Building A Solar-Powered, Supercapacitor-Based Speaker

Inspired by many months of hours-long load shedding in South Africa, [JGJMatt] decided to make a portable speaker that can play tunes for hours on a single charge and even charge off the integrated solar panel to top the charge off. None of this should sound too surprising, but what differentiates this speaker is the use of two beefy 400 F, 2.7 V supercapacitors in series rather than a lithium-ion battery on the custom PCB with the Ti TPA2013D1 Class-D mono amplifier.

Insides of the speaker prior to stuffing and closing.
Insides of the speaker prior to stuffing and closing.

The reason for supercapacitors is two-fold. The first is that their lifespan is much longer than that of Li-ion batteries, the second that they can charge much faster. The disadvantages of supercapacitors come in the form of their lower energy density and linear discharge voltage. For the latter issue the TPA2301D1 amplifier has a built-in boost converter for an input range from 1.8 – 5.5 V, and despite the lower energy density a solid 6 hours of playback are claimed.

Beyond the exquisitely finished 3D printed PETG shell and TPU-based passive bass radiator, the functionality consists out of a single full-range speaker and an analog audio input (TRS jack and USB-C). To add Bluetooth support [JGJMatt] created a module consisting out of a Bluetooth module that connects to the USB-C port for both power and analog audio input.

Charging the speaker can be done via the USB-C port, as well as via the solar panel. This means that you can plug its USB-C port into e.g. a laptop’s USB-C port and (hopefully) charge it and play back music at the same time.

For those feeling like replicating this feat, the Gerbers, bill of materials, enclosure STLs, and everything else needed can be be found in the tutorial.

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Speaker Science Project

They probably won’t please the audiophiles, but [KJMagnetics] shows you that can create a pair of speakers with some magnets, some plastic cups, and a bit of magnet wire. Creating speakers out of junk isn’t a new idea, of course. However, there’s something pleasant about the build. Maybe it is the symmetry of the cups or the workbench look of the woodworking.

We couldn’t help but think that this would make a good science fair project or a classroom activity. Especially since there is a good write up on how speakers work and it would be easy to make simple changes to test different hypothesis about speakers. For example, what happens with more or less wire in the coils? What magnets work best? What does best even mean? Is it louder? Less distortion?

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Homemade Omnidirectional Speakers In A Unique Enclosure

While studying acoustics in college (university for non-Americans), [Nick] had a great idea for an omnidirectional speaker. Some models available for purchase have a single speaker with a channel to route the sound in all directions, but [Nick] decided that a dodecahedron enclosure with 12 speakers would be a much more impressive route.

To accommodate the array of speakers, the enclosure needs twelve pentagons with a 58.3 degree bevel so that they fit together in a ball shape. After thinking about all of the complicated ways he could get this angle cut into the wood pentagons, he ended up using a simple circular saw!

Once the enclosure was painted [Nick] started wiring up the speakers. The equivalent impedance of the array of 8-ohm speakers works out to just around 10 ohms, which is easily driven by most amplifiers. The whole thing was hung from a custom-made galvanized pipe (all the weight adds up to about 15 kilograms, or 33 pounds for Americans, so the rig needed to be sturdy). We’ve featured other unique speaker builds, but this is the first 12-speaker omnidirectional speaker we’ve seen. [Nick] is happy to report that the speakers sound great, too!

Fully Integrated HiFi Studio Monitor

Studio Monitor and PCB

Have you ever wanted to build a high quality audio crossover and amplifier? [Rouslan] has put a lot of thought into making his dual amplifier studio monitor both high quality and simple to build.

With a concise schematic, a meaningful block diagram, and simulation results to boot, his well-written post has everything you need to build self-powered bi-amped speakers based on the LM4766 from Texas Instruments. It is great to see simulations which verify the functionality of the circuit, this can go a long way when working with complicated analog filters and audio circuitry. For those of you who do not have access to PSPICE (an expensive professional simulation tool), [Rouslan] uses LTspice from Linear Technology. TINA-TI from Texas Instruments is another great free alternative.

Additionally, [Rouslan] goes over the typical issues one has with a bi-amplifier studio monitor, such as phase misalignment and turn-on pop, and then provides a solution. Note that his project is powered by 20VAC, which requires an external transformer to convert the 120VAC in the wall to 20VAC. Be careful with high voltages! In the future, adding a high quality voltage regulator will most likely increase the performance.

His post finishes up with a very clean circuit board, which he ordered from OSH Park. With such a complete design, there is nothing keeping you from building your own. Go out and put that old speaker sitting in your basement to good use!

If you don’t have an old speaker sitting around, check out these very cool DIY speakers.

DIY Pringles Can Speaker

Looking for a fun weekend project? How about making your own speaker from scratch using some very basic materials?

[Go Repairs] makes a bunch of how-to videos for Instructables in a style very reminiscent of the classic Art Attack from the 90’s — very clear, concise and he’s even got the accent!

The project requires only what you see in the photo above. The lid forms a simple plastic cone of the speaker, the magnets are the core, and using some paper, tape, and enamelled wire a very basic voice coil is constructed. Don’t expect amazing sound quality out of it, but it certainly looks like a fun project for junior hackers as it requires no fancy tools or equipment!

Stick around after the break to watch the video — does it remind you of Art Attack also?

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