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Live digital audio in plain English part 2

Never mind the bit clocks… it’s a word clock primer

My last blog dealt with translating audio into a digital signal. The next step is keeping that signal in time when it’s being captured, processed and sent to different parts of the system. This is where the fabled word clock comes in. If anything weird ever happens with a digital set up, like odd clicks or pops over the PA, you can seem wise beyond your years by nodding sagely, saying “Hmm, it sounds like a clocking issue”, then making your excuses and leaving before any further questions can be asked. However, you can become a rare and very valuable member of your audio team by actually learning what word clocks are, how they work and how to fix the most common problems they can cause. They might seem strange and complicated, but they are of course not black magic. It’s all about crystals.

So… what is a word clock?

Any device receiving audio sees a string of 1s and 0s. How does it know whether 0000011100001011 is two samples, reading 00000111 (= 7) and 00001011 (=11), or the second half of a sample, a full sample (01110000 = 112), and the first half of the next one? As you can see, the resulting values can be very different, so it’s essential to get it right to the exact bit.
A word clock is a signal that is sent at a very accurate frequency of one square wave per sample (the bits in each sample make up a ‘word’). This signal is produced by passing an electrical current through a small crystal inside a word clock generator. The rising edge of the resulting wave means 1; the falling edge means 0. The clock runs alongside the audio signal, with 1 usually meaning “this is the start of the sample” and 0 meaning “this is the end.” Different shapes and sizes of crystal resonate at different frequencies, then more subtle changes are controlled by variations in the voltage running through the circuit and temperature. Some clock generators even keep their crystals in tiny ‘ovens’ to keep the temperature constant.

What the clock?

Clocks are necessary for a few different stages in the signal path. AD convertors might take a fixed number of samples per second, but they still need to make sure those samples are evenly spaced. If they aren’t, the waveform will end up deformed when reproduced by something that is in time. Thinking back to the video analogy from the last post, it’s like film taken on old hand-cranked cameras: uneven capturing of the signal leads to weird inconsistencies when it’s played back. In audio, it’s referred to as jitter. This can also happen when an accurately-captured signal gets reconverted with an unreliable clock, like a film being played on a clunky projector (see figure 1). Clocks used to trigger the capturing of the signal are often called sample clocks. There are also bit clocks, which produce one cycle per bit. These days they are only used for signal transport within devices, for example from one PCB to another. You’re very unlikely to encounter a problem with a bit clock, and if you do there isn’t much you can do except send it back for repair. You might also hear people referring to word clock as sync clock, signal clock or simply clock.

An AD converter with a stable word clock (represented by the square wave at the top) captures an accurate waveform (left), but if it’s converted back to analogue through a DA converter with an unstable clock, the waveform will become deformed (right). Source: Apogee Knowledge Base http://www.apogeedigital.com/knowledgebase/fundamentals-of-digital-audio/what-is-jitter/”

 

One clock to rule them all

A stable clock compared to a jittery one, compared to one whose frequency has drifted. Jitter is caused by a varying clock frequency, whereas a clock that has drifted has a pretty stable frequency. It’s just the wrong one. Source: Apogee Knowledge Base http://www.apogeedigital.com/knowledgebase/fundamentals-of-digital-audio/word-clock-whats-the-difference-between-jitter-and-frequency-stability/”

What we are really interested in for live audio is using word clock to keep multiple devices, e.g., the front of house desk, monitor desk, and system processors, in sync. Think of it like keeping a band in time: most digital devices on the market have their own internal clock, so it’s like each member of the band having their own click (or metronome if you’re that way inclined). If it’s a solo artist, there’s no problem. Even if the click wanders a bit, it probably won’t be noticeable, because there’s nothing to compare it to. However, when there are several members, they need to stay in tempo. Neither clocks nor clicks are perfect, and even if everyone starts off together, they will eventually fall out of sync (known as frequency drift. See figure 2). It makes sense to choose one person to keep the beat for everyone else, like the drummer. Much in the same way, you need to designate one device in your system to be the master clock, and the other devices are slaves who sync their clocks to the master. Sometimes, it can be even better to get a separate device whose only job is to keep time, i.e., an external word clock generator. This is like hiring a professional conductor for the band. Much like a conductor though, they can be very expensive and for the most part aren’t necessary as long as you have a good enough band/set up.

