Building A Subwoofer Box Out Of Decking Material

September 12, 2024 by Lewin Day 8 Comments

When you go to build a subwoofer box, wood is the most common choice. When it came to his project, though, [Startup Chuck] decided to go a different route entirely. Rather than the usual plywood or MDF, he decided to try Trex decking instead. Why? He had some lying around, and he suspected it might just sound good.

If you’re unfamiliar with it, Trex decking is a composite material made of recycled materials like reclaimed wood and plastic film. The best part, though? Trex decking is twice as dense as MDF. That makes it good for speaker box use because it flexes less and thus absorbs less energy from the subwoofer. [Chuck] walks us through cutting out the parts for the box and the subsequent assembly. Ultimately, it’s not dissimilar from building a speaker box out of wood; the material is simply not that different—just denser.

[Chuck] also puts his new sub through some quick little tests, demonstrating that minimal vibration is passed through to the enclosure itself. He reports that the final build has a “nice, deep sound.” Meanwhile, if you don’t like working with your hands, you could always 3D-print your speaker enclosures instead.

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How To Turn Cheap Speakers Into Something A Little Better

July 5, 2024 by Jenny List 25 Comments

[Adam Francis] bought some cheap speaker drivers from AliExpress. Are they any good? Difficult to tell without a set of enclosures for them, so he made a set of transmission line cabinets. The resulting video proves that a decent sounding set of speakers shouldn’t have to cost the earth, and is quite entertaining to watch.

The design he’s going for is a transmission line, in effect a folded half-wave resonant tube terminated at one end and open at the other, with the speaker close to half way along. There is a lot of nuance to perfecting a speaker cabinet, but this basic recipe doesn’t have to be optimum to give a good result.

So after having some MDF cut to shape and glueing it all together, he ends up with some semi decent speakers for not a lot of money. The video is entertaining, with plenty of Britishisms, but the underlying project is sound. We’d have a pair on our bench.

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Simplest Speaker Oscillator, Now Even Simpler

April 30, 2024 by Dan Maloney 21 Comments

It never fails. Lay down some kind of superlative — fastest, cheapest, smallest — around this place and someone out there says, “Hold my beer” and gets to work. In this case, it’s another, even simpler audio oscillator, this time with just a loudspeaker and a battery.

Attentive readers will recall the previous title holder was indeed pretty simple, consisting only of the mic and speaker from an old landline telephone handset wired in series with a battery. Seeing this reminded [Hydrogen Time] of a lucky childhood accident while experimenting with a loudspeaker, which he recreates in the video below. The BOM for this one is even smaller than the previous one — just a small speaker and a battery, plus a small scrap of solid hookup wire. The wire is the key; rather than connecting directly to the speaker terminal, it connects to the speaker frame on one end while the other is carefully adjusted to just barely touch the flexible wire penetrating the speaker cone on its way to the voice coil.

When power is applied with the correct polarity, current flows through the wire into the voice coil, which moves the cone and breaks the circuit. The speaker’s diaphragm resets the cone, completing the circuit and repeating the whole process. The loudspeaker makes a little click with each cycle, leading to a very rough-sounding oscillator. [Hydrogen Time] doesn’t put a scope on it, but we suspect the waveform would be a ragged square wave whose frequency depends on the voltage, the spring constant of the diaphragm, and the spacing between the fixed wire and the voice coil lead.

Yes, we realize this is stretching the definition of an audio oscillator somewhat, but you’ve got to admit it’s simple. Can you get it even simpler?

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No Active Components In This Mysterious Audio Oscillator

April 23, 2024 by Dan Maloney 39 Comments

What’s the simplest audio frequency oscillator you can imagine? There’s the 555, of course, and we can think of a few designs using just two transistors or even a few with just one. But how about an oscillator with no active components? Now there’s a neat trick.

Replicating [Stelian]’s “simplest audio oscillator on the Internet” might take some doing on your part, since it relies on finding an old telephone. Like, really old — you’ll need one with the carbon granule cartridge in the handset, along with the speaker. Other than that, all you’ll need is a couple of 1.5-volt batteries, wiring everything in one big series loop, and placing the microphone and speaker right on top of each other. Apply power and you’re off to the races. [Stelian]’s specific setup yielded a 2.4-kHz tone that could be altered a bit by repositioning the speaker relative to the mic. On the oscilloscope, the waveform is a pretty heavily distorted sine wave.

