GreyWyvern
Well-Known Member
@DuckJordan is magical afterall. Remember, he can touch lamps with his bare hands too!
Portable "FOH" Rack
- Thread startersdauditorium
- Start date
DuckJordan
Touring IATSE Member
I'm starting to wonder, if I just have exceptions to the rule all the time....
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I've heard speaker coils (well, technically, the cylinder on which the coil is wound) knock against the back of the magnet, from improper shut-down and start-up sequencing. The "thud" (usually) doesn't totally destroy the speaker right away, but it does cause the cylinder end to flare out / deform a little each time. Eventually the deformed cylinder starts to scrape the magnet and the speaker sounds like scratchy crap. (At that point, it's destroyed.)
I've also come across speakers where the glue holding the coil cylinder to the cone has cracked. These too sound like crap and need immediate repair, before the cylinder becomes completely detached from the cone. (I can only imagine such damage occurred from the momentum of a sudden and very loud transient... such as the "pop" or "thud" that some equipment emits upon start-up and shut-down... and likely slammed the cylinder into the magnet.)
I've also seen people rip off their headphones and rub their ears in pain, while shouting every swear word in modern English vernacular... and of other languages too... because of a loud switch-on / switch-off "pop" somewhere up the signal chain. (I've even done this myself -- guilty as charged.)
And of course, crowds don't usually take well to something that sounds like a surprise gunshot in auditoriums with very powerful PA systems.
I've also come across speakers where the glue holding the coil cylinder to the cone has cracked. These too sound like crap and need immediate repair, before the cylinder becomes completely detached from the cone. (I can only imagine such damage occurred from the momentum of a sudden and very loud transient... such as the "pop" or "thud" that some equipment emits upon start-up and shut-down... and likely slammed the cylinder into the magnet.)
I've also seen people rip off their headphones and rub their ears in pain, while shouting every swear word in modern English vernacular... and of other languages too... because of a loud switch-on / switch-off "pop" somewhere up the signal chain. (I've even done this myself -- guilty as charged.)
And of course, crowds don't usually take well to something that sounds like a surprise gunshot in auditoriums with very powerful PA systems.
DuckJordan
Touring IATSE Member
I'm not saying you should make a habbit of turning off the amplifiers last. I just doubt the "facts" about the damage...
GreyWyvern
Well-Known Member
Really?! Seriously man, just stop. With both this and the lamp thing. There is plenty of evidence that touching lamps can shorten their life and "pops" as a result of incorrect power up/down sequence can damage speakers. That is why the manufacturers warn you about those things. Does it happen everytime? No. That doesn't mean it doesn't happen at all though. Just because you may not have been paying enough attention to lamp life or know when a speaker may have needed repair (since you are lighting and not sound), doesn't mean you and those around you are the "exception to the rule." There is another word for people like you and it isn't lucky. Just the fact that the manufacturers have warnings about these things is proof enough that they do happen. They are actually trying to save you time, trouble, and money. That's what was so funny about what @DELO72 said. Relamping/avoiding fingerprints on Lamps
It is stupid to argue just for the sake of arguing, which you are doing. Stop. Please.
Dionysus
Well-Known Member
Indeed, it is rather rare for power off/on to damage speakers, but it DOES HAPPEN. I have seen it. Its rare but why not power off/on in the correct sequence and eliminate the chance for said damage? Its such a simple thing to do that reduces chance for damage and such.
Putting a single bullet in a revolver and pointing it at your head will 1/6 or 1/8 (depending on the revolver) of the time, so would you argue that playing russian roulette will never kill you because you've done it twice and did not die?
Putting a single bullet in a revolver and pointing it at your head will 1/6 or 1/8 (depending on the revolver) of the time, so would you argue that playing russian roulette will never kill you because you've done it twice and did not die?
FWIW, in a properly installed and tuned system with responsible gain structure and limiters, it's not as easy to blow a speaker up. Digital consoles have also gone a long way to reducing the amount of power-up pop. Sound systems aren't exactly the wild west they used to be in terms of things you need to know to not blow them up.
But, alas -- there are a great number of people who do not understand gain structures and like to use their amplifier's gain knob as a general purpose volume knob or more egregiously leave the amplifier's gain setting wide open. When that happens and someone sends a pop through the system (especially when the DSP is lacking appropriate limiters or there is no DSP), they send a much higher intensity signal out to the loudspeakers.
