Paul concludes his discussion on the power systems for lighting and sound systems this week-please take a moment to share your appreciation and thoughts with him for his time in contributing this information: Paul.Austen@ecd.com
I may have been too hard on my contractor and electrician last blog.
Their reactions to my requirements for power was as stated. I just don't
want to suggest that ALL contractors and electricians are like this. One
point needs to be clear, don't assume they will know your real power
needs. What you call your meeting room will make a huge difference in
their bias toward the room's need for power. Call it a Gym and you'll
likely get florescent fixtures design to illuminate the floor surface to
a level required by some sporting standard. Call it an auditorium, and
you'll get a different bias then if you call it a sanctuary. So be clear
on your needs for power early on in the design. If it's multi-purpose,
as many large rooms are, you may end up with several different lighting
systems to meet the needs.
Also, much of the need to power in your room may be handled by your
hired audio/visual consultant. They will likely get it right, and I
suspect one reason why this kind of information is not "taught" is
because such specifications are part of the audio/visual consultants
"bread and butter." However, it's not rocket science, and local codes
(it varies by city and state) as practiced by the electrician will
result in a safe system. Your knowledge how much power service is
required is all you really need to insist on when plans are being made
for power.
I mentioned "Isolated Ground" at the end of the last blog entry and I
thought I'd at least describe in words what that means and the
advantages.
The round pin on the average US power plug is meant to be an earth
ground, which means there is a conductor from that plug pin all the way
back to the mains panel and a grounding (earth) point. This is designed
to give a path, other than your body, for the "hot" voltage (120 V) to
flow safely to earth should there be a "fault" in the machine using
power. A fault is when the "hot" wire in the machine by mistake touches
a metal part, like the machines chassis. The chassis, which you can also
touch, is connected to the round pin by the green (green/yellow) wire in
the line cord. If a fault inside the machine happens, and the round pin
is NOT connected to earth via this round pin and the green wire, the
chassis becomes "hot" and now you can become the conductor back to
earth, depending on what kind of shoes you are wearing at the time. :-)
That is why it very bad practice to remove the round pin from power
cords. In most states, it's a violation of fire and safety codes as
well.
Now that's all real nice and safe, however, there is an audio reason why
this is less than good. That reason is because ALL your mic and line
level signal wires have a shield to keep noise out and this shield also
connects to the same chassis as that green wire round pin in the line
cord. This usually is done by the "sleeve" of a TRS plugs and or a
direct wire from pin 1 on XLR plugs inside the chassis of your
equipment. Why is this so bad? Because this green wire ground back to
the mains panel is fine for electrical fault currents, but it's NOT good
for RF noise and other ground noise which runs through all electrical
conduits and ground wires. These are sometimes called "noisy grounds" or
even "dirty grounds." What you need is a "clean" ground and you get that
by using an isolated ground electrical systems.
Here's how you do it?
You use those real cool orange outlets, which offer only one advantage
(besides the cool color and $13.00 each). They give you another
electrical connection screw on the side which connects to the round pin
in the plug WITHOUT connecting to the metal bracket which mounts it to
the electrical box (the noisy ground) in the wall. Then you run a fourth
wire (typically baby blue) in the conduit back to your technical (or
star) ground point. This fourth wire makes no contact to any metal,
conduits, or green witres along the way. It can be connected to other
"clean" isolated earth points at either end to shunt RF noise to ground.
This separates the noisy conduit/green wire ground system needed by the
electrician to meet code from your super clean isolated technical
ground. The only place where green wire ground, isolated ground, and the
mains panel neutral (white wire) come together is at your technical star
ground, typically in the mains electrical panel, where you will find: a
Neutral (white wire) buss, a Green wire buss and your isolated ground
buss. All three of these will connect to the "technical ground" rod
located as near this panel as possible. Now you have a safe round pin
conductor for your chassis AND signal shields which is NOT part of the
noisy electrical green wire ground needed in the rest of building.
For further details on this and other power systems for audio and visual
systems I still recommend "Power and Grounding for Audio and Audio/Video
Systems, A White Paper for the Real World" Copyright 2005-2007 The Audio
Systems Group, Inc. by John M. Woodgate, and Jim Brown which can be
found at: The Audio Systems Group, Inc. http://audiosystemsgroup.com for
more details on the issues regarding grounding for audio systems. This
has real cool schematic drawings showing how all this works and the real
advantages.
Also I recommend the presentation: "An Overview of Audio System
Grounding & Shielding" Tutorial T-2, by Bill Whitlock, President, Jensen
Transformers, Inc. www.jensen-transformers.com They have many articles
on this subject worth looking through.
