February 26th, 2007, 12:26 PM
Caught in the Middle: The View from the Mobile...
Part I: Introduction
When working in the mobile world, you get caught in the middle sometimes.
Not that its bad…I love mobile work…I choose it! Its just interesting seeing what people perceive life in the mobile is like.
What is it like working in a mobile? Mobile work is the combination of the best and worst of live show production mixed in with the best and worst elements of studio work. You shake it all up, and then try to produce results with that capture the spirit and enthusiasm of live shows while providing the tonal quality that listeners expect.
And lets not fool ourselves…the listeners that we all have to serve are becoming increasingly educated. They may not know WHY something sounds good or bad, but they know that SOMETHING sounds bad.
So how does this get done?
How does a live production get translated into something that sounds good on a CD? How do you take a studio band and make them sound good equally on all TVs? What concerns are paramount in getting the job done and what sacrifices do you have to make in order to make the show work? What tools are used in the process?
Stay tuned…and welcome to the mobile channel…
Last edited by clicktrack; April 5th, 2007 at 01:15 PM.
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March 5th, 2007, 05:53 AM
Part II - Why “Caught in the middle?”
The name I chose for this thread may sound more derisive than it actually is meant. The phrase “Caught in the Middle” is used to denote how the mobile world literally is a cross-section of disciplines between the live world, the broadcast world and the studio world.
Let me give you an example. Lets take the live world and assume you’re a house tech with a venue. In this world, an engineer is under a fairly strict deadline. “The show must go on” is as much the truth as it is cliché. At worst, the house tech may be the “face” of the venue for the majority of the day until the concession staff or house manager make it in, usually well after sound check.
If this is the case, then the house tech has to split their time and talents between getting the band loaded in, wired, provide a basic monitor mix, get a sound at FOH, deal with management, point artists in the direction of hospitality facilities, wonder why the rider items haven’t arrived yet…the list goes on. While getting a good sound is a priority, it isn’t THE ONLY priority for the live house venue guy…simply by the nature of the beast. The house guy has to be multitasking like there’s no tomorrow.
So when it comes to mic placement, that kick mic, when placed in the vicinity of the hole and there’s enough of a “thud” coming out…well its time to move on to the next issue. Good enough.
Hell, even if the show has a dedicated sound crew, their time could very well be eaten up by keeping an eye on the house crew in order to make sure that the day moves on at a proper pace from their end. So again, there won’t be a tonne of microscopic work done to get THE perfect kick sound. “Good enough for jazz”, right?
Now on the other side of the spectrum…lets take the studio environment. C’mon…how long does an average studio engineer spend on getting the perfect kick sound or just enough “crunch” from a cabinet. Lets just say its not out of the ordinary to spend huge chunks of time making sure placements are exactly right. Right for the player, right for the song, right for the room, right for the kit. Just right.
Now, again, this makes perfect sense and, at the risk of making a Seinfeldian reference, not that there’s anything wrong with that. there isThat’s what they’re being paid for, and that’s a good thing. You have the space, you have the time, you want to make sure that those sounds going to tape are as good as they can be…saves work later. Why take time to eq the kick later when moving it an inch farther out of the hole will get you EXACTLY the “thud” you’re looking for?
From the mobile’s perspective, we are, as the name suggests, caught in the middle. When placing mics, for example, something that sounds “good enough” in the house may be such because it has the benefit of the house to augment its sound. Inside the truck, however, we don't have 600 cloth seats to help shape the sound of that "thud". We may have a pathetic "doo" sound.
So the house guy has an absolute right to look at his watch and scowl when the mobile guys want to take an extra 5 minutes to work on the drum kit micing. We definitely understand! Why? Well because its him who has to deal with the fallout if the day schedule falls behind. He has to tell the Front of House staff to hold the doors…he has to make sure that dinner breaks are adhered to and that the crew have an adequate time to eat…he has to make sure that, if it’s a house gig, the show ends on time and the crew is struck…otherwise sometimes massive overtime charges result. Not to mention issues with noise bylaws if the venue is in a populated area and other not-so-insignificant concerns. Even though to us, it may be “just 5 minutes”, it doesn’t take many of those to set a production day well back. So its well within his right to scowl.
