Hello everyone , so in this instructable I will be showing you guys how I built this simple boombox using plywood by means of a few handheld electric tools.Building speakers as well as other small projects which I could actually use in my day to day life has always been my passion and kind of like a hobby as well.We all love that feeling which we get when we get to tell others " Yeah, I made that " ;-) .
So this is a really simple boom box that is entirely made out of plywood and MDF board. It took me 9 days to built as I only had limited tools.This boom box has 4 speakers - two subwoofers and two tweeters which gives out a total of 30 watts of power. I have used 2 different kinds of tweeters- a silk diaphragm as well as a piezo electric one.I decided to do this because I realised that the piezo tweeter covered the really high frequency notes better than the silk diaphragm tweeter.
The boombox is designed with dual rear facing passive radiators .Passive radiators acts as a substitute for bass ports.They take up less space inside the enclosure as compared to bass ports and prevents vent airflow noises as well.But what I love about them the most is to see them vibrate when the bass hits which makes the whole boombox look a lot cooler ;-) .
The boombox runs on a 12.6 volt ,3S 2600mah 18650 battery pack which gives upto 6 hours of playtime depending on the volume.You guys could use NCR 3400 mah 18650 cells for longer play time.
The boombox supports FM,USB, bluetooth,SD ,AUX and also comes with an IR remote and on-speaker buttons for easy music control and tuning.
Step 1: THINGS YOU WILL NEED :-
I ordered almost all of my components from AliExpress.Most components are cheaper there but it might take upto a month or two to arrive at your place according to where you live .
1. YAMAHA TA2024 Amplifier X 1:
TA2024 is a special class T amplifier.And whats special about class T amplifier is that it offer both the audio fidelity of a Class-AB and the power efficiency of a Class-D amplifiers.Its a15 watts per channel amplifier when its running on 4 ohms load . I have used this amplifier before on an other project and was impressed by the fact that it dosn't heat up as much as other amplifiers with the same specifications, so thats why I decided to use this amp for this project.
2. 3 inch ,15 watt sub Woofers X 2:
Always choose a speaker whose impedance matches with the amplifier that you are using so that you wont face any heating issue with the amplifier.Here I have chosen a pair of 3 inch ,4 ohms woofers which according to the datasheet of the amplifier will be aperfect match.
3. DC-DC step down Buck converter X 1:
This is a module that uses the principle of switching to very efficiently step down the voltage.It is by every way better and way more efficient that any voltage regulator ICs like IC7805 . Our project needs it because we are using a 12.6 volt battery to power a 5volt audio decoder.So we need it to stepdown 12.6 volts to 5 volts.
Passive radiators are a substitute for reflex or bass ports. Usually for small enclosures,production of low frequency requires a long port ,so passive radiators are used instead.Passive radiators also avoids air flow noises which usually occurs in ported speakers.The main factor affecting the performance of a passive radiator based speaker is the mass of the metal plate on the radiator . The mass should be varied for tuning.When using woofers , always try to go for a passive radiator that is the same size or bigger than the speaker(not too big).In this project I have chosen a rectangular passive radiator which I decided to place on the back of the boombox.
5. 3S 12V 18650 10A BMS X 1
A BMS (Battery Management System) is very important when connecting rechargeable batteries in series.The BMS makes sure that all the batteries are charged and discharged equally.It makes sure the same amount of current is drawn from all the batteries when in use.A BMS also limits the maximum current that can be drawn from the battery pack so that the cells wont be overloaded.The BMS dosn't have a voltage regulator , so its really important that you use a 12.6 volt charger when charging the battery pack.
6. Frequency Crossover X 2 :
A crossover usually has an Inductor (copper coil) of thick wires and a series of capacitors.So a cross over has 1 input and 2 outputs. The inductor blocks the high frequencies.The output from the inductor is given to the subwoofers. The capacitor blocks the low frequencies .So the high frequency output from the capacitor is given to the tweeters.The tweeters could blow up if the output from the amplifier is directly connected to the tweeters without the capacitor stage.
7. 12.6 volt Charger(2.1 mm pin) X 1:.
8. XL6009 DC Adjustable Step up boostconverter X 1:
This module also works on the principle of switching.Its a step up module.Here we are using it so that we get a constant 12.6 volt at the amplifier's power input even when the battery voltage goes below 12.6V
9. Tweeters X 2:
The tweeters cover the all high frequency notes in music. Here we are using a piezo electric as well as a magnetic silk diaphragm tweeters.I tried different combinations and I was most satisfied when I used both at the same time.Always make sure yoy are using a filter capacitor or a crossover brfore using a tweeter.
