement curves for a few seconds and says: “They are different loud and have no eggs! ne?”

"True, let's exclude the "eggs", this is due to the fact that not all woofers are running and the coupling is missing. If this confuses you, you can mute the woofers at the beginning or limit the noise in the band. That's it! I'll just level it up and copy it to the other banana. Now we start all modules and check all measurement positions again. You see? Much more homogeneous than before.’

“Yes, well, but HF is missing behind and LF let's turn that in, huh?”

Kalle grumbles: “HF can we really compensate for what we mustn't be so loud here anyway but LF ... that can't be done?”

Jupp warps the face: ‘Why, is it the same or not, is it?’

‘God, Jupp, no! The RF loss is due to the attenuation by the air and can be caught up. However, the LF loss is due in the shorter near-field range due to the larger wavelengths, because the range in which only -3dB instead of -6dB occurs per distance doubling is smaller. You can calculate this by rollover, length of the array in the square multiplied by the frequency, divided by twice the speed of sound. At 3.5m array length, this is about 1.75m at 100Hz, 17.5m at 1kHz and 175m at 10kHz theoretically. If there is anything at all, because even with 3dB level loss per distance doubling that is a lot. Starting from one meter, this is up to 128m seven doublings and until then about 21dB loss! Plus wind, which the simulation programs like to forget. Anyway, I'm drifting! That's not something you can fix with an EQ! This has now been bought with the line array in principle. Let's turn on the whole banana and listen.”

Jupp switches off the mutes on the system controller, grabs Kalle under the arm and says: “Come on, old man, we still have a show to drive today, don’t we?”

Kalle replied: “I'll give you an old man! Take your legs in your hand.”

Kalle and Jupp stroll in the zombie step from front to back through the sound area of the StageRight banana.

‘And Jupp, what do you notice?’

"Yeah, that's better, isn't it?"

‘Aha, nothing else?’

Jupp stops abruptly: "Come on, that's another catching question. I'd better check out Smaart, wouldn't I?’

Jupp runs the whole banana and checks the amplitude frequency responses at the 3 unchanged microphone positions in the Smaart.

‘Look, Kalle, here at the front of the microphone position is somehow more low-mid around 300-500Hz, can that be?’

"Very good Jupp! ...by the way, old men hear something like that without a measuring instrument.’

“Then let's take a parametric EQ for the lower elements and take something out of it, shall we?”

"No, it doesn't work. This is a time problem not a level problem!”

“I don't understand, there's more levels and no more time, right?”

‘Cause and effect Jupp’, explains Kalle. ‘The cause is on the timeline, the effect on the level level. We have now hung a curved line array line. Just imagine, this is completely grade, i.e. all modules at 0°. What exactly happens now on the vertical centre axis?’

“There is a hotspot because all woofers arrive at the same time and at the same relative levels.  The levels add up to the maximum. Now when I move out of the vertical 0° axis, phase angles and individual levels change and so do the sum levels, no?’

“Very good! You can listen. If you now approach it with a parametric EQ, nothing changes in the situation except that you shift it relatively. We need time glue, a phase EQ!" says Kalle.

Jupp shines: ‘Ha, huh? You mean all-pass filter, don’t you?’

“Exactly! I'll show you. Do you see the phase shift?  We are now paying for this after the manufacturer has painstakingly built a phase-linear FIR preset for the device. I pack an all-pass filter in each of the three ways, which is exactly the same and starts approximately in the area where I want to correct. You see, now nothing happens at all, except for the overall phase jump through the all-pass filter. Now we just have to change an all-pass filter, so that exactly in this frequency range where the beaming frequency takes place, the phase angles change so that the hotspot is distributed over a larger area. JuppZupp and ready!’

Jupp is thrilled: ‘Geil! You Kalle, why isn't the hotspot right in the vertical middle?’

“Because we did not just angle to 0°, but rather in a J-shape. The curving angle suddenly changes sharply to the front, which also shifts the hotspot. In addition, there is the entire angle of inclination.’

‘Ah, so. That's why the manufacturer can't build that into his preset, can it?’

“Exactly! To do this, he needs to know how the thing is angled and hangs. It's basically not a witchcraft and beamsteering systems are based on knowing exactly this variable, because they are always angled to 0°. The next logical step is to let the calculation software talk directly to the processing engine. And if it is still possible to verify by measurement in real time. This can then be used to control the sound pressure distribution.’

“That's even cooler, isn't it?”

Kalle waved off: "Don't flip out right now. Unfortunately, there is no free beer in audio technology!

You pay for it by smearing the impulse response.”

Kalle claps his hands three times, as if he wanted to give his servants the agreed sign. “But we should be getting ready. The band is coming soon, and I still have to understand the desk that Gottfried bought with spontaneous enthusiasm. And he throws the bowl in the cardboard box in front of my feet with the nice hint: Better check the firmware. There are bugs with the stagebox. Stand at the PA Forum.

“Really? No?’

 Jupp, he doesn't have them all. As if we had nothing else to do. Check which bus is driving in the Kaff towards the Internet. I'm about to go crazy. So let's quickly do the Allignment Top/Sub phase.”

‘That's right, Kalle. Let's get ready, shall we? I'm putting the measuring microphone forward.”

‘But not too close to the front.’

"What's too close, isn't it?"

