Off-Grid Party Sound Systems

Whether its for a mobile bike party or a solar powered concert, a 12V or 24V sound system is the key.  I recently built several systems for mobile bike parties and this article has a pile of details.  You can also check my Easy Bike Party Sound System project if you want a simpler and smaller system and my Bike Party Sound Trailer for specific tips on a trailer design.  If you want to just purchase finished speakers built according to the principles of this guide, we sell them at MonkeyLectric.

This article covers:

• A simple but efficient setup where you just pick the right parts and plug it together
• A true Active 12V speaker - an ultra-efficient speaker with integrated 12V or 24V internal amp.
• Choosing efficient speakers and amps
• Choosing a battery
• Weatherproofing and vibration proofing

The goal of this project is to achieve sound levels needed for off-grid dance parties while reducing weight and power use.  Compared to common setups, we achieved power reduction of 50-80% and weight reduction of 20-40% with equivalent sound output.

My friend Deep runs Flashdance, and we used his system as a reference point to compare our work against.  Deep has an amazing tricycle setup that lets him bring the party wherever he goes.  San Francisco has rather notorious hills though, so our goal was to see if we could cut the weight of his setup without sacrificing any of the sound.  A big key to cutting the weight is to see if we can use something much smaller than a car battery - and that means being more efficient about power use.

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This project is brought to you by MonkeyLectric and the Monkey Light bike light
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Step 1: A word about Efficiency

The key to any battery-powered sound system is efficiency.  Home and car sound gear is not designed to be efficient or light - it just isn't a concern in those applications.  Low efficiency means you need lots of power to make the same amount of sound, and lots of power means a big heavy amp, a big heavy car battery, and maybe a big heavy inverter too.  An efficient speaker can produce 5x the volume from the same amount of power.  An efficient amplifier is 2x better than a standard one, plus its far smaller and lighter.  Together this means that with a bit of attention paid to your component choices, you'll get way more output for the same amount of power.

Lets take a look at Deep's current system.  He's got:

• 2 nice Yamaha powered speakers (they have a built-in amplifier)
• An inverter because the Yamaha's need 120V
• A car battery

Another option I see some people using goes like this:

• 2 big auto-sound speakers
• a big auto amplifier
• a car battery

Either way there is a lot of inefficiency.  Using 120V powered speakers, the amp inside the speakers is moderately efficient (not the best, not the worst).  we lose a good chunk of efficiency because of the inverter.

With auto-sound gear, you don't need an inverter but the problem is that it all the parts have very poor efficiency.  I think this is due to marketing forces at work - the folks selling you this stuff learned that if the amp and speakers are bigger and have higher watt ratings, they make more money selling them.  but, those high watt ratings are only needed because the gear is so inefficient.

Comments

[liquidflorian]

Sorry to necropost, but is their a way to have the portable sound system run off of a power supply and charge the battery at the same time?

[SunShine.1111]

Hey, did you ever get an answer to your question? I'm wondering the same thing...

[mat_scientist]

This system worked perfectly with an ipod as a source but when I tried playing music from my laptop, I got a very disturbing hissing noise. I suspect a grounding problem but I have no clue about how the ground my 24V Sla battery to my aluminium mac... any idea?

[panasuiks]

I'm running into the same mental block that tamadoctor did. Both the woofer and the horn in the B212XL's are rated at 8 ohms. If we use the TK2050 as an integrated amplifier, won't both the woofer and the horn only receive 40w-60w of power? Hopefully I'm just missing something...

[fernandonh]

Would you have any additional instructions on the process of connecting the battery to the amp? I purchased the speaker, monoxover and the TK2050 and I will be installing the crossover before the amp as you instructed. I am just a bit lost on connecting the batter to the amp.

Thank you so much!

[fernandonh]

I found an used active Behringer B212a and I wonder if I can do the same project on that one. Do you think I can use the amp that is already inside the B212a plus the MonoXover?

[chriscab]

Thanks for the great instructions, Dan! Last night I debuted my setup with a TA2020, 12v/8Ah SLA & Gemini RS-308, created from your wonderful instructables, at the SF Bike Party and it was definitely a success. Got some great comments from people who were impressed with the sound coming from such a compact package. No trailer or car batteries for me, everything was mounted on my rear rack. I'll post pics later. Now with this portable powerhouse, tailgating and bbq picnics will be even more of a party!

So of course, I've now gotten the bug on wanting to get louder and cleaner. I'd like to upgrade to the TK2050 with the monoXover and another SLA. My question is: To get full power from the amp with 24V, I'd still need a pre-amp to boost the signal going to the amp, correct? And if so, should it go between the source/MP3 player & x-over, or x-over & amp?

[kristoballa07]

Chriscab, did you ever get any advice on this question? I am doing a similar set-up and am also wondering where the pre-amp/mixer should go.

