Zebrano Bluetooth Speaker - How to Build DIY

This is a bluetooth speaker, a completely custom design with the focus on audio quality over portability. That said, if you're looking for a light BT speaker to take anywhere, this is not for you.

It features:

• 16V - 11700mAh Battery pack
• Zebrano wood front
• TPA3116D2 BT Amplifier
• 1 x 6-1/2" Subwoofer
• 2 x 6-1/2" Passive radiators
• 2 x 4" Mid range woofer
• 2 x 1" Dome tweeter

It produces a very impressive sound, especially on the lower frequencies. This was my first serious speaker built, and I'm very happy how it turned out.

Wood

• 1 x MDF sheet 121x122 cm 18 mm - black - 70% PEFC (this does not have to be black)
• 1 x Wooden baffle (in this case: ZEBRANO 610x235x21 mm)

Drivers

• 1 x Dayton Audio DCS165-4 6-1/2" Classic Subwoofer 4 Ohm
• 2 x Dayton Audio DSA175-PR 6-1/2" Designer Series Aluminum Cone Passive Radiator
• 2 x Dayton Audio RS100-8 4" Reference Full-Range Driver 8 Ohm
• 2 x Dayton Audio DC25T-8 1" Titanium Dome Tweeter

Battery pack

• 12 x Samsung 18650 Li-ion battery- 2900mAh - 8.25A - INR18650-29E
• 3 x 18650 battery holder (4 batteries)
• 1 x Li-ion-Li-Po Protectioncircuit (BMS) - 4S

Crossovers

• 4 x Capacitor - ME-3,30T3.450 | 3,30 µF | 3% | 450 V
• 2 x Capacitor - ME-1,50T3.450 | 1,50 µF | 3% | 450 V
• 2 x Resistor - DNR-8.0 | 8.0 Ω | 10 W | 2%
• 2 x Inductor - AC20-10 | 0.10 mH | 0.21 Ω | 5% | 20 AWG
• 2 x Inductor - AC201 | 1.0 mH | 0.73 Ω | 5% | 20 AWG

Electrical

• TPA3116D2 amp + BT
• Solder
• Head shrinkable tubing
• Audio jack plug
• Power cables
• Audio cable
• Jack chassis
• ON/OFF switch
• AC/DC power plug chassis

Miscellaneous

• Wood screws
• Universal foam tape - 10mm wide
• Speaker dampening material

Science

When the focus of a speaker is on audio quality, it is important to have some basic knowledge about drivers, volumes, etc. Google "how to build a speaker" and there's a ton of information varying from very simple to extremely complicated. You need to find the balance between the time you want to put into the science/understanding how the speaker works and how much time you're willing to spend on the whole project.

It needs to be perfect

If you're like me and you're spending a very generous amount of time, effort and money into a project like this, it has to be perfect. Now that is something you'll never achieve and you will need to accept that not everything will be perfect. You're limited to the tools and experience you have access to.

Design

So when designing a speaker like this; set a realistic goal. In my case; "I want a speaker that is both aesthetically pleasing and sounds great. It does not need to be extremely loud."
Once you know what kind of shape and volume you want, you can start drawing. I put my whole design in a 3D program; Solidworks. This way it was easy to determine the volume and size of the speaker.

Not all components are equally as important to get right. When building a speaker, the drivers are pretty high on that list.

Drivers

You need to find drivers that fit your budget. In my case; I planned on spending a maximum of 500 euros (yes it's a lot and you don't need to spend this much) on this speaker. So I looked for a total driver package of about 200 euros. Probably the most important thing is the volume recommended for the drivers.

Design

There are two ways to go about chosing drivers and designing your speakers. Design the enclosure first, or chose the drivers first. By designing the enclosure first, then finding drivers that match the size and volume, you can tweak the enclosure afterwards while still keeping your desired design. It will just be a little larger/smaller/wider/etc.

In my case; I wanted 5 drivers. One subwoofer and a 2 way left and right channel (a midrange and tweeter each). The baffle (where the drivers are mounted) needs to have enough surface to support all this. So this is where you'll start. Then design the enclosure around it and ensure you have enough volume for the subwoofer.

You can get as crazy as you want, but keep in mind that you'll have to build it as well. An enclosure in a star shape might be cool, but will take a long time and a lot of precision to make. Instead, I recommend to design something you're comfortable building (or at least not too far outside your comfortzone).

Baffle

The baffle is probably the most important side of the enclosure. Your drivers will be mounted on this, so it needs to be strong enough. If you're going with a subwoofer, think about the vibration this will make and how strong the baffle will need to be to stay still.