“We now want to align the phase positions in the takeover area at the measuring position. Of course, the whole thing cannot work over the entire surface, because the distances are also unequal. We are therefore looking for a position that is suitable to make it particularly good and, on the other hand, is suitable to function representatively for the largest possible area. To say it with the customs stick: The relative distance difference between the top loudspeaker and the subwoofer should be zero from the measurement position, but not more than 1.4m from all other positions on the sound surface. If you're too far ahead now, the angle is too steep, and it's already drifting apart at the FoH. If you're too far behind, it's not good in the front. And there are actually the best places. The sound police are usually there as well. You notice that the measurement position is not entirely unimportant, but it does not change the geometry.’

“I only understand the station, I now put the microphone at the FOH. Except for you, nobody hears what's going on. Why 1.4m, no?’

Kalle becomes impatient.

‘80Hz, 120 degrees, the FOH is in the middle. You bring the next geometric axis into play, I'll do it myself.’

Kalle takes the measuring microphone out of Jupp's hand and goes on the 0 degree axis of the StageRight banana in the front third and places the measuring microphone with the capsule pointing upwards towards the sky.

“Now you've built up the micro wrong, that's free-field equalisation, right?”

“Well, I wanted to know if you are still on the matter, do I have to let this point forward now or can I let this stand?”

“This can stand still, the differences are somewhere between 10kHz and 20kHz and we don’t care what happens to the sub-alignment.”

"Very good Jupp"

‘Thank you, huh?’

‘And, nevertheless, the wrong answer.’

“But now it's enough, what's next, huh?”

‘The microphone shall have a linear phase frequency response in all directions of sound incidence.

Come on, let's be good, did you install the low cut in the top way?’

“Of course I can do this now, right?”

“But from, I'm going to get coffee again. Do you want to too?’

‘Yep.’

Jupp takes the first shot with the StageRight banana solo, saves the curve, mutates the top path and muted the subs. Screws seriously on the delay until the phase frequency responses in the takeover range are superimposed on each other at the same slope, adjusts the subwoofer level and says: ‘Where is my coffee, do you have to do everything yourself?’

Then Kalle bends around the corner and mutters to himself: ‘Nothing has been heard yet and the little one is already flying high. Here's your coffee jupp’

‘Thank you.’

“Now we're through, aren't we? I'll put a strap on the organ.”

Kalle muted the entire PA and plays his favorite song today at a low overall volume. Jupp grabs Kalle's arm and says:  "Then let's go rabbit"

The two run the entire area several times like zombies on standby and look at each other.

‘Yes, but equally thin everywhere.’

Jupp precipitates: “Let's make the subwoofers louder, shall we?”

“I would be more in favour of a LowShelf over everything. If we only make the subs louder, there is a risk that comb filter effects will arise due to the slope slope of the Top LowCut. In addition, it sounds much more homogeneous if I have more leeway for the Toneing have and can compare smoother.’

‘Do as you say. But give me back the eggs that the system has, huh?’

“Yes, come on now. But you also have to keep in mind that now it is quiet, later it is louder.”

Jupp wants his bass. Stur he says: ‘Well, what? That doesn't matter to the PA or do you think that goes into the limiters, right?’

“No, but at the listening level we are currently driving and what Melissa allows us to do afterwards, we are loosely talking about 20dB difference when it comes to the perception of the same volumes of our hearing. And that's what we do, after all, not for the meter! Hey there comes the band, now it's over with the tech stuff. You go on stage and you're tame, aren't you?’

Jupp nods. “Clearly boss, I'm putting on another coffee, they're probably still close to yesterday's wedding, aren't they?”

EPILOG

The rusty side door of the Old Transit opens and the rocked cowboy boot from Udo pelletizes through the stuffed car in the direction of the much too bright morning sun. 

The saturated cough, reminiscent of a seal enclosure, resounds across the square, and Udo puts his shirt in his underpants far too deep and far too long with his left hand. With his right hand he nibbles a piece of bird shit from the tinted side window that ran over the sticker with the inscription ‘Don't laugh, your daughter could sit in here’. 

'Karl,' yells Udo. ‘Do a trick. I have to smoke” He is immediately believed when you hear his smoky, whiskey impregnated organ. What would Kalle give for such a voice! He himself is more like a shot puppy and has to convince with content. With Udo, it doesn't matter what he says. It just always sounds so cool that the sense doesn't matter.

“Kalle! You old skeptic! What have the others done today?" Udo greets his long-time Tonfuzzi, who considers himself his best friend. Before Kalle can answer, Michael Udo's neatly rocked guitar case is enough and he strolls casually to the stage, where Jupp receives him with fresh coffee.

‘Jupp You are my husband’ greets him and takes the coffee out of his hand. Swinging the cup like a sceptre, he strolls leisurely to the edge of the stage, where his microphone stand marks his position like a rock in the surf. Udo carefully secures the coffee, plugs in his guitar and turns to Jupp in a quiet and nonchalant voice: ‘And what? Did the professor do a doctoral thesis on it again?’

Jupp nods affirmatively like a desecrated choirboy in the confessional, turns to Udo and asks: ‘Why only?, why only?, why only?’, ‘Because he can!’, Udo replies respectfully.

Udo takes another sip of coffee and speaks into the open microphone with the sonorous voice of a fairytale uncle:
‘Wat he all net understands: Et jeit he net um jode Sound, et jeit um Volume!"

– E N D E –