Introduction: Portable Bike Speaker Sound System

There are many options for portable sound systems, but none that fit my unique requirements. I needed a portable sound system that could:

  1. Be loud. I need a system that could project clearly in large, open spaces.
  2. Offer superb sound quality. I did not want to sacrifice quality for efficiency or volume.
  3. Offer power-efficiency // long battery life. My system needed to last at least 12 hours without being charged.
  4. Be rugged. I needed a system that could be knocked around or continue functioning through exposure to all kinds of weather conditions.
  5. Be (relatively) light. I needed a system that weighs less than 20 pounds for carrying on a bike long distances.
  6. Be cost-effective. I didn't want to spend a fortune on this system.
  7. Be easy to use. I needed a system that anyone, without instruction, could use easily and would not require regular maintenance.
  8. Be compact. I needed a system that could easily fit on to the back of my bike.

This list was a major challenge but, ultimately, I put together a system that meets these requirements and I wanted to share what i put together with the rest of the world. While my primary use for this system is a week-long bike tour (RAGBRAI in Iowa), this system can be easily adapted for other niches.

Build List

Power Tools Needed

  • Power drill
  • Jigsaw or hacksaw

Cost:

My total cost was approximately $225. Your mileage may vary depending on when and where you purchase these items.

Specs:

Total Weight: 13-14 pounds (6kg)

Step 1: Speaker Assembly

I didn't get images of spray painting the speaker enclosures but this required that I disassemble the enclosures, including the speaker screen.

Note: even if you are not disassembling the speaker screen, I highly recommend you pop it out and apply glue to the rim, then reseat the screen. They are otherwise only held with a small patch of adhesive that will likely fail before long. If using Gorilla Glue for the first time (as I was) you should know that it will expand, so apply sparingly!

  1. Using 8x #8-1/2 in. screws, attach the speaker to the back of the speaker enclosure screen.
  2. Attach the quick-snap speaker wire to the speaker. Strip the ends and attach the other end to the inside of the speaker enclosure.
  3. Optional: sodder the wire to the terminal in the speaker enclosure.
  4. Once finished, re-attach the speaker screen to the enclosure

Step 2: Establishing Speaker Mount

My rear rack had two pre-drilled holes that I used to secure one end of the board that I would use to mount the speaker system. I drilled two holes into the board and then fed a #10-24 screw through each, secured by a wing nut. I went with the wing nut because I wanted to be able to easily tighten the screws by hand, or remove the nuts by hand to more easily remove the entire system from my rack.

I attached two Superklip PVC Pipe Clamps with wood screws, then snapped my 2' PVC pipe into place. Each clamp is rated to hold 84lbs. so the PVC pipe is securely in place, but can be easily removed if needed.

Note: In the photos you can see that the board extends beyond the end of the rear rack. Although this makes the system less stable, this was an intentional decision. I wanted the speakers to be hanging from the PVC pipe rather than upright so that road vibration and other forces wouldn't cause them to move over the course of a weeklong bike event. Given that they are hanging, the enclosure on each speaker ends up obstructing the area in which the rear panniers would be placed. I could have made a wider design that clears the panniers, but decided that I prefer a more narrow profile that extends off the end of the rear rack.

Summary for Step 2

  1. Drill two holes in 20" piece of Top Choice Whitewood Board
  2. Secure whitewood board to rack with wing nuts.
  3. Attach superklip clamps to the opposite end of the whitewood board.
  4. Clamp PVC pipe into place.

Step 3: Cut the PVC Pipe Down to Size

With the speakers assembled and seated in their enclosure, hang them from the PVC pipe.

I used painters tape to decide where I would cut the PVC pipe. I used a jigsaw to cut through the PVC pipe but you could just as easily use a hacksaw. After cutting the PVC pipe, I sanded the ends and attached PVC pipe end caps to each side.

Summary of Step 3:

  1. Attach speakers to PVC
  2. Cut PVC to desired length if necessary
  3. Close off the ends of the PVC with end caps.

Step 4: Mount the Electrical Equipment

The Project Source 13-in Tool Box ends up fitting perfectly on the Top Choice Whitewood Board from Lowe's, so that the "legs" at each corner of the toolbox come to fit snugly along the edges of the board.

To secure both the board and the toolbox to the rack, I ended up using a U-bolt (pictured) and threaded it behind the back of the rack.

A hole was drilled on each side of the tool box to accommodate the speaker wire. I was able to place the amplifier, battery, bluetooth receiver and ground loop noise isolator in the tool box without much difficulty. Eventually, I removed the face plate of the amplifier and returned it to the tool box to give it a more slim profile, but you can play around with the arrangement that works best.