“Mirga Gražinytė-Tyla conducting the City of Birmingham Symphony Orchestra at the Snape Maltings Concert Hall during the Aldeburgh Festival, 2017, by Matt Jolly. https://en.m.wikipedia.org/wiki/File:Mirga_Gra-inyt–Tyla_conducts_the_CBSO,_Aldeburgh_Voices_and_Aldeburgh_Music_Club_at_Aldeburgh_Festival-crop.jpg”

Each device still uses its own clock when following the master. They constantly monitor at what phase in the cycle the incoming clock signal is and compare it to their own. If the two fall out of time, the device can adjust its clock (usually by varying the voltage running through the crystal) until it’s locked in sync. The circuit that does this is called a phase-locked-loop. It’s like a band member nudging the speed of their click or metronome until it matches the conductor. However, some common sense is needed. You don’t want to constantly adjust for every tiny discrepancy, nor do you want everyone to follow when the conductor is obviously wrong, like if he sneezes or falls over. A phase-locked loop’s sensitivity can be adjusted, so it ignores fleeting differences and remains locked to the last signal it received if the master clock outputs major errors or drops out of the system. The device will then continue at that speed until the master gets reinstated or replaced, but will slowly drift if this doesn’t happen. The sensitivity can also be adjusted depending on how good the device is compared to the master. If your conductor isn’t the best, it might be better to listen to your own click when in doubt (or invest in a better conductor). In the next post, I’ll discuss how all this relates to our real life setups.

Performance Anxiety

I think pretty much everyone has at least once in their lifetime experienced anxiety in one way or another. Personally, my anxiety is a good old friend I have had with me for years. It is something I always have struggled with and there is different reasons to why that is, but some reasons that stands out the most is; I am a perfectionist and I am not best friends with failure.

For a lot of people, I think it is hard to admit that you suffer from anxiety and the impact it may have on your life. I used to be like that because I felt like I was overreacting.

In my previous blog post ‘A lesson about fun & failure,’ I briefly mentioned and touched on the subject about failure. My anxiety, and probably for a lot of people, is linked to the fear of failure.

I have studied music for many years; I began at the age of 11 to play classical piano. I love playing the piano, and I learned sight-reading from an early age. I played Mozart, Beethoven, Bach and I to this day absolutely love their compositions. But, what I could not get my head around was that I could not play those pieces perfectly every time. I got so angry with myself for messing it up to the point where I stopped enjoying playing the piano because I felt like I was failing.

Throughout college, I had to go through plenty of live performances, all of which I suffered terrible anxiety attacks from. I simply did not want to be on stage; I could not deal with the pressure and the possibility of failing. The pressure I put on myself, not anybody else, I’ve realised now later in life.

This is one of the main reasons I chose to work behind the stage and what makes me love and care so much about live performances. For me, it is so important that artists feel comfortable whilst being on stage because I know what it feels like when you don’t.

Performance anxiety is so important to acknowledge and to deal with in all aspects and careers of life. We put so much pressure on ourselves, from such an early age, it affects our mental health severely. It’s good to be ambitious, but when is it too much? At what point do we tell ourselves ‘hey it’s getting a bit too much now’?. Especially within the music industry, it is a very fast-paced industry and you’re expected to be multi-talented from a young age.

Sometimes it is not about overcoming your anxiety, sometimes it is merely about becoming friends with it. Nowadays I handle it in such a way that I give myself some time and space. I analyse what is going on in my life, usually my anxiety flares up when I’ve got too many things going on at the same time and really should’ve said no to a couple of jobs. I get terrible anxiety when I am new to things, especially jobs, to the point where I feel nauseous and overthink every possible scenario that might happen. But when this happens I tell myself that everything will be ok, one way or another.

We are only human in the end of the day, and as I have learned along the way, it is perfectly normal to feel anxious sometimes. However, if you feel like you need help to improve your anxiety and mental health do not hesitate to get in touch with your GP. There are also great apps to manage and improve your mental health here: https://apps.beta.nhs.uk/category/mental_health/.

 

The Perfect Moment

In the last couple of weeks, I have had some really good and interesting conversations with sound engineers, musicians, family & friends about waiting for the right moment. It seems that no matter what career path we have taken in life, we seem to have one thing in common.

We think that we one day will feel like we are ready, but the truth is; we never will feel like we are. There always seems to be an excuse to why we should not do something because we do not feel confident enough.

I would never have gotten to where I am today if I was waiting for the perfect moment, that moment when I would feel ready. Even now, I still feel like I am not ready, but I now also know that I probably never will be! Because how else will we learn if we do not challenge ourselves and throw ourselves into the deep end?

I have done FOH sound at so many gigs where I just felt like I was not competent enough. However, I said yes, I went for it because I knew that I otherwise would not learn and get to where I wanted to be, and I wanted it so badly. And in the end, I was competent enough, because otherwise I would not have been offered the job in the first place. I think we all know a little bit more than we give ourselves credit for.

Being confident is a struggle. Especially when you are young. But at some point, you have to start trusting yourself and your abilities, because if you do not trust yourself, well then, who will? The only trust that I carry with me every day is that I know that no matter what happens, I will come up with a solution. It does not matter how, but what does matter is that at the end of the day, I do my job and I make it happen.

