Bike-Based Sound-Systems

During January’s Critical Mass there was considerable interest in the little red boom-box strapped to my bike…

January's Mass

  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…


The genius of Jethro

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…

sound system 1 sound system 2 sound system 3 sound system Bike-Beatz sound systembudget

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).


Battery + Speakers

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. 


Kenwood KAC-7201 2-channel amplifier

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:


Nice kit, but a bit of a mess at the moment…

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:

sweet case

This design also used 6×9 speakers, so I imagine that my set-up will look something like this when it’s finished

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!


**UPDATE 20/03/14**

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!

The sub-woofer of destiny

The sub-woofer of destiny

Author: Harry Walton


About Cycle Chic

A student in Edinburgh with a passion for Dutch bikes and Dutch cycling culture.
This entry was posted in Bike Riding, Bike Sound-System, Bikes, Critical Mass, Edinburgh, Uncategorized. Bookmark the permalink.

8 Responses to Bike-Based Sound-Systems

  1. Jethro Gauld says:

    Great post Harry and thanks for the mention. I’d suggest a cheap pair of double panniers with plywood on the inner walls which you can bolt everything onto. Fairly waterproof/inconspicuous and easy to take on and off the bike.

    • waltonharry says:

      Hey Jethro,
      I considered going down the pannier route, but given how directional the sound is I really need to secure the speakers to the front rack and have them pointing forwards.

      I’ve found a big piece of wood that I can use as a platform, and if I put a few wood screws up through that and into the speaker boxes then at least they will be secure. I can use zip ties to secure the battery (in the same way that you did), and then maybe just screw the amp into the back of the speakers once they’re mounted. It won’t be weatherproof, and I’ll still need a fair few bungee cords, but until I can get my hands on some decent tools + materials it is at least a working solution.

  2. Pingback: Another party on a bike… | Edinburgh Critical Mass

  3. Angus Calder says:

    Very Cool! Did you get it sorted? If so, how’d it turn out? If not, what kind of tools etc do you need? Got some tools/material lying around here, you’d be welcome to use…

    • waltonharry says:

      Hey Angus,
      I ended up screwing everything onto a temporary base and it worked out fine on the day. I really appreciate the offer of help/supplies, but I just found out that I have access to the university workshops so I should be sorted with tools/materials for now. All I really need to do is build a box/case so that everything is a little less exposed and a bit more portable. I might do that this month, or I might hold off until I get my hands on a decent sub…

      Thanks for the offer of help though, that really is kind

  4. Pingback: Critical Mass Pedals on Parliament! | Edinburgh Critical Mass

  5. Pingback: Critical Mass ride is on the rise in Edinburgh!!! | Edinburgh Critical Mass

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s