Paul Austen
Monday, February 22, 2010
Monday, February 15, 2010
Power Systems for Lighting and Sound
One of devoted few who have been following this blog, Paul Austen, has graciously assisted me in covering this most important topic. I bring up, again, the importance of knowing what you don't know, and in this case, I feel that Paul's experience far exceeds my own, and so I leave you in his capable hands for this week.
As many times as I have sought help in the area of power systems, I'm
surprised by how little info there is. And if you leave it to the
electrician or building design folks for your auditorium, they will put
one plug under the place on the stage where they think a pulpit may
stand, thinking the "sound system" will be under the preacher's control.
When I told the electrician we needed 50KVA for sound and 150KVA (200
KVA is enough, professional systems may want 400) for lighting, and a
"technical" ground (what's that?), their jaw fell off.
Today's lighting systems, even with LEDs kicking in, require serious
energy and good grounding. Sounds systems are going the opposite of
lighting, with more and more energy (Wattage) at lower and lower cost,
10KW to 50KW systems are common and you cannot provide that kind of
energy into the room without a power system to match.
Let's talk sound power systems first. The simple rule of thumb is to
take your power amps RMS (not peak) power rating at the load (Ohms) you
are applying and double it, if it is a 2 channel amp. This is the
Wattage you should have available to power it. By Wattage, I mean supply
Volts (typically 120V), times the supply Amperage capacity (typically 15
Amps or 20 Amps). Translated, a single breaker in a panel in most
buildings will be 20 Amp at 120 Volts. This means the maximum Wattage
your amp can consume from this circuit is 120 X 20 = 2400 Watts. Your
electrician will tell you that you can only use 80% of this, which is
1920 Watts, but that is under continuous load. As you know, you usually
don't use you amps full capacity continuously. And this does not
consider that most amps are only about 50% to 80% efficient at turning
energy in to energy out. This is just a rule of thumb, however, and will
serve well at planning the needed power service.
So you can added this up real fast. If you have a 1000 Watt per side
amp, times 2 for both channels, that's 2000 Watts. That will take one 20
Amp at 120 Volt circuit to power that single amp without the risk of
popping a breaker. Two 500 Watt per side amps can be powered on one 20
Amp 120 Volt circuit as well. If you are setting up a system with 4
monitor amps and a good 4 to 8 amps for house, with 250 to 1000 watts
per channel RMS, or more, you will need 6 to 10, 20 Amp 120 Volt
dedicated circuits for power. And this is a "modest" system. This may
surprise some electrical contractors, so be ready for some push back,
but facts are facts. And don't forget your video systems. These systems
are often linked together by and audio feed to video recording or
broadcast. So they must be powered from the same power system as the
audio to prevent nasty "ground loops" between power systems which get
connected together by audio or video shields between systems.
Lighting is a little more straight forward, since the energy consumed by
each fixture is right on the fixture or bulb and this is continuous, so
the 80% rule suggested by the electrician comes into play. You can tell
your electrician how many fixtures and their Wattage and they will
understand well how to power them.
As for the power systems themselves, here is the best way to set up a
new installation: Insist on a transformer isolated systems feeding a
panel dedicated for your sound system. I recommend a 20KVA to 100KVA 208
Volt 3 phase "wye" service, depending on the expected Wattage size of
your system. You must use a "K" rated transformer because the loading
will not be "balanced" so the neutral needs to be full size inside the
transformer. Your electrician will know about this. Also, if the
transformer is located near your power panel and sound system, or near
the auditorium, make sure it's one that does not make a lot of noise so
you don't have to listen to the humming. This transformer may step down
from a 480 Volt 3 phase power system or just isolate from a 208 Volt 3
phase "wye" system, depending on what is coming into the building. If
your service is single phase, the same need for isolation via a
transformer exists, it just uses a little different transformer.
Transformer isolation for the lighting system is also recommend, since
it helps prevent the electrically noisy load of lighting systems from
getting back through the power system. Lighting systems will require
100KVA to 400KVA at 208 Volt 3 phase "wye" power. You can use a single
phase system, as well, it's just less common. Its best to have a power
panel near the point in the room where you are going to distribute the
power.
I placed my sound power panel and transformer on one side of the stage,
and my lighting power panel and transformer on the other to keep the
system as physically separate as possible to prevent electrical noise
cross talk.
Make sure the electrical contractor keeps these systems separate.
Conduits carrying power to audio and video systems must NOT be mixed
with conduits carrying power for lighting, even though they may be near
each other. All power runs must use separate neutral (white) wires.
Don't let the electrician use a common neutral wire for two or three
separate circuits, a common practice for power systems in general room
lighting. This is for the same reason you require a "K" rated
transformer; the loads are not balanced and thus cannot share a common
neutral.
