I listen to music a lot and I generally use these headphones or laptop speakers but let’s
face it, laptop speakers do not sound that great and using headphones for too long is
not recommended. I do have these external speakers that sound amazing but using them
is not exactly straightforward. I will be taking them apart and replacing all the electronics
with perhaps a raspberry pi as the control unit, but that’s more involved and I’ll
get to it in a later video, so do subscribe if you’d like to watch that.
For today, we are going to build this modular, USB powered Bluetooth speaker system. The
audio quality is not as great as the bigger speakers but it is surprisingly good when
combined with a suitable enclosure like this. I will be using these for general, everyday
listening as it is a very convenient setup. You can even add a battery pack to it to create
a portable speaker system or add more speakers. So let’s begin!
Here’s what the electronics setup will look like. We need two speakers for stereo sound.
We will be using the commonly available, 2” full range drivers. These sound pretty good
when used with a right enclosure. Next, we need a way to drive them and we will be using
a class-D amplifier. If you don’t know anything about amplifiers then just keep in mind that
class-D amplifiers are digital in nature and are also very efficient compared to the older
class A or class AB amplifiers. This means that they don’t generate as much heat, are
compact and easy to use for DIY projects like this. We will be using the HT6872 amplifier
chips and since the chip is designed to drive one channel, we will be using two chips for
this build
We also need the main Bluetooth module and for this, we will be using the CSR8645 module
that is also very commonly available online. It is sold as a pre-programmed module that
handles all the Bluetooth related tasks like pairing with your phone, controlling the volume,
decoding music and pretty much everything else that’s needed. The audio output from
this module is of a low amplitude and it can only be used to drive headphones and that’s
the reason why we need the amplifier section as the speakers need a lot more power to produce
sound.
Finally, we need a power supply to power everything. I wanted to use a 5V input as that would mean
that we can power the unit using a single USB cable which makes it even more convenient
to use. We can use a microUSB breakout board to obtain power. We will also create a filtering
board that will add a bit of filtering and reservoir capacitors to handle the surge in
current requirements at higher volumes.
I would strongly recommend you purchase the Bluetooth module and the amplifier as a combo
like this one as that will simplify the wiring for you. BBox2 contains a project kit that
uses the CSR8645 module along with the amplifier chips and speakers. It makes use of through
hole components and I will be using that board for this video.
Let’s start by building the power supply section. If you’re using a microUSB breakout
board then you don’t have to anything apart from soldering some wires to the board. I
do not have a breakout board with me but I do have a lot of battery charger PCBs so I
will make use of one of them. I began desoldering all the surface mount components but the charger
IC contains a thermal pad at the bottom of the chip so I had to use the hot air rework
station to remove it from the PCB. A quick clean later and the PCB was ready for use.
Like I mentioned earlier, we will be creating a small filtering board using a protoboard
as a stable power supply is critical for correct operation. The combo module needs a single
power supply and we will supply it with 5V. Here’s what the wiring for the filtering
board looks like. We add a 100nF capacitor across the 5V supply to take care of the high
frequency noise and we also add a 1000uF electrolytic capacitor to act as a reservoir. You don’t
necessarily need such a high capacitor value but I would like to add it as I tend to play
music which has a lot of low frequency beats and that can cause a surge in the current
requirement which the power supply may or may not be able to handle. There are different
ways to solder it all together and this is the way I’ve done it. We then need to solder
wires to the 5V output and solder the wires from the breakout board which acts like the
input.
If you are using the module from BBox2, then we also need to create a 3.3V power supply
and that’s what we’re going to do next. The 3.3V power is only used by the Bluetooth
module and since it does not consume a lot of current, we can simply use a linear voltage
regulator like the LD1117 that will give us a 3.3V output. Here’s what the additional
3.3V section will look like and we add the 100nF and 1000uF capacitor to this output
as well. Once again, there are different ways to build this and here’s the way I’ve
done it.
We then need to wire the power supply section to the main board and if you’re using the
combo module then this is what it would look like. The switches are optional but it’s
a good idea to add at least the volume buttons. If you’re using the BBox2 version then this
is what the wiring will look like. We simply need to wire the additional 3.3V supply.
