How to build a mobile Soundsystem for protests/raves [34c3]

Either for a proper squat rave or for a demonstration - to empower people to reclaim space in the city, they need the right and cheap tools to do it. To achieve this, i want to share my recent experiences in building a loud and cheap (<200€ is possible) mobile sound system.
First, i will give you an overview on all the important parts of a sound system and show you whats important for getting enough energy to power the amplifiers for a full night. I will also give you an overview on which amplifiertechnologies exist, and which fit best for our purpose. Afterwards i will show you how to choose the right speakers to get the biggest bang for the buck.

Transcript

1. 1 / 37 How to build a mobile soundsystem petrosilius@posteo.de - http://oscillating.space/ • A short overview on the history of soundsystems • Motivation for free open air partys • Components of a soundsystem • Power supply • Amplifiers • Speakers • Additional stuff • Example cost calculations • Workshop: Build a soundsystem
2. 2 / 37 A short overview on the history of soundsystems • Beginning in the 50s in jamaica – Disko on wheels – Reggae, Jazz, Blues • Since mid 70s in northamerica with Hiphop&Disko – Ghettoblaster • (Illegal) Rave culture in europe since end of 80s – UK – Germany • Freetek, Teknivals get massive police repression • Nice Arte Docu: Sound System - Tontons du sound
3. 3 / 37 Motivation for free open air partys today • Its nicer to party outside in the sun • Overcrowded clubs in Berlin • Nice to organise your own partys • Less opportunitys to play in clubs • Nonviolent protest • Its fun fun fun fun
4. 4 / 37 Components of a soundsystem Power supply Amplifier Speakers DJ Equipment Yeah!
5. 5 / 37 Maximise the Yeah! factor • The only formula for today... – The longer the music the better – The louder the music the better – The less money the better
6. 6 / 37 Power supply - Generator • Advantages – Lots of power to use – Standard power plugs • Disadvantages – Burning old dinosaur shit to get power - WTF?! – Smelly and leaking liquids – Forbidden in parks - Ordnungsamt can sue you instantly – Heavy (but you can also get small ones)
7. 7 / 37 Power supply - Batteries • Standard liquid car batteries – Acid liquids can leak – Bad stuff – Advantage • Cheap – Disadvantage • If not standing vertically it can leak acid • Acid is unhealthy and environmental hazard • Need to refill with liquids from time to time
8. 8 / 37 Power supply - Batteries • Solid material Batteries – Gel- or AGM-Batteries – Sealed to prevent leaking – Advantages • No leaking • Without maintainance (no refill) • Resistance against deep discharge – Disadvantages • Expensive (approximately 2x as standard)
9. 9 / 37 Power supply - Batteries • How much Power is in a Battery? – Amount of power in Ampere Hours (Ah) – Discharge curve – State of charge readable by Voltage of Battery – Discharge until 11.8V is ok – Below 11.8 the battery gets destroyed slowely – Destroyed battery irreparable – Only 70% of capacity usable
10. 10 / 37 Power supply – Solar Power • Advantages – Recharge batteries – Sustainable energy • Disadvantages – Only usable in the sun – Additional cost (Solarpanels + Inverter) – Not good usable without batteries • Cost – Depends on the power but > 150 €
11. 11 / 37 Power supply – By Bike • 30W – 100W per Person • Advantages – Generate power independently from the weather – Generate power from Beer/Food (Healthy!) • Disadvantages – Buying is expensive: www.oekotrainer.de – DIY
12. 12 / 37 Power supply - Buying tips • For mobile music batteries are the best • Additional cost for Solar or generator is too high • Buy only new batteries • Solid material batteries because they are leakfree • The bigger the batteries the smaller is the price for the power ( € / Ah ) • Use good chargers for AGM-Batteries (highvoltage) • Bicycle Generators are nice but complicated
13. 13 / 37 Components of a soundsystem Power supply Amplifier Speakers DJ Equipment Yeah!
