A Class D Amp Made From Scrap

[Boolean90] needed an amplifier for a subwoofer, and had a lot of parts sitting around in a scrap bin. His project, a Class D sub amp made out of scrap, is a great example of what you can build with the right know-how and a very large pile of junk.

With digital logic and PWM chips, a Class D amp is one of the simpler ways to get a lot of amplification easily in an efficient package. It’s really not that complicated; an audio signal is turned into a PWM’d square wave, this is sent out to a Mosfet bridge, and finally out to the speaker.

Most Class D amps have a switching frequency of hundreds of kilohertz to the Megahertz range, but since this is an amplifier for a subwoofer that has a cutoff frequency of about 1kHz, the switching frequency doesn’t need to be quite as fast. [Boolean] is using a 50kHz carrier frequency; it’s more than high enough to recreate low frequencies.

With the completed project, [Boolean] has an extremely loud amplifier that has around 75-150W of output power. The subwoofer is only rated for 200W, but with the volume [Boolean] is getting, this isn’t an amp he’ll be rebuilding anytime soon.

Parametric Spherical Speakers Are Not A Moon

A good speaker enclosure is not just about building a box out of plywood and covering it with carpet, although playing with 1F capacitors is pretty cool. No, for a good speaker enclosure you need the right internal volume, the right size bass port, the right speaker, and it should definitely, certainly, not be a moon.  [Rich] figured out he could do all of this with a 3D printer, resulting in the NOMOON: The NOMOON Orbital Music-Making Opensource, Openscad-generated Nihilator.

This work is a continuation of earlier work that designed parameterized speakers in the shape of Borg cubes. Now [Rich] is on to Borg scout ships,  and this version has everything you would expect for speaker design.

The NOMOON is available on the Thingiverse Customizer with variables for the internal diameter, the volume of the enclosure in liters, wall thickness, speaker hole, bass port, and wire holes. Of course a customized design is also possible with a stock OpenSCAD installation.

[Rich] has printed a few of these not moons and even with a speaker with terrible bass response, he has a pretty good-sounding setup as far as Youtube videos go. You can check that out below.

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Let the Bass Cannon Kick It!!

If you’ve ever found yourself immersed in the wild realm of electronic dance music, then chances are you’ve probably heard [Flux Pavilion]’s dubstep banger ‘Bass Cannon.’ The music video released for the track shows [Flux] and his minion [Doctor P] performing twisted audio experiments on unexpecting research candidates by blasting them in the face with strong waves of sound vibrations, which blew back the hair of the people strapped to the chair. The audio trials took place inside what looks to be a warehouse filled to the brim with speakers, heavy duty subs, and sound boards; making it more like a ‘room of bass’ rather than a bass cannon itself. Yet, it inspired one of Hackaday’s Alum to literally create a bass cannon himself. And as you can see in the video below, his device packs quite a punch.

Most of us know [Adam Munich] as the guy who built this portable x-ray machine that could look through just about anything. He’s also built a nuclear bomb detector and has documented several radiation safety techniques, but every once in a while he decides to make something utterly ridiculous like this! He describes his homemade bass cannon as having a variety of fun and exciting uses including a mobile party on one’s shoulders, a way to frizz your hair, or an electrifying method to scare the neighbors.

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Camera trick lets you see sound waves in falling water

24hz-water-camera-trick

From this still image you’d think the hose dispensing the water is being moved back and forth. But watch the video after the break and you’ll see the hose is quite steady, as is the standing wave of water. It’s bizarre to be sure. Knowing how it works makes cognitive sense, but doesn’t really diminish the novelty of the demonstration.

This is the second time [Brasspup] has posted a video of this phenomenon. The newest version does a great job of showing several different patterns. But even the first segment from a year ago, which has over 4 million hits, shows the water moving against gravity. We also saw a similar rig in a links post a year ago.

We’d call it an optical illusion but it’s really more of a technological illusion. The water is falling past a sub-woofer speaker which is tuned to 24 Hz. At the same time, the camera filming the demonstration is capturing 24 frames per second. As was mentioned then, it’s much like flashing a light to freeze the water in mid-air. But the flashing of the frames is what causes this effect.

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A folded horn enclosure to make the most out of a subwoofer

To make the most out of his home theater sound system [Baccula] built this folded horn enclosure for as much bass sound as possible. The design was conceived by [Bill Fitzmaurice] who thought there needed to be a better way to use the subwoofers which are typically used in home systems. His design is called the Tuba HT and it is aimed at a 15″ speaker. [Bill] charges for the building plans, but we don’t mind living vicariously through [Baccula’s] construction album.

As you can see, there are a lot of wood parts that went into the cabinet. It starts with a base of 2×4 framing. From there the plywood sawdust really starts to fly as each component is produced. During assembly [Baccula] is careful to fully glue each joint — you don’t want to find out that your sub cabinet vibrates after you get everything installed. All together the new piece of living room furniture stands three feet tall and deep and two feet wide.

The album has no captions but you can read a bit more about the project in the Reddit comments.

The weighted companion cube will never threaten to stab you and, in fact, is a subwoofer

From the techPowerUp! forums comes an awesome weighted companion cube subwoofer built by the metonymical user named [Cube].

This build started off as a coffee table that was to have an oval glass top (no word if the edges were going to be blue or orange). The guts of the cube are taken from a 400 Watt sub. As any good sub builder would, [Cube] kept the air volume and port tuning of the donor box.

We’ve seen a companion cube sub before that featured EL wire for a ‘glowing cube’ effect, but [Cube] may have taken things a little too far by including glowing rings on each side of the cube. The rings lit by 2,500 LEDs mounted on pieces of perspex and wired point-to-point. While [Cube] claims he’s ‘not a electronics guru,’ he certainly has a lot of patience to assemble those lights.

Check out [Cube]’s YouTube build video after the link. Credit to [Todd] for sending this one in.

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Doorway subwoofer

doorway

We’ve seen some crazy speaker builds in the past (massive folded horns for example). [DiscoJones] wanted to build a set of speakers that could reach very low frequencies and be very efficient. Instead of constructing a large box, he built a baffle that could be placed in a doorway and use the blocked off room as an enclosure. It has eight 12inch subwoofers, eight midrange drivers, and four tweeters. The speakers are fairly cheap and he built a simple crossover to help them work a little better together. The goal was always deep bass though, so don’t expect very high fidelity from a setup like this.