Green Outdoor Sound




Introduction: Green Outdoor Sound

About: Industrial Arts, Appalachian State University. Recession has dried up my field (commercial printing & packaging), but have found new work in staging, lighting, sound systems, sets, productions and events.

As many Instructables members, I have sometimes been hard-pressed to find useful, practical applications for my inventions, designs, and refinements.

So... combining my homemade portable wind generator, and homemade portable sun tracking solar panel, I hit upon the idea of an outdoor sound system that would be powered by them. After two years of field tests, incremental developments, and triaI and error, I finally have a system that is proven to be a real crowd pleaser.

Prowling the flea markets and yard sales, I was able to scrounge, repair, modify, and piece a viable sound system together. The speakers were fitted with sturdy carrying handles, as well as screw mount bases to solidly fit onto modified camera tripods. Old ghetto blasters were repaired and refitted to function as 12VDC high wattage A-B class audio field amplifiers. Aged-out deep-cycle lead acid batteries, from my light electric vehicle, were more than welcome to the new system, where they were amp/load tested and given a revised lowered Amp-Hour designation, and then fitted with sturdy carrying handles.

"Use it up...
Wear it out...
Make it do...
Do without."

-- A wise saying from one of my mother's sampler-stitched pillows

In an effort to do a startup on the cheap, I set up a free webspace on my EarthLink account:

But it's obvious that it's so long-winded and convoluted that it's unreasonable to expect anyone to not make a typo and actually be able to land on the webspace. But a friend of a friend set me up with a free: domain which really simplifies everything for everyone. And, especially for commercial purposes, I highly recommend this approach.

Green Outdoor Sound is a unique, lean-and-mean, portable high-performance outdoor sound system that can be transported, and even packed, into any remote location. Completely independent of the power grid and gas generators, it can provide clear, full volume outdoor sound for up to 750 people.

And, as the world enters that murky and uncertain energy-poor future, it's so obvious that we'll all still sing and dance. Right?

Composed of 17 stand-alone speakers, wired and wireless, the system is arranged throughout and around the outdoor audience. And while none of its 12 wireless speakers exceed 20 watts RMS each, the sound is seamlessly spread evenly over the entire listening area, without distortion, and fine-tuned to proper audio levels everywhere. All speakers are mounted on tripods, and carefully adjusted to ear level, for maximum effect.

Everything is powered by 12 Volt pre-charged battery packs, plus a small portable 12VDC wind-powered generator, plus a 12VDC portable sun tracking solar panel plus two more 12VDC stationary solar panels. You may have noted that the current draw of the sound system clearly exceeds the recharging capacity of the existing wind generator and solar panels, but I'm now playing catch-up in that area and will soon build a portable, 12 Volt 120 watt sun tracking solar panel.

For performing artists, I usually flank them with two wired speakers, 60 watts RMS each, so that they can "feel" the sound in a quite natural way, as well as those in the audience who desire to be near the stage for the full-volume effect. Two more wired speakers, 30 watts RMS each, are also set up and positioned as needed. We also have 12VDC-to-120VAC capability, for those who prefer to use their own sound mixers.

I also have a 12VDC portable 14 watt RMS lectern, with microphone, which is also wired into the overall sound system.

The system is quite unorthodox, even for a green operation:

After designing and building the portable wind generator and portable sun tracking solar panel, I was not really surprised at the relatively meager amount of renewable power that man can extract from nature. With this in mind, I set out to find something useful that this green power could do. And with existing wireless technology, the idea of green outdoor sound seemed to show great promise. Sound evaporates outdoors. And the traditional setup of large, high wattage audio speakers, on the stage, sends sound outward to the crowd, as well as upward into the atmosphere: Those near the stage drown in sound. Those farthest away from the stage experience low volume. And sound propagates to nearby areas, disturbing others with unwanted sound. But the system, of 17 separate, widely scattered speakers, provides full volume and clear sound to everyone, while neighboring groups and parties hear nothing. And I found a way to do this with a total combined power output of 292 watts RMS. Although radical for outdoor sound this very concept has been well-known, and practiced, by indoor/office acoustics experts for decades.

Effective service area of the outdoor sound system:

With the wireless system, maximum range (transmitter-to-speaker) is as follows:
Remote rural areas, free of power lines: 150 foot radius = 213x213 foot square
Urban parks and backyards: 100 foot radius = 142x142 foot square
Urban block parties, with power lines: 50 foot radius = 71x71 foot square
And note that the 900 MHz transmitter, on its 6 foot mast, would have to be positioned in the middle of the audience to achieve effective sound over those maximum areas. Also keep in mind that, for performing artists, the effective area reduces to about a 100x100 foot square, with a high-density arrangement of our speakers, to deliver clean, strong sound.
For outdoor festivals, rallies, or picnics, where the sound system is used simply for public address or background music, the maximum areas, noted above, can be serviced, with background noises less of an issue.

