OK, so here's my project:
I've got a 1999 Ford Ambulance with a 7.3L powerstroke and I'm converting it into an epic mobile DJ soundstation for outdoor parties (killer right?).
I'm going to need to run at least 4 Yamaha P7000s's on it as it's going to be high powered enough for an outdoor concert for 500+ people.
I want to run a pair of 18" folded subwoofers, with a pair of mid arrays per side and then a pair of tops, total system power around 8000-10000 watts. It's going to be a baby monster and I need some constructive criticism and a plan for moving forward, thanks in advance!
I've got a 1999 Ford Ambulance with a 7.3L powerstroke and I'm converting it into an epic mobile DJ soundstation for outdoor parties (killer right?).
I'm going to need to run at least 4 Yamaha P7000s's on it as it's going to be high powered enough for an outdoor concert for 500+ people.
I want to run a pair of 18" folded subwoofers, with a pair of mid arrays per side and then a pair of tops, total system power around 8000-10000 watts. It's going to be a baby monster and I need some constructive criticism and a plan for moving forward, thanks in advance!
You need to be looking at 115V generators not inverters. An inverter would simply pull too much current.
I would imagine he's looking at a 230V generator, you're probably struggling getting those high powers from only 110V supply?.
I suppose it depends how many amps he's planning using?.
Each P7000 is good for 3.5kW so a diesel generator of 15kVA at least with four. At 110V that is 137Amps! 230V is approximately half. So a 63Amp cabling for 230V or 125Amp for 110V may just cope. An inverter on a 12Volt battery is out of the question.
I've been checking the specs. on those Yamaha amps, the output power specs. are a bit vague to say the least (with no mention of RMS) - they claim power consumption of only 650W - makes rather a mockery of the claimed 3.5kW output 😀
But as you say (and as is blindingly obvious) you use a generator, not an inverter for such applications.
I suppose an inverter would be 'possible', but the massive cost of the inverter and the huge stack of batteries required would be somewhat cost prohibitive (and obviously NOT 12V) - and you'd probably need a truck to transport the batteries.
Decent generator, job done, probably a trailer sized one you tow behind the van - and mega useful for many other purposes.
What I would say though, is make sure to take plenty of fuel - then some spare fuel as well, plus some extra fuel in reserve 😀 (been there done that 😛)
The other thing is, powerstrokes diesels idle nicely; the ambulance people leave them idling all the time. A big honking 24 V 200 A alternator belted to the engine would get you back in the inverter area. Be sure to use twin Vbelts or a 1" v belt. Or, they make 240 V 60 hz generators for such applications, which means you have to build/buy a diesel fast idle control system to make the speed stable under varying load. Geophysics trucks used to do that all the time, before data acquisition systems became 3 amp systems. The 7.3 L diesel is so popular, somebody probably has already packaged the AC generator + fast idle control system for resale. This means you don't have to attach with a steel cable the 15 kw generator to a concrete pad in the ground to keep people from stealing it. Forget chains, thieves would cut them in ten seconds.
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how about this?
Kohler Power: 25EFORZDB: 25 kW: 25EFORZDB: Commercial Vehicle: Mobile Generators
I could easily install a second fuel tank under the bed with a second fuel pump
Kohler Power: 25EFORZDB: 25 kW: 25EFORZDB: Commercial Vehicle: Mobile Generators
I could easily install a second fuel tank under the bed with a second fuel pump
Wow, you put 25 k aC generator under the body, you would have enough spare power for party lights and maybe to cook a hot dog, too. Also a generator under the bed is less of a theft target than a trailer.
Look at motor home solutions. I imagine you would be shocked at the price of a 4 cylinder diesel generator. Anything that heavy would have to go between the axles, not in the back corner like a motor home. Heat problem.
Look at motor home solutions. I imagine you would be shocked at the price of a 4 cylinder diesel generator. Anything that heavy would have to go between the axles, not in the back corner like a motor home. Heat problem.
650w draw is running pink noise to clipping. That's 1/8th power - ie, 9dB crest factor (peaks are 9dB above the average signal level), considered representative of most music by amplifier manufacturers.