In my case; I went for a Zebrano wooden baffle. It's solid wood, relatively hard, and most of all, I find it very good looking. The characteristic of the dark lines in the light wood make for an eye catcher.

Before you start drilling holes, make sure you know which of the drivers need to be in a seperate chamber. In this case, the mid-range drivers need to have their own (~1,5L) chamber. The tweeters do not require any. Meaning my enclosure will be split up in 3: The main chamber (for the subwoofer) which is about 19 litres, and the two for the mid-range drivers.

Keep enough space around the holes for the drivers to build these chambers in the enclosure, and still be able to mount the drivers properly (they stick out on the back, duh).

Enclosure

Do a quick google search on what material you should use for your enclosure. You'll find that most people recommend MDF. Mainly because it's a homogene material. Equally heavy and dense in every square mm. It's (almost) ideal, there's HDF, but that is a bit overkill (too much).

Crossover

Probably the most important electronic pieces in the speaker are the crossovers. These ensure that the audio signal is split up into high tones (which are sent to your tweeter) and medium/low tones (which are sent to your mid-range woofer).

If you happen to use a subwoofer, I recommend buying the amplifier listed above, as it's capable of separating the bass signal from the mid and highs. You can plug the subwoofer directly into the amp and it works perfectly fine.

Designing your crossover

This... is complicated. You can get as deep into this as you like, the truth is that it will take you some time to understand how they work, let alone be able to design one. There are some tutorials out there that I recommend you watch and read. They do a far better job at explaining than I will. There's software to simulate what they will do, I do recommend you use that to test your setup before buying anything.

If that is all too much for you, you can copy mine. Parts are listed in the supplies section, how to solder them together will be shown in the building section.

Amplifier

Any sound system that is not "plug&play" (most things with a 3.5mm audio jack, like headphones for your phone) needs an amplifier. An amplifier boosts the signal that is sent from the source to ensure it is strong enough for the drivers to play. The most important information you need to know, before buying an amplifier board for your speaker is the following: Impedance (in Ohms), the input and output power (in Watt) and the output channel setup (2.0/2.1/5.1/etc.)

Again, do some research on this if you wish to use a different one than me, if not: Use the TPA3116D2. This board has built in bluetooth, it's not too expensive (mine cost me 24 euro's) and will provide enough power for this setup.

Battery pack

An amplifier needs power, usually a specific voltage for boards like the TPA3116D2. This board is capable of 2 × 50 W Into a 4-Ω BTL Load at 21 V. This is only the left and right channel, the bass channel is capable of putting out 100W. THIS DOES NOT MEAN YOU HAVE TO RUN IT AT 21V. I run it at 16V because I don't need it to be extremely loud. The TPA3116D2 works anywhere between 12V and 25V. So your battery pack will need to output anything between those voltages AT ALL TIMES.

Building your own battery pack is easy, as long as you understand how electronic power works. The easiest and best option by far, is using 18650 Li-ion batteries. There are many tutorials on YouTube which explain how to make these. I recommend you watch one (or more) of these.

The essential parts are:

• The BMS (Battery Management System). You'll see 3S, 4S, even 5S or higher out there. My BMS is 4S and will ensure the amplifier gets 4 x 3.65V (Nominal battery voltage) = 14.6V as a minimum at all times.
• The 18650 batteries themselves (make sure the maximum output is higher than what you need so they don't overheat)

ATTENTION: When choosing your BMS ensure you calculate with the nominal voltage, not the maximum. Eg: BMS 3S: 3.65V x 3 does not meet the minimum requirements for the TPA3116D2 (12V), but 3 x 4.2V (maximum voltage) does.

Finally! We can start building. You have your design, drivers, crossover, battery pack, amplifier and any misc. parts you want on your speaker thought out. Let's get started.

Precision is important

Please, for the love of god, do not speed through this as fast as possible, to get your speaker done as fast as possible. The result will disappoint you. Instead, take the time to carefully measure, check and double check your plan before you make holes you can't put back. You can always trim, not add wood. That said, I used a laser cutting machine to draw (not cut) the lines on my sheet of MDF. This way there's less room for human error. I cut all the wood using the machines available in the workshop at my University. Use the tools you have on hand, if you do not have access to a proper wood workshop, it's fine to use a handheld circular saw. Just make sure you're careful and precise.

