During January’s Critical Mass there was considerable interest in the little red boom-box strapped to my bike…
What’s inside? How did you make it? Is it complicated? Can I make one?
In an attempt to answer these questions, I’m going to begin by being completely honest and telling you that I didn’t make it. The inventor/mastermind is a guy called Jethro who was kind enough to lend it to us. Jethro built the wee boom-box for Critical Mass down in his native Brighton, but since moving to Edinburgh he now has to work on Friday nights and so can’t come along to our rides. This sucks because Jethro loves Critical Mass (and we love Jethro). But anyway…
Under the bonnet you can see what we’re working with. The (grey) rectangle to the right is a 12Volt/7Ah lead-acid battery, which is connected to the (red) Sony Xplod 444Watt amplifier, and then on to the speakers (which were taken from an old TV). The audio input (not pictured) comes through a standard headphone jack that splits into two (red + white) RDA cables before going through the amplifier.
It’s a simple set-up, but getting the wiring right takes some ingenuity, and so Jethro’s creation is truly a thing to behold. Although the circuit itself is impressive, my favourite thing about this artefact is the way in which all the components are built into their very own handmade housing – complete with carry handle + rack mounts.
Inspired by Jethro’s initiative and inventiveness, I was keen to have a crack a making one myself. However, having not studied electronics since I was 15, and knowing next to nothing about volts, amperes, ohms, and watts, it took a fair few evenings of internet browsing before I was confident enough to even begin planning.
All I knew was that I wanted to build something bigger, ideally with more bass so that the music would have more depth. In the course of my research, I discovered that there were many possible options…
The range of bike-based sound-systems is clearly varied, and I bet that a few of these produce some truly epic bass. I know for a fact that the purple one (known as ‘The Beastbox’) is in regular attendance at London’s Critical Mass, and I can tell you from experience that it is stomach-thunderingly loud!
However, given that Edinburgh’s Mass is a bit smaller than London’s, and given that Edinburgh is decidedly hilly, and given that my bike already weighs ~25kg, I wasn’t too keen on building a beastly trailer system. Not only would such a system require massive speakers (which I don’t have) and a trailer (which I don’t have), but these things tend to get pretty expensive. Here is a guide to building one, in case you are interested.
Keeping it simple, and following Jethro’s example, I thought it best to stick with 12Volt lead-acid batteries and basic car audio components. In the end I went for a Panasonic battery with 15Amp hours and paired this with some 550Watt 4-way Pioneer 6×9 speakers (as found on car parcel-shelves throughout Essex).
The story of the amplifier that I plan to use is a long one, and so (in the interest of brevity) I’ll say that I just happened to have an 800Watt Kenwood amp lying around at home.
So, there you have it. All that remained was for me to get my hands on some suitable cables, connectors, fuses, switches, terminals etc.
Along with some useful and friendly advice, I found everything that I needed on a website called 12Volt Planet, and so once it arrived I was ready for the first big test…
Would everything work together? Have I connected it correctly? Would I inadvertently simultaneously blow the amp and electrocute myself? (What’s that burning smell…?)
Well, I’m pleased to report that not only did I survive, but (much to my surprise) everything worked perfectly! It wasn’t just ‘sound’ that came out the speakers, but good sound. BIG sound. Big sound with considerable bass and volume. And with only 11 days left until the next Critical Mass ride I was quite relieved about this.
That said, there is one hurdle left before the new sound-system is ready for its first big outing. At present, the system looks like this:
As a format this is fine in my living room, but it isn’t very portable. And this is obviously problematic if I am to take it out for a couple of (potentially damp) hours at the end of February…
This being the case, does anyone have any ideas as to how I could make it work?
One option would be to fabricate a frame for it, just to hold everything in place; maybe something like this:
Although this construction wouldn’t be overly complicated, I lack both the materials and the tools to build such a thing. If you have any ideas or possible sources of resources then please share them in the comments or contact me directly through the Edinburgh Critical Mass Facebook group.
I’m sure that I’ll come up with a fix by the end of the month, but just in case anyone has access to a workshop it would be nice to build something sturdy.
Either way, stay tuned for a follow-up post about how this problem ends up getting solved!
In addition to the amplifier that I ‘just happen to own’, there is also a substantial sub-woofer waiting for me to collect it from my home in London. I will be going down at the very end of March so should have it up and running in time for Pedal on Parliament and the Critical Mass ride in April. WATCH THIS SPACE!
Author: Harry Walton