Set the battery to 12V output and you're all set! On my recordings, the output of the battery at 12V was 4.5-amps. I've had no issues with the set-up and, in my tests, you should be able to get 7 hours of play time on one battery at maximum volume. On a recent ride playing music at less than full volume, I drained the battery from 65% to 45% in 2h20m (10% per 70 minutes). YMMV

Step 4 Summary:

  1. Drill holes through board and tool box for the U-bolt and secure to the rear rack.
  2. Drill a hole in each side of the tool box for the speaker wire
  3. Connect your amplifier, battery, bluetooth receiver, and noise isolator and you're good to go!

Comments

author
Quadrifoglio (author)2016-06-08

Congratulations on your Runner Up finish.

author
Kogalskaben (author)2016-05-19

Try using and other amplifier then the Lepai, my experience has shown that the Lepai is so poorly build that the ta2020 chip doesnt perform optimal. Try buy some amps without casing, they are extremly cheap when you do that. Cased amps are the expensive ones. Take a look at the maxamp 20, a realy good sounding and even more efficient amp. You can allways adjust the volume on the audioplayer. I realy æike the look of your system, it looks wicked.

author
NickS180 (author)Kogalskaben2016-05-19

Thanks for the tip! Messing around with electronics is definitely something I'm less comfortable with but I'm looking to learn/improve. I looked up the amp you recommended but I'm not sure how to connect the following: (1) audio in via aux cord, (2) DC power supply, and (3) speaker wires. Are all of these connections present or will I need to buy additional supplies?

author
Kogalskaben (author)NickS1802016-05-23

1. You get a jst connecter with it, where you can solder a jack socket onto. or you can order it a socket on.
2. Power supply can be connected via the connectors next to the left and right sound out connector or solder to the board.
3. There are screw terminals/connectors.

author
NickS180 (author)Kogalskaben2016-06-01

Thanks for your response - I ended up ordering a new amplifier but won't receiver it for a short while. I had some difficulty tracking down the maxamp20 but I liked what I saw with the TDA7492 which, if nothing else, should be an improvement on the ta2020. In any case, I'm feeling more comfortable navigating the world of amplifier boards.

author
Kogalskaben (author)NickS1802016-06-03

Thats good to hear, hope it will improve the System.
take a look at speakerplans . com's forum, under the 12v section, lots of good reading in there.

author
Quadrifoglio (author)2016-06-01

It looks like something from the 1960’s Disney Tomorrowland with the “futuro”, rocket pod assist styling. The overall fit and finish is tight. It gets my vote.

Is the Ground Loop Noise Isolator because of a hum problem or were you following a car install as a guide?

Everyone has their opinion on Class T DC powered amps; I like and own several of the Dayton Audio DTA-1 amps.

author
NickS180 (author)Quadrifoglio2016-06-01

Hey thanks for your comment! Others have also mentioned the resemblance to 'rocket boosters.' Admittedly, that wasn't the intention at conception but given the party atmosphere of the weeklong event where they're (primarily) being used, I think the aesthetic works well.

Good question about the ground loop noise isolator - I'm using the same battery to power both the amplifier and the bluetooth receiver, which results in feedback from the battery. You can get around this with bluetooth receivers that feature a built-in battery (e.g. Mpow Streambot) but I'd decided against those because most advertise theoretical battery life of 10-hours, meaning for my purposes I'd need to consistently worry about recharging the bluetooth receiver mid-day. In my original plan, I had tried using a separate 10,000mAh battery to power the bluetooth receiver, but I found that the battery would regularly shut-off because the bluetooth receiver was not continuously drawing power. The Poweradd Pilot Pro battery, on the other hand, remains powered on so long as there's something plugged into one of the ports (regardless of whether it's drawing power). With the ground-loop noise isolator, I can reliably use the Poweradd Pilot Pro without getting feedback.

I've continued tinkering with the design a bit (replacing the wood with a steel chassis, which has allowed a more compact design). I looked into the comment regarding the Lepai//ta2020 amplifier and eventually felt I'd gathered enough information (and confidence) to purchase a TDA7492 amp board on ebay. I'm currently waiting for it to arrive and, if there's an improvement, I will post with updates.

I did strongly consider the Dayton amp and ultimately decided on the Lepai only for reasons of power (15WPC vs. 20WPC). If you've compared your Dayton amps to the performance of the Lepai 2020 I'd be curious to hear your thoughts! Thanks for reading!

author
Quadrifoglio (author)NickS1802016-06-01

I hadn’t considered the bluetooth receiver. Two connected devices on a single power source at different potentials is an invitation to a ground loop. Interestingly, if you Google for instructable ground loop, there are a bunch and a bunch of them include bluetooth.

I haven’t tried the Lepai, but based on specs, testing, and reviews, the Dayton has equivalent useable power (about 10WPC), much lower noise, and much better sound. No point in changing. However, in your application of overcoming traffic noise and wind noise, I suspect it is less about the nuances of sound quality and more about following Spinal Tap’s advice to turn it up to 11. That is, until you hit speaker distortion.