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Ask Slashdot: Cheap and Fun Audio Hacks?
An anonymous reader writes: A few years back I discovered that even a person of limited soldering skills can create a nifty surround-sound system with the magic of a passive matrix decoder system; the results pleased me and continue to, It's certainly not a big and fancy surround system, but I recommend it highly as a project with a high ratio of satisfaction to effort. (Here's one of the many, many tutorials out there on doing it yourself; it's not the long-forgotten one I actually used, but I like this one better.) I like listening to recorded music sometimes just to hear how a particular playback system sounds, not just to hear the music "as intended." I'd like to find some more audio hacks and tricks like this that are cheap, easy, and fun. Bonus points if they can be done with the assistance of a couple of smart children, without boring them too much. I have access to Goodwill and other thrift stores that are usually overflowing with cheap-and-cheerful gear, to match my toy budget. What mods or fixes would be fun to implement? Are there brands or models of turntable I should look for as the easiest with which to tinker? Are there cool easy-entry projects akin to that surround sound system that I could use to improve my radio reception? I'm not sure what's out there, but I'd like to get some cool use out of the closet-and-a-half I've got filled with speakers and other gear that I can't quite bear to toss, since "it still works."
It's fairly common, but you didn't mention it, so a simple circuit hooked up to christmas lights can be fun.
"First they came for the slanderers and i said nothing."
Not boosted/normalized audio sliced down to a 128 kbit stream.
Listen to a decent record from the 70s for inspiration.
One of the coolest hacks I have encountered is the use of a computer sound card's audio input(s) to create an oscilloscope.
Google provides lots of links on the subject.
If it weren't for deadlines, nothing would be late.
What part of that is a decoder? It's adding more speakers to a 2 channel system.
It also reduces the output impedance, which increases distortion.
Dee Ess Pee. Solder today for little boys. You wrong way wire you break power transistor.
Its rather simple to make a basic SONAR system with Matlab/Octave. If you can get enough identical speakers/microphones, you can start building phased arrays and directional microphones.
USB sound cards generally have less electrical noise, and rather good effective number of bits and sample rates.
... I had fun building an ultrasonic microphone to listen to laughing rats, bats etc from a cheap microphone capsule. I think that a lot of small electrets (such as those in hearing aids) have a good response to high frequencies. But there is an investment required in that you need a DA converter with a high sampling response to digitise your recordings. If you have a soundcard with 192kHz inputs, then the rest is pretty cheap, and the circuits can be pretty simple.
With a bit more investment of time in the electronics, there are a bunch of "make your own bat detector" schemes with frequency dividers - http://bertrik.sikken.nl/bat/index.html
Try a singing Tesla coil. Kids will love making music with lightning.
There is a lot you can do beyond just audio. Put a low freq wave in a horizontally oriented speaker cone and see how it interacts with eg slimes/liquids. Or a high powered speaker with glass or other solids to see how/when it breaks. Noise cancellation techniques etc are also great and useful to explore at every level of the system. Compounding waves, masking and the idea of when tones become 'information'. Visualizing electric wave forms or even making a lung system in speakers is really cool too.
Custom electronics and digital signage for your business: www.evcircuits.com
Audio is a signal with information, computers process information. That's the end of 1980s closets full of electronics.
One of those cracked screen phones could be set up to get audio streams off wifi. The Bluegrass radio app gets a bunch of eclectic stations.
As you seem to turn your kids into geeks anyway, you could build a cheap Theremin with them and teach them to play the Startrek theme song.
http://www.instructables.com/i...
http://www.thereminworld.com/s...
The O2 headphone amplifier is an extremely clean amp that can drive almost any headphones. It sounds great. Pair it with a clean DAC, rip all your CDs to FLAC, and you can listen to your music from your computer with the very highest in fidelity.
If you can solder, you can build the O2 amp for $30 to $40 worth of parts.
http://nwavguy.blogspot.com/2011/08/o2-summary.html
The guy who designed the O2 also designed a really good DAC. He wanted to release it as a DIY project but the realities of the DAC chip business mean that it was only practical to sell a complete DAC board. But you could make a project out of building an O2 amp in an enclosure with the DAC board built-in. (I have such a device but I can't solder; I bought mine from JDS Labs, pre-built.)
http://nwavguy.blogspot.com/2012/04/odac-released.html
I am friends with a world-class audio expert, and he agrees that the O2+ODAC is the best way to spend your money. It's as clean as $1000+ solutions.
