Calculating power needs for remote audio installation

[kemmler3D]

Does anyone have any idea what the actual power consumption of an amplifier is, playing music?

At the outlet, it can be tens of watts, but it tends to be less than you'd guess from the power ratings of the amps. I did a few tests with a kill-a-watt type meter a while back. This was for a ~100w class D amp at full blast playing bass-heavy music. I managed to get it into the high 30s.

Idle consumption on an NC500 monoblock is 12W.

I think if you're going with efficient horn-type designs and you don't want rave-level bass, then you can probably get away with a 50w or so amp which I'd guess will only be pulling an average of 20ish watts from the outlet during the events, at most. There are plenty of portable power banks that can do this. Even if you go with lithium ion, a 100W / 150wH power bank is only about $100, and this should get you at least a couple hours.

The only thing you really need to concern yourself with is bass efficiency and desired output. Especially because it's outdoors, the bass will tend to be weak and even if you don't need "a lot of" bass, you might not be satisfied with a truly low-power setup.

But I guess you can probably get "high power" with an actual draw of only 50w or so. It's only when you get to PA/Concert levels of bass that you really need a lot of juice.

The rest of the power draw is a rounding error in comparison. I would guess that the idle losses dwarf the actual power draw for >300hz or so.

 

[voodooless]

Yeah, just build a copy of a Danley Jericho horn, and be done with it! This one will do:

J2-96 | Danley Sound Labs

Containing 42 drivers in one full-range, array-able horn, the J2-96 loudspeaker produces incredible clarity despite its massive power.

www.danleysoundlabs.com

113 dB sensitivity, impedance is 4 ohm or lower, so can run from a cheap class D amp. You’ll need only a few watts with this one

 

[kemmler3D]

Yeah, just build a copy of a Danley Jericho horn, and be done with it! This one will do:

J2-96 | Danley Sound Labs

Containing 42 drivers in one full-range, array-able horn, the J2-96 loudspeaker produces incredible clarity despite its massive power.

www.danleysoundlabs.com

113 dB sensitivity, impedance is 4 ohm or lower, so can run from a cheap class D amp. You’ll need only a few watts with this one

Only 600lb with 42 drivers... will it fit in a shopping cart?

 

[AdamG]

I was thinking it might be fun to host music nights in my local park. Basic idea, I built two or more really good speakers, large enough for an audience of perhaps 40 people on picnic blankets, then we listen to music for two hours.

The speaker design and layout is another discussion altogether, but I was wondering, realistically, what kind of battery system I would need to do this for, say, two hours.

I am assuming I'd be using relatively high efficiency speakers, probably with active or at least hybrid crossovers. Loud, live level bass is not an objective, I'm not trying to create an all night rave scenario. I am not a bass expert but I assume some kind of bass horn would be the way to go for this system. Amplification would be class d of some kind; I assume some drivecore amps or something like that but minimalism is another goal.

Other than amplification, source would be some kind of digital player and of course dsp.

So, anyone willing to do some back of the envelope calculations to see what wattage and how many watt hours I need?

Why not use a quiet small generator? Use 100 foot extension cords. Battery’s for this will be heavy and maintenance high to haul around and charge up. Just a suggestion. They have small 1400 watt generators that are down to 60db.

 

[kemmler3D]

Why not use a quiet small generator? Use 100 foot extension cords. Battery’s for this will be heavy and maintenance high to haul around and charge up. Just a suggestion. They have small 1400 watt generators that are down to 60db.

Would certainly work, but 1400w is nearly enough for a full DJ setup for 100 people if you're smart about your subs, probably overkill for this.

 

[617]

Why not use a quiet small generator? Use 100 foot extension cords. Battery’s for this will be heavy and maintenance high to haul around and charge up. Just a suggestion. They have small 1400 watt generators that are down to 60db.

I'm not trying to create a PA as much as a very beautiful, easily deployed object which creates very good sound.

I was inspired by a movie night they do at the park, they had a little generator running for a projector and a small PA system. It was quite quiet, but I'm looking for a system I can push down the street on a handtruck and then across some grass. Total distance maybe 200 feet.