Take 50w idle draw, that's 600w = 1/8th power. The power delivered on peaks that just nudge the clip lights would be 4800w minus some amplifier inefficiencies. 3.5kW is entirely doable.
All that said, I really don't like the Yamaha P series. We've broken a few of them without trying.
Something new and switch-mode will be more efficient, lighter, and put out more power. Those Yamaha amps have some serious BS-factor in the names, worse than Behringer. (P7000S = 3.2kW bridged into 4ohm; NU6000 = 2x2kW = 4kW).
OP, I'd see if its possible to build a monster TH inside the ambulance bay (after the generator is inserted) which you can pack everything else into. To set up, you'd pull out the mid-highs and put them next to the ambulance, amp rack goes just outside the loading bay and you're set to go. Why have external subs that you've got to pack, when you could have a subwoofer with a steering wheel?
Chris
If these amps were rated the way they used to be back in the 70's (full sine wave current draw) you couldn't run them off a standard 120 or 240V wall socket. At least not meet code doing so. Peaks will draw 40A or more, but so does your 3/8" drill - every time you start driving a screw with it. Manufacturers started using a more representative signal to rate AC draw, so that bigger and bigger amps could "run off a standard wall socket". If you put out full blast for more than a few seconds, the breaker at the panel will pop. But the amp would over heat if it didn't, and chances are the voice coil is already starting to smell. Some amps are better at dealing with this type of "overload" than others, and the best advice as to this sort of robustness is that you get what you pay for.
Which was my point 😀
But it's quite simple, if it only takes 650W maximum from the mains, then it's power output is some what less than 650W.
Power output is simple to measure, you feed a 1KHz sine wave into a dummy load, just before it starts to clip. Calculate the RMS power from that with a little maths - dead easy, repeatable, accurate, and reliable.
Anything else is a purely imaginary figure.
I would expect any PA amp to meet such a test? - if it doesn't then it's not worthy of the name.
Most any PA amp, even Behringer, will do that long enough to make the measurement. Can you leave it running like that for 2 hours? Nope. The old CS-800's could - can't say as much for even the most expensive ones now. Of course, your load (opr speaker?) would have to be able to take it, and you'll have to jam a penny or screwdriver or something up against the breaker handle to keep it from tripping.
So how do they justify the power rating, not really being "continuous"? Simple. It sounds like absolute trash to run it that way. Sometimes DJs do, but that doesn't mean you're supposed to.
So how do they justify the power rating, not really being "continuous"? Simple. It sounds like absolute trash to run it that way. Sometimes DJs do, but that doesn't mean you're supposed to.
To be fair, you don't really need it to be able to run like that continually, but certainly a reasonable time (plenty of time to do the test) - and expect the amp (and load) to get HOT!!.
I would imagine if an amp managed 2 hours, then it would manage continually just as well.
Obviously, and again a correctly rated speaker would be able to.
The various dummy loads I've 'thrown together' over the years have been well spaced apart - and you don't go near them 😀 (unless you're making toast).
Not if you've got sensible mains 😀
Although to be fair again, some of the ludicrous claimed powers aren't possible on 240V either (not on a single plug, as they are internally fused at a maximum of 13A).
Sorry guys but no modern power amp will deliver full power sine waves for more than a a few seconds before cutting back output or tripping a breaker, they just aren't built that way anymore. The tests now use noise signals with 6-12dB crest factor and they typically test with those signals on some kind of duty cycle, this better represents real music. That means the steady state current draw from the amp will be a surprisingly small number but it will draw large peak currents for very short periods of time, so the supply needs to be robust.but not as big as you may think. Sizing it based on sine waves would be massive overkill, as stated most amps can't support them anyway so there is simply no need. I have several of those Yamaha amps and they have worked very well for me, they sound excellent at hi frequencies and also work fine on subs as long as they are used within their limitations.
The criminally insane option would be to use a couple of high-power automotive alternators driven from the engine. With sufficient RPM and field current they can deliver MUCH more than 13.8 volts, like the + and - 100V rails for a big power amp. You might need to rewire the rectifiers on one alternator to get the -100V.
Slightly less insane... just use autosound amps. Mono sub amps that'll put 1600W RMS into a 2 ohm load aren't unusual. Upgrades to the charging system will be necessary, probably multiple high-output alternators (as used on emergency vehicles, big trucks, boats).
