How to make a Bluetooth speaker for under $25

Andrew Overby
11 / 27 / 17

In a recent project, I created a Bluetooth speaker from the ground up. However, it is even easier to create one out of an old speaker cabinet lying around your home, or found for cheap at a yard sale or thrift store.

STEP 1: FIND YOUR SPEAKER

It all begins with the speaker. I found this Yamaha desktop speaker at a local thrift store for $2.50. Any speaker lying around the house works great too. The perk to converting these speakers is they were likely to go under numerous types of product testing so the speakers are idealized for the cabinets they are in. All we will have to do is add the Bluetooth module and power to the speaker.

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STEP 2: SPEAKER SPECIFICATIONS

In order to find out what type of amplifier you will need to purchase, it is essential to know the impedance (ohms) and output (watts) of the speakers. An amplifier too high in power will destroy the speakers and an amplifier too high in impedance can overheat due to current flowing too quickly.

If the speakers you have, such as mine, do not indicate a datasheet number or mention their power output, no sweat. Most, if not all speakers will display their impedance which is a good start. To test the power, I connected an amplifier I had around the house that was 25 watts. I simply wired in the speakers, and turned the volume knob up until I heard them distort. At this point, the knob was about 3 / 5 of the way to max volume. I set up a proportion ( 3 / 5 = x / 25 ) in order to find the number of watts I want the speakers to comfortably handle, calculated to be 15 watts.

STEP 3: FINDING THE RIGHT AMPLIFIER

Now that you know the specifics of the speakers you will be using, finding the right amplifier comes down to how much you want to spend, and what features you would like the amplifier to include. Since most amplifiers can now be purchased as modules, it is very easy to slide these inside the speaker cabinets because they do not take up much room. It also gives the user the ability to create add-ons, such as volume knobs and portable power accessories.

For my project, I found an amp with a TPA3110 15W x2 digital amplifier board with Bluetooth 2.0 built in. The board can be found at the link below:
https://www.amazon.com/gp/aw/d/B075R13CV5/ref=ox_sc_act_image_1?smid=A2KRDQ1AI5Y5G6&psc=1

I was looking for the cheapest option of amp because I wanted to spend the least amount as possible on the project. Understand that buying a cheaper amplifier module can sacrifice the sound quality. A class D or class T amplifier with Bluetooth 4.0 are the best options if you are comfortable with spending the money ($15-$20 more).

Another important thing to note is fitment. Since the speakers in my cabinet were 2.5 inches, I could not exceed that dimension with the amplifier or else it would not be able to fit inside.

STEP 4: POWER OPTIONS

Another important factor with your speaker is how you want to power it. If you would like to make it portable and battery powered, this will cost significantly more (up to $70). However, I decided to power my amplifier by a 12V AC-DC wall plug. Buying this power supply made for an easy, affordable way to get efficient power to the amplifier. To find what supply is right for you, read the data sheet provided with your amplifier in order to see the power requirements. A link to the one I purchased can be found below:
https://www.amazon.com/gp/aw/d/B076PMMH3B/ref=mp_s_a_1_2?ie=UTF8&qid=1511052103&sr=8-2-spons&pi=AC_SX236_SY340_QL65&keywords=12v+2a+power+supply&psc=1

STEP 5: WIRING THE AMPLIFIER

Since the speaker I will be wiring has a mono channel, I had to wire my amplifier accordingly. If your speakers have two sets of power and ground wires, simply wire up your amp using the defined labels on the board (soldering is typically required for these amplifiers). If it is mono, wire the positive (power) wire to the right channel positive lead and the negative (ground) wire to the left channel negative lead. This will ensure that the speaker output is the same throughout both speakers.

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STEP 6: WIRING THE POWER

This is where you get to be creative. I had a toggle switch laying around, so I wanted to be able to power the speaker on and off while it was always plugged in. The wiring was simple for the three prong switch, as shown below:

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I used the including 12V female adapter that came with the power supply kit to include in the speaker for easy connection to the cabinet.

I had to create a custom mount in order to house these accessories, so I removed the old wire leads and replaced them with a custom fabricated back plate, which came out to look very seamless, especially if it were painted to match the cabinet.

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STEP 7: CLEAN IT UP

After ensuring all your connections are secure (hot glue and soldering works great), all you have to do is throw everything back in the speaker, screw up the holes, and you are set! Enjoy the ease of Bluetooth control from all around your house!

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