Calculating power needs for remote audio installation

[617]

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?

 

[Doodski]

what kind of battery system

It is very inefficient to use a battery for powering 120 V AC equipment. Especially with the power requirements that you have. Better to buy a car amp and run it off a battery that does not leak, does not spill acid, is compact and no dangerous hydrogen off-gassing.

 

[robwpdx]

The current version of the Mackie SRM450 uses 160W AC so 2x for 2. The 15" Thump sub is 76W AC (52 pounds). Your mixer/playback gear will use maybe 10W.

Battery > inverter > sound system.

Your sound system uses about 410 Watts @120VAC, with a 90% efficient pure sine wave inverter, you will need about 460 Watt hours per hour of operation.

That is within the capability of the medium size LiFePO4 "solar power packs" made by Goal Zero, Bluetti, Ecoflow etc. They will have a Watt hours Wh, and an inverter capability in W. You can throw a solar panel on them and charge them up in the day, or plug them into 120V AC to charge them.

 

[Doodski]

The current version of the Mackie SRM450 uses 160W AC so 2x for 2. The 15" Thump sub is 76W AC (52 pounds). Your mixer/playback gear will use maybe 10W.

Battery > inverter > sound system.

Your sound system uses about 410 Watts @120VAC, with a 90% efficient pure sine wave inverter, you will need about 460 Watt hours per hour of operation.

That is within the capability of the medium size "solar power packs" made by Goal Zero, Bluetti, Ecoflow etc. They will have a Watt hours Wh, and an inverter capability in W. You can throw a solar panel on them and charge them up in the day, or plug them into 120V AC to charge them.

Nice stuff. What kind of battery/brand and model do you think is suitable? Preferably a gel cell at a minimum or a lithium core instead of SLA battery. SLAs are so stupidly explosive in confined spaces.

 

[617]

The current version of the Mackie SRM450 uses 160W AC so 2x for 2. The 15" Thump sub is 76W AC (52 pounds). Your mixer/playback gear will use maybe 10W.

Battery > inverter > sound system.

Your sound system uses about 410 Watts @120VAC, with a 90% efficient pure sine wave inverter, you will need about 460 Watt hours per hour of operation.

That is within the capability of the medium size LiFePO4 "solar power packs" made by Goal Zero, Bluetti, Ecoflow etc. They will have a Watt hours Wh, and an inverter capability in W. You can throw a solar panel on them and charge them up in the day, or plug them into 120V AC to charge them.

This is what I'm thinking. I'm not engineering a battery solution, I want a power bank I can charge at home and then plug into.

I hadn't considered mobile audio solutions, I guess they have a lot of dsp functionality built in.

 

[robwpdx]

Nice stuff. What kind of battery/brand and model do you think is suitable? Preferably a gel cell at a minimum or a lithium core instead of SLA battery. SLAs are so stupidly explosive in confined spaces.

Lithium ion are the lightest. But Lithium ion batteries can catch on fire and you can't put them out easily.

Slightly heavier and slightly more expensive, and for portable applications taking over LiFePO4 "Lithium iron phosphate" - they are my recommendation. There are 2 constructions: cylindrical cells and prismatic cells. The cylindrical cells are more resistant to swelling but heavier.

They are all made in China. Many have US or European warehouses and warranty support. I would look at the warranty and fine print. For this application you are not an industrial user stressing them. If you are charging them below 32F they need an automatic heater.

A 100AH 12v, so 1200Wh LifePO4 battery weighs about 35 pounds. The premium brands are Victron and Battle Born.

In China on the manufacturing lines for cells, they get a range of quality. They sort the calls by quality. The best Grade A cells go into the most expensive batteries. You need 4 cells in series to get 12v. So a finished battery will have a combination of series and parallel cells. The lesser calls are matched in groups and go into lesser quality batteries on down to the fraudulent batteries.

Will Prowse has a youtube channel on batteries and does battery teardowns https://www.youtube.com/@WillProwse He has a shop mobile-solarpower.com for DIY rating DIY batteries and there is a DIY solar forum. Inverters-r-us is anther shop. Sure there are many more similar resources.

 

[Doodski]

Jackery Explorer 500 Portable Power Station - Jackery CA

Jackery Explorer 500 Portable Power Station, featuring a 518Wh battery and a pure sine wave inverter, is the most portable and lightest power station available. With an MPPT charge controller, lightweight design, and compact size, the power station is ideal for charging home appliances like...

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Fort 1000 1120Wh LiFePO4 Portable Power Station

BougeRV Fort 1000 1100WH Lifepo4 Portable Power Station allows you to power your electronic devices on the go. It is equipped with a lithium iron phosphate (LiFePO4) battery, which is known for its high energy density, long lifespan, and safety.