Maximum size crowd the outdoor sound system can handle:

Up to about 750 people, with clear sound, to my standards. Although far more than that number could be squeezed into the area serviced by the speakers, large crowds do absorb sound, not to mention the natural conversations and chatter our sound system would be expected to overcome. Setting all of the speakers on individual tripods, and carefully adjusting them to ear level, I make every effort to provide quality sound, whether the crowd is standing, sitting, or laying on picnic blankets.

Dealing with overcast days, and with no wind:

In the San Francisco Bay Area, such conditions are to be expected. That's why all of the batteries, and battery packs, arrive on location, fully charged, and ready to perform (our local power grid is 80% geothermal). And, even if disfunctional in such a setting, the green devices never cease to generate curiosity and excitement.

Battery capacity of the outdoor sound system:

I can operate for 7 to 9 continuous hours, per day, depending on the over-all sound volume. During the day, the batteries are constantly rotated back and forth to the portable solar panels and wind generator, but neither are actually required for a one day event, as all of the batteries will arrive fully charged and ready to function.

Performing artists, such as a dance troupe, usually provide their own soundtracks, to broadcast over the sound system:

In an effort to handle anything that comes my way, the equipment is on hand for, and can routinely handle: mp3 digital files, music CD's, and audio cassettes. But note that if an audio cassette is supplied, it is required that the soundtracks must be in the same order as the dance performances.

Live musicians will also need to plug into the sound system:

I have a basic 12VDC 6-channel sound mixer, solely for performing artists. The sound is then ported over to the master 9VDC 4-channel sound mixer via a highly directional 5.8 GHz wireless system (or just simply hard-wired). But I can also provide portable 120VAC power (non-sinusoidal: modified sine wave output) to a musician's own multi-channel sound mixer (these usually run on 20 watts or less), as most musicians naturally feel more comfortable with their own tried-and-proven audio equipment. If the sound mixer(s) is hard-wired to the main amplifier, be sure to connect both with a ground wire.

Green outdoor lighting:

I have two 180-LED flood lamps, each being the equivalent to a 250 Watt quartz halogen lamp, mounted on top of 7-foot tall tripods, for stage and area lighting. But their relatively low-angle glare, even when diffused, may be a concern for performing artists in certain situations. Being entirely portable, conventional tall, high-angle stagelight scaffolding and sandbags are out of the question.

Getting permission to set up the wind generator and sound system in regional, state, and municipal parks:

In such cases, I will always contact the appropriate authorities and get their okay first. It's great, of course, if the organizer of the event has already done the homework on this, but I will always contact them anyway, and explain and verify everything with the park staff before proceeding to the planning process. Most wind generators are large, noisy, scarey, not truly portable, and certainly not at all appropriate in a park environment. But mine is small, cute, and whisper-quiet. As for the park noise ordinances, they are strictly worded to always give the park staff the upper hand in enforcing undesirable sound violations. But spot checks by the park staff, after I set up, always convinces them that the sound system is completely contained within the designated area and no unwanted sound propagates to nearby areas.

Obtaining a license, to play soundtracks and provide sound for live performing artists, in public places:

Most of the Instructables readers of this article, more than likely, have an outdoor sound system that is probably too small to get noticed, busted, and fined. And, while virtually all soundtracks are copyright protected and as such any unauthorized, amplified playing in a public place (that is, outside of your home) is prohibited, even though you legally purchased every soundtrack. But the spirit of the law allows us small guys to freely operate, almost anywhere, without a license, under most conditions. Read on.

Most of the places where one would set up and operate an amateur/semi-professional outdoor sound system, such as public and private parks, wineries, schools, festivals, etc., already have what is known as a "Blanket License" to play amplified copyrighted music and soundtracks, which would, naturally, also cover your operation. Just be careful not to sign a liability contract, for those locations, that contains statements that may hold you responsible for any copyright arrangements.

As far as setting up for backyard and block parties, or street festivals, you're still okay to go, as long as you're not the main organizer, selling tickets to the event.

A good start is to contact one of these three performing artists copyright licensing organizations:

ASCAP (The American Society of Composers, Authors and Publishers):
1-800-505-4052 (toll free), or visit their website at:

BMI (Broadcast Music, Inc.):


Even if your operation eventually grows to the point of needing a license, the process is simple, and not as expensive as you'd think. You would probably want to simply opt to purchase a "Blanket License", since you'll more than likely need to play an array of music to entertain the crowds. A performing rights organization, from the list above, will then allow you to play any of the songs in their vast catalog. They'll get back to you, probably with a few questions, and set up a license fee, tailored specifically for your operation.