On the other side, if the resulting tracks are delivered to a studio for post work, is it wrong for the studio engineer to scowl at the amount of top there is on that kick mic? Not really. Now he has to sit and spend time eq’ing the track and make sure it fits, where, in his mind, if the mobile guys took just 5 more bleeping minutes to position the mic properly…
You see where I’m going.
Hence the name “Caught In The Middle”.
Oh…and there’s one other factor to consider.
Many live guys think that “pshaw…you guys got the easy gig…we (in the house) don’t have the ability to hit rewind! We gotta get it right the first time!”
Whereas there is some validity to that (Yes, I record sound checks!), consider the case when we are going to live broadcast. There's a bit of a mantra I've heard other mobile guys talk about and I've taken it as my own:
"You only have one chance to get it right!"
At broadcast, not only do we share the same pressure as the live guys to get it right immediately, we do have one added pressure; In the live world, if you make a mistake, people hear it and its gone. In the mobile world, if you make a mistake, people can rewind it, play it again, and point out EXACTLY where you made your mistake. Over and over again!
Add to that the fun of having a trigger happy tv or video producer on comm only too ready to inform you that there's "no bass in the mix"...when you're already miles ahead of him trying to find out why the channel isn't plugged in onstage...
Lol...Allow me to take a brief moment...I gotta admit...it is a circus when I look at it from this perspective. What an organized chaos. I love it!
Alright...back to it...
Now for a bit of a reality check.
I'm not trying to come across down on studio guys or house guys. Just the opposite. I've done the house tech thing. Been there...understand the pressures that come with the gig.
In reality, the majority of the house guys we’ve worked with have been very accommodating. In fact, we work hard to be as efficient as possible in order to maintain the production day’s schedule and to get the tones we want as quickly as possible. When they see we’re just trying to get our job done without hindering what they need to do, they do what they can to accommodate that much more.
As well, the studio guys we’ve worked with are pretty damn good as well. Knowing the budget NEVER leaves enough time to load in and get the sounds we’d all prefer, they take it in stride knowing that we are trying to get them as pristine tones as we can.
Every once in awhile, though, as to be expected, you come across a venue guy or a studio guy who likes to make sure that everyone knows that they are treading on their “turf”. These are the guys who are sure to, at some point in the day, make sure that everyone involved in the production knows that “they have been doing this for xyz years, and THIS is the only way to do things…”
Those are the days that we feel like we’re Caught In The Middle…
Last edited by clicktrack; April 5th, 2007 at 01:16 PM.
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April 5th, 2007, 01:14 PM
Re: Caught in the Middle: The View from the Mobile...
Part IIIa: Connecting the Stage & The Signal Path – The Splitter.
Initially, this chapter was going to be a full out discussion on stage connections. As I started writing, I find that one portion of this discussion deserves a significant amount of attention…the splitter.
The discussion on stage splits is one topic that I find intriguing. Intriguing in how simple the concept is…intriguing in how critical it is in the structure of the show, intriguing in how so many in the audio industry really don’t give it much thought.
While planning a show day, load in, etc, one of the first questions I’ll ask is “when is load-in?" Occasionally, I’ll get a quizzical look and be told, “Why? Oh you don’t need to be there for that…just show up before sound check”.
The reason why? Getting the split and organizing how things will work between FOH, Monitor-land and the mobile is the time (if not before!) to solve any split issues. And trust me…there can be lots!
Before I go there logistically, let me explain a bit more of what the splitter does and why its so important to not only us in the mobile, but to the entire audio crew.
The Split – Theory & Operation
In short, a microphone splitter is a means to provide one output (typically a microphone, but it can be a powered instrument via a DI) into 2 or more console inputs or preamps. There are many ways that this is done, but there are truly only a couple of ways to achieve this without placing a detrimental effect on the sonic performance of the microphone and/or the electronic performance of the consoles in general. Some means are actually recipes for disaster!
Wye No Wye?
The most simple means to create a mic splitter is a simply “wye” cable.
Read my typed lips.