P.S. Article about the guy who designed the O2 and ODAC: "the audio genius who vanished"
http://spectrum.ieee.org/geek-life/profiles/nwavguy-the-audio-genius-who-vanished
lf(1): it's like ls(1) but sorts filenames by extension, tersely
Make something that will somehow bypass the eardrum/nerve interface so that people like me that have had severe never damage in the inner ear canal can enjoy music again. Who knows where it could go from there but I know I would be eternally grateful!!! Oh yeah, no wires in my brain please!!!
...but, back in high school, one of my science teachers glued a tiny mirror to the center of a speaker cone. He then reflected a laser off of it onto the wall. When he played music though it, the vibrations made a very cool low cost laser show! Now that lasers are cheap and plentiful, I've always meant to recreate that laser show. One of these decades, I'll get around to it! ;-)
Dynamic range compression is one of the audio effects I use most often.
Glue a Front Surface mirror to a woofer
Point a Laser at the mirror
Play music with lots of bass through that speaker
Add a second speaker at an opposing angle to get X Y control
We are Dead Stars looking back Up at the Sky
Not a hack, per se -- but to do tubes and wrench on 'em yourself pretty much means you're a hacker.
Hook 'em up to horn speakers and you can get very good sound for not much dosh. Depending on many factors ridiculously good sound is possible, actually, for not much dosh.
It teaches about electronics. And also teaches basic mechanical skills, what with the screwdriver, wrenches, soldering iron, etc etc -- it's more than just audio.
No, really -- but be safe, triple-digit VDC will really @#!% you up and there's plenty in your typical power amp.
Just be careful you don't step in the quite deep quicksand of hardcore audiophilia. There's a balance.
The "Civilized World" jumped the shark ca. 1973.
One of the hacks I always wanted to do ( and still looking for parts for) is a flame speaker. I plan to do it outside maybe even in a bonfire if I can keep the wires from melting.
Star Trek, there maybe hope.
I'm guessing that the quadraphonic decoder you built was some version of the Dynaquad - am I correct? (I actually have a Dynaquad-encoded copy of The Beach Boys album 'Surf's Up'). And I think the link you provided is David Hafler's version of the same basic concept. Either one of these decoders could do fascinating things with even normal stereo recordings. I did a LOT of playing around with passive decoding in the early-to-mid-70's when I was a teenager - I just loved playing Dark Side of the Moon...
I also did some satisfying work on active versions of Hafler/Dynaquad decoders. The sound is both better and more amenable to adjustment. All you need are one or two decent quad op-amps, some capacitors and resistors, a solderless breadboard, a power supply of 18 volts or so, and an extra power amp or receiver with accompanying speakers. The op-amps are configured to provide the sum of the two stereo channels, (mono), and the difference between the two stereo channels, (L-R or R-L depending on your phasing). The two stereo channels are fed to one stereo amp and speakers, and the sum and difference outputs from the breadboard are fed to the other stereo amp and speakers. This setup prevents electrical interaction and impedance irregularities which occur in a fully passive setup like that in the link you provided, so the speakers sound better. And with separate volume, balance, and tone controls, you can more easily tailor the sound to your liking. Also, with extra op-amps it's easy to have both L-R and R-L. (On some recordings, having both of these can produce some interesting results). It's cheap, it's pretty easy, it uses 'junk' amps and speakers to good advantage, and it's lots of fun. At least, it's lots of fun for people like you and me... :) Plus, hooking everything up, troubleshooting any errors or other problems, tweaking the sound, and listening to the differences should keep the 'smart kids' interested for a while.
I got some new Polk bookshelf speakers just before Christmas, and I have several amps and additional pairs of speakers. It might just be time to start playing with passive 'quad' decoding again!
'The Economy' is a giant Ponzi scheme whose most pitiable suckers are the youngest among us and the yet-unborn.
My suggestion is not super cheap at $589 yet very satisfying: an Elekit tube amplifier kit. Elekit is a good japanese kit brand and their tube amp kits are very well regarded. In fact a similar quality ready made product would cost a lot more.
Here is the link to the importer in Canada who delivers to the Americas. He supplies the construction manual in English, this is I think not the case if you buy straight from the japanese Elekit website: http://www.vkmusic.ca/TU-879S....
For passive surround and goofing around, noting beats a single speaker hooked to the positive terminal of the left and right. Four speakers as in the article doesnt work well enough due to loss of power.