[sweber1]

Thumbs up to Dan and a little update from denmark.
Last summer me and my friends stumbled across this tutorial - and i just wanted to share our result with all of you, and Dan. This project was completed in a couple of months, we are now building a high efficient woofer to go with the system.

We went with a couple of behringer b212xl speakers - they were available used for a cheap price and have a fairly high efficiency . Installed the monkey electronics filter and a sure electronics 2x150w amp in each speaker as covered in this tutorial.
The DJ case consist of a welded steel frame as we wanted to fill this baby with acid-fluid power (read: car batteries). It can contain 7 batteries, delivering about 400Ah at 12v. We've installed a 17" inch tft monitor, which ran native 12v input through an expensive dc-dc converter to output precise 12v as the monitor needed. A computer on 12v from fitpc (in retrospective it's too slow for DJ apps - but great for winamp.. Actually an ipod would have been sufficient). We also found a nice 3 channel 12v mixer to put in.

The system can run approx 10 hours on 3 car batteries on 80% volume.

Iv'e learned that noise in this ungrounded system can be a bitch. The dc-dc converter made so much noise along with the tft that we needed to put it on seperate batteries to reduce the noise transmission from them. Also using a trafo between speaker and mixer helped a lot. And of course shielded cables.

We held a nice party for around 150 people as you can see in the images.

cheers

[dofnicom]

Could you take this concept and create a rechargeable wireless speaker by mounting a battery in the speaker and adding a UHF Wireless Mic Receiver to the equation like a Nady DKW-8U. I am a DJ and sometimes I need remote fill speakers in weird places. A self contained powered wireless speaker would be nice. 8" or 10" with the 100Watt amp and wireless receiver. The receiver is DC14V 0.4A.

[fatdumpa]

great article. very comprehensive. iv had this hi-fi speaker lying around for ages, using it to put drinks on. so i think il have a stab a powered mono speaker, maybe with one of these cheepies, (any good?)

http://www.ebay.com.au/itm/230608706091?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_3755wt_907

and one of those

http://store.monkeylectric.com/ProductDetails.asp?ProductCode=XOVER1

both mounted in the box, and a 12 volt battery yet to be acquired.
any of you experts know what kind of volumes i can expect from this kind of set up?
the speaker isn't massive i know, but it's a convenient size, and i can always swap it out for a bigger one.

[jeisenkramer]

What do you think...a car battery with an inverter, a powered PA speaker with the two amps pushing out 200w total and two guitar amps - a 30 watt and a 60 watt. How long would this last us? This will be on the back of a pickup truck.

Any feedback would be huge.

[ivica12]

Hi!

I am new to this so I have a couple of questions. Would it be a problem to connect 4 ohm speakers? I'm looking at these specifically http://www.thomann.de/gb/peavey_pro12_messengerserie.htm

Also, these seem cheap and have a big SPL, however the brand is unknown (and obviously being much cheaper than others I am a bit worried about the quality) http://www.thomann.de/at/the_box_pa15eco_mkii.htm

Thanks for the help!!

[n0ukf]

Most amps have a range of acceptable impedance they can drive (like 4-16, read your amp's specs). If your amp only goes down to 8 ohms output and you can use two speakers per channel, you connect the two 4 ohm speakers in series. If 4ohms is the maximum output impedance and you have two 8 ohm speakers, connect them in parallel.

[imBobertRobert]

lol i thought that it was a wheel chair connected to a bike with speakers on it. IDEA! the sound-chair!

[macwhiz]

Thanks for the idea! Time to go wheelchair hunting! Maybe electric?

[dfuller11]

I have obtained 2 SLA batteries (from computer back-up systems). They are marked "Cycle Use" 14.5-14.9V ("Standby use" 13.6-13.8V).
They are hardwired w/ a nylon plug with three terminals (marked "+"," -", and "S" (ground?)).

Anyhow, I have been unable to get them to take a charge from the 12V charger I have. Perhaps I need a more powerful charger? How should I treat the "S" terminal? (see photos).

Many thanks.

[Elorrum]

Lepai makes a small 2.1 amp, probably ta2020? that I used with 8AA batteries, 2" 4ohm speakers mounted in PVC 3" pipes, a DVC subwoofer built into a plastic bucket lined with batting. great near field, and loud enough for shouts from 50 yrds to "turn it up" but not loud enough to do so. Working with a sure 100W 24v amp with line arrays in composite fence posts as next project.

[slaterbsb]

Hello!

This is amazing!

I'm currently pricing a system, and had a couple questions:

If I have a pair of B212XL or B215XL should I have a single DTA-100a or will I need one for each speaker?

[chriscab]

With this setup of 24V, TK2050, and a mixer/preamp, what should be the current rating of the switch and fuse?