10. DC Jack(2.1 mm) X 1:
For the charging port
11. Bluetooth Audio Decoder X 1:
12. 18650 battery(capacity of your choise) X 3:
Our power house.There are 1000s of different manufacturers for 18650 cells . Be sure to get one from a good manufacturers . 18650 cells could get dangerous if it has defects and not charged properly.I have attached the links of two types which I have personally bought and found that its good and safe.
13. DC toggle Switch X 1:
14. Connecting wires
15. 4000uf (or higher) , 16 volt capacitor
16. Wood glue
17. Spray Varnish
18. Wood sealer
19. Sand paper
20. 3mm LEDs
21. Thick double sided padding tape
22. All the necessary screws
23. 18 mm plywood sheets.
24. 5mm plywood
25. M3 and M4 nuts and bolts
Step 2: TOOLS REQUIRED:-
1. Philips Screw driver
2. Soldering Iron
3. Jig Saw
4. Sand paper
5. File(flat and triangular)
6. Rotory Tool(sanding bit, drilling bit,disc cutting bit,hole cutting or engraving bit)
7. Hot glue gun
10. Drill set
Step 3: SPECS:-
1. Total output power : 30 watts
2. 12.6 volt , 2600 mah battery
3. 6 hours of play time (depends on volume)
4. Charging time : 3 hours max
5. Dual Passive Radiators
6. Supports USB, AUX,FM,Bluetooth and SD card
7. Button feature and IR remote
8. Pywood housing and stainless steel handle
9. Neodenium silk diaphrag as well as piezo electric tweeters
10. Superb Bass
Step 4: CUTTING OUT THE FRONT PANEL:-
1. The first step is to draw the design on to a sheet of 5 mm plywood .The design should be determined according to the size and placement of the speakers you are using . In my case, I was using 3 inch speakers , so took the measurements according to that.
2. Using a jig saw , cut out this shape from the sheet . Be very careful while doing this as you could easily injure yourself.
3. File the edges and make it smooth and even.
Step 5: CUTTING HOLES ON THE FRONT PANEL:-
1. Draw 2 circles of 3 inch diameter where you want to place the speakers.
2. Attach the cutting guide to your rotary tool.Use a cutting bit or an engraving bit . I used an engraving bit so that I could cut out the circles slowly and smoothly.
3. Drill a hole somewhere inside the circle near the brim . Position the cutting setup through that hole from the other side,then start cutting and move towards the brim. Once you reach the brim, follow the circle.
4. Cut out both the 3 inch holes like this.
5. 1 inch holes for the tweeters can be drilled out using a hole bit and a drill.
6. Using a disc cutting bit , cut out the square holes for the bluetooth decoder and the Dc switch
7. Place the speaker on the 3 inch hole and mark the points for drilling holes for the M3 bolts which are going to be used for attaching the speakers to the front panel
8. Drill these holes using 3 mm bit.
9. File and smoothene the holes made for the switch and the decoder using triangular file.
Step 6: CUTTING OUT PLYWOOD RINGS FOR THE FRAME:-
1. Place the front panel on a sheet of 18 mm plywood and draw the outline
2. Draw the second outline inside the first leaving 8 mm gap between the both . This 8 mm is going to be our wall thickness
3. Drill four 1 inch holes on each corner touching the inner outline . This is done so that we get a point to start cutting with the Jig saw and it also helps when cutting curves.
4. Place the jig saw in one of the holes and start cutting out the ring. Cut the inner outline first and then cut the outer piece off
5. Similarly cut out 3 such rings.
Step 7: LAYERING THE PLYWOOD RINGS:-
1. Applying wood glue on both the surfaces stick all the rings together as seen in the pictures.Wipe off the excess glue using a cloth.
2. You don't have to worry if the rings are not aligning perfectly as we will sand everything down to perfection in the following steps.
3. Wood glues work best when a load is applied during the drying period . People usually do this using clamps , but since I didn't have any I used a huge bucket filled with water to act as the compressing load.
4. Let the glue dry overnight.
Step 8: SMOOTHENING THE FRAME:-
1. All the major imperfections are sanded down easily using the rotary tool and a sanding bit
2. The remaining sanding was done using different grades of sand paper by hand moving from rough to super smooth sand paper
3. Sand it until you are satisfies with the finish.
Step 9: MAKING SURE THE FRAME WILL BE AIRTIGHT:-
For the passive radiators to function properly , it is really important that the enclosure is completely airtight.
