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.

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

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

[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?

[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?

[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.

[sbriggs]

That's brilliant! I've found the whole instructable very informative. Thank you! If you don't mind me asking a couple of questions (I'm pretty new to all this!).
- You say that having an efficient amp like the T-class you use is x2 better. Does this just mean it drains the battery less quickly? Because in terms of ensuring the amp is suitable for the speakers, we still use the power per channel rating given to the amp to compare with the RMS power of the speakers, yes?
- By choosing efficient speakers and perhaps deciding to use pre-amp crossovers, we can achieve "more output for the same amount of power". My question is, is it a problem to run a speaker/woofer at way below its RMS power? I understand that it wouldn't be being used to its full potential, but I just wanted to check it wasn't actually damaging in any way. Say I used the mini ipod TA2020 amp (so 20W/channel) with say an efficient (98dB SPL @ 1W/1m) 250W RMS speaker. Is this an issue?
- Finally, I have a pre-amp for my record player to connect to the cheap Hi-Fi system I own. Would this do the same job in boosting the MP3 player's signal as the powered mixer you use before running it into the TK2050 amp?
Sorry for the barrage of probably-quite-mundane questions but your instructable has got me hooked and I really want to learn and build more!

[dan]

- running a speaker below rated power: this is no different than turning down your volume knob below 100%. so of course it is no problem. speaker power rating is always the maximum the speaker can handle. to put it another way: never use an amp with a higher power rating than the speaker. your amp should always have lower power rating than the speaker to avoid speaker blowouts. an amp with 50% the power rating of the speaker is very reasonable. if the amp only has 10% of the power of the speaker then you just won't get as loud as the speaker is capable of - but that might be fine for your application. most amps are protected from overheating and blowout electronically, while speakers often are not.

- a pre-amp serves the same function here as the powered mixer. so yes, that will work.

- 't-class is 2x better': yes, i mean it has equal sound output to normal "A/B" amps with 1/2 the power use. so, that means you can use a smaller, lighter battery.

[N.I.Patterson]

Hmm. The received wisdom in general (at least in live sound applications and amongst long in the tooth audiophiles...........I do both I must confess!!) is that there is no issue to running a speaker with an amp well above its power rating ( I ran my own expensive reference 200w speakers with a BGW 750a no problem, it's hugely powerful.). To be precise a speaker likes to 'see' clean UNDISTORTED power up to its maximum rating. An over specified (in terms of power with regards to the speaker) amplifier will drive a speaker cleanly without any distortion. Running an underpowered amplifier into a speaker though for fairly long periods (say over 15mins at a guess at least) at high levels will produce lots of evil distortion. This distortion over time will cause the voice coil of the speaker to heat....more likely past the point of no return and cause it in turn to burnout. An underpowered amplifier is capable of exceeding its specifications by quite some way in general. A 20wpc rms amplifier may produce (at a guess) 80wpc channel of something that cannot really be said to resemble music. We all know its signature sound, harsh, objectionable, edgy etc. We choose to ignore these warning signs when we are drunk, ignorant, distracted (driving) and on and on. The speaker will let you know that you have exceeded its and the amplifiers limits by refusing to party anymore. So that speaker that was capable of handling 40wpc rms has just been ko'd by a little 20wpc amplifier. Running a speaker with a big amplifier (as big as you like really) is a good idea BUT YOU HAVE TO BE REPONSIBLE THE SAME AS RUNNING IT WITH A LOW POWERED AMPLIFIER. No matter what wattage of amplifier speaker combination you use you can blow nearly any speaker......I think. If it sounds distorted and you play it like that for long enough something may well give. Things break. Speakers are things with finite capabilities. Also if you are playing rap/reggae/drum and bass/r&b and what not AND boosting the bass and treble still further you are inviting trouble. Music like this will sap any reserves even from a well specified amplifier. Power ratings tthough are not going to save your speakers from misuse. Your ears, experience and knowledge of application of the speakers specifications/parameters may. I venture this info by the way from having, in a past life, had to deal with distressed customers who no matter what you enlightened them to previously went off on a tangent and returned with 'toasted' speakers. Oh well after repairing said speaker they were definitely a little more 'open' to any further information you could give them! Oh yes amps are protected, at least professional amps are, from burnout but speakers have to fend for themselves as they are the 'messangers'. Messangers (Julian Assange maybe?!!!!) tend to get shot at the best of times!!