OK, so now that you set it up with three speakers in a triangle, put on beasty boys 'cheack your head'. Yes, a digital/CD version. You're welcome!
After that, play live music recordings off of lp's
I've got a friend who's a cabinet maker and loudspeaker designer. For years he crafted full-range curved diaphram electrostatic loudspeakers. Nowadays he's into horns. One day I dropped by his shop and he blew me away with something he'd been doing with Dayton Audio Sound Exciters (well, that's what they're called today on Amazon's web site). They're transducers.
Get yourself two 2' x 3' pieces of 1/2" thick piece of foam core from an art supply store. Attach two of these Dayton Audio Sound Exciters to each of them. Wire them in parallel and connect them to an amplifier. The tricky part is that you have to suspend them in mid-air. Hang them from your ceiling or something. The sound you'll get out of them is very, very good - especially considering you'll have less than $75 in the whole project. I'd put it equal stuff you'd spend about $1000 to $1500 at Best Buy.
They aren't what I'd call extreme hi-end, but they sound much, much better than anyone would think. Would make for a great garage or shop system.
In physics class, I fondly remembered a teacher setting up a fixed rate oscillator, around 500hz, placing speakers a few metres apart, and getting us to walk between them.
The resulting effect is a pleasing and distinctive phase superposition and cancellation effect. The audio will ripple in volume depending on where you are in the room.
Physics in motion!
Sorry to go slightly off-topic; I sometimes envy those that can enjoy music for sustained periods of time. Listening, even to my favourite music (renaissance and baroque lute), makes my feel stressed out after a short while. However, there is one project I would like to accomplish - but it's hardly for beginners, I suspect.
I have a large conservatory in which I grow orchids, mostly. One of the problems you get in a space enclosed in glass is that important parameters like temperature, humidity and air movements can vary enormously in different locations, and it would be interesting - useful even - to have a simple network of cheap sensors, that would measure these and report them to a computer (which could be a RaspberryPi). Unfortunately, I don't have enough practical knowledge about electronics to know where to begin. I know what I could do with the data - I could have hours of fun analysing them.
"Hacking" sounds illegal and in this day and age, if something just sounds illegal it probably is, and it's best to err on the safe of caution. You should not alter equipment or modify it, you can only use as specified in the contract. Buy something that meets your criteria and be content with it. If nothing in the market can meet your criteria, then probably there's something wrong with you.
You can make a fun spike mic to listen to people in another room with old parts.
Take an old phono cartridge and carefully attach a metal nail to the tiny stylus end (where the diamond is).
Then plug it into an old phono amp as usual, and listen with headphones.
If you drill a hole on your side of the wall, big enough so the nail doesn't touch the edges, but lightly presses against the wall of the next room, you might be able to hear what's going on.
(Don't use this illegally!)
If you hold a big sea shell over your ear, you can hear the sea.
http://www.openmusiclabs.com/p...
Useful and you couldn't get simpler.
Whether you want to bring your kids to loud concerts is another story though.
you can use a flame as a speaker. Cool thing is you can't burn it out by overdriving it!
1) create a large wide flame. e.g. for gas flatten a tube into a long thin jet.
2) put two electrodes in the flame
3) boost your audio into the high voltage range. a high voltage transformer can do this.
Now say "I am the great and powerful oz!" into the microphone.
4) get really excited and build a redonkulously large version with 6 foot tall pulsating glames and a a kilowatt amplifier.
Some drink at the fountain of knowledge. Others just gargle.
I've never done it but I've always wanted to play with acoustic imaging in heaphones. Clearly a two speaker system has 2 degrees of freedom and therefore cannot have any 3D effects. Yet we know that our ears can tell sounds that come from behind from those that come from ahead. This is because our brains process the sound for a reverb or delayed echo. So you cread the 3D effect by delaying the left ear's sound slightly and feeding it to the right ear.
that of course is just fake spacial assignment. THere's some way to be more clever about what you delay based on the dolby encoding to assign the delayed sound correctly. I don't know what that is but it can't be a lot more complex than your matrix decoding of the sum and difference channel. The difference is that instead of sending it to the rear speakers, you now have to delay it. Here's a websearch with a couple leads on this:
http://www.headphone.com/pages...
