A Graphic Equaliser The Analogue Way

There was a time when any hi-fi worth its salt had a little row of sliders on its front panel, a graphic equalizer. On a hi-fi these arrays of variable gain notch filters were little more than a fancy version of a tone control, but in professional audio and PA systems they are used with many more bands to precisely equalise a venue and remove any unwanted resonances.

On modern hi-fi the task is performed in software, but [Grant Giesbrecht] wanted an analogue equalizer more in the scheme of those fancy tone controls than the professional devices. His project makes for a fascinating foray into analogue filter design, as well as an understanding of how an equalizer combines multiple filters. Unexpectedly their outputs are not mixed because it proves surprisingly difficult to ensure all the filters have the same gain, instead they are in series with the signal path passing through all filters.

The resulting equalizer is neatly built upon a PCB with a 4-AA-cell power supply, and makes for a self-contained audio component. Unexpectedly such analogue equalizer have been few and far between here at Hackaday so it’s particularly pleasing to see. We’re more used to graphical displays for off-the-shelf devices.

Voice Controlled Stereo Balance With ESP8266

A stereo setup assumes that the listener is physically located between the speakers, that’s how it can deliver sound equally from both sides. It’s also why the receiver has a “Balance” adjustment, so the listener can virtually move the center point of the audio by changing the relative volume of the speakers. You should set your speaker balance so that your normal sitting location is centered, but of course you might not always be in that same position every time you listen to music or watch something.

[Vije Miller] writes in with his unique solution to the problem of the roving listener. He’s come up with a system that can adjust the volume of his speakers without having to touch the receiver’s setup, in fact, he doesn’t have to touch anything. By leveraging configurable voice control software running on his computer, his little ESP8266-based devices do all the work.

Each speaker has its own device which consists of a NodeMCU ESP8266 and X9C104 digital potentiometer inside of a 3D printed case. The audio terminal block on the gadget allows him to connect it inline between the speaker and the receiver, giving [Vije] the ability to adjust the volume through software. The source code, which he’s posted on the Hackaday.io project page, uses a very simple REST-style API to change speaker volume based on HTTP requests which hit the ESP8266’s IP address.

The second part of the project is a computer running VoiceAttack, which lets [Vije] assign different actions based on what the software hears. When he says the appropriate command, the software goes through and fires off HTTP requests to the nodes in the system. Everything is currently setup for two speakers, but it shouldn’t be too difficult to expand to more speakers (or even rooms) with some adjustment to the software.

It’s not the first voice controlled speaker we’ve ever seen, but it does solve a very specific problem in a unique way. We’d be interested in seeing the next logical step, which would see this technology integrated into the speaker itself.

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Gorgeous Omnidirectional 3D Printed Speaker

With all due respect to the hackers and makers out there that provide us with all these awesome projects to salivate over, a good deal of them tend to prioritize functionality over aesthetics. Which isn’t a bad thing necessarily, and arguably better than the alternative. But for many people there’s a certain connotation around DIY, an impression that the final product is often a little rough around the edges. It’s usually cheaper, maybe even objectively better, but rarely more attractive.

Which makes builds like this absolutely beautiful 3D printed Bluetooth speaker by [Ahmsville] especially impressive. Not only did he engineer a fantastic sounding speaker that projects stereo sound no matter where you are in the room, he clearly gave a lot of thought into making the final product look as good as it sounds.

The 3D-printed enclosure provides separation for the four internal speakers and two passive radiators, as well as holding the electronics. A custom made 3S battery powers the Bluetooth module though an isolated step-down module, and the twin 18 W TDA2030 amplifiers feed their respective pair of drivers.

The device is surrounded by an impressively detailed 3D-printed mesh, which is then wrapped with some speaker grill fabric to give it a very professional look. In the video after the break, [Ahmsville] shows a time-lapse of building the speaker, as well as a demonstration of how it sounds on his desk.

If you’re more about function than what the finished product looks like, we’ve covered speaker enclosures made out of various types of actual trash which you can take a look at.

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Knock-Off AirPods Merged into Bluetooth Receiver

Whether or not you personally like the concept of the AirPod Bluetooth headphones is irrelevant, as an Apple product one thing is certain: all the cool kids want them. That also means that plenty of overseas manufacturers are pumping out janky clones for a fraction of the price for those who are more about the Apple look than the Apple price tag. Are they any good? No, of course not. But that doesn’t mean you can’t do something interesting with them.

[Igor Kromin] took apart a pair of fake AirPods and was predictably underwhelmed. So much so that he didn’t even bother putting the things back together. Instead, he took the two poor Bluetooth audio receivers and combined them into one slightly less poor Bluetooth audio receiver. It probably doesn’t meet the classical definition of a “good” use of time and/or money, but at least he got some entertainment out of a product that was otherwise destined for the trash.

As you might imagine, the left and right “AirPod” each has its own battery, Bluetooth receiver, and speaker. It has to, as they have no physical connection to each other. That also means that each receiver is only playing one channel, making them useless individually. What [Igor] realized was that he could put together a little PCB that combines the two audio channels back into a regular stereo 3.5 mm audio jack.