Another factor at play is when the correct crossovers, high-pass, and low-pass filters have not been used for each speaker type. Sending a pop to a speaker at the frequencies it's designed to handle is bad. Sending a full-range pop to speakers elements unprotected from the frequencies above or below their rated frequency handling is worse.
You would be surprised how many installations I encounter where:
1) The gain structure where the amplifiers are set wide-open and it's up to the person at the console to keep all fo the inputs gained way down.
2) None of the loudspeaker manufacturer's specified filter settings are included in the DSP.
3) The HF signal is routed to the LF and vise versa.
4) The DSP is used as a matrix router and has minimal or no system tuning whatsoever.
But, alas -- there are a great number of people who do not understand gain structures and like to use their amplifier's gain knob as a general purpose volume knob or more egregiously leave the amplifier's gain setting wide open. When that happens and someone sends a pop through the system (especially when the DSP is lacking appropriate limiters or there is no DSP), they send a much higher intensity signal out to the loudspeakers.
Another factor at play is when the correct crossovers, high-pass, and low-pass filters have not been used for each speaker type. Sending a pop to a speaker at the frequencies it's designed to handle is bad. Sending a full-range pop to speakers elements unprotected from the frequencies above or below their rated frequency handling is worse.
You would be surprised how many installations I encounter where:
1) The gain structure where the amplifiers are set wide-open and it's up to the person at the console to keep all fo the inputs gained way down.
2) None of the loudspeaker manufacturer's specified filter settings are included in the DSP.
3) The HF signal is routed to the LF and vise versa.
4) The DSP is used as a matrix router and has minimal or no system tuning whatsoever.
AsherSB
Active Member
Back to the rack- The QSC TouchMix provides hardware to mix with, but has a built in access point for app based control. It doesn't come cheap at $900 or so for the touchmix-8 but about the same price as a wireless mixing system, a router, and an iPad. Unless you already have a Sennheiser system I would opt Shure instead, really anything will work as long as it's UHF and a known brand. Audio technica's system 10 also looks nice, but I don't have any experience with it. I agree with whats been said about the EQ and power sequencer, both expensive and unnecessary. Other then those I would go with @Footer's recommendations, but maybe a smaller case and drawer.
sdauditorium
Active Member
Thanks for the help. We're working on quotes for the back-end of the system (installed, distributed system in the gym as well as proper processing, amps, etc.). The reason I'd prefer Sennheiser is for consistency. Our auditorium and football field all utilize Sennheiser (22 wireless in all), and my experiences have been great thus far in nearly 15 years. It's nice to be able to swap out handhelds or body packs without worrying between venues. The TouchMix was sort of the leading contender and had been on my radar, so it's good to see that mentioned.
@MNicolai, you need to google gain structure, then re-read your last post.
If you're referring to my remark about amp gains being left wide open, that's because wide open means different things to different manufacturers. Gains on the amps should be consistent with attenuation for artistic blending defined in the DSP, but the gains for the amps should be based on feeding a sine wave into the amp and measuring the output with an oscilloscope, not by just setting the amps wide open and relying on each manufacturer to engineer their product with perfect precision.
I'm not up to speed on the exact levels and voltages we look for when we do this because I'm not the guy in our shop in charge of that process, but whenever we get a new rack built up in our shop, we hook it up to 8ohm loads, burn the amplifiers in, and monitor the waveforms with oscilloscopes for abnormalities. Aside from making certain the gains are dead-on, it stress tests the amplifiers to make sure they won't fail prematurely.
Manufacturers are inconsistent between models and other manufacturers, and sometimes even between copies of the same model. Just setting the gains wide open doesn't do what you'd think it would.
The side issue to this being that when the gains are thrown wide open without being tested and measured, we oft see there are other issues in the gain structure that result in someone barely lighting up the meters on the console when the system is freakishly loud. That's more a reflection of the installers overall approach to gain structure though than of the effect that just incorrect amp gains have.
I'm not up to speed on the exact levels and voltages we look for when we do this because I'm not the guy in our shop in charge of that process, but whenever we get a new rack built up in our shop, we hook it up to 8ohm loads, burn the amplifiers in, and monitor the waveforms with oscilloscopes for abnormalities. Aside from making certain the gains are dead-on, it stress tests the amplifiers to make sure they won't fail prematurely.
Manufacturers are inconsistent between models and other manufacturers, and sometimes even between copies of the same model. Just setting the gains wide open doesn't do what you'd think it would.
The side issue to this being that when the gains are thrown wide open without being tested and measured, we oft see there are other issues in the gain structure that result in someone barely lighting up the meters on the console when the system is freakishly loud. That's more a reflection of the installers overall approach to gain structure though than of the effect that just incorrect amp gains have.