Some drink at the fountain of knowledge. Others just gargle.
take apart your couch, get a giant subwoofer coil, remove the paper cone, and bolt a large weight to the center instead, and mount the speaker on the couch frame. make sure the cross-over is sub 20Hz so you can't hear it in the audio range (otherwise it will be distracting). for more kicks mount three, one for left, one for right and one for the matrix-center channel. drive it with a lot of amps.
Some drink at the fountain of knowledge. Others just gargle.
How about adding a cheap spring reverb to your existing audio system. There are a number of other effects that you can do pretty cheaply that maybe fun to play with, but that one seems like a good cheap start with minimal technical skills required for the build.
You can also expand upon your existing system and work in a cheap karaoke system. If your kids want to sing or play instruments along with the music add extra inputs and a mixer, maybe add the reverb effect in for extra coolness and have family fun night in the living room.
The added lighting effects are cool ideas also, if you bring an arduino into the mix you can level up your project complexity and have lights that pulse and move with the rhythm all over the room. Or you can add a voice activated component so that you don't need the TV remote anymore. Have it turn on your devices and change channels for you.
Many of these projects have been done before multiple times and you can find easy guides on instructables.com
Around Thanksgiving, the Linux Voice podcast had a "find of the fortnight" about a small, cheap Bluetooth 4.0 module that can easily be added to an existing system. The card is designated KRC 86B, and a raw board is about $10. As a raw board, there is programming in place that handles everything you need to send audio from your phone and the board has audio in and out all configured. I think they are the same ones that are used for Bluetooth connections in new cars these days.
Bare boards have soldering pads, but no connectors. I paid a bit more for one ($14) that already had all the connectors attached - all I did was provide micro-USB power, and connect to my receiver with a standard audio miniplug. Pair and play!
There are tutorials all over the place on how to gracefully integrate these things into your existing box, but mine's just dangling out front. Despite the simplicity and low cost, the sound is excellent! Don't take my word for it, they're about $10, just do it!
I recall there was an article many years ago that mentioned how to use an extra set of speakers adjacent to the main speakers to eliminate audio crosstalk similar to vintage Polk SDA speakers and Carver Sonic Holography, I don't remember the wiring diagram but it used the same amplifier as the main speakers with the additional speakers wired in series and out of phase. The ideal listening position was fairly narrow and the results were hit and miss depending on the recording. Maybe an old Polk SDA review can help: http://www.polksda.com/srsrevi...
Lots of people do equalization, but mostly just by ear. Tools to use SCIENCE to do it are now cheaply available.
1) play music out of your computer with an equalizer. I use Foobar2000. There is a free 31-band stereo equalizer plug in available for it. http://www.foobar2000.org/comp...
2) play some Pink Noise through it. Pink Noise is equal energy per octave, so on a log frequency graph of SPL it should be flat. Of course, it won't be b/c speakers and rooms are imperfect, but now you have a goal. Download a pink noise sample, or make one with something like Audacity. Probably use a non-lossy file format.
3) get a smartphone app with a Real Time Equalizer. iphones have consistent mic performance, so the software can usually correct for it well, but I have had some bits of software behave oddly. I paid a few bucks for this one ( http://www.studiosixdigital.co... ) I understand there are android apps also. You can buy a measurement mic for your phone cheaply ( http://www.parts-express.com/d... ) if you want.
4) The RTA will measure your SPL vs Frequency, and your pink noise sample is sound that should have flat response. So use your equalizer software to twiddle the sliders until things are flat. Microphone location makes a difference!
So if you have a smartphone and a computer this can be done for somewhere between free and $50. Some people are good at equalizing by ear, but bringing some tech to the table will help most people get better results.
-- "Oh. This guy again."
Build a Gainclone amp. Relatively easy, and the components don't cost a fortune (unless you get fancy)
http://diyaudioprojects.com/Chip/chip.htm
Guitar distortion pedals can be a cheap and easy thing to build. The simplest form is just an amp (either op-amp or single transistor) followed by clipping diodes. One potentiometer to control the voltage out of the amp stage (higher voltage means the diodes clip more, means more distortion) and another controls the output volume by dropping the signal to ground. And if the kids are the ones playing the instruments, they might enjoy the different effects that can be gained by just using one diode, or mismatching them (silicon one way, germanium the other). Any instrument can be run through a homemade one, even a microphone if someone plays non-electric instruments.
with a simple ac power cord from an old lamp, you can demonstrate that pickles fluoresce when 110 volts is applied to the ends. and as a bonus, the same setup cooks hot dogs efficiently.
Star Trek transporters are just 3d printers.