Let us start making excuses for why we should do things and not wait for the ‘right’ moment. Take a leap, trust your knowledge and admit your flaws. Know what you need to work on, put yourself out there. Take that chance and make it happen. If you feel insecure, that is OK, we all feel insecure at times. But that does not mean that you do not know what you are doing. That does not mean that you do not have the ability to make something happen. Do not wait around for that perfect moment, just do it.

 

Grow Your Ears for Music

Imagine if, on the first day of school, your teacher had stood up and said “Look, we’re going to try this thing called reading. It isn’t for everyone. Some of you will just have an eye for words, and some of you won’t. If you find you don’t have the knack, you might as well just leave it.” I like to think that would be greeted with a bunch of toddlers falling over laughing, but you would expect that questions would be asked about the teacher’s career choice at the very least. It is absolutely ridiculous to think that the ability to read is predetermined and cut and dry, so why do we listen to people who say only those with an ear for music can become great sound engineers?

The jury is still out on whether there is such a thing as an innate, genetic talent for hearing and music. Even if there is, the thing about genes is they very, very rarely account for the whole spectrum of differences amongst the population. A gene might give you a head start, but the environment in which you grow up can influence the development of that skill as much, often more. Even for child prodigies, an initial flair gets nurtured (or perhaps smothered) by parental encouragement and hours upon hours of daily practice. It is much the same with sound engineering. Some people might take to it quicker than others, but everyone benefits from practice and study. A skill being hard-earned does not negate its value, otherwise, why would we bother going to school? When I started out I was in awe of what my more experienced colleagues could pick out in a mix, and how quickly they could not only detect but identify the cause of a problem. I didn’t think I’d ever be able to do it. I’m still far from perfect, but there are plenty of sounds I don’t even think about how to fix now; I’ve heard them so many times I automatically know what to do. I’m still discovering new aspects of my favourite songs that I’ve listened to since I was a teenager. Fancier professional earphones can only partly explain that!

So where has this belief that only the golden-eared chosen few can make it in the music industry come from? I suspect it’s people who have been told all their lives that they have an ear for music. When people do well, they like to find logical reasons for that success. The special gifts that they are born with, combined with what they feel was hard work, mean they deserve everything they have earned. Of course, they often do, but too few people acknowledge the roles that the help of others and luck play in a field as fickle and competitive as ours. Similarly, if you don’t make it, it is easy to say that you simply weren’t cut out for it, that you didn’t have a good enough ear. Only successful people want to believe that they live in a meritocracy. In reality, it takes the support and advice of countless colleagues and a big chunk of luck, in addition to skill and determination, to get your break. However, this doesn’t mean you should give up now. You can work to improve your knowledge and skillset and grab as many opportunities as you can. Put yourself in the path of luck as often as possible and be ready when it hits.

Anyone who knows me knows I’m not one for baseless positive thinking. I don’t think we can all become astronauts, as long as we simply believe in ourselves: there aren’t enough shuttles, and someone has to do all the other less exciting jobs. However, someone does have to be an astronaut. Someone has to mix that fantastic up-and-coming band. Someone has to system engineer that stadium tour. Someone has to do all those myriad jobs that don’t get as much attention but can be just as satisfying (and often better paid!) like RF tech, comms tech, or installation engineer. Who gets to decide? Your school music teacher? That lighting guy? Some blogger? What do they know? Even if an ear for music is encoded in your chromosomes, are they suddenly geneticists? How did they get a sample of your DNA anyway? Don’t be put off by other engineers telling you that you don’t have what it takes either. However subconsciously, they are reassuring themselves that they deserve to be where they are and are trying to protect themselves from the competition.

In research on geniuses, one of the most important factors is their passion for their subject, known as the ‘rage to master.’ They study and practice so intensely not just because they’ve been made to, but because they want to because they must. They don’t feel right if they aren’t working on their “thing.” The author Hunter S. Thompson once wrote a brilliant letter when he had been asked for life advice, in which he advocates finding a lifestyle you enjoy and creating a career around it, rather than the other way round: “The goal is absolutely secondary: it is the functioning toward the goal which is important.” Let’s be honest, sound engineering is competitive, but you don’t need to be a genius. If sound is what you love, don’t wait for some authority to tell you that you have what it takes, to give you permission to do it. Decide now that you are one of those special people, and just do it. The Department of Who Does and Doesn’t Have an Ear for Music will never know. Maybe you won’t make a living out of it, but the only way to find out is to put yourself out there, learn, practice and improve. Even if you never get a gig bigger than the local bar, if no one hears your mixes, if no one subscribes to your podcasts, the important thing is that you enjoyed the process, and so the net positivity of the whole world is up.