In fact, I received a phone call from SESAC, who was very helpful about explaining, in simple terms, the ins and outs of the licensing process. And although my outdoor sound system was, in their opinion, small potatoes and not worth worrying about getting a license, we had a long conversation about my green outdoor sound system, as they are always keen to keeping up with new technology, for the benefit of their performing artists membership.

All of the batteries for the portable equipment are rechargeable:

The batteries range from heavy, powerful rechargeable deep cycle 12V lead-acid batteries, down to rechargeable 1.25V AAA and 8.4V transister radio nickel-metal hydride batteries. They arrive on location precharged, with an ample supply of precharged backup batteries. And I have the on-site capacity to recharge any and all sizes, and types.

Dealing with radio interference with wireless sound system:

Carefully selecting and fine-tuning to a radio frequency, that is relatively clean and free of unwanted radio signals, is a routine part of the setup process. Based on my experience, I have settled on the 900 MHz (low-end microwave) frequency simply because it is not used much any more and there is much less radio traffic there to deal with. I also use a substantial 900 MHz main transmitter, powered by a 18VDC power source, plus a high-gain antenna, and mounted on a 6 foot tall tripod, which will drown out any stray 900 MHz radio signals that might happen to appear in the area of operation.The monophonic sound is also transmitted via a left and a right stereophonic transmission (= 2 frequencies) which naturally reduces any effect of an unlikely radio interference by 50%. And it's not uncommon to have to deal with nearby power lines, with their characteristic low-end 60 Hz RF interference, which does reduce the effective range of the 900 MHz system. With the wireless system, 60 Hz RF interference from nearby power lines reduces the maximum range (transmitter-to-speaker) to these conditions and ranges:
Remote rural areas, free of power lines: 150 foot radius = 213x213 foot square effective area
Urban parks and backyards: 100 foot radius = 142x142 foot square effective area
Urban block parties, with power lines: 50 foot radius = 71x71 foot square effective area
But the exceptionally effective 900 MHz transmitter is routinely expected to drown out such 60 Hz RF interference within those ranges. And note that the 900 MHz transmitter, on its 6 foot mast, would have to be positioned in the middle of the audience to achieve clear sound over those maximum areas. In the unlikely event of a total 900 MHz drown-out (has never happened), I would simply use the highly directional 5.8 GHz wireless system to connect the three wired sound amplifiers, with five wired speakers, on opposite sides of the audience. Although 65% (12 speakers) of the total sound system wattage is wireless, and 35% (5 speakers) is hard-wired, a hard-wired + 5.8 GHz mode would perform satisfactorily.

The entire sound system can even be transported to a remote wilderness meadow, as long as the trail is graded and well maintained:

In the equipment inventory, I have two lightweight fold-up pushcarts (75 pounds capacity, each) with 20" pneumatic tires, two backpacks (50 pounds capacity, each) with self-standing frames, as well as one lightweight fold-up hand truck (40 pounds capacity). In such situations, I do require accurate GPS coordinates, a name and detailed description of the area, as well as in who's jurisdiction the event will take place. Also note that about 8 to 16 man-hours would be required to transport the equipment to and from such an event, over just a short one-mile trail, so an overnight bivouac at the location may be required.

Signage: Green Outdoor Sound can also produce full color posters for an event:

With my graphics background, I can quickly design and print up 13 inch x 19 inch full-color posters. I can take an event organizer's BMP, JPEG, or lettersize PDF or Microsoft Word file (or any type of file, actually) and scale it up for a clean, full-size poster printout. My inkjet printers are unique in that they can also routinely print rigid poster board, up to 12pt (.012") thick, without bending it.

I have two hard-working 13x19 deskjet printers that will quickly produce the posters, on time. And I refill our inkjet cartridges, on location.


For those who want to go into more depth, for a light and portable outdoor sound system, I highly recommend checking out another Instructables article, as this cat brings up some interesting points and ideas:

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    6 years ago on Introduction

    Did you really intend to say: Acoustic Shells?

    Acoustic sound panels absorb sound, while acoustic shells, as a backdrop, reflect sound outward to the crowd/audience.

    Acoustic shells are definitely green and ecological, as I've seen them, alone, and without electrical amplification, adequately project sound from a chamber orchestra outward to a large outdoor audience.

    But they have to be hard and rigid to work properly, and also quite large, which makes them not exactly portable.

    But you've definitely got me thinking about this.