Grounding (Earthing)
With a transformer in the system, the secondary (output) of the
transformer is by design "isolated." This means the neutral from the
transformer must be grounded (earth) for safety. Do not let your
electrician connect the nice clean isolated power out neutral from the
transformer to the same "dirty" ground (earth) wire which comes up from
the main power system in the building. A separate ground must be
established at the output of the transformer. This may be any "approved"
metal grounding method allowed by code, but it must be separate from the
"mains" ground. It may include: metal beams nearby which go to the
foundation, the cement rebar, or an approved grounding rod driven into
the ground, or a combination of all of these. This is your "technical
ground." ALL circuits must be connected to this ground at the power
panel. This is what is called a "star" ground power system since there
is a single ground point and ALL circuits extend out from this point.
I will not get into "Isolated" ground systems except to say it is the
king of grounding systems and should be used if at all possible. The
links below talk about it in more detail.
The lighting ground system does not need to be so isolated, but it does
not hurt.
As many times as I have sought help in the area of power systems, I'm
surprised by how little info there is. And if you leave it to the
electrician or building design folks for your auditorium, they will put
one plug under the place on the stage where they think a pulpit may
stand, thinking the "sound system" will be under the preacher's control.
When I told the electrician we needed 50KVA for sound and 150KVA (200
KVA is enough, professional systems may want 400) for lighting, and a
"technical" ground (what's that?), their jaw fell off.
Today's lighting systems, even with LEDs kicking in, require serious
energy and good grounding. Sounds systems are going the opposite of
lighting, with more and more energy (Wattage) at lower and lower cost,
10KW to 50KW systems are common and you cannot provide that kind of
energy into the room without a power system to match.
Let's talk sound power systems first. The simple rule of thumb is to
take your power amps RMS (not peak) power rating at the load (Ohms) you
are applying and double it, if it is a 2 channel amp. This is the
Wattage you should have available to power it. By Wattage, I mean supply
Volts (typically 120V), times the supply Amperage capacity (typically 15
Amps or 20 Amps). Translated, a single breaker in a panel in most
buildings will be 20 Amp at 120 Volts. This means the maximum Wattage
your amp can consume from this circuit is 120 X 20 = 2400 Watts. Your
electrician will tell you that you can only use 80% of this, which is
1920 Watts, but that is under continuous load. As you know, you usually
don't use you amps full capacity continuously. And this does not
consider that most amps are only about 50% to 80% efficient at turning
energy in to energy out. This is just a rule of thumb, however, and will
serve well at planning the needed power service.
So you can added this up real fast. If you have a 1000 Watt per side
amp, times 2 for both channels, that's 2000 Watts. That will take one 20
Amp at 120 Volt circuit to power that single amp without the risk of
popping a breaker. Two 500 Watt per side amps can be powered on one 20
Amp 120 Volt circuit as well. If you are setting up a system with 4
monitor amps and a good 4 to 8 amps for house, with 250 to 1000 watts
per channel RMS, or more, you will need 6 to 10, 20 Amp 120 Volt
dedicated circuits for power. And this is a "modest" system. This may
surprise some electrical contractors, so be ready for some push back,
but facts are facts. And don't forget your video systems. These systems
are often linked together by and audio feed to video recording or
broadcast. So they must be powered from the same power system as the
audio to prevent nasty "ground loops" between power systems which get
connected together by audio or video shields between systems.
Lighting is a little more straight forward, since the energy consumed by
each fixture is right on the fixture or bulb and this is continuous, so
the 80% rule suggested by the electrician comes into play. You can tell
your electrician how many fixtures and their Wattage and they will
understand well how to power them.
As for the power systems themselves, here is the best way to set up a
new installation: Insist on a transformer isolated systems feeding a
panel dedicated for your sound system. I recommend a 20KVA to 100KVA 208
Volt 3 phase "wye" service, depending on the expected Wattage size of
your system. You must use a "K" rated transformer because the loading
will not be "balanced" so the neutral needs to be full size inside the
transformer. Your electrician will know about this. Also, if the
transformer is located near your power panel and sound system, or near
the auditorium, make sure it's one that does not make a lot of noise so
you don't have to listen to the humming. This transformer may step down
from a 480 Volt 3 phase power system or just isolate from a 208 Volt 3
phase "wye" system, depending on what is coming into the building. If
your service is single phase, the same need for isolation via a
transformer exists, it just uses a little different transformer.
Transformer isolation for the lighting system is also recommend, since
it helps prevent the electrically noisy load of lighting systems from
getting back through the power system. Lighting systems will require
100KVA to 400KVA at 208 Volt 3 phase "wye" power. You can use a single
phase system, as well, it's just less common. Its best to have a power
panel near the point in the room where you are going to distribute the
power.
