Modified JBL Loudspeakers

A Rock The Bike exclusive! Our DC mod eliminates the need for AC power for your loudspeakers, making Pedal Powered Stages up to 44% more efficient.

Pedal Powered Stage
Above:  Modified PRX 612 wedge monitors in use as the band ZH performs. Also shown in aerial configuration in Rock The Bike’s Pedal Powered Line Array (suspended from Bamboo Tripod).

An awesome combination of light weight, efficiency, and Pro Audio clarity. The Modified JBL PRX loudspeaker has been an essential building block of our Pedal Powered Stage, and is in use by the Pleasant Revolution, SHAKE YOUR PEACE!, University of Oregon, UC Santa Cruz, Cello Joe, and the Mobile Music Project. Not limited to Pedal Power use, the Modified JBL PRX line is an amazing Mobile Sound speaker as well. The applications are as broad as your needs: bike parties, press conferences, or full-on concerts. We can help you craft a selection that will handle crowd sizes from 50 to over 1000 people.

Pedal Powered Stage

Normally, Pro Audio equipment runs on AC power, which in outdoor use must come from an extension cord from a nearby building, a gas generator, or an AC-DC inverter. If you’re starting your Pedal Powered Stage from scratch or are ready to upgrade your loudspeakers, go with Rock The Bike’s Modified JBL PRX. They deliver great sound with no AC power and save you up to 44% in power usage.

44% power savings– how’s that possible?  It’s true! We scientifically measured the power consumption of these loudspeakers in AC mode and Modified DC mode, by running a bass-heavy tone into the speaker and confirming that the audio output level was equal. The speakers used 35% less power in DC mode, for the same audio output! Add to that that the 9-10% efficiency penalty that most AC-DC inverters take, and you get a 44% power savings by using them in DC mode. In practical event use, this means you get the same amount of clean, clear, danceable music, but with 40% fewer pedalers. You can do amazing things with even one pedaler. In the world of Pro Audio, 44% is an unheard of efficiency gain, and the PRX line, with its digital Crown amplifiers, was already known for being an efficient loudspeaker.

JBL did the hard work of creating a full line of great-sounding loudspeakers. We cracked the code of getting them to run on good clean Pedal Power. You can combine these loudspeakers in a number of ways to create a small or medium-sized festival stage, or mobile sound system. We modify the speaker, adding a power jack that accepts a DC Split-Rail Power from our Split-Rail Pedal Power Utility Box.

Normally pro-audio gear is well beyond the abilities of the average person, in terms of ease of setup and use. But because these are powered speakers, it’s fairly straightforward. A ‘powered’ speaker means that the amplifier is in the speaker. You simply connect the power cable and the audio signal, and turn the volume knob to the desired setting. The speaker does the rest. For a press conference, you can run a microphone right into the speaker — you don’t even have to own a mixer. Similarly for mobile sound, you can run an MP3 player right into the speaker.

LiveOnBike performance
Above: A Modified PRX 612 in use for a LiveOnBike performance by the Shook Twins.

We sell the full line of JBL PRX Loudspeakers, however due to space considerations we keep a very low inventory of this item. Please get your project started early with us in order to hit your key event deadline.  Here’s the rundown of the speakers in the PRX Line.

612 — great sounding wedge monitor for live bands. Also can be thrown on the back of almost any cargo bike.

615 — similar but with its 15″ woofer, it can be used as a respectable main speaker as well.

635 — a dedicated 5″ midrange woofer in this speaker renders vocals and instruments with great clarity. 15″ woofer delivers plenty of bass. Discontinued

625 — most bass  possible within a single loudspeaker. A towering main that is well suited to dance music. Slightly harder to carry due to its height.  Discontinued 

618 XLF — The PRX subwoofer makes dance music come alive. To fully render the kick drum in live music or the beat in dance music, you need a subwoofer. For medium and large Pedal Powered Stages, there is no substitute. The sub also includes a built-in crossover that allows your mains to focus on mid-bass and higher. This way you get the best sound out of your mains and can run them louder before they distort.

bicycle powered stage
Above: The Modified JBL PRX 615 is a solid main.