Slightly less insane... just use autosound amps. Mono sub amps that'll put 1600W RMS into a 2 ohm load aren't unusual. Upgrades to the charging system will be necessary, probably multiple high-output alternators (as used on emergency vehicles, big trucks, boats).
If you use autosound amps, there goes your 18" driver option for folded horns. Unless you can find a good 2 ohm driver (or live with half the power). And no, an 18" auto sub doesn't have the right parameters to drive a horn. And the dual LAB12 option is only good if you're tuning low (30 or below). Which may be ok.
But then you're still stuck with the problem of how to power the tops. Getting enough power at mid/high into 4 or 8 ohms may be tough. Unless you're thinking line array from the start (wiring for 2 ohms or less is easy, and using a dozen amps is possible).
But then you're still stuck with the problem of how to power the tops. Getting enough power at mid/high into 4 or 8 ohms may be tough. Unless you're thinking line array from the start (wiring for 2 ohms or less is easy, and using a dozen amps is possible).
Car amps usually have incredibly imaginary power ratings, and it would be cheaper to buy a generator than the huge stacks of batteries (and short live) that would be required.
I also doubt such amps would cope with PA use 😀
This is absolutely inverter generator territory like the Honda I series.
Many construction grade genies will barely if at all operate switching power supply devises. These need a stiff true sine wave feed. Modified or step sine (most inexpensive genies) offers little actual voltage rise time in the modified sine and leave no time for a switched supply to pull current. An additional problem is this type of current draw significantly distorts the wave form because a small gen is not a stiff powersupply which causes much heat in the gen windings and the harmonics can de-regulate the RPM speed control.
Like has been mentioned, the cost of batteries and inverters, or the radical modification of the existing charging system and all the possibilities of having all of the above issues anyway, the smart money is to just rent a Honda I when you need one or buy one if this is a regular gig.
The Honda Inverter generators have several significant advantages to nearly everything else, they are super quiet, the engine speed is not locked to output frequency so it can operate anywhere from idle to full throttle while maintaining 60Hz while maintaining better than grid power and it will be worth something when your done with it, unlike a pile of batteries and wire.
Make it even easier and buy a suitable 230-120 stepdown transformer and connect it to the 230V output and never again worry about ballancing the leg to leg load that is also an important aspect of using portable power.
If your serious about this, jump over to ProSoundWeb and search the power and ground forum for the Guy Holt paper on portable power. Never before have I seen such a wealth of information on portable power for sound, film and lighting.
Stay safe! Do it right.
Barry.
Many construction grade genies will barely if at all operate switching power supply devises. These need a stiff true sine wave feed. Modified or step sine (most inexpensive genies) offers little actual voltage rise time in the modified sine and leave no time for a switched supply to pull current. An additional problem is this type of current draw significantly distorts the wave form because a small gen is not a stiff powersupply which causes much heat in the gen windings and the harmonics can de-regulate the RPM speed control.
Like has been mentioned, the cost of batteries and inverters, or the radical modification of the existing charging system and all the possibilities of having all of the above issues anyway, the smart money is to just rent a Honda I when you need one or buy one if this is a regular gig.
The Honda Inverter generators have several significant advantages to nearly everything else, they are super quiet, the engine speed is not locked to output frequency so it can operate anywhere from idle to full throttle while maintaining 60Hz while maintaining better than grid power and it will be worth something when your done with it, unlike a pile of batteries and wire.
Make it even easier and buy a suitable 230-120 stepdown transformer and connect it to the 230V output and never again worry about ballancing the leg to leg load that is also an important aspect of using portable power.
If your serious about this, jump over to ProSoundWeb and search the power and ground forum for the Guy Holt paper on portable power. Never before have I seen such a wealth of information on portable power for sound, film and lighting.
Stay safe! Do it right.
Barry.
Modified or step sine only applies to inverters, a plain (non-inverter) generator wouldn't have that problem as it's a proper sine wave.
Although I'm a bit puzzled as to why switch-mode supplies wouldn't work anyway, as they draw their power from their reservoir capacitors, and a modified sine 'should' charge that perfectly well.
But in any case, there's no 'cheap' solution to this problem 😀
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