Power wise to put on a big concert must be incredible - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 17, 2018, 05:15:45 am
content: This must be a lot of fun and as as a guitar master, extra fun.

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 17, 2018, 05:16:35 am
content: I bet a lot of wires and transistors were hooked up

author: Nitrousoxide
author_rank: Regular Contributor
timestamp: July 17, 2018, 05:21:13 am
content: I work in live theatre. I can say for medium venues, they have approximately 90-100 dimmable channels (triac based dimmer). Each dimmer is usually 12 channels and connects via a 30A 3-phase plug, then you have each 240v cable going from the patch bay to the dimmer, its a LOT of cables. If you're not careful the patch bay can end up like a rats nest.... perfect task for the newbs to untangle.The most annoying thing is eliminating ground loops... and bloody video LED walls, those things radiate more EMI than the sun....Quote from: lordvader88 on July 17, 2018, 05:16:35 amDon't forget fiber optics! At that range most of the MADI (or equivalent protocol) would be sent and returned over fiber due to losses.

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 17, 2018, 05:27:26 am
content: they are a bunch of proper old geezers

author: dmills
author_rank: Super Contributor
timestamp: July 17, 2018, 02:39:21 pm
content: Power usage is actually going down significantly at large events as tungsten sources (outside of theatre where we really need the spectrum and useful colour temperature shift) die off to be replaced by either discharge or LED.The sting in the tail with discharge is that because they do not usually hot strike well the lamps tended to stay lit for the whole gig, neither LED not Tungsten has this issue.Sound power is never a particularly interesting size of load, mostly because average power is so very much lower then peak power, but you try telling a noise boy that yes, that 50kW rig really will do just fine on that notionally 10kW feed (it will, but no way the sound guy will believe you).There was pretty much a step change in speaker performance about 10 years or so back, efficiencies went way up, and pattern control improved massively, a modern PA box is in the well north of 105dB/W @ 1M, so you can make a LOT of noise with not very much amp, and some modern speaker hangs approximate a cylindrical wavefront in the near field, so only fall off at 3dB per doubling instead of 6dB.Sound these days tends to follow the 'get it digital as quickly as possible' school of thought, you just don't see cables the size of my arm carrying 64 individually screened pairs any more, instead you just scatter a few MADI (Or these days, Dante or AES67/Ravenna) boxes around the stage and run a coax, fibre or cat 5 out to the desk. Not very rock and roll maybe, but a couple of 1U network switches and a Gig-E over SFP and fibre link is smaller, lighter and very much cheaper then humping great flightcases of arm thick cable with delicate 160 pin ends.Modern amps sometimes do not even have an analogue input any more, instead sitting directly on a data network, and in fact integrating such things into powered speakers is not uncommon, you just wind up running ethernet to a switch mounted on the flying hardware and running power and data to each box.It changes the system engineers job somewhat and sometimes wireshark and knowing how to use a fusion splicer is more important then knowing how to solder!Time was a synced pair of 500kVA machines was fairly standard at these things, these days you might run a pair of 250kVA machines and load shed a bit if you lost one of them.Agreed that LED can be a curse, mainly from my perspective because all the power supplies leak small amounts of earth current that adds up and can take out a RCD even while you are still well within total current limits.Regards, Dan.

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: July 18, 2018, 03:46:47 pm
content: Compared to THIS?https://youtu.be/lACcBSKg4uY?t=57Most concerts are battery-powered.

author: dmills
author_rank: Super Contributor
timestamp: July 18, 2018, 05:01:19 pm
content: Yea, Jarre was awesome!The single biggest load at that gig was probably the Ion lasers, horrifically inefficient things (Think 10kW of input for maybe 10W of light out the snout)!I am not at all sure you would be allowed to do it these days, I think the CDRH would probably throw a hissy fit.Regards, Dan.

author: Gyro
author_rank: Super Contributor
timestamp: July 18, 2018, 05:38:14 pm
content: I remember reading an article decades ago which said that the road crews always carried a very large ground spike and lots of brine to ensure that there was a solid Neutral. Apparently, with the PAs on one phase and the lighting on another, a weak neutral could get pulled an awful long way when a song ended and the lights came up.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 18, 2018, 05:52:13 pm
content: Quote from: dmills on July 17, 2018, 02:39:21 pmI always wonderd if these reduce the power when the shutter is closed, so they stay lit but draw less.QuoteWhat was this down to ?