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Jackery Explorer 1000 Portable Power Station - Jackery CA

Equipped with a 1002Wh battery capacity and multiple ports, Jackery Explorer 1000 Portable Power Station is one of the most powerful power stations. The built-in MPPT charge controller ensures efficient and stable solar charging to power CPAP machines, electric grills, computers, cameras, and...

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[robwpdx]

This is what I'm thinking. I'm not engineering a battery solution, I want a power bank I can charge at home and then plug into.

I hadn't considered mobile audio solutions, I guess they have a lot of dsp functionality built in.

What is your intent with the DSP?

 

[617]

What is your intent with the DSP?

My assumption is that for peak efficiency, a passive crossover would be best avoided.

I'm actually thinking a mono speaker might be the most elegant. I can design a very sculptural mono speaker and people can sit around it.

 

[robwpdx]

My assumption is that for peak efficiency, a passive crossover would be best avoided.

I'm actually thinking a mono speaker might be the most elegant. I can design a very sculptural mono speaker and people can sit around it.

I suggest active speakers, and the ones above are all active. If you want a general purpose DSP with a user interface, I suggest the DBX Driverack PA2. It has EQ, it will so auto EQ with an analog measurement mic, and it has a compressor.

The PA2 has your line level sub crossover - that would be good for your use case.

It has an iPad app, I would recommend, then you might need a WiFi access point. The PA2 is 22W and your access point would probably be about 5W.

There are many YouTubes on the PA2.

I would try out the speakers outside without the sub, then add the sub if you need it. I have heard these speakers outside for years, they really fill a space. The PA2 is useful outside too, though I would get a little rack case for it.

If you already built your speakers and can haul them, you can add some class-d plate amps, and some may have a sub out. Hypex and dozens of others make plate amps. The Mackies have a molded plastic shell, so lighter, are a bit more weather resistant, have handles, service, have good resale value, and can be brought used. I have also used the JBL EON15 II which is equivalent. I don't know the current JBL EON line.

BTW, many of the power pack companies are in their July 4/Summer sale period, some on Prime Day, sales may repeat Labor Day, Black Friday, Memorial Day, etc.

 

[Biblob]

Maybe something like this could be of use?
Portable power stations: Powerstation from Anker

This is just one, they have more solutions, depending on the power requirements etc.

 

[617]

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?

 

[Doodski]

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

In could be active speakers with the amp internal or separates. Perhaps email the maker of the active speakers or amp and speakers that you want to get and see what they advise you of as per actual current draw at idle and at music playback levels.

 

[617]

In could be active speakers with the amp internal or separates. Perhaps email the maker of the active speakers or amp and speakers that you want to get and see what they advise you of as per actual current draw at idle and at music playback levels.

I'll be building the speakers. That's most of the fun.

 

[Doodski]

I'll be building the speakers. That's most of the fun.

For a woodworker this will be a cool project. Perhaps make it with 2 wheels and a handle so you can wheel it out to location like it's a hand truck. After you make the speakers you can operate the amp with the speaker and find the power requirements for the listening levels you need. Then apply those to the power supply sizing and voila you have your size of the power supply figured out. Those power supplies can get expensive so sizing is critical.

 

[voodooless]

Since speaker efficiency will be the largest contributor to power usage, I would actually start there. 3dB more efficiency will have your power needs.

Efficient speakers are general large though.. so not ideal for mobile usage. So possibly a larger battery pack may be more economical after all.

You may raise efficiency by expanding horns with movable panels… just an idea.

 

[617]

Since speaker efficiency will be the largest contributor to power usage, I would actually start there. 3dB more efficiency will have your power needs.

Efficient speakers are general large though.. so not ideal for mobile usage. So possibly a larger battery pack may be more economical after all.

You may raise efficiency by expanding horns with movable panels… just an idea.

Great idea. I'm thinking a mono installation would be best, so maybe something less than 2m tall I can move with a hand truck. The bulk of that could be a small horn loaded sub, then some kind of omni array on top.

 

[voodooless]

For a sub, I’d recommend a tapped horn. These may be easy to make: https://www.martinsson.cc/blog/static.php?page=static140228-173656

 

[617]

For a sub, I’d recommend a tapped horn. These may be easy to make: https://www.martinsson.cc/blog/static.php?page=static140228-173656

A small horn sub is definitely what I'm favoring. The bill fitzmaurice designs are what I'm familiar so thanks for showing me these alternatives.

 

[Waxx]

Look at the 12V soundsystem scene. They build mobile party systems running from car batteries on lorry's or bikes or similar chariots.

This is one of a friend of me, FLPSTRT named and roaming arround in Puurs (Belgium) with reggae and dub. That name has a meaning, but hard to explain. He can play 6-8 hours on 1 car battery, and this goes loud and low. Enough to give small parties. They use regular high sensitive pa drivers and car amps/dsp's running from 12 volt, and in this case modify the technics pickup and dub preamp psu to run from 12 also.