THESE HAVE ABSOLUTELY NO PLACE IN OR ON A STAGE AT ANY POINT.
NONE. NADA. NOWHERE.
If someone gives you one, please introduce him or her to Slipperman and his theory of “Cack Filleting as a martial art”.
When you take a wye cable, you are performing a multitude of sins, all which are bad, bad, bad, bad, bad, bad. The first of which is creating a sum-total lower impedance as seen by the mic.
All console and preamps have a specification item called input impedance. Impedance is a term used to describe the effective resistance of an AC circuit. In order for the mic to perform, a voltage is generated by the mic capsule and transferred across the cable into the console. To maximize this voltage, the mic needs to have a “low impedance” output (somewhere in the order of 150-300 ohms) and the console/preamp needs to have a “high impedance” input (typically around 10x that of the mic, so 1500-3000 ohms).
By connecting the inputs of two consoles together, you cut each console’s input impedance in half. As a result, more voltage is consumed at the input stage of the console, which places an unnecessary load on the mic capsule. The entire sensitivity of the capsule is DRASTICALLY affected as well as the frequency response.
“Fine…so the mic is quieter. Who cares? I’ll add more gain.”
Ignoring the fact that your now quieter mic sounds like absolute ape shit, adding more gain causes another problem…noise.
You remember that little talk on impedance about 2 paragraphs ago? Well, I glossed over one fact purposefully at that point. Earlier, I stated that a high impedance input at a console would maximize the voltage coming from a low-impedance output from a mic. That wasn’t quite true. What you are actually doing with a high impedance input is maximizing the voltage as compared to the noise within the signal path.
Many people much smarter than I realized a long time ago that noise is going to be around in the circuits we play with. Minimizing the noise has always been the name of the game. That figure you hear thrown about everywhere called Signal To Noise Ratio (SNR) is exactly that…how much signal can you get compared to the amount of noise.
BTW...Don’t confuse my usage of the term "SNR" here with the spec you’ll see on the console itself, or on a CD. In this case, I’m talking about how much signal you have compared to the noise on that simple connection between the console and the mic.
So coming back to you adding gain to your ape-shit sounding mic. Now that you’re using your handy-dandy wye cable, you’ve lowered the input impedance of your consoles, drawing more voltage into the circuit, placing a load on the capsule, providing less signal across the cable as compared to the noise. So, you now increase gain to make up. However, you’re now increasing the amount of noise in your signal path as well.
So, everything still sounds like absolute ape-shit.
Except now its ape-shit smothered in a nice roux of noise.
Just because you used a wye cable.
Yet, the fun doesn’t end there.
If your two desks are located at a great distance from each other, then it’s probably not feasible that the desks are powered from the same circuit. Although this is the preference, you can’t always have it all. So, you turn on both consoles and all you hear is “buzzzzzzz” in one, the other or both desks. 60 Hz ground hum.
Now that you have a wye connecting your mic, you now also have connected your console’s grounding schemes together. Ignoring the fact that you have now defeated all the effort that some poor engineer put into creating a quiet power supply on your console, (shame on you!), you create a situation where the two consoles, despite both being grounded, have a potential difference between what they individually see as ground. And what is potential difference called, kiddies? Yep…voltage! Between the ground of one desk and that at the other, you’ve formed a voltage that has nowhere to go but into your system…making noise.
So to solve that what do you do? If you say cut off the ground pin on one of the desks, you should be shot. Not only is that amazingly unsafe (you can kill someone), but it is VERY VERY UNSAFE. That Someone killed could be you...if you're lucky. (Do you sense a little repetition here?)
So, the wye cable creates a hell that you don’t want to deal with…Too many variables to work with while you're on a location recording. Stay away…FAR away from wye cables.
Unfortunately, wye cable splits are more prevalent in the industry than anyone likes to admit. Many consoles (and I mean many!) come with a split “built in”. When you RTFM (Read The F******* Manual) and take a glance at the electrical schematic, you see that the output of the split is just tied off of the input…essentially providing a...yes, you guessed it…a ‘wye’ cable. What kills me is that a good many VERY reputable manufactures of boards that you see regularly see in use in live venues are guilty of this.