It’s a bit of a mystery to [Stelian] as to how this works without something to provide at least a little gain. Perhaps the enclosure of the speaker or the mic has a paraboloid shape that amplifies the sound just enough to kick things off? Bah, who knows? Let the hand-waving begin!

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apple airtag being opened to remove the sounder

Apple AirTag: Antitheft Or Antistalking?

February 24, 2024 by Dave Rowntree 37 Comments

Occasionally, the extra features added to a product can negate some of the reasons you wanted to buy the thing in the first place. Take, for example, Apple’s AirTag — billed as an affordable way to link your physical stuff to your phone. If some light-fingered ne’er-do-well wanders by and half-inches your gear, you get notified. The thing is, the AirTag also has an anti-stalking measure, which after a while, notifies nearby iPhones, should the tag move but not be near your iPhone!

In a recent video, [David Manning] explains that this feature is great for preventing the device from being used to track people. But it also means that if said thief happens to own an iPhone, they will be notified of the nearby tag, and can find it and disable it. So in the end, it’s a bit less useful as an anti-theft measure!

The solution is to pop the back off the tag and yank out the little sounder module from the rear plastic. You lose the ability to locate the tag audibly, but you gain a little more chance of returning your stolen goods. Apple could easily remove this feature with a firmware update, but it’s a matter of picking your poison: antistalking or antitheft?

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Reggaeton-Be-Gone Disconnects Obnoxious Bluetooth Speakers

February 23, 2024 by Bryan Cockfield 29 Comments

If you’re currently living outside of a Spanish-speaking country, it’s possible you’ve only heard of the music genre Reggaeton in passing, if at all. In places with large Spanish populations, though, it would be more surprising if you hadn’t heard it. It’s so popular especially in the Carribean and Latin America that it’s gotten on the nerves of some, most notably [Roni] whose neighbor might not do anything else but listen to this style of music, which can be heard through the walls. To solve the problem [Roni] is now introducing the Reggaeton-Be-Gone. (Google Translate from Spanish)

Inspired by the TV-B-Gone devices which purported to be able to turn off annoying TVs in bars, restaurants, and other places, this device can listen to music being played in the surrounding area and identify whether or not it is hearing Reggaeton. It does this using machine learning, taking samples of the audio it hears and making decisions based on a trained model. When the software, running on a Raspberry Pi, makes a positive identification of one of these songs, it looks for Bluetooth devices in the area and attempts to communicate with them in a number of ways, hopefully rapidly enough to disrupt their intended connections.

In testing with [Roni]’s neighbor, the device seems to show promise although it doesn’t completely disconnect the speaker from its host, instead only interfering with it enough for the neighbor to change locations. Clearly it merits further testing, and possibly other models trained for people who use Bluetooth speakers when skiing, hiking, or working out. Eventually the code will be posted to this GitHub page, but until then it’s not the only way to interfere with your neighbor’s annoying stereo.

Thanks to [BaldPower] and [Alfredo] for the tips!

A 360° View Of A Classic Drive-In Speaker

December 18, 2023 by Kristina Panos 22 Comments

Readers of a certain vintage no doubt have pleasant memories of drive-in theaters, and we are chuffed to see that a few hundred of these cinematic institutions endure today. While most theaters broadcast the audio on an FM station these days, the choice is still yours to use the chunky, often crackly speaker that attaches to the car window.

Seeking to relive the drive-in audio experience at home, [codemakesitgo] picked up a drive-in theater speaker on eBay and turned it into a Bluetooth device that sounds much better than it did in its weather-beaten days outside.

There isn’t a whole lot to this build — it’s essentially a new speaker cone, a Bluetooth receiver, an amp, and a battery. The real story is in the way that [codemakesitgo] uses Fusion360 to bring it all together.

After 3D scanning the case, [codemakesitgo] made sure each piece would fit, using a custom-built model of the new speaker and a 3D model of a custom PCB. Good thing, too, because there is barely enough clearance for the speaker. Be sure to check out the brief demo video after the break.

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