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12v system for remembrance service

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cabby View Drop Down
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    Posted: 09 October 2018 at 10:26pm
Old fart here, new to forum. I have been tasked with sorting out a PA system for the service in our cemetery for Nov 11th. Budget.  little as possible.
We can get power but its 150mt away, been offered a 3kva gennie but concerned about noise, then i saw a clip for a 12v set up and thought, way to go.

we have.  from days gone by stepsons disco 100w passive speakers and stands, along with lots of cables and mic's and from a "friend"  2 leisure batteries 12v 20h 90amp, ( im taking it the 20h is hours ) . its suggested all we might need is a car amp and battery mixer. 

anything else we would need?? how big an amp and type of mixer. 

all wants to be cheap as its for almost single use then will go into store until next years service. 

were in Brandon in Suffolk if anyone has any old kit they can donate or help with assembly. 

time is getting on and i have to get it right pretty quickly.  appreciate any help. thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote imageoven Quote  Post ReplyReply Direct Link To This Post Posted: 10 October 2018 at 12:05am
Is it just for speech amplification, or music too? How long do you need to run for? What size crowd or area are you trying to cover?
Keep pushing on, things are gonna get better.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cabby Quote  Post ReplyReply Direct Link To This Post Posted: 10 October 2018 at 11:41am
just speech, less than an hour, maybe 300 people
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Post Options Post Options   Thanks (1) Thanks(1)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 10 October 2018 at 2:37pm
Traditionally you would do this job with some 100 volt tin trumpets (Grampian horns) and and an "Adastra" style amp. The advantage of the Adastra type being that it works from 12 or 24v and has a mic input already there. Not high quality sound at all, but good enough for voice.

Your 100w disco speakers won't be as efficient as the trumpets, nor will they have 100 volt transformers in them. But, you could add the transformers and use the Adastra anyway, and it will probably still be loud enough. 



You could use a car amp instead, but then you have the problem of getting a 12 volt mic preamp/mixer. There aren't many about. I ended up spending a lot of time modifying the power supply of a Behringer unit to get it to work with my rig. It was not easy. You could of course use a small inverter to power the mixer, however this is more expense and likely to generate buzz.



Edited by studio45 - 10 October 2018 at 2:43pm
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (1) Thanks(1)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 11 October 2018 at 9:52pm
Yamaha MG06 is a compact mixer than runs off 12v Wink
"Battery Acid Sound System" blog hopefully happening in 2017
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 4AC Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2018 at 9:09am
For this kind of application, I would think reliability and long-life would be highest priority.
Secondly, speech intelligibility and clarity should be top notch.

If its once a year only, wouldn't it be a better option to rent a couple of quality battery powered speakers? Most common types I know of: Fohhn Easyport and Sennheiser LSP. These kind of speakers do not even require a separate mixer, which is unhandy in this environment and another piece in the chain that can cause issues.
If I were you, I wouldn't want to take the risk that some of the crowd couldn't hear a thing of what is being said. Or even worse, that one tiny part of your own DIY creation starts to break down at a critical moment.
When renting, you can assume that you'll be getting quality equipment that's being serviced regularly. Also, the rental company will have some good microphones and so on available. In others words: a reliable solution.

If renting isn't an option, you could even try to find one of the above speakers used. But remember the batteries have a limited lifespan, so at some point they need replacing. There are also more affordable options to buy new, for example from dB Technologies, Samson and so on.

To my opinion, you shouldn't be messing around with DIY stuff for these applications. Unless you really know what you're doing and have a suiting budget to spend.



Edited by 4AC - 12 October 2018 at 9:15am
uǝɿɿɐʌǝ6ɯo sı ʇsʞǝʇ ǝzǝp
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cabby Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2018 at 3:22pm
4AC ,  BUDGET zero or what ever i care to spend from my own pocket. And thats the problem,  we had a service last year for a Polish memorial and no system against my advice on that occasion theres was a house just over the wall who would supply mains and trip and using my lads kit. 

Ive been saying for 10 months get something, they ( our council ) could even run a mains from there work hut. The issue is its 100mt and ive said to get  a good lead. Its £100+ , i then sourced  2 battery speakers, mics etc £200+ either would be an option but they say not needed. 