[dan]

yes, if you hear distortion you should turn things down until it stops. i still recommend an under-powered amp because it will not be able to blow the speaker in seconds, perhaps only after a long time playing with highly noticeable distortion. an over-powered amp on the other hand can blow the speaker in seconds simply by turning up the volume knob. in a home-theater setup that might not be a big risk, but in an outdoor/mobile environment there is a lot of chaos and its way too easy to have someone bump your volume.

[N.I.Patterson]

Good point Dan, your brand of real world experience supercedes theoretical advantages I concede. I did sound for my brother recently at a very big christmas golf club party (he runs a successful Motown/popular music act) and he impressed upon me to address the routing of the cables for the system with a little bit more care "never underestimate drunk people" he said!! Yes in the chaos of live performance of any kind a variable may arise that will leave you with more than a touch of egg adorning your countenance!! I guess also in a home situation if you have an inquisitive toddler sharing your home space you may rue the day you placed an amplifier capable of armageddon lovingly into the heart of your system.

[sbriggs]

Thank you so much for your help!
I've just remembered I've got my grandad's old PA system in the attic. They're colossal, probably massively inefficient, 16ohm 70W beasts. I'm gonna see if I can work them/one into some sort of system. Perhaps in a bi-amp system with one TK2050 amp trying it's best to get them going and then a smaller TA2020 running the higher frequencies through some bookshelf speakers.
It started here! Thanks for your brilliant instructable and helpful advice!

[stiltPro]

Would love to learn about a upgrading from a Dayton /Soundpax system using transducers / exciters to a more powerful system that is still very light weight.

We use the Dayton DTA-1/SoundPax mini amp with the pyramidal cardboard speakers
http://www.newscientist.com/article/dn1921-collapsible-cardboard-speakers-unveiled.html
inside our Dancing Christmas Tree costumes.

http://www.youtube.com/stiltpro#p/u/38/XLGrnc3NneE

The sound you hear is from that system. Very good in a quiet setting, but would like more volume for parades.

Any suggestions?

We also like to use them in our Giant Parade Puppets.


Bill Coleman
http://www.stiltwalker.com/

[saltvand]

The TK2050 thaqt I have looks i little bit different. See it here: http://img411.imageshack.us/img411/4465/img4302r.jpg IS there a way I can increase the volume on my model?

[dan]

oh, the other solution is to use a powered mixer to boost the mp3 player signal before the amp. i'm using a Rolls MX51s which is about $50.

[dan]

you have the 4-channel version. i think yours must have the pre-amp chips on the underside of that daughter-board. can you un-plug the daughter card and post a photo of the bottom side of it? (close up, use macro-mode on your camera).

[Mr.Doom]

Nice job and great instructable. I am working on my third "boombike" and could not agree more about using high efficiency drivers in this application.

Although it is hard to compete with the prefab pro-audio speakers I was able to build a set using a pair of the new inexpensive Peavey Pro 10 neo drivers http://www.parts-express.com/pe/showdetl.cfm?Partnumber=294-3214 and a array of cheap piezo tweeters for less than price of one prefab box. Using sonotube I was able to keep the weight down to 14lbs per speaker and by using 2 speakers I get a extra 3db spl.

I disagree about going mono because when stereo effects are implemented properly you can get another 3db increase in perceived loudness and some recordings just sound better in stereo.

Also the Sure and other T-amps are more efficient if you can draw a 4ohm load and in fact is the only way to get the maximum wattage out of them. Unfortunately few high efficiency drivers are 4ohm or dvc 8ohm.