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Picture of Build a Bike Boom Box
How it all started: I ride my bike in a community ride every week, and the folks there wanted some way to enjoy music on the ride. I tried a regular boom box, but it's just not made for bike mounting. Being an engineer, I decided to make my own bike-mounted sound system. This is what I came up with.

Take a look at http://www.cathodecorner.com/bikeboombox/ showing the system in detail.

The amplifier circuit board is of my own design. It uses a Texas Instruments Class D stereo amplifier chip to provide 15 watts per channel of clean sound with very low battery drain. I designed a circuit board with everything needed for a nice bike system, including a charging port for your MP3 player.

The amplifier board details are http://www.cathodecorner.com/bikeboombox/cdamp/

 
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Step 1: The components

Picture of The components
The bike boom box is made of three main parts: the rack, the tube and the amplifier board. A pair of 6.5" marine speakers and a battery pack round out the system.

The amplifier circuit board is available from my one-man company Cathode Corner for $100 assembled. you may also download all the design info from my website and build your own if you are good at surface-mount assembly.

The 6" sewer pipe is available from any big plumbing supply house (not Home Depot or Lowe's, unfortunately) but needs to be cut carefully, a task that I describe how to do.

The bike rear rack is available at any decent bike shop. You may already have one on your bike.

Parts required:

A fully assembled CDAMP amplifier board with angle brackets
A battery pack, Li-ion 18650x4 series cells with protection circuit (Batteryspace)
A 14.4V Li-ion charger (Batteryspace)
A 5.5mm/2.1mm DC power plug to fit the amplifier board (Digikey or Mouser)
A pair of Kenwood KFC-1652MRB marine speakers (eBay)
Two each .250 and .187 quick-disconnect crimp terminals to fit the speakers
Three feet of two-conductor speaker wire, 18 to 22 gauge
A rear bicycle rack, standard aluminum type (local bike shop)
Two feet of 3/4" Sch. 40 PVC electrical conduit
18" length of 6" Sch. 40 ABS sewer pipe (big plumbing supply house)
One foot of 3/4" to 1"x1/8" 6061-T6 aluminum bar stock (hardware store)
A dozen #8x3/4" sheet metal screws
Two 8-32x1/2" machine screws, flathead preferred
Two 6-32x3/8" machine screws, nuts and lockwashers or nylock nuts

Tools required:

Electric drill and/or drill press
Fractional drill bit set, up to 3/8"
Countersink, #8 screw head
Hacksaw
#1 and #2 Phillips screwdrivers
Sharpie marking pen
Small file, square or flat
(optional) Large miter box or the parts to make one and a crosscut saw

Step 2: Cut the tube

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It's not easy to cut a piece of 6" sewer pipe with nice square ends. I ended up building a custom miter box for the task. Mine is not ideal; a carpenter could do a much better job of it. Feel free to copy my design which is pictured here. The pipe is 6-5/8" in diameter.

The boom box body is a 16 inch long piece of pipe. You also need to cut two pieces one inch long to be used as reinforcements for the speaker mounting screws.

Step 3: Cut the arcs

Picture of Cut the arcs
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Cut each of the one inch long rings in half, using the miter box as a holding fixture. Then cut each of these arcs in half to make eight same-sized pieces. You will need six of these to build the housing.

Step 4: Glue the arcs in the tube

Picture of Glue the arcs in the tube
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You will need three large clothespin-type clamps and a fresh bottle of ABS solvent cement for this step. A reference line on the outside of the pipe is helpful to align the arcs at the two ends with each other. I used the printed text on the pipe as a reference.

Place the pipe end-up on a piece of newspaper. Apply ABS cement to the inside of the pipe where one arc will be placed. Use the arc itself to see how long of a cement spot to make. Then apply cement to the outside of an arc. Press the arc into the cement spot on the inside of the pipe, align the edges flush with each other, and apply the clothespin clamp. Align everything again, making sure the clamp is not skewed in our out of the pipe, which will make the arc wander up or down. Use a paper towel or rag to wipe off the excess cement from the joint.

Repeat for the other two arcs on that end. The gap between any two arcs will be about 3/4" to 1" wide.

Let the assembly dry for an hour (longer if it's cold outside). Then remove the clamps, flip the pipe over and cement the other three arcs into the other end of the pipe.

Let the whole thing dry overnight before mounting the speakers.

