IMG_20200603_111545Please give a warm welcome to the “Rolling Lion Hi-Fi“! As you’ve probably guessed, we’re quite the fans of dub and sound system culture here, and it was only a matter of time before we started building our own sound! We decided to begin with a mobile, 12v battery powered, 3-way system for home/studio use and small open air sessions! This was our first attempt at building our own rig, and we’re quite happy with the results! Since we’ve been receiving some questions about the sound, we decided to create a walkthrough of the process, and the components we used.

I’d been thinking about building my own sound system for quite some time, but mainly due to storage constraints and often moving house and studio or travelling for longer periods of time, it was never really a practical endeavour! Upon returning to Berlin in March from some winter travels, and learning that the future of our next events was up in the air, I decided to use the “lockdown” time to work on some other projects. With a new base of operations on the outskirts of Berlin and a full wood workshop, there was nothing left to keep me from starting on this one!

Why a 12 volt sound system?

I decided to start this next chapter of the odyssey with a “mobile” version of a 3-way sound system – with 3 separate sections for low, mid and high frequencies – which could also be used at home / in the studio, and eventually mounted to a cargo bike for the odd open air session here and there. The system is fully powered by a 12 volt “leisure battery” (Varta LA95). We’re still working on optimizing the sound and power efficiency, so we’re not quite sure yet how much juice / longevity we’ll be able to get out of it!

Did you use plans for the design?

IMG_20200517_130500I began by scouring the internet for different plans (“Speakerplans Forum” and “12v Sound Systems” Facebook group have both been great resources!), and eventually settled on the Cubo15 design – a 62cm cube powered by a 15″ driver – which would amplify the lower frequencies between 40-100 hertz. After asking a lot of colleagues about other recommended designs for the mid / top sections (and receiving various responses from everyone I asked!), I decided to just start on the Cubo, and then build the other sections according to my own vision of how I wanted the sound to look! I could have spent months researching different aspects of sound design, frequency response and whatnot, but as a practical learner, I decided to just begin the project. After all, sound systems are a constant learning curve, and there will be plenty of time to learn about the various aspects and make any necessary adjustments to the design!

How did you construct the rest of the sound system?

12v Sound System V1. 0After I finished building the Cubo15 – using 15mm birch ply, I installed the Eighteensound 15ND930 15″ driver I chose to provide the low-range frequencies. Although the original design calls for 18mm birch ply, I decided to use 15mm to cut down on some of the weight, and used the same wood for all cabinets. Next I built a custom designed mid-cabinet (62*30*30cm) which houses 2x 8″ drivers (Eighteensound 8NMB420), providing the mid-range frequencies between 100 – 2,000 hertz. Then came the top-cabinet (62*20*20cm), which houses 2x 1″ compression drivers (Eighteensound HD1050) attached to “horn flares” (Eighteensound XT120), thus providing more balanced sound coverage. Once everything was built, all drivers and speaker ports installed, all connections glued and screwed, it was time to give the wood a nice finish. I chose an all-natural wood glaze (Deutsch: Holzlasur), with an Oregon Pine tone, which gave the wood a slightly darker, orange hue.

Afterwards I built a simple cabinet to hold all of the various components and cables, battery, amplifier, DSP and capacitor, and also added some hexagonal speaker grilles and protective speaker foam to avoid any dust or damage to the drivers.

Which other components did you use?

IMG_20200604_173305The music signal is sent from the source (for now a phone or laptop) into the input of a t.Racks 4×4 mini DSP (digital signal processor), which splits the input (music) signal into the appropriate frequency bands for the respective drivers (app. 40-100 hertz to the subwoofer, 100-2,000 hertz to the mids and 2,000-20,000 hertz to the tops). Using their proprietary software, you can choose flexible cut-off frequencies and crossover points, adjust delay times between and equalize the various outputs.. quite a powerful bit of kit! The 4 outputs of the DSP are then connected to the 4 inputs of a 4-channel, 1200w car amplifier (Pioneer GM-D8704), sending the respective frequency bands to the respective channels on the amp, and further on to the drivers. The subwoofer is wired in “mono bridge” mode on Channel A (left and right), and the mids and tops each get their own separate power and signal from Channel B (mids left; tops right). Between the 95ah AGM gel battery (Varta LA95) and the amplifier there is an 80A fuse to help prevent any power surges, as well as a capacitor (Crunch CR-1000 Power Cap), which is used to store power and keep a steady flow to the amplifier, preventing any potential power losses.

How does it sound?

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The first sound check was surprisingly good for having just wired everything up and making some intuitive adjustments in the DSP software! At first we tested the sound in the workshop, driving the levels up to a point where the mid and top cabinets began to vibrate off of the subwoofer! After fastening a tension belt around the stack (which is about 110cm tall), we continued making some adjustments in the software, until we found a balance we were happy with. On the next day we rolled the stack into the garden, and were surprised to realize the bass was even stronger / warmer outdoors (using the same settings)! There’s still a lot to be done, but we’ll get to everything in due time.

What’s next?

IMG_20200622_182136Now I’m working on tidying up the wiring connections (done), so everything fits nicely into the components case! A friend is stopping by in the next days to help measure delay times, SPL (sound pressure level), HPF (high pass filter) or cut-off point for the lower frequencies in order to preserve battery longevity and get the most out of the system (done). This weekend we’ll be doing the first proper soundcheck and open air session in the garden (assuming the neighbours let us!). And “finally”, we have a cargo bike that needs to be fixed up a bit, and then we can hit the road for the first proper outbound session (and done!)!

Shout outs to Joe Redub & Darkwing Dub for the input, as well as everyone on the Speakerplans Forum and 12v Sound Systems group for supplying so much knowledge!

12v Sound System Schematics