 

Keeping It Real

Using psychoacoustics in IEM mixing and the technology that takes it to the next level

SECTION 1

All monitor engineers know that there are many soft skills required in our job – building a trusting relationship with bands and artists is vital for them to feel supported so they can forget about monitoring and concentrate on their job of giving a great performance. But what do you know about how the brain and ears work together to create the auditory response, and how can you make use of it in your mixes?

Hearing is not simply a mechanical phenomenon of sound waves travelling into the ear canal and being converted into electrical impulses by the nerve cells of the inner ear; it’s also a perceptual experience. The ears and brain join forces to translate pressure waves into an informative event that tells us where a sound is coming from, how close it is, whether it’s stationary or moving, how much attention to give to it and whether to be alarmed or relaxed in response. Whilst additional elements of cognitive psychology are also at play – an individual’s personal expectations, prejudices and predispositions, which we cannot compensate for – monitor engineers can certainly make use of psychoacoustics to enhance our mixing chops. Over the space of my next three posts, we’ll look at the different phenomena which are relevant to what we do, and how to make use of them for better monitor mixes.

What A Feeling

Music is unusual in that it activates all areas of the brain. Our motor responses are stimulated when we hear a compelling rhythm and we feel the urge to tap our feet or dance; the emotional reactions of the limbic system are triggered by a melody and we feel our mood shift to one of joy or melancholy; and we’re instantly transported back in time upon hearing the opening bars of a familiar song as the memory centres are activated. Studies have shown that memories can be unlocked in severely brain-damaged people and dementia patients by playing them music they have loved throughout their lives.

The auditory cortex of the brain releases the reward chemical dopamine in response to music – the same potentially addictive chemical which is also released in response to sex, Facebook ‘likes’, chocolate and even cocaine…. making music one of the healthier ways of getting your high. DJs and producers use this release to great effect when creating a build-up to a chorus or the drop in a dance track; in a phenomenon called the anticipatory listening phase, our brains actually get hyped up waiting for that dopamine release when the music ‘resolves’, and it’s manipulating this pattern of tension and release which creates that Friday night feeling in your head.

Missing Fundamentals

Our brains are good at anticipating what’s coming next and filling in the gaps, and a phenomenon known as ‘missing fundamentals’ demonstrates a trick which our brains play on our audio perception. Sounds that are not a pure tone (ie a single frequency sine wave) have harmonics. These harmonics are linear in nature: that is, a sound with a root note of 100 Hz will have harmonics at 200, 300, 400, 500 Hz and so on. However, our ears don’t actually need to receive all of these frequencies in order to correctly perceive the chord structure. If you play those harmonic frequencies, and then remove the root frequency (in this case 100Hz), your brain will fill in the gaps and you’ll still perceive the chord in its entirety – you’ll still hear 100Hz even though it’s no longer there. You experience this every time you speak on the phone with a man – the root note of the average male voice is 150Hz, but most phones cannot reproduce below 300Hz. No matter – your brain fills in the gaps and tells you that you’re hearing exactly what you’d expect to hear. So whilst the tiny drivers of an in-ear mould may not physically be able to reproduce the very low fundamental notes of some bass guitars or kick drums, you’ll still hear them as long as the harmonics are in place.

A biased system

Human hearing is not linear – our ear canals and brains have evolved to give greater bias to the frequencies where speech intelligibility occurs. This is represented in the famous Fletcher-Munson equal-loudness curves, and it’s where the concept of A-weighting for measuring noise levels originated. As you can see from the diagram below, we perceive a 62.5 Hz tone to be equal in loudness to a 1 kHz tone, when the 1k tone is actually 30dB SPL quieter.

Similarly, the volume threshold at which we first perceive a sound varies according to frequency. The area of the lowest absolute threshold of hearing is between 1 and 5 kHz; that is, we can detect a whisper of human speech at far lower levels than we detect a frequency outside that window. However, if another sound of a similar frequency is also audible at the same time, we may experience the phenomenon known as auditory masking.

This can be illustrated by the experience of talking with a friend on a train station platform, and then having a train speed by. Because the noise of the train encompasses the same frequencies occupied by speech, suddenly we can no longer clearly hear what our friend is saying, and they have to either shout to be heard or wait for the train to pass: the train noise is masking the signal of the speech. The degree to which the masking effect is experienced is dependent on the individual – some people would still be able to make out what their friend was saying if they only slightly raised their voice, whilst others would need them to shout loudly in order to carry on the conversation.

Masking also occurs in a subtler way. When two sounds of different frequencies are played at the same time, as long as they are sufficiently far apart in frequency two separate sounds can be heard. However, if the two sounds are close in frequency they are said to occupy the same critical bandwidth, and the louder of the two sounds will render the quieter one inaudible. For example, if we were to play a 1kHz tone so that we could easily hear it, and then add a second tone of 1.1kHz at a few dB louder, the 1k tone would seem to disappear. When we mute the second tone, we confirm that the original tone is still there and was there all along; it was simply masked. If we then re-add the 1.1k tone so the original tone vanishes again, and slowly sweep the 1.1k tone up the frequency spectrum, we will hear the 1k tone gradually ‘re-appear’: the further away the second tone gets from the original one, the better we will hear them as distinct sounds.