Well I guess everyone has their own style. My typical modus operandi:
1. Play a sample song or other "test signal", similar to the typical programme material, through the main mixer.
2. Set the main mixer's faders to 0 dB.
3. Raise the input channel gains until the output VU meters mostly stay at or slightly below 0dB.
4. Set the FOH EQ/FX rack's "programme EQ" trims to 0 dB.
5. Raise the power amplifier gain controls until the sound level is at the loudest you anticipate you will need it for the upcoming show.
For non-permanent systems that always have their controls tweaked and re-tweaked and bumped around between installations anyways, I find this works well.
I tend to facepalm when I see techs twist the amplifier knobs all the way clockwise as one of the first steps, before even running the first sound check signals through the system.
1. Play a sample song or other "test signal", similar to the typical programme material, through the main mixer.
2. Set the main mixer's faders to 0 dB.
3. Raise the input channel gains until the output VU meters mostly stay at or slightly below 0dB.
4. Set the FOH EQ/FX rack's "programme EQ" trims to 0 dB.
5. Raise the power amplifier gain controls until the sound level is at the loudest you anticipate you will need it for the upcoming show.
For non-permanent systems that always have their controls tweaked and re-tweaked and bumped around between installations anyways, I find this works well.
- There's no need to consult data sheets or product manuals for all your audio sources, be they +4 dBu or or -10 dBV, or something else, or a consumertrash gadget's headphone jack that could be pretty much anything.
- Your faders pretty much always end up landing in a nice range; never maxing out, and never being too loud while still at the bottom end.
- Should you misjudge the amplifier gain setting and your master fader is stupidly high or low, you can always tweak the FOH rack's trim.
- Should anything ever go wrong in ANY of the upstream equipment or its connections, causing a "pop" in the audio signal... the amplifier gains are NOT "wide open", therefore the resulting "bang" in the speakers won't be as traumatic.
- Hiss and noise is kept to a minimum -- Everything upstream of the amplifiers is being operated at levels that achieve best SNR.
I tend to facepalm when I see techs twist the amplifier knobs all the way clockwise as one of the first steps, before even running the first sound check signals through the system.
TimmyP1955
Well-Known Member
Yes to a CD player, preferably one that will read discs of MP3 and MP4 files as well as standard audio CDs. Then hope that it will read the home-burned CDs that you are handed (I once had a disc that neither my CD player nor my WinXP machine would play.
You don't need a power conditioner, just a good power strip. Though for digital widgets, a UPS would be nice. At my day job we use these:
http://www.provantage.com/tripp-lite-smart3000net~7TRPM002.htm
http://www.newegg.com/Product/Product.aspx?Item=N82E16842106109
You don't need a power conditioner, just a good power strip. Though for digital widgets, a UPS would be nice. At my day job we use these:
http://www.provantage.com/tripp-lite-smart3000net~7TRPM002.htm
http://www.newegg.com/Product/Product.aspx?Item=N82E16842106109
TimmyP1955
Well-Known Member
Amps wide open is the safest way to go. If you set your limiters with your amps wide open, no one can render your limiters useless by turning the amps up beyond where you had them.
I'm no audio guy, but I do pay attention to what they do. With the changes in technology, there's always something new, so I would not get married to any one product. All the stuff that you find you're not using any longer (old cd players, etc.) can be put into a secondary rack that you can patch in or something. A rack with a top mixer is the way I would go, but what you put into it is going to be up to you.
That's only if your "limiter" is a device permanently bolted into the power amplifier rack, and permanently connected to the amplifiers... and locked out from tampering.
But if the cables being plugged into your power amplifier line inputs are disconnected & reconnected for every new show setup, that theory goes out the window.
And if the limiter settings are not locked, someone could just as easily change your limiter settings as they could hypothetically change the power amplifier gain settings. Therefore you're not really protecting anything.
That's only if your "limiter" is
Ui16 console ... works with any device android or ios ... 10 users at the same time ... also has included wifi access ... also includes usb for recording or playback of .mp3.wav etc.
Im usually in the get 4 wireless mic if you are getting three also check out the ulx-d quad
As for a rack skb gator etc but get one with a caster board !! Rule 1 if it's not on wheels it doesn't go.
Im usually in the get 4 wireless mic if you are getting three also check out the ulx-d quad
As for a rack skb gator etc but get one with a caster board !! Rule 1 if it's not on wheels it doesn't go.
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