 

[617]

Would certainly work, but 1400w is nearly enough for a full DJ setup for 100 people if you're smart about your subs, probably overkill for this.

This is the perspective I need. This is not for dance/rock/reggae/electronic music, this is for pleasant easy listening without disturbing people too much.

Might be nice to listen to a string quartet or a solo piano or a guitar recital in the park while eating a slice of pizza and having a beer. That's the idea - but since I design speakers I am thinking I can achieve a level of fidelity beyond a typical PA. Maybe that's arrogance though; getting wide pattern coverage is not easy.

 

[617]

@Patrick Bateman do you have any recommended unity horn designs for this kind of application? If I want to a directional speaker I think a unity horn would be ideal.

 

[droid2000]

Instead of using batteries, you could just rent a quiet generator and place it 100' from the crowd. You won't hear it over the music and audience chatter.

 

[AdamG]

Instead of using batteries, you could just rent a quiet generator and place it 100' from the crowd. You won't hear it over the music and audience chatter.

Great idea! Look up a few posts.

 

[Doodski]

A generator solves many issues and for convenience it is pretty nice. The thing is operating in a park with a generator on the end of a extension cord is looking for a theft to take place. Somebody may steal that generator.

 

[droid2000]

Great idea! Look up a few posts.

i really need to start reading earlier posts before i put quill to ink

 

[droid2000]

A generator solves many issues and for convenience it is pretty nice. The thing is operating in a park with a generator on the end of a extension cord is looking for a theft to take place. Somebody may steal that generator.

This is where his craft skills come into play after he's done building the custom speakers. Booby trap that SOB and set up a video recorder so we can all watch.

 

[kemmler3D]

A generator solves many issues and for convenience it is pretty nice. The thing is operating in a park with a generator on the end of a extension cord is looking for a theft to take place. Somebody may steal that generator.

So, this actually surprises me, but if you don't actually need high wattage / current, a 100-200w / 100-200Wh battery pack can be cheaper than a 1400w generator these days. And of course, it's silent and exhaust-free... random example: https://egretech.com/products/300w-portable-power-station-plume-300 ... I think a generator may become the better choice once you need more than ~50 watts continuously.

If @617 is building a unity horn and doesn't want the police to break up these events, he'd better not use more than 50w.

 

[voodooless]

Only 600lb with 42 drivers... will it fit in a shopping cart?

Nothing a few caster wheels won’t fix a shopping cart is superfluous

 

[antcollinet]

I guess my question here is how much energy capacity do I need?

I mean for example, I found a parts-express plate amp, it's a great product with a 600W amplifier and a 200W channel with DSP all in one. It even has wireless bluetooth stereo mode. Limiters, PEQ, crossovers, all I need.

So if I get one of these, and want to run it two hours, I would need a 1600Wh power bank. But there's no way it would be running at 800W the whole time.

Does anyone have any idea what the actual power consumption of an amplifier is, playing music?

Well you are playing outside - so no reflections or "contained" sound. A difficult space to fill with sound.

So I suspect you will be playing at the maximum undistorted power you can get from your system. Lets assume your music has 9dB dynamics, and higher peaks your are prepared to distort, then the average power is going to be around 9db down (1/8 power), so around 100W continuous?

This post might contain traces of speculation.

 

[antcollinet]

Have you looked into legal ramifications?

Licensing for public performance.
Permissions from whoever runs the park?
Liability insurance (running electrical - especially if thinking of a generator - kit in a public place)

Etc.

 

[voodooless]

Have you looked into legal ramifications?

Licensing for public performance.
Permissions from whoever runs the park?
Liability insurance (running electrical - especially if thinking of a generator - kit in a public place)

Etc.

You had to spoil it all, didn’t you

 

[antcollinet]

You had to spoil it all, didn’t you

We seemed to be drifting away from "a group of friends taking a boombox to a park and partying"

 

[617]

Have you looked into legal ramifications?

Licensing for public performance.
Permissions from whoever runs the park?
Liability insurance (running electrical - especially if thinking of a generator - kit in a public place)

Etc.

I am the mayor and I can do what I want until they vote me out