Step 5: Drill the amplifier holes

The amplifier board has a row of connectors and switches on one side. It also comes with a pair of angle brackets that allow it to be mounted with two 8-32 screws. you can download a PDF file with a drawing of the panel hole positions and sizes at http://www.cathodecorner.com/bikeboombox/cdamp/CDAMPC-art.pdf. Print it out, cut out the rectangle and tape it to the tube to use as a drill guide.

Center punch the hole centers onto the tube.

Drill all the holes out to 11/64" first, which is the size of the 8-32 mounting holes at the ends of the row of holes. Then enlarge them all except the two end holes to 1/4", then drill the bigger holes out to 23/64" or 3/8", then the three biggest holes to 13/32".

Countersink the two end holes to fit an 8-32 flathead screw.

File out the double hole with a small file to permit a USB plug to fit through it.

Check that the amplifier board fits in the holes.

Step 6: Drill the speaker holes

Picture of Drill the speaker holes
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The speaker holes may be drilled in the tube after the cement has thoroughly dried on the arcs. Each speaker has six screw holes spaced equally around the edge. We use all of them for a stable mounting job. The speakers come with long stainless steel screws that require pilot holes to be drilled in the tube. A 7/64" bit is about right.

Set the tube up on end and place a speaker in one end. Rotate the speaker so that two mounting holes are centered on each reinforcement arc. Center the speaker on the tube and mark the holes with a Sharpie.

Remove the speaker from the tube and start each hole with the drill. Place the speaker back on the tube to double-check the hole positions and correct if necessary. Remove the speaker again and drill the six holes about one inch deep.

Turn the tube over and repeat the above procedure for the other end, being careful to align the holes at one end with those at the other end so that the speakers aren't rotated relative to each other (that would look bad).

Step 7: Cut and drill the conduit pieces

Picture of Cut and drill the conduit pieces
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Cut two 10" long pieces of 3/4" PVC conduit. File the burrs off the ends. Mark each piece for three holes in a row, one in the middle and one 1-1/2" from each end.

Drill three 11/64" holes in each piece at the marked locations using a vise and drill press if possible, but a handheld drill will work. Drill all the way through the pipe since the other side needs large holes to let the screws through into the pipe.

Turn the pieces over and enlarge the holes on this side to 3/8" diameter. I used a Unibit step drill to save time.

The last photo shows what the finished holes should look like.

Step 8: Mount the conduit pieces on the tube

Picture of Mount the conduit pieces on the tube
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This is a tricky step because several pieces are flopping around at once. The goal is to attach the two pieces of conduit to the big tube so that the rack will sit on them in the right place.

First, temporarily install a speaker in the end closest to the amplifier holes using two screws. This is the front speaker. The rack's upturned front end will have to clear the speaker, so it has to be there to get the fit right.

Place the tube on the workbench upside-down, that is, with the bottom of the speaker pointing up. The amplifier holes will be about 30 degrees above center. The speaker has a center line molded into the grill to make it easy to align with the center of the rack.

Place the two conduit pieces on top of the tube and hold them in place with the upside-down rack. See the picture to understand what this means. Position the two conduit pieces about 1/4" away from the end of the tube with the speaker grill. This end has the upturned end of the rack also. Check the centering of the rack with the speaker grill to be sure the rack is properly positioned on the tube. While holding everything just so, get out your Sharpie (you had it handy, right?) and mark the tube at each end of the conduit. The important end is the one near the speaker, unlike the photograph.

Now take off the rack and conduit, and hold up one conduit piece at the mark. Using a handheld drill with a 7/64" bit, drill a hole through the conduit hole closest to the speaker. Install a #8x1/2" screw in the hole you just drilled.

Align the conduit carefully with the direction of the tube. Drill a hole in each of the other two conduit holes and install screws in them.

Repeat the procedure for the other piece of conduit.

Hold the rack on the tube-conduit assembly and see how it fits.

Step 9: Mount the rack to the conduit

The aluminum bar comes into play in this step. Hold it across the rack resting on the conduit pieces, and mark where to cut it off and where to drill two holes that will contact the conduit. See the photo for details.

Cut the bar with a hacksaw, then cut another piece of identical length. File down the saw burrs.

Center punch the hole marks, then drill a 11/64" hole in each position with the two bars stacked on each other to get the holes in the same place. Or drill one bar and transfer the marks to the second bar, then drill it.

Now that the bars are made, use them to hold the rack onto the conduit pieces. Hold the assembly together with one bar in place. Put the bar against the rack's center support rod as shown. Drill 7/64" holes through the bar holes into the conduit, then install screws into these holes. Repeat for the other bar, but it doesn't have to be in any particular position. See photos.