Most bike music projects use car audio componentry, because it is cheap, widely available, and will work on 12 volt DC power such as a motorcycle battery. However, car audio equipment cannot amplify musicians at a concert, because it does not have the efficiency, overall listening levels, and clarity required. It was designed for small enclosed spaces, not large open spaces. That’s why you need Pro Audio equipment. Our modified JBL PRX loudspeakers are the best of both worlds. They provide concert quality sound and are ready for DC power, i.e. Pedal Power!

Above: The Modified PRX’s are fairly lightweight and can be towed by trailer or hauled on cargo bikes.

The package: lightweight but great sounding. All modified JBLs are made out of quality plywood — not plastic — and have a durable coating for dings and drops.  They can all be carried by bike, and with the exception of the 618 subwoofer and the 625, they can all be lifted by one person.

Above: Engineer Jake reviews the modifications of our JBL PRX amplifiers.

bicycle powered stage

Above: Locura’s bassist Izzy Wise digs the punch of the Modified JBL PRX 618 XLF Subwoofer.

bicycle powered stage

Our latest generation of Pedal Power Utility Box has ‘Split Rail’ outputs that connect directly to these speakers. You can ignore the AC power sockets.

Elevating the speaker on a stand (or by using our custom Line Array) puts them above ear level, which dramatically improves the clarity of the music when there are multiple rings or rows of people listening.

human powered stage

Above, left: 3 modified JBL PRX 612 loudspeakers suspended in a Line Array configuration at Bicycle Music Festival.

Since we do modify the circuit board, your JBL factory warranty will be void. We offer a 2-year warranty on this item. Here are some points that should reassure you that your investment will retain its long term value:

  • We maintain a relationship with JBL’s official Bay Area service point, JK Sound, and can take care of any issues that come up. JK Sound has successfully repaired amplifiers and replaced drivers for speakers post-mod.
  • After our initial R&D phase in 2009-10, we have had very few problems with this line of speakers.

We have confidence in these loudspeakers and stand behind the DC mod. We have been selling these to sponsored musicians in the Bay Area with great results, and without any warranty problems. The modified JBL PRX loudspeakers are also the secret behind Rock the Bike’s most famous art bikes, including the Blue Whale and El Arbol below.

El Arbol the bike tree
Above: El Arbol, the Bike Tree, uses the active components from the PRX 635 and 612.

  • Can I use my own speakers / mixer and still benefit from your Pedal Power system?

    What’s unique about the speaker is that it’s the only Pro Sound loudspeaker that can take DC power, i.e. bike power, as an input. Most Pro Sound loudspeakers require AC power. For the Pedal Power world this means you have to use an inverter to turn DC power into AC. But it only gets turned [...]

  • Basic questions to consider when crafting your Pedal Powered Stage

    The technical needs of a Pedal Powered event vary greatly depending on audience size, venue, and power needs of musician’s devices. The questions in this post will help you to know what features are most important for you, and how much power you’ll really need. Please answer these questions and email us using the contact [...]

  • What are the elements of a Pedal Powered Stage?

    What follows is an explanation of the key elements of a Pedal Powered Stage. If you are ready to buy individual components, please see the Pedal Powered Stage products section of our online store. If you’d like a custom quote for a Pedal Powered Stage, please start by emailing us with the answers to our [...]

  • "It's just plain impressive" says Climate Cycle customer

    “It’s just plain impressive that one person can produce that much sound with moderate effort. I hope you’re proud of your work. When our photographer gets us the shots, we’ll be sure to float some good times your way!” -Joey, Climate Cycle

  • SHAKE YOUR PEACE! Frontman Very Happy with Mod JBL PRXs

    I’ve been carrying 5 of these speakers on bike to pedal powered concerts for over a year now with my band SHAKE YOUR PEACE!, and I’ve been very happy with them. They’re light, thunderously loud, and the pedal power hack that Rock the Bike did has all been working great. I’ve had no tech issues [...]

  • CelloJoe Enjoys High Fidelity Sound in Mod JBL PRX Loudspeakers

    Hi. My name is Joey Chang aka CelloJoe and I have been using a Rock the Bike Modified JBL Pro PRX 612 for over a year. I have ridden many miles with this speaker strapped to my xtracycle bicycle and used it in many settings from the street in downtown SF to festivals all over [...]