While he was at it, he also wired the individual buttons on each headphone to a center button on the PCB which would allow him to physically synchronize them. Even still, [Igor] mentions that occasionally they don’t come on at the same time. But what do you expect for something that’s nearly a 20th the price of the original?

The last time we saw a hack related to the Apple AirPod, it was when somebody threw them out the window, so one might presume most hackers prefer their iDevice tethered.

Empty Can Upcycled Into Portable Speaker

We aren’t suggesting you go digging through the trash looking for empty cans, but if you’ve already got some empty cans in the privacy of your own home, you could certainly do worse than turning them into unique enclosures for your electronics projects. Better than sitting in the landfill, surely.

This hack from [Robin Hartley] turns an empty Cadbury hot chocolate can into a portable speaker that’s sure to get some attention. But don’t be fooled: a surprisingly amount of engineering went into this project in the form of a 3D printed structure on the inside of the can. Even if you aren’t big on the idea of putting your next project into a piece of literal trash, there’s something to be said for how professionally everything fits together in this build.

The key to this build is the 3D printed “skeleton” that holds the speaker and circuit board in place. An especially nice touch is how [Robin] designed the mount for the speaker: as it had no flange to attach to, he made a two piece clamp that screws together around the rear of the speaker and holds it in place.

You may wonder why somebody who’s clearly as well versed in CAD and 3D printing as [Robin] is might want to use an empty can as an enclosure; surely he could just design and print a case? Undoubtedly. But the goal here is to reuse what would otherwise be trash, and that occasionally means taking the “scenic” route as it were.

To take this concept to the next level, check out the upcycled speaker box we recently covered. We’ve seen some gorgeous home audio builds that started as a curbside find, but depending on how lucky you are, it’s almost like cheating.

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Making A Vintage 1990s Sound Board Do Rapid Fire Silently

Sometimes a mix of old and new is better than either the old or new alone. That’s what [Brad Carter] learned when he was given an old 1990s sound board with a noisy SCSI drive in it. In case you don’t know what a sound board is, think of a bunch of buttons laid out in front of you, each of which plays a different sound effect. It’s one way that radio DJ’s and podcasters intersperse their patter with doorbells and car crash sounds.

Before getting the sound board, [Brad] used a modern touchscreen table but it wasn’t responsive enough to get a machine gun like repetition of the sound effect when pressing an icon in rapid succession. On the other hand, his 1990s sound board had very responsive physical buttons but the SCSI hard drive was too noisy. He needed the responsiveness of the 1990s physical buttons but the silence of modern solid state storage.

And so he replaced the sound board’s SCSI drive with an SD card using a SCSI2SD adaptor. Of course, there was configuration and formatting involved along with a little trial and error to get the virtual drive sizes right. To save anyone else the same difficulties, he details all his efforts on his webpage. And in the video below you can see and hear that the end result is an amazing difference. Pressing the physical buttons gives instant sound and in machine gun fashion when pressed in rapid succession, all with the silence of an SD card.

A SCSI2SD card is a nice off-the-shelf solution but if you want something a little more custom then there’s a Raspberry Pi SCSI emulator and one which uses a Teensy with a NCR5380 SCSI interface chip.

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Cross-Correlation Makes Quick Work Of Ads

Once relegated to the proverbial Linux loving Firefox user, ad blocking has moved into public view among increased awareness of privacy and the mechanisms of advertising on the internet. At the annual family gathering, when That Relative asks how to setup their new laptop, we struggle through a dissertation on the value of ad blockers and convince them to install one. But what about mediums besides the internet? Decades ago Tivo gave us one button to jump through recorded TV. How about the radio? If available, satellite radio may be free of The Hated Advertisement. But terrestrial radio and online streams? [tomek] wasn’t satisfied with an otherwise sublime experience listening streaming Polish Radio Three and decided to build a desktop tool to detect and elide ads from the live audio stream.

[tomek] was aware of this hip knowledge domain called Digital Signal Processing but hadn’t done any of it themselves. Like many algorithmic problems the first step was to figure out the fastest way to bolt together a prototype to prove a given technique worked. We were as surprised as [tomek] by how simple this turned out to be. Fundamentally it required a single function – cross-correlation – to measure the similarity of two data samples (audio files in this case). And it turns out that Octave provides it in the box. After snipping the start-of-ad jingle out of a sample file and comparing it to a radio program [tomek] got the graph at the left. The conspicuous spike is the location of the jingle in the audio file.

At this point all that was left was packaging it all into a one click tool to listen to the radio without loading an entire analysis package. Conveniently Octave is open source software, so [tomek] was able to dig through its sources until they found the bones of the critical xcorr() function. [tomek] adapted their code to pour the audio into a circular buffer in order to use an existing Java FFT library, and the magic was done. Piping the stream out of ffmpeg and into the ad detector yielded events when the given ad jingle samples were detected.

[tomek] packaged that tool into a standalone executable, but the gem here is the followup post. After removing ads in the online stream they adapted a RaspberryPi to listen to an FM receiver and remote control their Yamaha tuner over the network. So when the tuner is playing Radio Three the Pi notices and ducks the audio appropriately to avoid those pesky ads. Video of this after the break.

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