Step 10: Take it apart

Picture of Take it apart
The rack and speaker have to come out to install the amplifier board, battery and speakers with cables. This seems backwards, but it's the only way to get everything installed properly.

Remove the screws that hold in the two rack clamping bars. Pull off the rack.

Remove the screws holding in the speaker and take it out.

Step 11: Install the amplifier

Picture of Install the amplifier
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The amplifier and battery pack are installed in this step. First, some cables have to be made. Unfortunately, the Kenwood speakers assume professional installation is available and so don't come with terminated cables like the cheap speakers you can find at Target. So you need to crimp some quick-disconnect terminals on to some wire. The positive terminal is the standard .250" size, but the negative is the oddball .187" size. Radio Shack and Ace Hardware sell the necessary terminals. Get the red ones that fit smaller wire.

I used some wire from a standard audio speaker kit - 22 gauge zip cord with a black stripe on one wire for polarity identification. I made the black stripe be the minus wire and gave it the .187" terminal.

Strip about 3/16" of wire from the other end of the cables and attach to the speaker screw terminals as shown. Then connect the battery wires - red to positive and black to negative. Finally, mount the amplifier board in the tube using two 8-32 x 1/2" flat head screws.

Put two lengths of double-sided sticky foam tape on the battery pack along both edges of one side, then stick it into place on the bottom of the tube.

Step 12: Install the speakers

Picture of Install the speakers
It's finally time to put in the speakers for real. Pull one cable out one end of the tube and the other speaker cable out the other end. Plug the terminals onto the speaker tabs as shown.

Now is a good time to test the system by plugging in a music player, throwing the power switch and seeing if music comes out.

Mount each speaker in its end using the six screws supplied. It's hard work. You can use an electric screwdriver (that's what we call a variable-speed drill with a #2 Phillips driver bit) to make it easier, but be careful as the screw reaches the end of its travel.

Step 13: Finishing up

Picture of Finishing up
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Install the rack on the bike using the hardware and instructions supplied with it. Then install the boom box onto the rack with the two clamp bars and the four screws. congratulations, you're done!

It's time to mount the music player to the bike's top tube or wherever you want it. There are commercially available devices to do this such as the iConsole, but it's expensive. I use a 2x4" sheet of industrial-strength Velcro, wrapped around the top tube and stuck to the back of my iPod Nano.

A one meter long 3mm to 3mm audio cable is usually just right for connecting the player to the boom box. Use the USB cable supplied with the music player to keep it charged via the USB charging jack.
Barry_L1 month ago

Very cool project, excellently designed :)

BryanM111 months ago

In the final portion of Step 9, when you are mounting the steel bars to the conduit - do you just screw into the conduit, or are there connectors (nuts) on the inside of the conduit? I would think these screws could come loose, thus making the metal plates fall off and the entire thing not be secured to the rack?

cjackson114 years ago
How about using a bazooka 8" amplified sub woofer
SG1Oniell4 years ago
Could you perhaps couple this with instructable with the friction drive bike generator instructable to recharge the batteries as well as your ipod and any other device?
That's not a box., it's a cylinder... a boom cylinder. Nice instructable .
The correct term would be tube...a boom tube. Not tobe confused with a theatrical boom tube,or boom stick...
Is it a good idea to use a Pb-Cl battery instead of a li-ion?  for biggest autonomy...
nice engineering & craftsmanship!

it would be cool if you posted a youtube video so we could hear it in action. i like the punchier sound of sealed designs like this than the boomy sound of ported designs. i bet your rig sounds crystal clear.
cool looking install. i haven't seen anyone use a bass tube on a bike system until now. i always pictured them on the sides of bikes in the saddle bag area, but it looks cool on top of your rack like it's a rocket engine.

if anyone is looking for a forum dedicated to bicycle stereos, stop by the bikeology website's forum. the owner of the site has built some pretty ambitious & LOUD trailer systems, but we'd like ANYONE with any kind of bike system or even just interested in them to visit.

as many different systems as people have built, it would be nice to have a community that shares info & ideas as well as a common place for everyone to show their rides off & just hang out.
Dracanse5 years ago
 hey i made one  before i saw this a few weeks ago but it has a amp so check it out
DIY Dave6 years ago
Cool
I have never had a good Kenwood product, i have two stereos i will not use just because they are kenwood.
abadfart6 years ago
i might stick one of these on my sisters bike
best idea ever
Gamer64606 years ago
This is a really cool idea. I've decided to build one too... I've got an amp-6BASIC on order from http://41hz.com. I also decided to build and put in a 3 channel EQ. I picked up some halfway decent 3-way car speakers to pop on the ends of the PVC tube. I'm probably going to go with Lithium Ion batteries too.