I placed my sound power panel and transformer on one side of the stage,
and my lighting power panel and transformer on the other to keep the
system as physically separate as possible to prevent electrical noise
cross talk.
Make sure the electrical contractor keeps these systems separate.
Conduits carrying power to audio and video systems must NOT be mixed
with conduits carrying power for lighting, even though they may be near
each other. All power runs must use separate neutral (white) wires.
Don't let the electrician use a common neutral wire for two or three
separate circuits, a common practice for power systems in general room
lighting. This is for the same reason you require a "K" rated
transformer; the loads are not balanced and thus cannot share a common
neutral.
Grounding (Earthing)
With a transformer in the system, the secondary (output) of the
transformer is by design "isolated." This means the neutral from the
transformer must be grounded (earth) for safety. Do not let your
electrician connect the nice clean isolated power out neutral from the
transformer to the same "dirty" ground (earth) wire which comes up from
the main power system in the building. A separate ground must be
established at the output of the transformer. This may be any "approved"
metal grounding method allowed by code, but it must be separate from the
"mains" ground. It may include: metal beams nearby which go to the
foundation, the cement rebar, or an approved grounding rod driven into
the ground, or a combination of all of these. This is your "technical
ground." ALL circuits must be connected to this ground at the power
panel. This is what is called a "star" ground power system since there
is a single ground point and ALL circuits extend out from this point.
I will not get into "Isolated" ground systems except to say it is the
king of grounding systems and should be used if at all possible. The
links below talk about it in more detail.
The lighting ground system does not need to be so isolated, but it does
not hurt.
Tuesday, February 9, 2010
McMinnville 2010
Ok, so my first post for 2010 will be talking about the 26-part evangelistic series I just got done directing in McMinnville, Oregon. We started January 8 and finished February 6, with Wednesdays and Thursdays off. Two weekends we produced four programs in 26 hours (Friday night, two Saturday morning, then Saturday night). The crew held up very well, and we still had our sense of humor at the end of it. :)
I'll get to my regular posting schedule next week, but I thought you might enjoy some images from the series. For you technophiles, here's the raw equipment information: we shot with four Canon XLH1 HDV cameras connected to a Ross Video Synergy 100 MD (Multi-Definition) switcher. Genlock is supplied by a Ensemble Designs unit run over Canare multi-core cable, which also carries HD-SDI, Timecode In, and Timecode Out, with one spare conductor should one of the others break. Tally is run over a custom-built system on a Cat5 cable, and connects to a Marshall 7" LCD monitor that sits atop the camera. Tripods come from Sachtler, and custom-built camera and tripod stands allow for maximum flexibility in positioning in both horizontal and vertical axes.
My directing station consisted of two shallow racks, side-by-side, with a 3-screen LCD Marshall HD-SDI monitor and a Marshall 17" LCD multi-input screen in each (one 17" for Preview, one for Program). The 17" monitors also served as the monitors for the Mac Pro capture computer. Capture is handled through a Kona 3 running into Final Cut Studio 3 using the ProRes 422 HQ codec. The data is captured to an Apple XServe RAID unit with 4TB of storage, I believe.
Ok, now to the pictures. : )
This is Camera 3, one of the two center cameras
The speaker, Jac Colon, stands in front of our "window effect." The Producer and I, in designing the set, wanted to take a strong departure from traditional "Adventist" set design and have something other than a fake plant sitting outside the window. In our case, we designed with a Tuscan theme, so why not have a Tuscan landscape outside the window? We also wanted a late afternoon/early evening color temperature, hence the orange glow.
This is how we achieved the effect-we purchased a stock image of a real Tuscan landscape with very particular lighting parameters. The Producer wanted to have a "sunlight streaming through the window effect," so once we found the picture that matched that, we had it printed locally and our set builder constructed the frame for the image. I then lit the image with two Selecon Acclaim fresnels (lamped at 575w) and gel'd with some extra gels I pulled of a gel string from a color scroller. The third Acclaim, with the same gel, is mounted up above the picture, shooting through the window. The purple on the rock is provided by Elation Opti 30 LED fixtures. 
This is what my directing station looked like. My lighting director is in the foreground. We ran the show on a PC desktop with Jands Vista app as the show control. Our lighting rig consisted of: 16 ETC Source 4 Jr. fixtures (lamped at 575w), 2 Elation Opti Tri 30 LED fixtures, 3 Selecon Acclaim fresnel fixtures, 4 Elation Opti 30 LED fixtures, and 2 Elation PowerSpot 575 moving head fixtures. A relatively small rig, but it had pretty good punch. If I had to do it over again, I would have put my backlight truss span over the top of the set, instead of behind it-it would have allowed for separate lighting of the set vs. the speaker...of course, my front light truss hangs were about 4 or 5 feet too low anyway. :( I'll do better next time!
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