Who says you can't have it all? Good looks and a great sound!
My name is 'Holman" and I'm a Bluetooth speaker in the form of mans best friend - a dog of course! Why is my name Holman? Well, that's the name of the manufacturer of the PVC pipe I used and the name grew on me as I completed the project!
Whilst this might look like a complex project if you have access to the metric PVC pipe and a 3D printer I'm actually quite easy to make. If you don't have access to the metric PVC pipe then I suggest you print your own (see the separate step for the models).
Before you get started - take a look at the video I've uploaded and if you like this project then please click the "Thumbs up" icon and subscribe to my channel!
Step 1: Materials & Tools - an Introduction
Unfortunately this build does require you to have one special tool, namely a 3D printer. I recently took the plunge and got a Lulzbot Mini and have had a few weeks of fun getting to grips with this technology. I have to say its been pretty painless and most, if not all of the mistakes have been of my own making so I think I can recommend this as a good option for 3d printer noobs such as myself.
NB: This instructable is not sponsored by Lulzbot and this is not an advert just an honest opinion of my 1st hand experience.
Another thing that might put you off (but I hope it doesn't) is that the 3D printed parts are all held together with various sizes of metric PVC piping (usually used for rainwater/waste water pipes). If your in a inch/imperial location the solution is to print the pipe parts as well and so I've also included models for those parts in a separate step. (although the models are 'untested)!
Other than that the tools and skills are:
5) Soldering (very small amount)
Overall I'd rate the project as requiring moderate skills.
Step 2: The Heart of the System, the Amplifier
This is not a 'boom box' and my aim was to make a good sounding system that you can listen to all day. There are many cheap-ish PCB amplifiers out there on eBay/aliexpress/bangood and some of them need to be avoided. I did a lot of research and tested about 6 in total before landing on this one....
This is a 2.1 (Stereo + Sub-woofer) Class D amplifier with a Bluetooth 4.0 and line input. During my research I bought and tested a number of boards most of which were of dubious performance. The board I recommend seems to much better than most and doesn't suffer from the following issues that other boards have:
1) The amplification is not 'overblown'. The TPA3116 chip seems to drive the speakers without distortion. The loudness is enough to fill a room - whilst there is a rich base from the sub-woofer, don't expect this to shake the house down - it won't. I've gone for quality of sound not quantity!
2) A lot - and I mean most Bluetooth amplifiers on eBay that I have tested have a basic problem in that the Bluetooth module puts a high pitched whine onto the audio. I understand from other sources is that this is most likely due to the Bluetooth modules power supply not being properly isolated from the amplifiers power supply. The module I have chosen is silent in this regard!
3) This Bluetooth module doesn't emit a loud "connection successful" alarm when it connects to its source - maybe its just me but I found this irritating when testing other units.
4) The 4 potentiometers on the board actually all have a function - bizarre but on other boards I tested one or more pots seem to be doing nothing and clearly have not been implemented properly.
5) The TPA chips have heat-sinks
6) The kit comes with 4 nice aluminum/black knobs, a line input lead and a remote LED & associated lead.
All in all this is a nice amp for the price - I've done the hard work. No need to look any further! If the above link is broken then you should be able to find this boards at other sellers, priced between $30-40USD (June 2017)
Step 3: The Speaker Drivers
Well, for a 2.1 stereo system like this we need at least 3 drivers. As we have a sub-woofer for the really low frequencies I choose an 'full range' driver for the upper frequencies. I got both these drivers from Parts Express in the US. Being in Australia I had a delivery charge to pay but as the prices themselves seem to be very competitive and I didn't mind the extra for the shipment. Both the drivers are fairly popular so you might be able to find them locally if your not living in the US.
Full Range Driver
Fountek FR58EX 2" Neodymium Full Range Speaker Driver
Tang Band W3-1876S 3" Mini Sub-woofer
To ensure the drivers performed well I modeled them in the speaker cabinet design software "basebox pro". I include the design files here if you are a HiFi aficionado and want to check out the full parameters. I also include the spec sheets in PDF format.
The full range speaker drivers are a closed box design whereas the sub-woofer is a vented type with the tail of the dog is the functional external port!
NB: I'm a bit of a noob at speaker box designs - any expert advice welcome!
Step 4: Print Out All the 3d Parts!
OK - so there are a heap of parts to print out and depending on what level of quality you choose it could take some time. Have patience - just take it one piece at a time.
