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Newbie looking for advice please

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happy camper View Drop Down
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Joined: 02 October 2011
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Post Options Post Options   Thanks (0) Thanks(0)   Quote happy camper Quote  Post ReplyReply Direct Link To This Post Topic: Newbie looking for advice please
    Posted: 02 October 2011 at 4:39pm
After hosting a few parties with large rigs and generators for a while, we've decided to try and get something similar working but using 12v.

To start off we have a few things, I wonder if anyone can give us any advice please


firstly we've some great batteries, something like 1040 ah and 70 amps per hour, which seemed to be able to run the old rig for a few hours through a cheap 1650w inverter so not expecting any problems on the power front,

we would obviously have to run the decks through the inverter but also we would look to use car amps to start off as we have a few not being used at the moment, we have 2 car, both 240w each; the first one is a Boss amp-240 and the other a Sony xm-255ex

just wondering the best way to wire these up, they're 120w per channel but I'm thinking we would like to somehow combine all the wattage into one channel, is this possible??

We're going to be using some pa speaker cones along with them, probably 12" ones

any advice on this would be really helpful, the thinking is either to raise some money and eventually either get a bigger power amp which we can use with an inverter or just add more car amps to the setup as it grows (would this be possible!!?)

if anyone can help point us in the right direction that would be great, thanks!
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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 03 October 2011 at 11:17am
You need to be a good deal more specific about requirements wrt :-

Portability - do you need to plonk it down well away from vehicle access ?
Run-time - a few hours ? Whole weekend ? Longer ?
What kind of SPL ? CD's/mp3/vinyl ? Live music ? How many peeps ?
To what extent are you able/willing to get involved in electronics building/wiring/modding/testing ?

I can describe my little setup (in fact its the larger of a few), which might illustrate a couple of points of principle.

I have a pair of fairly standard 12" + CD PA cabs - 8 ohms each, rated at about 150W each.
Portability is a major issue for me, as I don't have a car/vehicle, and I live on the 3rd floor - no elevator, and a somewhat dodgy back .....
I don't need run-times of more than about 6-7-8 hours.

So I use a _good quality_ car amplifier powered by 2 smallish car batteries (leisure/deep cycle would beb better, but I got the car batteries for nothing :-) .... and its easier to carry 2 x 45Ah car batteries than 1 x 85Ah leisure battery)

The amplifier is a Vibe litebox 2-channel jobbie - rated as 500W "max power" .... car amplifiers are nearly all rated this way .... the real power is usually 30-40% of the headline/marketing power.
But its good quality - sounds clean and sweet - to me anyway.
One thing I like about the Vibe brand is that you can speak to a proper tech in the UK and ask questions etc.

Now this amplifier is rated as "2 ohm capable" - meaning you can use a 4 ohm load across the bridged output - i.e. my 2 x 8 ohm cabs paralled across the bridged output works fine .... it drives the amp quite hard, but has proven perfectly OK so far. It gets pretty hot ... I have a plan to add to add some forced cooling to it + 1 or 2 other additions via a DIY "outer chassis".

Its a class GH design  meaning the power efficiency is decent - better than ordinary class AB, but not as efficient as good class D.
In general, car amplifiers are not designed for power efficency. If you want long run-times, look into a module design mentioned by someone in here a few months ago. Needs about 48-50V DC ..... but if you can group your batteries into banks of 4 - you might well go that direction. But then you'd need to do a bit of electronics building/DIY. Have a look at

http://www.ebay.co.uk/itm/600W-Class-D-Power-Amplifier-Balanced-Input-2-Ohm-/250508323440?pt=LH_DefaultDomain_0&hash=item3a5375aa70#ht_3723wt_903





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