14. 14 / 37 Amplifiers • Most important technical spec is the efficiency – The more efficient, the less power gets wasted to heat – Heat needs to get cooled with even more energy – If amplifier gets too hot it turns off / gets destroyed – Good amplifiers have more than 80% efficiency – Class D / digital amplifiers have a good efficiency – Old analgue Class A / B amps got ~60%
15. 15 / 37 Amplifiers • Possible amplifier setups for a soundsystem – Class D / Digital car amp – Step-Up-Converter + Class D amp board – 230V-inverter + normal 230V PA-equipment
16. 16 / 37 Amplifiers • Amplifier power rating in Watts – The only right rating is Watts RMS / Sinus! – Watt PMPO: fake power rating • Also called „Pure Mystic Power Output“ • Its the power you can put on the speaker before it catches fire – Ohm load of the rating is also important: • Example: – Power rating: 50W RMS @ 4 Ohm – Matches: 25W RMS @ 8 Ohm
17. 17 / 37 Amplifiers • Cooling – Car amps not build for heavy usage longer than 2h – Additional heatsink or fan is needed – Use thermal paste for better thermal connection – Use a huge area to connect the heatsink to the amplifier – Use a efficient 12V fan (high airflow / watt)
18. 18 / 37 Amplifiers - Buying tips • Get a car amp • Get a Digital amp with high efficiency (>80%) • Get a used amp from ebay / Kleinanzeigen to save money • No high power rating necessary for each output – 20W / 8Ohm for a small soundsystem – 100W / 8Ohm is enough for a big soundsystem • Analogue amps only good for small soundsystems because they generate too much heat
19. 19 / 37 Components of a soundsystem Power supply Amplifier Speakers DJ Equipment Yeah!
20. 20 / 37 Speakers - Setups • Most important part in the soundsystem • Different Setups possible – Classic 2.0: • Two fullrange speakers • One amp with two outputs – Additional Subwoofer 2.1: • Two speakers as mid-/high-Speakers • One subwoofer as low-Speaker / bass • Crossover needed to split the frequencys • Two separate amps necessary
21. 21 / 37 Speakers - Sensitivity • The watt rating of speakers is NOT equivalent to the loudness of a speaker • Sensitivity / „Wirkungsgrad“ is the important value – Given as dB/w/m in the technical specs – It says how loud is a speaker in a distance of 1 meter if you put 1W RMS of power from an amp to the speaker • The higher the sensivity, the longer the battery lasts at the party!
22. 22 / 37 Speakers - Sensitivity • How much watts needed ? – Loudness measured in dB – „Discoloudness“ = 100dB – Berghain = approx. 110dB – Speaker with 85 dB/W/m • 100dB: 32 W RMS • 110dB: 300 W RMS – Speaker with 94dB/W/m • 100dB: only 4 W RMS! • 110dB: 50 W RMS Loudness examples with Distance Loud ness dB Jet airplane in 30 m 140 Pain threshold 130 Discomfort threshold 120 Chainsaw @ 1 meter dist, 110 Disco @ 1 m infront speaker 100 Dieselmotor @ 10 m dist. 90 At a busy street 5 m dist. 80 Vacuum @ 1 m distance 70 Normal talking @ 1 m dist. 60 Normal flat quiet 50 In a quiet library 40 Quiet sleepingroom by night 30
23. 23 / 37 Speakers - Buying tips • Buy speakers by efficiency • Speakers should have > 92 dB/W/m efficiency • Match Watt RMS to power rating of the amp • Consider the ohms of the speaker (see amps) • Used speakers are ok to buy and cheap • DIY possible and very cheap – Speaker is basically just a wooden box – Wide-range speakers play bass/mids/highs – Lots of plans in the internet (see links)
24. 24 / 37 Components of a soundsystem Power supply Amplifier Speakers DJ Equipment Yeah!