I agree its the worst occasion when a system could let you down, its all coming out of my pocket. right now i have a car amp and good leisure batts and a 9v battery mixer on order for £20 im going to couple with the speakers i have and give a damn good trial. 

If any problems it will be nothing at all.  I might be back on this topic asking for help if unsure on any wiring etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cabby Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2018 at 3:29pm
Heres the plan.


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Post Options Post Options   Thanks (1) Thanks(1)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2018 at 7:13pm
Originally posted by cabby cabby wrote:

Heres the plan.



Well - thats kind of OK, but that bloke isn't very clued up. Really full of himself eh ?

Several points I'll make.

1) Make sure you use a class D car amplifier - much better power efficiency (i.e. the battery will last a good deal longer).

2) Using a PA type speaker is certainly the way to go, but they're nearly all 8R impedance, so not an optimal match for the amplier. But - most car amplifiers are bridgeable, so for a single 8R speaker running from a 2-ch car amplifier, its a no-brainer to use bridge-mode - it'll get more power from the amplifier as its a better impedance match.
If you have 2 x 8R speakers, try and go for a 4-ch class D amp, and bridge the 4 channels into 2.

3) The little voltmeter for the battery is a good idea, but the momentary switch is a bit unnecessary as the power consumption of the meter will be tiny compared to the amplifier.

4) Would be a good idea to put an in-line fuse in the croc-clip power cable if possible.

5) If running the mixer from the same 12V battery as the amplifier, check the setup first, as its possible to get ground-loop hassles (i.e. hum). If that _does_ transpire, you could get a (separate) small lithium battery pack (3S) to power the mixer.


Now - if you have 2 half-decent PA speakers (12 inchers would be good) .... they might very well be all you need. This is on the assumption that this event will be a solemn affair, and  that there'll be hush for these speeches .... so as long as you're not near a main road or in the vicinity of any other background noise, you'll be OK (for just speech) - even with 300 people. But it does depend a bit on whether the 300 peeps are sitting in rows etc. or milling around over a wider area.
Definitely put the speakers up on stands - just above head height.

My 2p anyway.




Edited by slaz - 12 October 2018 at 7:17pm
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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Post Options Post Options   Thanks (1) Thanks(1)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 13 October 2018 at 12:58am
I think an inverter is the way to go. They are fairly cheap these days and with a small mixer and amp will do the trick. I used to go busking round Europe and  used a similar setup.

Mine used a 20wpc hifi amp and a pair of JBL control 1s. You would probably need a bigger amp for 300 people but the "Disco speakers" would likely be quite a bit more efficient than my old JBLs.

It won't need to be "Make their ears bleed" loud for Rememberance day.
If it's got wheels or tits it's gonna cost a fortune
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cabby Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2018 at 10:32am
appreciate the last 2 posts, just for info the mixer will run off 1 or 2  PP3's and yes will use stands.
def for the inline fuse. 

as luck has the amp i have been loaned is a Pioneer GM-X602 class D bridgeable. 

 im going to set up at home and give a volume and clarity check, and then a duration check from a fully charged battery. any problems and it will prob be the inverter. and as Arnie says ,,, i will be back, to report on how it went or for more advice or inverter size . im hoping for the former. 


Edited by cabby - 15 October 2018 at 10:38am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2018 at 11:28am
The amp is a car amplifier and if the mixer is going to be run off 9v batteries why do you need an inverter? Possibly for a CD player or other music source?

The trouble might come from the amp, which is only 50wpc @ 4 ohms (your speakers are probably 8 ohm so that will bring it down to around 25 wpc). Plus car audio is notoriously over rated anyway.

What's your budget? I have a decent quality 1000 watt inverter and a cheap mixer. Can probably find a reasonable amp as well. Feel free  to drop me an e-mail. Addy is disguised to prevent being picked up by spambots but you can probs work it out

markieh (at) btopenworld (dot) com




Edited by markie - 15 October 2018 at 11:29am
If it's got wheels or tits it's gonna cost a fortune
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