Introduction: Old Speaker Conversion to Bluetooth Boombox

By Watch me on YouTube!
About: Nice to meet you! I'm Donny from Lithuania and I have a passion for designing aesthetic, yet durable and practical projects. Check my YouTube channel for more! ▶ http://www.youtube.com/c/DonnyTerek

HI everyone! Thank you so much for tuning in with me on this build! Before we jump in the details, please consider voting for this Instructable in the contest at the very bottom. Support is highly appreciated!

It has been a few years since I started building various portable Bluetooth speakers and boomboxes and even though it is truly satisfying to design and build your own portable speaker - one thing that I noticed for sure is that it does take quite a lot of time, usually a few weekends to build a decent speaker. Therefore I thought I would rather use an already built commercial speaker and attach a "rechargeable amplifier" to it! Not only is it much less time consuming but also a lot cheaper since you can get great quality second-hand speakers really cheap!

This idea of giving old items a brand new life has been with me for quite a while. Therefore I thought to give this old speaker built in the 80's a new life by converting it into a portable Bluetooth + WiFi boombox using the amazing Up2stream Pro audio receiver which can connect to your streaming device via WiFi or Bluetooth 5.0 and with its own app it is a breeze to use. Let's get into the details of this build next!

Step 1: Parts and Plans

As always I am trying my best to provide you with the full parts list, build plan templates - both metric and imperial and a wiring diagram. All of these you can find below! Make sure to zoom in for a better view.

Make sure to double check the measurements of the template with a ruler before proceeding the build since every printer is different and might shrink/enlarge the template.

Parts:


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Tools:

For the main building material of the insertable panel I chose 6mm (1/4") MDF board which is cheap, easy to cut and shape. Plywood can be used as well.

Attachments

Step 2: Speaker Choice and Wiring

When choosing the speaker for this conversion build the most important parameters would be the impedance and the RMS output of the speaker. Also, since we are using a powerhouse of an amplifier which can output nearly 50 Watts of clean power in the palm of your hand and costing around 3$, it is best to use a 3-way speaker consisting of a subwoofer, a midrange driver and a tweeter. Ideally you would want a 3-way 4 Ohm speaker rated for up to 50 Watts.

I chose to use the legendary 3-way speaker - the Radiotechnika S-50B built in the 80's which I got for cheap. It still plays great though it does have a few dings and scratches and a missing dust cap from the subwoofer but it is a great bargain for what it is. It is an 8 Ohm speaker rated for up to 50 Watts.

The wiring is quite simple, mainly consisting of the battery pack, the Bluetooth+WiFi audio receiver and the amplifier. The output of the amplifier is connected to the input of the crossover that is built in the speaker itself. Take note at number 9 in the wiring diagram - two 1k Ohm resistors connect the Left and Right channels to produce a mono channel that is connected to the input of the amplifier. Since we are using high capacity 18650 Lithium Ion cells, you can expect around 4 hours of playtime. It is best to spot weld the batteries together to form a battery pack but you can also solder them - make sure you watch a few videos on YouTube about safely soldering 18650 batteries first. Main objective would be to keep the batteries as cool as possible when soldering and trying to apply the heat for no more than 5 seconds not to damage the cell.

Step 3: Cutting and Gluing the Panel

I have to say - this is a super simple build from the woodworking perspective - the panel that is screwed in to the speaker consists of only 2 square panels and 2 support pieces to hold the weight of the batteries, amplifier and the audio receiver. As I wrote in the previous step - make sure you print out the panel template and glue it down on a piece of 6mm (1/4") MDF board for best results. Then mark the holes with a hole punch and drill them out accordingly. I highly recommend using a step drill bit for larger holes. All the tools used can be found in the list in the previous step.

Once I got the holes drilled out and the rectangle cut out for the voltage indicator, I used a hand router to engrave a few millimeters into the board on the inside face of the panel. This helps to tighten the switches and buttons in place better. I also sanded the edges round and smooth for a nicer finish.

When the panels are nice and ready, glue them up! Also note that I drilled a few extra holes for the zip ties to hold the battery pack in place - an afterthought but works well.

Step 4: Wrapping the Panel

A quite straightforward step - wrapping the front panel in vinyl. I chose this carbon fiber look which looks great if done properly. Make sure the front panel is dust-free before applying the carbon fiber vinyl. A little bit of heat helps to stretch the vinyl around corners. Once the vinyl is in place, use your fingers to push out any air bubbles or wrinkles. Be careful stretching it around corners - it might tear easily with too much heat. A sharp hobby knife is your best friend here (do I need to mention to be safe with sharp objects) to cut out the holes in the panel and the excess vinyl around edges.

Step 5: Control Panel Assembly

To assemble the control panel first of all I screwed in the brass standoffs and then mounted the buttons, switches and the voltage indicator in place. I then attached the battery pack with zip ties and mounted the audio receiver and the amplifier using M3 nuts on the underside. After a bit of soldering later we have a fully working speaker control panel.

Before we mount the panel into the speaker it is a good idea to test if it works. Simply connect the amplifier's output to the input of the speaker and see if it plays. Once turned on it should play a short tune of the audio receiver pairing. You can also trim the amplifier output by using a small screwdriver by turning the small potentiometer on the amplifier. That way you can set the output power limit according to your speaker capabilities.

Step 6: Speaker Disassembly

Now that we have the control panel made and ready, we can start disassembling the speaker. Since it is most likely that everyone will be using a different speaker, the disassembly process may differ but the main thing is to take out the the speaker drivers and the crossover from the enclosure. Then you have to solder/connect a piece of wire to the input of the speaker crossover so that it reaches the panel where you will be mounting it. Once the speaker is disassembled to its components, you can drill out four holes for mounting the leather handle if you decide to make the speaker somewhat "portable". Simply drill the holes out so that the included threaded inserts mount in place from the inside of the speaker enclosure.

Once you decide on the placement of the control panel, mark a rectangle that is a bit smaller than the outer dimensions of the front control panel so that you can see where to cut. Once that is done, drill out four larger holes - one in each inside corner. Then using a jigsaw, cut the rectangle out and clear any dust that will be inside of the enclosure.

Step 7: Final Assembly

We're almost there!

Now that the rectangle is cut out, we can place the control panel inside and using a hole punch mark the holes for the screws. After drilling the holes that are a bit smaller than the screws, apply a strip of adhesive foam tape around the edge and connect the crossover cables to the amplifier output. You can now screw down the control panel in place. No need to overtighten the bolts, just enough to squeeze the foam tape all around and make an airtight seal.

Here we go! The speaker is all finished and ready to blast some tunes.

Step 8: Final Thoughts

I have to be honest with you - I can't get enough of this speaker! Definitely goes to my favorite project list. It blasts tunes really well and can shake the china cabinet with ease. It is incredible what a small Class-D amplifier combined with a high quality audio receiver can produce. This almost antique speaker has now been brought to a new life.

I am also very impressed by the sound quality of the speaker. By being able to adjust the equalizer on the app, the speaker can play the way I like it - the bass is deep and precise and the highs are not too harsh. It also has great battery life considering the battery size I have used. The WiFi connectivity is even greater - no worries of cutting out the connection if the speaker is moved to another room. It is also a amazing how easily the audio receiver can stream audio using Spotify, Deezer,Tidal, Qobuz, Napster, iHeartRadio or almost any other audio streaming service.

I definitely recommend this project it was super fun building one and the high sound quality just exceeds my expectations of the audio receiver and amplifier capabilities.

I am once again thankful for tuning in with me on this build and want to kindly remind you to consider voting for this Instructable down below! I'll see on the next build!

- Donny

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