This ability to hear frequencies distinctly is known as frequency resolution, which is a type of filtering that takes place in the basilar membrane of the cochlea. When two sounds are very close in frequency, we cannot distinguish between them and they are heard as a single signal. Someone with hearing loss due to cochlea damage will typically struggle to differentiate between consonants in speech.

This is an important phenomenon to be aware of when mixing. The frequency range to which our hearing is most attuned, 500Hz – 5k, is where many of our musical inputs such as guitars, keyboards, strings, brass and vocals reside; and when we over-populate this prime audio real estate, things can start to get messy. This is where judicious EQ’ing becomes very useful in cleaning up a mix – for example, although a kick drum mic will pick up frequencies in that mid-range region, that’s not where the information for that instrument is. The ‘boom’ and ‘thwack’ which characterise a good kick sound are lower and higher than that envelope, so by creating a deep EQ scoop in that mid-region, we can clear out some much-needed real estate and un-muddy the mix. Incidentally, because of the non-linear frequency response of our hearing, this also tricks the brain into thinking the sound is louder and more powerful than it is. The reverse is also true; rolling off the highs and lows of a signal creates a sense of front-to-back depth and distance.

It’s also worth considering whether all external track inputs are necessary for a monitor mix – frequently pads and effects occupy this territory, and whilst they may add to the overall picture on a large PA, are they helping or hindering when it comes to creating a musical yet informative IEM mix?

Next time: In the second part of this psychoacoustics series we’ll examine the Acoustic Reflex Threshold, the Haas effect, and how our brains and ears work together to determine where a sound is coming from; and we’ll explore what it all means for IEM mixes.

 

Multitasking – Why you should avoid it

Being multitalented is excellent and almost a necessity in the audio industry. It is expected of us to be able to do many different things, sometimes even at the same time!

However, I believe multitasking at work should be avoided if possible, and here is my reason why;

The other week I was asked to do a live recording of a band while they performed. We have set up multi-track recording via Dante, which means we can record straight into Pro Tools via a Cat 5 cable. This is great and makes life a hell of a lot easier when doing live recordings.

But also recently, having had a lighting course in the Jester 24 Zero 88 Lighting desk, I now also control the lights more in-depth than we used to.

So this one evening I was going to run the live sound, the lights, and record one of our four acts, while also making sure all the artists were looked after and ready to go for their allocated time slot.

I did not think much of it; I came in early to set up Pro Tools to make sure it was up and running. When that was set up, I prepared the stage and the setups for the different bands. I set up the lights; we had photographers in that evening so we made sure the lights hit all the sweet spots and set the colours, to make sure the artists would look great on picture.

I felt good about having everything set up, ready to go on time, and did not feel stressed at all.

Well, that was until I had the first act on who had almost finished their set. I thought I would do a test recording of the first act to make sure it sounded great for the second act; the band I had promised to record. At this point, I realised I did not get any signal from any of the wireless microphones.

Why?

Well, we have a Yamaha Rio 32×24 stage box, but our Shure Beta 58A wireless microphones we have are directly plugged into the back of our Yamaha QL1. Immediately, I felt fairly stressed as the first act walked off the stage and I simply did not have the time or hands to re-route it in the Dante Controller software.

As the second act walked on stage, I helped them set up and then quickly decided that the vocalist would have to use a wired Shure SM58 running it thru the Rio as I knew this route was already working. Not a big deal, but I definitely panicked for a second as I had promised and confidently said I would be able to record it, and there was just no room for any mistakes. Luckily, I managed and very quickly, came up with a solution though feeling ever so slightly stressed out.

I recorded the band, it sounded great, but I felt that my focus was definitely not where it should have been. It was a live show, and my focus should have purely been on the live sound.

My thinking was that everything was going to go well, it is not like we can predict disaster and obviously, we want all live shows/recordings to go well. However, something I have learned throughout the years it that most of the time, it does not run smoothly and you must leave room for mistakes. No matter how good you are, no matter how many things you think you can do, mistakes happen. Technology breakdowns happen. And when you are alone, you simply will not have the time to solve a problem, and you will cause yourself unnecessary stress.

I did, after all, run a successful night, the band was happy with the recording, photographers were pleased with the lightning, everyone was happy with the sound. However, I did learn my lesson, and next time I will get another pair of hands into the mix. It is simply just not worth the risk of messing up a show and recording because you decide to do everything on your own.

However, if you are ever having to multi-task and do several things on your own; leave plenty of room for mistakes because they will happen!

