Build a mobile sound system for off-grid concerts and dance parties!

This setup uses dual 12" PA speakers.  A hidden below-board 24V battery keeps the handling stable.  The flat-bed trailer design is easy to build, lightweight and durable.  We integrated ~150W amps inside each speaker, but other amp configurations are possible.

Compared to other trailer-based systems this project uses improved layout and components to greatly reduce weight and improve power efficiency without any added cost.   Overall power efficiency is 2x to 5x better than alternative setups.  Total trailer weight as shown is about 95 lbs, compared to a traditional car-battery-powered setup at 150 - 200 lbs.

This project is brought to you by MonkeyLectric and the Monkey Light bike light

Step 1: What you need

  • Bike trailer.  Not all trailers may be suitable, check the next step.
  • 1/2" Plywood (2' x 3' piece or so)
  • 2 x 12V, around 15Ah sealed-lead-acid (SLA) batteries (see below)
  • 24V battery charger (see below)
  • 24V amplified speakers (see below)
  • 3.5mm audio cables and Y cable
  • Small stereo mixer (see below)
  • mp3 player
  • mp3 player holder
  • lots of 1/4" bolts, spacers and washers
  • 15' of 16 gauge wire
  • electrical crimp connectors (home improvement and auto parts stores have these)
  • 10A circuit breaker


see next step.


I'm using 2 x 12V, 18Ah capacity SLA rechargeable batteries (also known as "sealed lead acid" or "gel cell").  Together this is about 1/2 the weight of a car battery and it powers my setup for 8 hours at full volume.  Reducing the sound volume just a little it will last much longer.  You can use bigger or smaller batteries depending on how long you need to run for.  SLA rechargeable batteries are very inexpensive and come in lots of sizes.  You can get new ones like mine for $35 each - try batterymart.com or batterywholesale.com or amazon.com.  You're looking for "12V SLA battery" or "Sealed Lead Acid battery".  This type of battery is often found at recycle centers in good condition, so you can get them for free that way - look for discarded computer back-up power systems.  You can use a lithium battery for even less weight, but it will cost around $400 for the same capacity.


These are mass produced for 24V scooters so they are only about $15.  Amazon.com has lots of them like this one, just search for "24v scooter charger".  A 2A charger is perfect here.


Using amplifiers that run directly from your battery (without an inverter) makes your setup a lot more efficient.  I have instructions on how to build battery-powered amplified speakers here.  We sell those same speakers fully assembled at MonkeyLectric.


parts-express.com and amazon.com have all the ones you need.


To get full volume from the setup you need a small powered stereo mixer.  The mixer will also let you plug in a microphone and additional sound sources so its convenient.  I used a Rolls MX51S, you can get this from parts-express.com or amazon.com, it does the job for about $55.  There are some other brands with similar models.

<p>Just get PA speakers with built in batteries, that's what I did, they're smaller than the huge ones shown here and they're 500w RMS each. I don't understand why you chose to power 12&quot; speakers with 150w amps. Mine also weigh half as much and can be properly mounted to the trailer bed, instead of lashed on with nylon webbing. Really, why are people still linking to this article.</p>
<p>Hi, <br>I've used these instructions to build several sound systems (Thanks Dan!). Here's my response to your concerns:</p><p>PA systems with built in batteries: Usually these systems don't give you much battery life, with form factor and weight being a higher priority. My first system will run for about 20-30 hours at full volume. I like that.</p><p>12&quot; speakers with 150w amps: The amp boards recommended here are very efficient, producing very little heat. Even 40-80 watts (which is what a tk2050 amp outputs to an 8Ohm speaker) gives you a lot of volume and good bass. Many systems advertise high wattage but much of that is wasted as heat. Also a larger speaker uses less energy than a smaller speaker to produce the same volume of sound (a little counterintuitive, but true). And, if you really want, you can get a 600watt amp board that is still similarly efficient.<br><br>Proper mounting: PA speakers also have proper mounting solutions, some people just choose to lash them with webbing.</p><p>Basically, if you could hear one of my systems, or any other one built in a similar way to this instructable, and listen to it play for tens of hours at a time I think you may change your mind.</p>
<p>Roy: I am a brand new newbie to this...and not electronic savvy. I just need to build a system for horse shows...to run off of the 12 volt system with wireless mic and aux. to a cd player. Any play-by-play instructions, or maybe a commercial unit that has good sound??? Thanks</p><p>Ron </p>
<p>Can you post a link to instructions for your system?</p>
<p>Where do you get a Tricycle like that.</p><p>I want one! Sooooo Cute.</p>
This is very cool. How long does the charge hold? It could be easily used for small gigs.
great but it could be greener if themps were powered by the bike (and the biker &hellip;)<br><br>LOL !&hellip;
who cares if its &quot;green&quot;
It was only a joke &hellip;<br>sorry
Don't apologize for caring about your future.
nah it all kool
Anybody who wants the planet to remain habitable.
Do u juse a car battery for powering it all?
Where can i get the barrel jack you used to power the speaker?
digikey, mouser, etc. search for &quot;binding post&quot;. the audio input is just a standard 3-foot male-to-female audio cable, with the female end glued into a hole in the black plate.
So cool, really like it. I have never heard this kinds of bike. amazing!!!!!
Bike Dj :) cool
i think u can add an alternator to charge the battery but great idea
cool man ... real coooooooooooooolllll.
Daaay -- ummmm! <br> <br>Get many &quot;Disturbing the Peace&quot; citations?
A cheap alternative to a Scraper that still looks BAYTASTIC. Love it!
cool me and my homie wanted to make one of these.
My friend and I were thinking about doing something just like this over the winter! This points out stuff we hadn't even thought about yet, great Instructable!

About This Instructable


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Bio: Dan Goldwater is a co-founder of Instructables. Currently he operates MonkeyLectric where he develops revolutionary bike lighting products. He also writes a DIY column for ... More »
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