25. 25 / 37 Additional stuf • Fuses are really important: – Choose by max current – 100W => 16A fuse – 200W => 30A fuse – 300W => 50A fuse • Cables: Cable cross section by power rating – 100W => 0,75mm² – 200W => 1,5mm² – 300W => 3mm² – 400W => 5mm²
26. 26 / 37 Additional stuf • Voltage display – To prevent deep discharge of the battery – Dont pay more than 5€ – Reminder: After 11.8V change the battery to prevent harming the battery • Equalizer for the soundsystem – Adjust the bass to avoid police – Adjust the highs
27. 27 / 37 Additional stuf • Inverter: generate 230V AC from 12V DC – Different types of inverters: • Rectangle • Sinus – Sinus for audioequipment – Pay attention to efficiency: higher than 80% ! – Advantage: Use regular 230V equipment – Disadvantage: Unnecessary voltage conversion which costs power and therefor hours of music – Needs to get cooled !
28. 28 / 37 Additional stuf • The horse: Transporter – Trolley – Sack truck – Shopping cart – Hand cart – Wheelchairs – Baby carriages – Wheelbarrow – Bicycle – ???
29. 29 / 37 Pics
30. 30 / 37 Pics
31. 31 / 37 Additional stuff • Lights – Use LEDs because they need way less power – Battery powered LED light strings • Laptops – Use laptop battery – If battery is over, remove battery and use only the laptop power supply (very inefficient to charge laptop battery from another battery) – MacBook Trick: Block middle pin of charger with ducktape to prevent loading of battery • DJ Mixer: use 12V Mixer (eg. Xone 22)
32. 32 / 37 Example cost calculation - Small soundsystem Type Name Spec Price Battery QUATPOWER LB12-12 AGM 12V / 12Ah 20 Amplifier Kinter MA 700 2 x 13W / 8 Ohm 15 Speaker DIY Visaton BG 20 40W / 8 Ohm / 92dB/w/m 25 Speaker Wood + small parts 10 Voltage display … 5 Horse Sack truck 24 Additional stuff Cables, Fuses and shipping 15 Sum 114 Resulting loudness 102dB @ 13W : Lasts 7h 108dB @ 2x13W : Lasts 3,5h Yeah! factor 82
33. 33 / 37 Example cost calculation - Bigger soundsystem
34. 34 / 37 Example cost calculation - Bigger soundsystem Type Name Spec Price Battery MaxBatt AGM Batterie 12V / 110Ah 130 Amplifier Ampire MBM 100.4 2G (used) 2 x 200W / 4 Ohm / 84% Efficiency 125 Speaker 2 x Thomann PA 302 (used) 300W / 8 Ohm / 96dB/w/m 150 Speakerstands 20 Equalizer 35 Inverter Arebos Sinus Inverter 300W / >80% Efficiency 30 Horse Hand carts 60 Additional stuff Cables, Fuses and stuff 45 Sum 595 Resulting loudness 116dB @ 2x30W : Lasts 13h Yeah! factor 73
35. 35 / 37 Conclusion • Efficiency is the most important spec in a mobile soundsystem • Use leakfree batteries • Dont do deep discharge of the batteries • Important to look after the efficiency of the amp that there is less need to cool it • Use crazy good efficient speakers to get the loud music for a little of power and for a long time!
36. 36 / 37 Linklist petrosilius@posteo.de • Bicyclegenerator: http://www.magnificentrevolution.org/diy/single-bike-generator/ • Amps: – Efficiency of a lot of amps http://amp-performance.de – Overview small amps: http://www.hifi-forum.de/viewthread-118-2855.html • Speakers – Pages with plans: Hififorum, Jobst Audio – Plan for Visaton BG20 Partyboombox: http://www.lautsprecher-berlin.de/partybox.html • Shops for soundsystem stuff: – Speakers: Geizhals.de – under „Lautsprecher“ filter with „Empfindlichkeit ab 92dB“ – Pollin.de & Reichelt.de for electrical parts, batteries and speakers • Inspirations for soundsystemconstruction: – https://www.hedonist-international.org/?q=de/node/414 – http://www.hifi-forum.de/viewthread-118-1591.html
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