It’s now time to power up and test the setup. When you first power on the system, the two
LEDs will blink rapidly indicating that it needs to be paired. We will use a smartphone
to scan nearby devices and this should show up as either the CSR8645 or the F-3188 module
depending on the firmware loaded onto the actual Bluetooth module. Simply tap the name
to pair and once paired, using the speakers is as simple as playing some audio. You can
use the volume buttons from the phone to control the speaker volume but do keep in mind that
you can also control the volume from the physical buttons themselves. If, for some reason the
speakers don’t sound loud enough then you can adjust the volume manually using the buttons.
If you keep the speakers on your table like this, then they will not sound great at all.
The speaker enclosure plays a huge role in determining the final audio quality which
is why I recommend building a simple enclosure for this setup. You do not have to 3D print
something and you can use a cardboard box, or even a can like this. I found a very nice
model on Thingiverse and I decided to use that for the build. This particular model
is modular which means that you can connect multiple speakers to create a soundbar which
is a pretty cool idea. If you wire multiple speakers correctly then the audio output can
be shared between all of them which means they will not be driven as hard and hence
they would not distort at higher volumes. If you decide to use the same amplifier chips
to drive multiple speakers then do keep in mind that the final speaker impedance should
be 4 ohms as that is what the amplifier is designed to drive. I decided to stick with
two speakers for this build as I can always add more later.
If you decide to 3D print this then keep a note that there are two files for the speaker
cover or fascia. I printed version 2 first but that didn’t close well with the speakers
I had so I then printed version 1 which was a near perfect fit. Printing the parts took
longer than I expected. The amplifier enclosure took just under 11 hours and that was using
the rough settings. The speaker boxes themselves were about 5 hours each while the other panels
were less than hour each. I did not print the bracket file as I didn’t want to use
it. Removing the supporting material was again a tedious process but there’s probably a
much better way to do it. In the end, it was definitely worth all the effort.
It was now time to put everything together. The amplifier cover had a small hole in it
and I decided to mount a power switch. All I had with me were these tiny double pole
double throw switches so I glued one in place, soldered wires to it and then snipped the
unused terminals. It was time to wire the power board which meant I had to remove the
red wire and I decided to replace it with a longer wire to make it easier to mount.
I also replaced the 5V and 3.3V output wires to make it easier for final assembly.
Once this was completed, it was time to mount the USB board. I marked the approximate location
and used an old soldering iron to create a slot into the plastic which was bigger than
what was actually needed. I then held the PCB in place and applied some hot glue to
align it. Once this dried, I then added some more hot glue all around to support it further
and even added some to the outside to try and cover up the excessive opening. I then
added some Kapton tape to the bottom and it was time to work on the speakers.
I decided to use 6x1/2” or 3.5x13mm self-tapping screws for the entire build. I pushed the
speaker wires through the enclosure, positioned the speaker in place along with the fascia
and screwed it all in place. I then attached the speaker unit to the amplifier section
by using 3 screws. Finally, I added the speaker cover to the end and this half was ready.
It was now time to work on the other section and since I was waiting for the final fascia
to get printed, I decided to attach the speaker enclosure first, followed by the cover and
then the speaker itself along with the fascia.
Next, I wired the main unit in place starting with the power supply and then the speakers.
I decided to hold the PCBs in place using double sided tape and at this point I realized
that it didn’t make sense to keep the Kapton tape so I removed that first. It was then
time to insert the PCBs in position and add the amplifier cover using 4 more screws. A
quick clean up and it was time for the moment of truth.
I inserted the USB cable and pressed the switch. The power ON sound means everything should
work as expected and sure enough, here’s the final result.
I don't think you would be able to make out the audio quality through this video but the speakers sound so much
better and louder when placed in an enclosure. Overall, I’m totally happy with this build
and there’s enough space to add more electronics to the unit maybe an OLED display, battery
or some more controls if you like. The approximate cost to build this is shown on screen. Keep
in mind that you can lower the price by ordering directly from alternate websites which may
have a longer shipping time. If you do end up building one of these, then please don’t
forget to share it with us on social media. We will be building another interesting project
next week so don’t forget to subscribe, like, share and leave a comment below. Thanks
for watching and I will see you in the next one.