 

 

Soldering for Beginners

Soldering is one of the most useful skills a sound technician can have. It can seem daunting at first, but it is surprisingly easy once you know how. It can help you understand your equipment and signal flow better, save you money, and there’s nothing quite like whipping out a soldering iron and saving a gig to silence the doubters. Entire books have been written on the subject, and it takes practice to perfect it, but I’m going to outline the very basics you need to get started.

A note on safety!

Soldering irons, unsurprisingly, get very hot! Keep your work area clear and well ventilated, only hold it by the handle, always put it back in its holder and don’t leave it unattended until it has cooled down. Remember that the things you are soldering will also get hot. Be careful not to melt the glue keeping a PCB in place, for example. I also need to point out you shouldn’t solder something in situ above you while lying on your back. Thanks, Tim…

Equipment

You will need:

A soldering iron!: Buy the best you can afford because it will last you for years. There are a few different types, each with their own advantages. Mains-powered irons can either be standalone or come with a station, which can control the temperature and give you a readout of it. Stations also include holders and sponges, so you have a neat setup. Battery or gas-powered irons are a lot more portable, and you don’t need to rely on a mains supply to use them. Non-temperature controlled irons might struggle to solder bigger items because they absorb the iron’s heat until it drops too low to be effective.

Tips: There is a whole world of iron tips out there. For sound work, you’re most likely to need an iron-plated conical tip. They need to be replaced periodically, so keep a few and clean them regularly.

Solder: Many people swear lead solder makes the best joints and is the easiest to work with, but it is also poisonous and bad for the environment. Lead solder has been outlawed, in the EU at least, for use in plumbing and consumer electronics due to its hazardous properties. It is still available for private use. There are a variety of lead-free solders on the market, but they still emit some toxic fumes, have a higher melting point, and the resulting joins may be more brittle than traditional lead ones. Whichever you opt for, pay attention to the percentages of each metal present in your solder: different combinations will have different melting points and strengths. 60% tin, 40% lead is the standard alloy traditionally used for electronics. Most solder comes with a flux core, which is a resin (rosin in the US) that helps bind and strengthen your joints and keep them clean. You can buy your solder and flux separately if you really want to, but that tends to be used for advanced repairs and is unnecessary for beginners.

Sponge and metal wool: Back when all solder contained lead, cleaning your tip on a damp sponge was fine. However, lead-free solder works at a higher temperature and the water from the sponge can cause the iron to dip below your optimum operating point, so repeated cleanings can cause the solder to crack and penetrate the tip. Using brass wool avoids this problem.

Solder sucker/desoldering wick: These help clean old solder away before you work your new join. Don’t just melt and reuse the solder that’s already there!

Helping hand iron touching

Soldering board/helping hand:  You can make a soldering board out of some wood and old cable connectors, so you just plug the cable you’re soldering into its corresponding socket on the board to keep it still. You can also draw wiring diagrams above each one to refer to as you go along. For some applications a “helping hand” might be more useful: it consists of a magnifying glass and two alligator clips on a heavy bass, so you can hold cables in place and get a better view while working.

Wire strippers and cutters: You can get by with just a knife, but a good set of wire strippers will save you time and the frustration of accidentally cutting through the entire wire you were trying to strip.

Method

Let’s take resoldering a broken leg on an XLR as an example.

XLR Short Earth

If you’re using a new iron tip, you can “tin the tip”: heat the iron up and melt a thin layer of solder evenly over the tip, so it’s shiny. This improves heat transfer, protects the tip from oxides and makes it easier to clean. Regularly cleaning and re-tinning the tip will improve the quality of your joins and help the tip last much longer.

Once everything is in place, you first need to remove the casing around the wires. Make a note of which wire goes where (if you ever get confused, just refer to a diagram or open another cable on the same end and compare it to the one you’re fixing). If there isn’t much wire left to work with, don’t be tempted to make a tight fix. It will take too much strain when the cable is moved and will break again soon after (The one exception to this is that some people purposefully make the earth leg shorter, like in the photo, as it is stronger and can take the strain instead of the other pins. This can be tricky to do, and subsequently repair, so is more of an advanced technique). Desolder the other legs of the cable, trim them to the same length and strip the wires back until you have just enough to work with. If you strip too far back, the metal from different legs can touch and cause all sorts of signal problems. If the broken leg is still long enough, just remove the old solder from its join and leave the other two legs attached.

Take the iron in one hand, and hold out a length of solder in the other. Then the important bit: heat the wire, not the solder! You need to heat the wire and its connector, so they melt the solder. If you heat the solder directly and try to drop it onto the join, it will just cling to your iron. While holding the iron on one side of the area, you want to join, touch the solder onto the other side. It should melt and flow around the wire and connector, binding them together. Avoid breathing in the fumes! Keep going until the whole area is covered, removing the iron as soon as you can to minimise the amount of extra solder you’ll need to clean off it. It should only take a few seconds to heat the wire; if nothing happens when you touch the solder to the join, or it only melts when you’ve held the iron in place for a long time, your iron isn’t hot enough. The solder on the join should look clean, shiny and smooth. If it is dull or uneven, it is a sign of a bad join and is liable to break again. You can just desolder and do it again until it’s right!