author: Old Printer
author_rank: Frequent Contributor
timestamp: July 18, 2018, 07:25:31 pm
content: Quote from: lordvader88 on July 17, 2018, 05:27:26 amThose are kids, these guys are proper old geezers.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 18, 2018, 07:52:04 pm
content: Quote from: Nitrousoxide on July 17, 2018, 05:21:13 amI'd guess they are EMC tested only as individual modules (maybe with a "favorable" test pattern..)

author: AndyC_772
author_rank: Super Contributor
timestamp: July 18, 2018, 09:01:04 pm
content: Quote from: mikeselectricstuff on July 18, 2018, 05:52:13 pmClass D amplification, perhaps?

author: JS
author_rank: Frequent Contributor
timestamp: July 18, 2018, 10:20:06 pm
content: Been on a few biggish stages, for 20k people or so... I don't remember but in the order of 100kW seems reasonable.Once (or twice) on a bad tap from the electrical network and you have the guy next to the volt meter telling the guy on the lighting desk how many lights he can use at once, funnyWe used the best phase for audio and the other two for lights, no sharing a single cable anywhere else but the main board, quite easy as audio and lights are different teams so the only time you need to agree is to bring the wires from stage to FOH.This was many years ago, on my late teens, for this year edition I was around and they called the electric company to install a new transformer and have an emergency generator for a few 100kVA ready to go right next to the stage, it wasn't funny anymore.JS

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 18, 2018, 10:30:53 pm
content: And of course , there is the famous album cover by “The Who”, showing the band sitting and standing on top of huge crates of heavy duty cabling.The album “Who Are You.”

author: james_s
author_rank: Super Contributor
timestamp: July 18, 2018, 11:58:50 pm
content: Quote from: mikeselectricstuff on July 18, 2018, 05:52:13 pmAs far as I know they don't, most HID lamps don't really like being dimmed, MH dimming ballasts do exist but they require some fancy tricks to keep the cathodes from cooling which causes them to sputter and blacken the arc tube. Since the lamps tend to be quite expensive I'd imagine the power consumption is secondary and the added complexity of drive electronics capable of dimming without causing reduced lifespan would not be worth it.I would expect that development of HID sources has pretty much frozen these days anyway and LEDs will eventually take over everything of this sort.

author: dmills
author_rank: Super Contributor
timestamp: July 19, 2018, 10:52:57 am
content: LED is fine for some things, but suffers from a brightness issue, you can make a large area emitter that puts out a lot of photons, but you cannot really make a high brightness (lots of photons from a small source) LED at this time.This is a problem if you want to do anything involving a sophisticated optical chain, and is why led is usually not seen in profile type lanterns (and when it is they often cheat by imaging the LED surface rather then having a focal plane in the gate like a real profile does. This is a problem when you use the shutters or a gobo.The big thing with speakers was a perfect storm of better magnets, better computer models, better DSP and cheap light weight multi channel power amplifiers at useful outputs.Regards, Dan.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 19, 2018, 01:37:26 pm
content: Quote from: dmills on July 19, 2018, 10:52:57 amIndeed!Class D amps fed by a switch mode power supply.

author: dmills
author_rank: Super Contributor
timestamp: July 19, 2018, 02:05:46 pm
content: The old Crown MA5000VZs and such like, (5U, and a 2 man lift) were dropped from the touring sound game like hot rocks just as soon as really reliable class D hit the scene. Same thing with analogue consoles and interconnection, ethernet or MADI is just so much less of a pain.I can now carry 6kW of amp with one hand, and far more importantly the amps are cheap enough to allow one per speaker driver, with output feedback to a DSP running a model of voice coil temperature and displacement, which lets you get one hell of a lot more out of a given driver without risking damage.There are even steerable (phased array) speaker hangs these days, which are very, very cool technology.Regards, Dan.

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 19, 2018, 04:30:48 pm
content: Sorry guys I was under the influence when I made this thread.But yeah some ET/EE gets paid good money for making sure it all works.