I designed and dropped in my own Power supply, with 5v for USB, and regulated power for the amp and EQ.

I figure, that with a little bit of work, I can have something nicer than anything I could get at the store.

I'll send a link to some pics when I get it completed
good job, found this from far away
http://www.oobject.com/category/boombox-bikes
now I is getting ideas.
How much did it cost? This looks like it is a very good system. I have a Terra Trike. Would it be hard to hear if you were going 30 mph? Your iPod cable looks longer than mine. Did they used to make them longer?
I paid about $200 for all the parts. The system is loud enough to hear riding in the bike lane next to heavy traffic at 35MPH. It can't overpower Harley engines, however. It gets REALLY loud when I bring it indoors if it's set to traffic volume. The iPod cable is a couple years old. Yes, they keep getting shorter - my 2003 iPod's Firewire cable is over 6 feet long! . You can get them in different lengths on ebay for cheap.
That's more than I have to spend right now. I have seen ihome bike speakers for $70, but of course they only work with ipods.
jarvist6 years ago
Maybe something like this amp: http://tinyurl.com/c3q5xe would be a suitable commercial product (£9 + £5 P&P)?

Virtualvillage also do a stereo chip-amp made up board for around £4, plus £4 P&P, and a slightly more expensive version of the above with a USB charging socket.
nixiebunny (author)  jarvist6 years ago
The last one you mentioned http://www.virtualvillage.com/Items/007650-009 does have potential. It would best be removed from the case, mounted connector-end-out, and the speaker terminals removed to run the wires inside. But it has most of the features of my board design.

I'll order one to see if the build quality is any good. The generic $20 class D amp board I got from eBay was a dud - it was hand soldered but they didn't solder the chip's heat pad to the board, and the chip itself was made by a defunct company. Nothing I would recommend.

You do get what you pay for.
nixiebunny (author)  nixiebunny6 years ago
I bought one of these units from China just to see its potential. As I feared, it's rather crappy. It had used, not new, power amp ICs in it, and they didn't bother to add heat sink compound when they assembled it. The USB charging port doesn't have the necessary resistors on the data lines to tell an MP3 player to accept a charge. So, yes, you could use one of these cheap amps, but it's not worth the aggravation to me.
Ah well, thanks very much for the update - I was considering getting one of those for a similar battery operated boombox (this one going deep underground on a caving expedition...)
Where on earth did they get used Power AMP chips from? Crazy!

I used one of those T-Amps in a previous 12v project (26ft sailboat I was singlehanding), which was extremely impressive - but they don't seem to be available anymore, and my one is now permanently epoxied to a bulkhead...