Finally, put the components back together and test your XLR with a cable tester. Never put an untested cable back into use after soldering it. Turn your iron off, put it somewhere safe until it’s cooled down, and enjoy your new skill!

Additional Resources

Illustrated easy guide to soldering (electronics-focused)

Once you are more comfortable soldering, you might want to make your own phantom power checker

 

Consideraciones para realizar un diseño de refuerzo Sonoro.

Que es el diseño de refuerzo sonoro? Reproducción del sonido en una determinada área de audiencia mediante medios artificiales, que tienen como finalidad realizar una amplificación del sonido para obtener un nivel de presión sonora homogéneo (se consideran aceptables las diferencias de +-6dB) en todos los puntos del recinto a sonorizar, además de asegurarle la inteligibilidad del mensaje a cada uno de los escuchas.

A continuación, mencionaremos algunas consideraciones a tener en cuenta para el diseño de refuerzo sonoro:

1) Consideraciones acústicas previas. Se deberá realizar un análisis de diferentes parámetros, tales como: Tiempo de Reverberación(RT60), inteligibilidad, Definición (D), Claridad de la voz (C80), RASTI, %ALcons.

PARÁMETRO ACÚSTICO VALOR RECOMENDADO
Tiempo de reverberación medio (500 Hz – 1 kHz), sala llena 0,7 ≤ RTmid ≤ 1,2 s
Claridad de la voz C50(“ speech average), sala llena C50 > 2 dB
Definición D (de 125 Hz a 4 kHz), sala ocupada D > 0,50
Relación primeras reflexiones ERR, sala vacía u ocupada 2 ≤ ERR ≤ 6
STI/RASTI, sala ocupada STI/RASTI ≥ 0,65

 

TIPO DE RECINTO REVERBERACION (s)
Cine 0.4 s
Salón de Clases 0.6 s
Teatro y Música Auto amplificada 1.0 s
Sinfónica 2.2 s
Iglesias 3.0 s

2) Debemos preguntarnos qué tipo de recinto vamos a sonorizar

 

3) Solicitud de planos del reciento a diseñar.  En este punto se recomienda tener medidas del lugar por medio de un scouting al recinto; se deberán solicitar planos en AutoCAD, tanto en vistas en 3D, 2D, plantas y cortes del recinto, para poder realizar un análisis exhaustivo. Asimismo, debemos recordar que este diseño se llevará a cabo en la práctica, por lo que no debemos olvidar hacernos diferentes preguntas que nos permitan determinar el alcance adecuado del proyecto: ¿que se espera de este diseño de refuerzo sonoro por parte del solicitante?, ¿existe alguna obstrucción visual posible?, ¿existe limitación en cuanto a peso del equipo?, ¿es un espacio abierto o cerrado? a nivel subjetivo ¿que se busca o que se espera?, ¿qué tipo de sistema se solicita: arreglo lineal o sistema convencional?, todo esto encaminado a determinar el alcance adecuado del proyecto.

 

4) Análisis de cobertura.  Se aplicarán y comprobarán diferentes técnicas de diseño apoyándonos de un software de predicción, tal como MAPPXT el cual se utiliza para medir y cuantificar parámetros. En este punto debemos ser capaces de resolver problemas de interacción entre altavoces, selección de nivel de presión sonora adecuado, análisis de la respuesta en frecuencia y fase en diferentes puntos del recinto, cobertura vertical, horizontal, ubicación de altavoces, ángulo de inclinación y peso de altavoces, distribución de señales para un adecuado ajuste del sistema buscando así una cobertura homogénea en todos los escuchas por igual. Asimismo, debemos aplicar parámetros de referencia o normas existentes según el tipo de aplicación; por ejemplo: en cines con formato de reproducción ATMOS existen normativas por parte de Dolby que ofrecen especificaciones a cumplir referentes a nivel de presión sonora, altavoces en pantalla, posición de altavoces, niveles de presión sonora en la zona de baja frecuencia, entre otros. En recintos deportivos existen normativas que ofrece la FIFA como guía para realizar un diseño. De igual forma, se deberá realizar el análisis de qué tipo de sistemas serán necesarios con base a las necesidades de cobertura de los altavoces: sistema principal, sistema frontal, sistema bajo balcón, sistema de retraso, sistema lateral, sistema de baja frecuencia, sistema multicanal 5.1, 7.1, por mencionar algunos. Al finalizar dicho análisis se genera una memoria de diseño del mismo.

