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The Bluetooth Speaker...!


This is my very first DIY and of course my first post. Prime intention of this site is to motivate and educate those who are interested in electronics and mechanical builds. As I was moving to a new house it was indeed a good thought to have a speaker with me, so I thought why not build one?

 MECHANICAL BUILD

          First of all, I was concerned about the casing. I did a quick research and found that solid wood and plywood showed the best acoustic properties, hence I went with those for the mechanical build. I first drew an outline of the speaker with approximate dimensions on a paper and then transferred them to the half inch teak, which was laying around, which was going to be the front panel. The whole length of the speaker which was 50cm was divided in half, and thereafter further divided to match the speakers and passive radiators

                                                                                   

            Teak is one of the best wood, known for the workability. I also found some round drill bits in the local hardware shop for around 250 rupees (4$). I've drilled 4 holes, each of 38mm, in those designated spaces in the wood, rounded off the edges with a sanding grip in a sander, and finished it with some couple of sandpapers varying from 60-280 grips. Though it was a real mess, it was worth it. At this point, I also made sure that all those speakers and radiators fit nicely (for the radiators I've made two holes at the ends and used a chisel to chip of the rest).
                                      
 


             After that was done, I gave the panel a couple of coats of teak finish which was also bought from the local store, the panel also received sand down after every coat with 280 grip paper. After the front panel was done, the sides, back, chambers, top, and bottom pieces were also cut down to measurement with the help of a circular saw, but now the pieces were cut on 4 layered plywood. And that was the complete mechanical part.

 ELECTRONIC BUILD.

 The electronic build was easy, literally. :)  It took me a full day to complete the circuitry. The list of components I used for the build are given :

 


  • 2 speakers (Mid Ranger,4ohm,3w,40mm)                                     200/-
  • 2 passive radiators 80mmx38mm                                                    70/-
  • 2 3w amplifiers (PAM8403)                                                            40/-
  • 1 Bluetooth module with USB aux inputs                                     210/-
  • 2m strip wires                                                                                   60/-
  • 1 47kohm potentiometer1 15w(5v,3a) boost converter                  160/-
  • 1 battery protection and charging board (TP4056)                           15/-
  • 1m shrinking tubes`                                                                            7/-

The circuitry was basic and was really easy with a bit of soldering. As it was a budget build to lower the cost I scavenged 4 working lithium ion 18650 cells from an old laptop battery which I found at a nearby service shop. Also, 2 speakers for the bass drivers were recovered from an old broken mini speaker. With that two successful recoveries, I cut down a cost of rupees 1800/- (25$).


It was a tight fit inside the case, though it came out great at the end. There was plenty of heat shrinks used and I tried to keep it minimal. I also made groves in the partition plywood for the speaker wires to move freely. For the volume control, I used a 47kohm potentiometer connected between the Bluetooth and amplifier. For the switch, I went with toggle switch which was capable of driving huge currents up to 8ampere. For fixing the partition plywood I used Fevicol SR glue. Then I positioned the speakers and radiators and hot glued them in place, used thicker wires for the speakers' connection as it drives in CURRENT! :).

With a bit of math, I found out that, with a capacity of the 2.2amp hour, 4 batteries would give a power output of 32.56Wh. With an average consumption of 7 watts, including conversion losses of 3%-4% the speaker would last about 4.5hrs theoretically, but I'm getting playbacks up to 10hours. And with a constant charging current of 1 ampere, it would take 9 hours for a complete charge. Usually, I keep it charging while I'm asleep


After nailing in the front panel with sides, back, bottom and partition plywood it was time to screw in the top panel, I used small screws so as to make it accessible when needed. For the volume knob, I again used a bigger drill bit to cut down a `circular piece, sanded and polished it to necessary and glued it to the pot.
Before screwing in, I put some wood granules and sponge for better acoustics. Once everything was done I used a foot by half carbon vinyl paper for its aesthetics. Molded and shaped the vinyl and heated it with a hairdryer and stuck it down to the case. And so, the project was done !!
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