http://www.tnt-audio.com/ampli/t-amp_e.html

So is there really no well-working chip-amp in a box that can be bought ready made for a sensible price?
rhino6 years ago
Thanks, I was looking for a generic mp3 boombox. All the ones I find are dedicated to the expensive, trendy, and far too popular IPod. I need one for one of the more sensible, less expensive, brands. Can you add a power amp to this to kick it up to about 40 watts? Do you take this to Burning Man?
nixiebunny (author)  rhino6 years ago
This device has a 15 watt per channel power amp. It's plenty loud for Burning man - I brought it there last summer. Actually, I had two - one for the camp and one for the bike.
this is very cool, very detailed insturctions, great instructable
Search eBay for TA2024 amp boards... about $25 will get you complete working amp board. Sure Electronics is one source. Maybe the chip manufacturer is defunct, but those chips have a reputation as great-sounding amplifiers.
nixiebunny (author)  bassbindevil6 years ago
Yes, I have one of those boards. Unfortunately, the fine folks at Sure's soldering facility hand-soldered the board and they never soldered the amp chip's heat slug to the PC board! I decided not to use it for that reason and that the connectors are not at all conducive to panel mounting. But don't let that stop any of you from using it.
maestro_au6 years ago
This is awesome! Great work. I have an aunty/uncle who want a sound setup to take with them to the outback and I might well end up asking if I can buy one of those amp boards. I did some quick math - 2 channels at 15 amps would be a current draw of something like 2.5A at 12V. Does this fit your experience with your unit? Also, Can you give me an idea of what the current draw looks like at low vs high volume levels?
nixiebunny (author)  maestro_au6 years ago
The beautiful thing about a Class D amplifier is that the current draw is rarely 2.5A. It only uses as much power as it needs to move the speakers at any instant, so the average draw is well under one Amp. This means that a 2AH battery pack will last for about 4 hours even when played at full volume (but not driven to a high distortion level).
dj.kazb0t6 years ago
Yay! You do Tuesday night bike ride in Tucson, AZ don't you? Hooray for engineering bike mods! And thanks for always bringing the tunes.
milt156 years ago
This project is great simply everything is taken into consideration also a nice option if you added dynamo to charge the battery looks like you are a good engineer
Nicely done-well written and a great idea. I wonder if the plombing supply shop would gut the pipe to size when you bought it. 2 boards wider than the pipe joined together at right angles to make a "vee" could also work to cut the pipe. The end of the pipe needed to be cut can stick out the end, or sawn through the boarfs and pipe at the appropriate place.
Transquesta6 years ago
Cool idea/proof of concept! I don't ride bikes (outside the one at the gym :-)) but the same general design would be great for campsites, shops and such. Now, about that pricey amp and iPod specific hook-up? How 'bout a sto-bought in-line am (est: $50.00 tops ) with standard connections for stereo mini phone plug?
nixiebunny (author)  Transquesta6 years ago
I would be delighted to use a store-bought amplifier if it was easy to mount and had connectors that are practical. I couldn't find one, so I made my own. If you know of a good one that I could buy, please point me to it. Also, the hookup is not at all iPod-specific. It has a USB charging port and an audio jack. I just happen to use an iPod.
That is well. Thats just tight
Punkguyta6 years ago
Why wouldn't you port the box?
nixiebunny (author)  Punkguyta6 years ago
I have thought about that. I'm not really into booming bass; I just want to hear the music. I'm not an acoustical engineer, so I don't have a feel for the best way to do it. I was thinking that a piece of 2" sewer pipe in a 45 degree street elbow would be a clean way to do it, but it may need a much larger port diameter to work well.
I never said you had to be a bass-head, but you will get not only a more natural sound, but also should make the music less distorted at high listening levels. As far as if you were to actually make a port, one or two holes the size of "C" sized batteries, that would be sufficient. The lower the woofer's resonant freq, the bigger the port should be, but even for a 12" subwoofer, a hole the size of a D sized battery, sometimes 2, is often enough, and is not really that much bigger. But basically speaking, a 12" sub is going to be around 40-20hz, whereas your speakers (good choice with the kenwoods btw), are most likely to be hitting up in the 120hz range, 80 at the lowest, and for this, you do not need a large port. Look at the ports on cheap computer speakers (yes the ones with the subwoofer, waste of money, might as well just buy a regular stereo with 2 speakers, it'd sound better *rant end*) The ports are roughly the same sizes I described (circumference of a C cell battery), and those subwoofers are rated closer to the 120hz range aswell. Experiment with it my friend, make a small hole and go bigger, as you can always take more off, but hard to glue plastic shavings back together eh? But if anything any kind of hole in the enclosure (as long as the rest is properly sealed), should make the sound, sound better by some marginal amount.
Junk Mail6 years ago
How many watts is the amp?
nixiebunny (author)  Junk Mail6 years ago
15 watts per channel into 4 ohms. It's a Texas Instruments class D amp chip, the TPA3100D2. You can follow the link on the intro page http://www.cathodecorner.com/bikeboombox/cdamp to learn more.
jakee1176 years ago
once I finish (ha ha) the atomic zombie chopper I've been working on for two
years, I may have to add this.

if I ever finish that project =P
isacco6 years ago
Very good Instructable! The desing is nice and simple. The object looks robust and well finished. The crafting step are well explained and illustrated. Congratulations
altomic6 years ago
nice. could be used as a new housing for that crappy old boombox that's been sitting around. how about installing an Ipod holding compartment? less wires out and aesthetically cleaner.
CarpetGnome6 years ago
This is pretty cool, well done and documented. I had a bike with a generator attachment, used to power a light, might be cool to use that to power the boombox.
hg3416 years ago
well i will do this when i make my e-bike i think it look really nice btw
f3rg6 years ago
Pretty cool. At first I thought you just mounted a Bazooka (http://www.sasbazooka.com/) on a bike rack, and I was like, how hard is that? :]
nixiebunny (author)  f3rg6 years ago
Yeah, I thought of using a Bazooka, but it solves a different problem (making your pickup truck windows rattle) so I rejected it. However, if you like the bikes that go boom, it would work just fine.
gmjhowe6 years ago
Excellent work! Simple idea, that seems to work perfectly. Do you find that you only tend to hear one channel with the speakers facing in two opposite directions?