 

5) Supervisión de montaje.  Una vez que se terminó la etapa anterior, lo más importante que se debe considerar y no debemos olvidar es que ese diseño se llevará a cabo en la práctica, por lo que debemos asegurarnos que el diseño se lleve a cabo tal como se planteó. En ese momento debemos contar con las herramientas adecuadas para poder supervisar dicho montaje, tal como inclinómetro, láser, cintas métricas y memoria de montaje.

Gabriella Galán Mendicuti estudió audio estudios como ingeniera de telecomunicaciones con especialización en audio y video en la Universidad Politécnica de Madrid. Ella ha estado involucrada en audio profesional durante los últimos 12 años con un énfasis especial en el diseño de refuerzo de sonido. Actualmente trabaja en Meyer Sound México como Especialista en Servicios de Diseño para México y América Latina. Ha participado en varios diseños de refuerzo de sonido de los lugares más importantes en varios países, como teatros, iglesias, espectáculos en vivo, eventos especiales y lugares.

 

 

Considerations for a Sound Reinforcement Design.

What is the sound reinforcement design? Reproduction of the sound in a certain audience area by artificial means, which have the purpose of amplifying the sound to obtain a homogeneous sound pressure level (the differences of + -6dB are considered acceptable) in all the points of the room to sound, in addition to ensuring the intelligibility of the message to each of the listeners.

We will outline some considerations to take into account for the sound reinforcement design

 

 

ACOUSTIC PARAMETER RECOMMENDED VALUE
Average reverberation time (500 Hz – 1 kHz), full room

Average reverberation time (500 Hz – 1 kHz), full room

 0,7 ≤ RTmid ≤ 1,2 s

0,7 ≤ RTmid ≤ 1,2 s
Clarity of the voice C50 (“speech average), full room C50 > 2 dB
Definition D (from 125 Hz to 4 kHz), occupied room D > 0,50

D > 0,50
Relationship first reflections ERR, empty or occupied room 2 ≤ ERR ≤ 6
STI / RASTI, occupied room STI/RASTI ≥ 0,65

 

ENCLOSURE DESING REVERBERATION   (s)
Cinema 0.4 s

.4 s
Classroom 0.6 s
Theater and Music  autoamplified 1.0 s
Symphonic 2.2 s
Churches 3.0 s

 

 

 

 

 

 

3) Request for drawings of the design to be designed. At this point it is recommended to have measurements of the place by means of a scouting to the enclosure; Plans must be requested in AutoCAD, both in 3D, 2D, plant, and court views, in order to carry out a thorough analysis. Likewise, we must remember that this design will be carried out in practice, so we must not forget to ask ourselves different questions that allow us to determine the adequate scope of the project: what is expected from this sound reinforcement design by the applicant? Is there any possible visual obstruction? Is there a limitation regarding the weight of the equipment? Is it an open or closed space? At a subjective level, what is being sought or what is expected? What kind of system is requested: the linear arrangement or conventional system? All this aimed at determining the adequate scope of the project.

4) Coverage analysis. Different design techniques will be applied and tested, supported by a prediction software, such as MAPPXT, which is used to measure and quantify parameters. At this point we must be able to solve problems of interaction between speakers, selection of adequate sound pressure level, analysis of frequency response and phase at different points of the enclosure, vertical, horizontal coverage, location of speakers, angle of inclination and weight of loudspeakers, distribution of signals for an adequate adjustment of the system looking for a homogenous coverage in all listeners alike. Likewise, we must apply reference parameters or existing standards according to the type of application; for example: in cinemas with ATMOS playback format there are regulations by Dolby that offer specifications to be met regarding sound pressure level, on-screen speakers, speaker position, sound pressure levels in the low-frequency area, among others. In sports venues, there are regulations that FIFA offers as a guide to design. Likewise, the analysis of what kind of systems will be needed based on the speaker coverage needs must be carried out: main system, front system, balcony system, delay system, lateral system, low-frequency system, system multi-channel 5.1, 7.1, to mention a few. At the end of this analysis, a design memory is generated.

 

5) Assembly supervision. Once the previous stage is finished, the most important thing that should be considered and we must not forget is that this design will be carried out in practice, so we must ensure that the design is carried out as it was proposed. At that time we must have the right tools to monitor such assemblies, such as inclinometer, laser, tape measures and mounting memory.

Gabriella Galán Mendicuti studied audio studies as a telecommunications engineer with a specialization in audio and video at the Polytechnic University of Madrid. She has been involved in professional audio for last 12 years with a special emphasis on sound reinforcement design. She currently works at Meyer Sound Mexico as a Design Services Specialist Tech Support for Mexico and Latin America. She has participated in various sound reinforcement designs of the most important venues in various countries, such as theaters, churches, live shows, special events, and venues.

 

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