[swilliams10]

One thing that you probably all ready know, but I'll say for anyone else who's considering this is, when choosing drivers to build your own speaker, you can't just choose whichever one that you like best, or have good specs, efficiency, etc, because, for example, if you choose a woofer that's not very efficient(lets say 85 db 1w/1m), and then a tweeter that has a very high efficiency(lets go with 100 db 1w/1m), there, you have a problem, and the high frequencies will be a lot louder than the lower frequencies. Another thing you have to consider when choosing drivers is their frequency ranges. Yes, the ranges given aren't the exact range of a driver, most drivers can play beyond the stated frequency range, but the stated frequency range is usually within a +/- 3db or so range, so any frequencies beyond that will be much quieter. If you choose a woofer that has usable extension up to 2000 hz, and then a tweeter that only extends down to about 4000 hz, you will have a large dip in the spl that is most noticeable around 3000 hz and such. Long story short, there's a lot more in choosing a driver than just finding drivers that look nice and that you like. For more detailed stuff, look at the speaker building bible on the parts express tech talk forum.

[netrunner]

For the older "SURE electronics" 2x100W @4ohm KT2050, its R18 and R33 to modifie. 6,8Kohm can be added in parallel.

That is 1 resistor lower then in the picture. Can be a mistake in picture.

http://www.sure-electronics.net/download/AA-AB010_Ver1.0_EN.pdf

[weener]

Hi there. I followed this great guide with great results! ... I've gotten myself a really hardcore off-grid party sound system - just what i was looking for. This tutorial is one of a kind.

BUT, i have to minor problems!

The setup:
2 x Behringer B215XL 15" with the above preamp and a Tripath TK2050 amp installed in each. Both are wired identical to each other!
Wired up to 24V.

1. one of the speakers are noticeably less loud than the other. We tried change their power source, audio input, and adjusting the preamp (tweeter / woofer screws) - Ideas?

2. When speakers are connected to the same power source - a loud noisy interference appears.. When one speaker is disconnected the noise goes away, also when they're on two different power sources. So the interference travels through the power cords?

I would really appreciate some help and ideas!

It's not a BIG problem, but it's annoying.

Below, a picture of the setup inside the speaker

Cheers

[dan]

about the speaker being less loud - the things you checked all are important. in addition, check that the woofer and tweeter are connected to the correct outputs on the amp. if you get the outputs reversed then the woofer signal is sent to the tweeter, and it is not as loud. need to adjust the preamp tweeter/woofer screws when you do this to verify.

your photos are a bit low-res, its hard for me to see the wiring detail.

[dan]

besides loose connectors, check that you have a 'common ground' between the two systems and any mixer or audio source. i have seen random noise is cases where the mixer was running on one power source and the speakers on a different one - if you have multiple power sources the ground needs to be connected together with a wire. check the wiring diagram in STEP 5 of here:
http://www.instructables.com/id/Battery-Powered-Mobile-Party-Sound-Systems

[damiengwalker]

Do you know if a phonograph preamp will work?
How much do you need to boost the signal by to make this work?

Thanks for the help.

FYI: I have the TK2050 and measured a power draw of 37 Watts (total) using an ipod and 2 8 Ohm speakers.

[cjones-2]

(removed by author or community request)

[cjones-2]

ahhh there !


and could I use this Valve Class A Tube Headphone Amplifier pre Bravo V2 AU1 as the level booster ?

[dan]

most headphone amps probably would work for this, yes.

[kwahlgren]

Are these t-amps bridgeable to Mono? I'm looking to use a Pioneer B20FU20-51FW driver and id rather have both channels powering it.

[dan]

no. the only way to use both channels is to use one channel for the woofer and one for the tweeter, that is one benefit of my monoXover device discussed later in the project.

[esmash]

So does this mean it is possible to send all 200w to one woofer? If so, how could this be done? Thanks

[tamadoctor]

I'm planning on building a stereo system. I'm looking at two of the Behringer B212XL's, two TK2050 2x100w Amps, and two crossovers. I'm also looking at an amp/mixer as you described elsewhere. The TK2050 is rated 100W at 4 ohms, however the B212XL is rated 8 ohms. So am I to assume I won't get full power out of this? Or could I instead wire one crossover into one amp, split the channels to the tweeter and woofer and run both in parallel to get full power and two mono speakers? I think I may be missing something here. Advice would be appreciated!

PS I'm digging the work you've done on your mobile DJ rigs. Thanks for posting!

[dan]

yes, if you used 1 amp you could wire both of the speakers to it but then you probably have your amp outside the speaker, a little less convenient. the sure amp will do maybe 60 or 70W with 8 ohms i think.

[Qsam]

so if u have an active speaker u still need an amp and a mixer?

[Zem]

Is there a volume control for the MKII TA2020? I'm thinking of buying that. Would it just be volume from the input device?

[dan]

no, most of the bare board amps you control volume from your mp3 player.

[Zem]

Okay, thanks!

[sbriggs]

Note that you MUST use a powered mixer to to get full power out of these, but even so these are the best deal going for a high power setup.

Could you explain this statement to me please? Is this as a power source or for the audio?

[dan]

i added a new step "mixers" to explain it better. let me know if it still does not make sense.