Baffle

Making the holes for the drivers can be tricky. You want them to fit just right to ensure there is no air leaking through, and you have enough room for the screws when mounting the baffle. Too little of an edge and it might split the wood. I used a circular saw on a pillar drill machine to ensure it was straight and exactly where I wanted them. Again; TAKE YOUR TIME.

Once all your panels are cut out, you're ready to build the enclosure. I recommend using tape to put everything together and check if it all fits.

Screws or glue?

I used screws and glue for the most important panels, the ones that will be stressed the most (because I plan on making a carrying strap on the sides, the side panels have screws into the top/back/front/bottom panels). The side panels will hold the other panels together, and because I wanted a smooth finish, I used only glue for the front/top/back/bottom panels.

Inner chambers

Before you build the chambers inside the enclosure. Mount the drivers onto the baffle and ensure everything fits. It's always different in real life than on paper. It is important that each of these chambers (for the mid-range woofers) are air tight, so I used a silicone kit to mount and close off the inner chambers. To ensure no air leaks out of your enclosure, you can seal it all up if you like.

Crossover

The crossover is probably the hardest to design, but the easiest to solder. I recommend drawing the components on paper and connecting them before even touching them with a soldering iron. This way you know exactly what you will be doing.

The battery pack

Next, there's the battery pack. If, and only if, you have access to a spot welding machine you can weld nickel flaps on the batteries directly. If not, I recommend you do the same as I did here. These are battery holders, specifically for PCB's, but the lips on the side are easy to solder together using some solid copper wire. The same applies here as on the crossover; Draw your setup before soldering anything together. It's important you get the BMS connected properly. Think about this before you do anything to the pack.

Baffle

This baffle is a solid Zebrano wooden plank. After testing multiple oils and laquers on the cut out pieces, I decided to use the SKYDD furniture oil from IKEA. It brings out the dark lines and makes the whole thing an eye catcher.

Enclosure

Painting the enclosure starts with sanding down all uneven edges. Be careful with using machines for this, as messing up in this stage means you either have an ugly paint job later, you have to fix it, or you have to build the whole thing again.

Battery and crossovers

First off, you need to place the battery pack and crossovers. I mounted both on a piece of plywood to be able to take them out easily if I ever need to.

Mid-range driver signal

Your mid-range drivers should be in a seperate chamber if you have a subwoofer, like discussed earlier. Make sure you can feed the signal to these drivers using an airtight option. I made brass pieces feeding the signal through the chamber sides (reference pictures) and soldered the wires onto these.

TPA3116D2

This amplifier features a master volume knob (red), treble volume, L/R channel balance, bass volume and bass frequency. The last one regulates up to what frequency the bass channel should play.

The way you wire this is shown in the diagram. The bass is obvious, the mid-range woofer and tweeters are L and R channel. These will go to your crossover, then they're split up to the tweeter and mid-range woofer.

You can mount your amplifier on a plastic panel (shown in the first picture), plywood or even metal. Unless you're willing to re-solder the potentiometers and connect them somewhere else (which has its advantages), you'll have to make sure your panel is air tight. Any air leaking decreases effectivity of the subwoofer.

Personally, I enjoy spending time on details, like the feet. In the pictures you see rubber feet, which are available online. I chose to make an aluminium piece around it, making the end result look very chique.

Take your time

The worst thing you can do is rush this phase. You just spent so much time on making the enclosure and baffle, soldering a battery pack, etc. And please do take your time when drilling a hole in your baffle, mounting the drivers, taping the enclosure with foam tape, everything! If something is a tight fit, fine, if it does not fit, DO NOT FORCE IT. Honestly, if you spent this much money and effort, make sure you're happy with the end result and don't let your enthousiasm make you rush the last phase.

Testing

That said, the first thing you will do, ofcourse, is test the speaker! Before fastening all screws and mounting the baffle into the enclosure, test the electrical setup. It won't sound great but you'll be sure the system at least works. Then assemble the whole thing and run it again. Make any adjustments, in my case to the foam tape and the passive radiator weight, and test again.

Final thoughts

Most importantly, enjoy your creation. Speakers are complicated and you can be proud of yourself for building it. Next time I'm building a speaker, I will NOT use a solid wood baffle. It's too much hassle as it bends, especially after making huge holes in the plank. I had to add foam and remove foam and apply pressure left and OH GOD, don't use solid wood!

I love the result though, I enjoy looking at it and listening to it. I'm extremely satisfied, every time I turn it on and enjoy the sound it produces.

Good luck!

If this has convinced you to build one of your own, good luck! Take your time and decide how much money (and time) you want to spend before you start. These things can get really costly and take hours and hours of your time.