  • Activist rapper Boots Riley's spoken word at the People’s Climate Rally Oakland, Rock The Bike's biggest event ever.

    Thanks to the Bay Area and System Change Not Climate Change organizers, volunteers, and attendeeds, and Rock The Bike crewmembers who came together for the People’s Climate Rally this past September 21 on the shores of Lake Merritt in Oakland. A major highlight of the event was Boots Riley’s spoken word and song during the peak of the event when at least 2500 people were in attendance. Skip ahead to 5:15 to hear the poem (warning, language!) Check out the awesome dance moves of the pedaler on the Tree during the song Ghetto Blaster (at 3:12). It’s inspiring to hear an activist talk about people power while using a people-powered PA system.

    In this second video, Rock The Bike’s Fossil Fool induces an outage in order to reenforce the message of people power:

    It was our largest audience size to date by more than double,  the previous being the 2013 San Francisco Bicycle Music Festival in Golden Gate Park at about 1000.

    The crowd size meant lots of new information to take in about live sound. (more…)

  • Many thanks San Francisco Bicycle Music Festival: World's largest Human Powered Music Fest.


    The 6th Annual San Francisco Bicycle Music Festival was our biggest ever and a milestone for our grassroots Human Powered Music Fest. Many thanks to the bands, fans, and our huge volunteer crew. Any one of the 3 phases of the day would have been epic enough. But we had a beautiful, idyllic daytime music festival in the park, an outrageous mobile party, and a post-modern urban block party all in one day. Daytime: 500+ people in a meadow, enjoying live music in the beautiful sunshine… Followed by a fire-truck dodging, freeway underpass screaming, Fossil Fooling LiveOnBike session, with captain Ariel using no electric assist to pull 3 performers and audio gear weighing 250 pounds on our Mobile Stage… Followed by a street party with an elevated stage,  a glowing Bike Tree, and a 3-person pedal powered stage lighting system.

    Rupa & The April Fishes perform at Golden Gate Park’s Log Cabin Meadow. Photo: Volker Neumann.

    We had 19 pedalers at the peak in Golden Gate Park! Plenty of power for our 10000-Watt sound system to run. In the distance you can see our Pedal Powered Line Array hanging from its bamboo tripod.
    We mobilized the entire festival on an outrageous LiveOnBike ride with yours truly, Fossil Fool, the Bike Rapper, performing with two bandmates on an elevated Mobile Stage towed by a Mundo. Above: the view from the Mobile Stage.

  • Pedal Powered Stage Gear

    This is the gear we use at our own Pedal Powered Stage events, including the San Francisco Bicycle Music Festival.


    A Pedal Powered Stage is a system that must include ALL of the following:

    The following elements are optional:

    • staging
    • lighting

    Creating a system yourself can be a great team-building experience but has a serious learning curve. Working with Rock The Bike will get you up and running much more quickly and with higher quality components. You’ll be able to put your focus on organizing events much sooner.

    Let our experience work for you. We’ve been Pedal Powering music events since 2007.  This will translate to less frustration and more empowering moments when you use our gear at your events.

    We would be happy to assist you in customizing a quote for your Pedal Powered Stage. Please note that the items in this category are often made to order. Please help us help you by giving us enough time to do our best work.

    If you aren’t sure if you want to purchase or rent, you can check out purchasing prices with the “BUY” button below, or you can contact us for rental quotes HERE, or email

  • Spinning Wheels Power Tunes

    This article features our 2 Modified JBL PRX speakers, 3 Mundo 500‘s, a pedal power Utility Box and the Biker Bar. Shaun O’Dell published this article in the Register-Guard on May 6, 2010.

    Look for a bunch of music lovers on Saturday who plan to pedal — not peddle — on behalf of live musical acts.

    Thanks to $10,000 in tourism grants, the University of Oregon Bike Program has been able to purchase equipment for this year’s Bike Music Fest that will help support live music acts by pedal power. The Bike Music Fest, which is incorporated into the Willamette Valley Music Fest, happens Saturday from 10 a.m. to 4 p.m. The larger music festival will continue until midnight.


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