You also have to keep an eye out for “direct outs”. Although most are electrical circuits that provide you with the choice of tapping off pre- or post-eq or pre- or post-fader, some are just electrical wyes that are masquerading as direct outs.
This, as a side note, is why, when told, “oh, our board has a split”, we rarely use it. And “direct outs” are the devil as far as I’m concerned (in terms of connecting a completely separate mobile feed. Connecting a recorder directly to the console is a totally different thing and direct outs are fine for this).
So, you see why I’ll feed ya to Slippy if you use a wye cable on one of my gigs. Hassle. Supreme hassle for what its worth.
A Tranny in the Clutch…
The typical style of mic splitter used on a show is a transformer-isolated style. This is a preferred method, in that the transformer provides electrical isolation between the various consoles and gives the microphone a uniform loading.
Many transformer-isolated splits have a direct connection as well as one, two or three isolated split out feeds. The direct connection is so that any condenser microphones can be fed phantom power, as DC Voltage will not pass through the transformer.
I say “more” uniform, because, it is not a perfect solution. Cheaper transformers add the problem of phase inconsistencies, so, like everything in life, you don’t get something for nothing. More expensive transformers provide better phase performance by better design, but at a significant cost. When you figure that a reasonable sized split is around 24 channels, adding $80 per channel adds a significant cost. Increase this to a capable 48 channel split system with two-way splits, and you can see the significance of the cost impact.
To Ground Lift or Not Ground Lift - Lift and Separate, Ladies! .
Transformers, however, don’t fully eliminate the grounding problems seen above. As a result, ground lifts aren’t always necessary, but highly recommended. A transformer isolated split isolates the signal conductors, but there is always a common ground point in the split...usually the chassis. When preamps or consoles are connected to the direct and the splits, this ground point becomes common to all consoles. This is fine when all the consoles are powered from the same leg of the input power. If they aren’t however, there will be ground potentials formed between the consoles, which can induce hum BACK into the conductors. Having ground lifts on each split safely breaks this potential, alleviating the induced noise.
The last category of split is the active split. These are more expensive per channel as they involve active electronics in order to process the signal. Some models provide buffers and basic DSP in order to preserve frequency response, but typically, active splits allow the following:
• Extremely long lines to be driven or
• To provide one input signal to more than 3 or 4 outputs to consoles.
Active splits are distant cousins to distribution amps.
Active splits, however, aren’t immune to problems. Depending on the design, headroom and grounding issues tend to be the main tradeoffs in exchange for better loading performance and drive capability. (Remember, you never get something for nothing!). Despite these, active splits do have their place in the industry, and the well-designed units of today are significantly better at handling these problems than in the past.
Direct and to the Point
Ahh, the age-old argument of who gets the direct output of the split…. monitor land, FOH-land or mobile land? There are multiple trains of thought to this argument, and there are elements of truth in all. From a mobile perspective, we do prefer having the direct. The reason being is that if there IS to be a noise issue, you can get over it easier in the house than you can on the recording. A small amount of buzz in a 40 KWatt system is nothing. That same buzz on a recording…it’s not only evident, but can render a recording useless.
I know that statement just pissed off a bunch of house guys (remember…I used to be one!), but keep in mind, not many house guys have had to remix a show and spend hours upon hours working around a buzz issue. By the time the post-production stage happens, the show is long gone and there is absolutely no chance at fixing the recorded tracks.
There are a tonne of very effective white papers on splitters, technology, etc. I’ve given an overview on the issues related to splits, however there is significant more tonne of more depth and breadth available than what I covered here. For more information, look at some manufacturer’s product white papers on the topic. Keep in mind that these white papers will be a bit biased to their products; however looking at them from an overall perspective can give you the true ins and outs of splits (pun fully intended) and the issues surrounding them.
1. Whirlwind: http://www.whirlwindusa.com/ftp/tech/tech06split.pdf
2. Jensen Transformers: http://www.jensen-transformers.com/an/an005.pdf
3. ARX: http://www.arx.com.au/Active_splitters.htm
4. Aphex: http://www.aphex.com/pdf/1788/Aphex_..._Long_Runs.pdf
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