Some items are required in multiples. I'd recommend printing one, then, when you are happy, duplicate.
I printed most of the parts in PLA which is the easiest material to print with. I did opt for ABS for the leg and paw ball and socket joints to take advantage of ABS's tougher properties. The ball and socket joints require a quick sanding of the mating surfaces before snap fitting them together.
Step 5: Pipework Parts (The Source of the 'Holman' Name)!
The cylindrical parts of the body, head, neck, legs and tail are all made from various sizes of metric PVC pipe (Holman brand). These were available at my local hardware store in handy 1m lengths. Here is a list of what you will require:
1) Body - 230mm of DN100 PVC pipe
2) Head - 150mm of DN80 PVC pipe
3) Neck - 100mm of DN25 PVC pipe
4) Tail (sub woofer port) - 280mm DN15 PVC pipe
Upper leg - 70mm DN15 PVC pipe
Lower leg - 40mm DN15 PVC pipe
Just in case you can't get hold of the metric PVC pipework I used on this project I've modeled the 4 sizes required and you should be able to print these out also. I should emphasize I have not printed these out and as such they are untested! (I have not modeled the holes that require to be drilled also).
Step 6: Drilling the Body for the Amplifer Knobs
The body (DN100 pipe) now needs to be prepared for the PCB amplifier by drilling the 4 holes to accommodate the potentiometers. Firstly, counter-bore a 'flat' using a spade drill. I used 14mm but 12, 13 or 1.2" should be OK. Secondly, drill out the center to accommodate the shaft of the potentiometer (8mm).
Step 7: Mounting the PCB Amplifier Inside the Pipe
Mounting the PCB amplifier is a bit tricky as it is a tad too 'tall' for the DN100 pipe. The best technique is to pre-wire the terminals with the speaker wire before installing it as the connections are inaccessible once the PCB is inside the pipe. To get the PCB inside the pipe I squeezed the pipe (gently in a vice) to elongate/ovalize the section. The PCB potentiometer shafts will then go into their respective holes and you can remove the pipe from the vice.
Step 8: Adding the Head and Body Ball Joints
This is a simple ball joint where I've printed the male part but the female part is the pipe used for the neck (DN 25 PVC pipe). The male ball is attached to the body and head in a similar way by drilling a hole and then gluing it into position with the shaped supporting washer on the inside of the tube. The neck tube then simply pushes over the ball to create a swivel & tilting joint.
Step 9: Flaring the Port (tail of the Dog)!
To allow the air a smooth passage to and from the port I flared both ends of the port. I 3D printed a male flare then heated the end of the pipe with a hot air gun (If you don't have a hot air gun then use a cup of nearly boiling water). With the end of the PVC pipe heated up, push it down onto the flare. Do this in a few stages and it should give a nice gentle curve for the air to flow over. I overcooked it a bit at the end and ended up 'upsetting' the tube a bit resulting in a bit of a ripple just behind the flare - oops.
As the tube passes through the rear housing, the 2nd flare can only be done after the tube is in-situ. The PVC tube is a tight fit but to ensure a good seal I used a 2 part epoxy to hold it in place for sure.
Step 10: Painting
All the parts can now be painted - your choice of colour!
To prepare the parts I lightly sanded the PVC tube with some 1200 grit wet/dry paper. This is to ensure a good 'key' for the paint on what is a very smooth surface.
The 3d printed parts were also prepared with varying grades of wet and dry paper. I didn't spend a whole heap of time on this and it's really up to you how much time you want to spend on this phase. I basically just removed the worst of the roughness and plastic burrs prior to applying the coats of spray paint.
I started with 2 coats of grey undercoat then finished off with up to 3 top coats of matte white (matte black for the full range mounts). Detail areas such as the pink tongue were finished using some artist acrylic paints.
Step 11: 24V Power and Full Range Speaker Wires
The 24VDC input to the amplifier and also the 2 wires for the Full range speakers travel through the neck of the dog. I sealed the hole afterwards (above and below) with a silicone sealant. It's important that this is sealed to ensure that the 'ported' sub-woofer performs as it should.
Step 12: Fitting the Neck
The neck provides the termination point for the 24VDC input required for the amplifier (2.5mm female jack about half way up the neck). When connected, the power lead looks like a leash! Later in the build I also included a collar which is made from a thin strip of Velcro I found lying around. I trapped the Velco behind the nut holding the jack in position.