1. Coat the inside of the frame with 3 layers of wood glue.
2. There are usually small holes on the cross section of plywoods . If such holes are present on your frame, fill them with wood glue or some other sealant like Mseal , let it dry , and then sand off the excess.
Step 10: PREPARING THE BACK PANEL:-
1. Place the frame on a sheet of 5 mm plywood or laminated MDF.
2. Trace out the outline onto the sheet.
3. Cut out the back panel using a jig saw the same way we did with the front panel.
4. Cut out the holes for the passive radiators using a jig saw and make them perfect and smooth using files.
5. Drill a hole for the DC charging jack.
6. Drill screw holes around the panel for attaching it to the frame.
7. Counter sink these holes using a larger bit so that the screw head would fit flat with the surface
Step 11: THE HANDLE:-
Here I used a small stainless steel cupboard door handle.
1. Holes for the handle are drilled on to the middle ring of the frame
2. I used a rectangular piece of MDF inside so that the load would be equally distributed over all 3 layers instead of just one.
3. Tighten the bolts with steel washers in between.
Step 12: ATTACHING THE COMPONENTS TO THE FRONT PANEL:-
1. The first thing I attached was the power LED with a 10 k resistor
2. Then I attached the audio decoder and the power switch followed by speakers.
3. I decided to use only the high pass section of the frequency cross over . So I removed that section and attached it to the front panel.
4. Both the tweeters were glued on to prevent nuts and bolts
5. All the areas where there is a chance of air leak was covered with hot glue.
Step 13: ATTACHING BACK PANEL TO THE FRAME:-
1. Matching holes were also drilled to the frame . These holes should be slightly smaller in width than the screw you are planning to use.
2. A layer of thick double sided tape is applied on the frame as seen in the picture and the excess is cut off using a razor.This layer acts as a padding which helps in making the enclosure airtight.
3. Without removing the yellow film , the back panel is screwed on to the frame.
Step 14: PREPARING THE BATTERY PACK:-
1. Make sure all 3 cells have the same voltage
2. Connect the cells to the BMS according to the circuit diagram.
3. The BMS will reset and start functioning for the first time only after the charger is connected to the output.
Step 15: ADJUSTING THE BUCK AND BOOST CONVERTER:-
1. Connect the input of the buck and boost converter to the output of the Battery pack .(Be careful with the polarity)
2. Connect the output of the boost converter to the multimeter and turn the golden screw until the output voltage shows 12.6 volts.
3. Similarly connect the output of the buck converter to the multimeter and turn the small potentiometer until the output voltage shows 5 volts.
Step 16: THE CIRCUIT:-
Step 17: COMPONENT PLACEMENT AND CONNECTION:-
1. The switch and the DC jack is connected to the back panel.
2. A 4700 uf capacitor is connected to the output of the boost converter.
3. Rubber based adhesive(fevi bond) is applied on the brim of the passive radiators as well as around its cutout hole . After waiting for 10 min , the radiators are pressed on and stuck in its required position.
4. The remaining components are also placed using this glue and connected to each other using wires according to the circuit diagram.
5. Hot glue is also applied just as insurance.
Step 18: CLOSING UP THE ENCLOSURE:-
1. All the wires from the front panel are connected to their respective points on the amplifier and and power supply according to the circuit diagram.
2. Wood glue is applied ,the frame and the front panel is joined and a load is placed on top as seen in the pictures.(be careful not to damage the speakers while doing this)
Step 19: FINAL FINISHING:-
1. Cover the whole front panel , Back panel and the steel handle using plastic tape and news paper.
2. Sand the edges and the corners of the front and rear panel so that it aligns flat with the main frame.
3. Do the final sanding using smooth sand paper.
4. Coat the frame with 2 layers of wood sealer and sand again.This is done to prevent the wood from absorbing the varnish when its sprayed on.
5. Hang the boombox by its handle in an open area and start spraying the gloss varnish evenly without forming drops. Apply 3 coats of varnish.
6. Add 4 rubber foot so that the speaker wont move around due to vibration while playing music.
AND THAT'S IT , YOU ARE DONE :-)
Step 20: MORE PICTURES:-
I hope I wrote the instructions clearly . Do let me know your opinions about my boombox on the comments section .I had to build the boombox using the only tools I had , so some of my methods of working with plywood wont be right, pleas do let me know where I have to improve. Meanwhile if anyone has any doubts with the built feel free to ask me .
If you guys like my instructable pleas do vote for me in The Audio Contest
Runner Up in the
Audio Contest 2018