Once the wiring is done the neck tube simply push fits over the ball to give a swivel & tilt joint for the head.
Link for 2.5mm jack
Step 13: Assembly - Legs to Body
The legs attach to the body with M6 x 35mm bolts. I printed a shaped washer for the inside of the tube to provide extra support against the tight clamping force required to keep the leg's in place. A cut down rubber grommet placed between the top leg joint and the PVC body provides the stiction force required.
An M6 Nyloc nut was used to ensure that the nut needs to stay in place (and not loosen over time).
Links for parts:
Step 14: Mounting the Full Range Speakers
The full range speakers mount to their respective housings with an adapter. The speakers already have a gasket on their front face so you should only need the 4 small self tapping screws (and M3 washers) to hold it in place.
Link for parts:
Step 15: Attaching the Full Range Speaker Housings
Each of the speaker housings has a shaped and angled profile that mates with the DN80 PVC pipe and hold the speakers so that they face away from each other slightly. This 'looks' right and also projects the sound for a pleasing stereo effect. I've molded a 10mm diameter hole into which a aluminum tube provides the main support for the driver housing and also provides a route for the speaker wires to come through from the neck. A smaller hole adjacent to the aluminum pipe allows a M3 or 1/8" bolt and nut to hold the housing in place.
The speaker wires can then be passed through the 10mm aluminum tube as you place the head assembly on the neck. These 10mm tubes require sealing with silicone for the 'closed' box design to work properly. Once the sealant has cured the wires can be soldered onto the +ve and -ve terminals of the speaker driver. The front face is then pushed into the rear housing. This joint was such a tight fit I didn't use any sealant/epoxy just in case I need to get back into the housing in the future.
The muzzle was now glued in position using the 3d adapter piece as I'd printed this out in ABS I was able to use std PVC cement for this large joint. Use a silicone sealant or Loctite superglue if you printed this part in PLA.
Links for parts:
Step 16: Mounting the Sub-woofer
The sub-woofer mounts to the front of the DN100PVC pipe with a custom 3D printed adapter part. The part has 6 holes ready for the M3 x 25mm bolts to hold it in place (1/8" or similar will be OK also). I used a small bead of silicone to seal the sub-woofer to the adapter and also drop in each screw hole. Again, this is to ensure that the sub-woofer enclosure is a good seal and that all the air movement is through the port and doesn't leak out where it shouldn't!
Link for silicone sealant:
Step 17: LED Indicator Installation
An 3m LED and an associated lead is included in the amplifier kit. The LED is blue and flashes slowly when looking for a Bluetooth connection then comes on steady when a connection is established. I should have drilled the hole before painting but I forgot!
Step 18: Line Input Installation
The amplifier PCB is supplied with a line input lead so I decided to tuck this away at the back. The Bluetooth connection is the primary connection but if no device is detected then it will use the line input as a sound source. I had to chop off the connector on one end of the lead and solder it to a 3.5mm stereo jack.
I had this grey stereo jack lying around - here is a link to one that would be suitable:
Step 19: Fitting the Back Cap
The back cap is a slightly looser fit in comparison with the others. To ensure a good (but removable) seal I wrapped a length of insulation tape around the circumference before pushing the cap in place.
Step 20: A Finishing Touch!
I added a dog tag with the Bluetooth code on it! The raised text was highlighted with a silver permanent marker pen
Step 21: Power on and Enjoy!
A plug pack is used to power the amplifier. For the best performance, I got a 24VDC pack which seems to provide enough power for this D class amplifier although it might be better to have a higher amperage version if you can get hold of one. Alternatively the amplifier would work well from a 24VDC battery.
Link to plug pack:
Once powered on the blue LED flashes slowly. To connect the Bluetooth open the setting on your device and scan/look for "YJS-68D V4.0". The code required for this amplifier is 5188. If the Bluetooth connection is successful then the LED will stay on (stops flashing) and you should be able to hear the music coming from the speakers.
If you don't have Bluetooth then you can use the line input jack.
The volume can be adjusted either from the device or via the knobs on the back of the dog. the knobs functions are (from the one nearest the neck backwards)
1) Overall volume
2) Tone Bass/Treble
3) Sub-woofer cut-off frequency
4) Sub-woofer volume
NB: with the Overall volume AND the sub-woofer volume cranked up to full can overload the amplifier causing occasional clipping/distortion
I hope you've enjoyed this instructable and I hope you are enthused to have a go yourself. Any constructive comments are most welcome.