Ask Slashdot: Cheap and Fun Audio Hacks? 135
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."
christmas lights (Score:3)
Flame speakers!!! (Score:4, Interesting)
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.
psycho Acoustic imaging headphones (Score:2)
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. THer
Couch subwoofer (Score:2)
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.
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That last degree of freedom is the combination phase and volume. Louder on the right than the left? Must be to the right of the listener. The brain then processes the phase of the soundwave to determine the angle forward or backward, up and down.
Now, the brain can't use that information alone to determine if some sound came from 45 in front or 45 behind (vision helps that), but height above ground can be approximated by echo and interference. Truthfully, the subconcious 'sound map' of the place you are at a
Get real audio recordings (Score:1)
Not boosted/normalized audio sliced down to a 128 kbit stream.
Listen to a decent record from the 70s for inspiration.
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I was there. There were a lot of them.
Deep Purple was great back then (1971?). Fast forward 30 years and people start hearing them again. I thought: "What the...?!?"
There are others, just do a little research... a good start is "Yes".
beatles albums. mastered masterfully.
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Actually, from an audio engineering perspective, this is quite true (at least for vinyl), since all records were run through a low cut filter in order to eliminate rumble/skipping due to low sonic frequencies distrubing the needle in a record groove.
If we are talking a clean, complete signal, vinyl records have plenty of deficiencies of their own, despire what so-called "audiophiles" might tell you.
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So your speakers work down to 3hz?
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Yes, they do. They work perfectly well. You can't hear them, but they work just fine.
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> Actually, from an audio engineering perspective, this is quite true (at least for vinyl), since all records were run through a low cut filter in order to eliminate rumble/skipping due to low sonic frequencies distrubing the needle in a record groove.
sub 20 hz would be filtered by the rest of the audio chain (hello psychoacoustic filter on all compressed music), or would end up disturbing the mix anyway. Judging the excursion of the speakers in some badly mastered techno records, i think that vinyl can
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I skip both vinyl and CDs, and simply go to hear music live. Or play it myself with friends.
It sounds so real and faithful that way.
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As a practical matter, the human ear filters everything below about 20 hz and above 10-20 khz (depending on age, noise exposure, and genetics). A carefully-produced CD at 16 bit/44.1 khz can reproduce everything that's audible...
Except that anything at 20 kHz will be a triangular wave when sampled down to 44.1 kHz for CD-pressing. (I think CD-mastering involves a 22 kHz low-pass filter because of this.)
Sound is more than a single pitch. It is the 'shape' of the wave — Mathematically speaking, that shape comprises a number of different frequencies, and at different phases relative to one another.
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No, it won't. 20kHz will be sampled and reproduced perfectly because the signal is over-sampled, a sharp low-pass filter applied, and the resulting signal will not contain any frequency content higher than 22.05 kHz - which includes any harmonics that might be part of your "triangular wave."
Don't believe me? You can see for yourself in this video [xiph.org] at the 5:40 mark, where Monty shows how a 20kHz frequency is reproduced perfectly using a 44.1kHz sampling rate.
It's worth your while to watch the whole video. His signal generator and oscilloscope are both analog.
Do you even know how CD's work? They are digital. They provide a discrete time-based signal of audio amplitude.
If you were in my class, I would fail you. If you were my grad student, I would cut your funding.
Take a 44.1 kHz digital sample of a 20 kHz signal. Route that signal through a "true" D/A converter to speakers (or an oscilloscope), and you will get a triangular wave, as I said before, albeit with some 'walk' due to the introduction of false harmonics to the signal. That is, phase non-uniformity
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Vinyl at one point, if played with the correct cartridge and stylus, could reliably produce up to 45 khz, used to multiplex 4 channels (true quad, not matrixed) in the SQ system. It did (and does) have problems with warping, the need for a better turntable/pickup system than many users had to avoid quick wearout, issues with cleaning and scratching, IOW the real world. Many vinyl recordings (if you go beyond Top-40 and similar mass-market pop) do have a wide and relatively clean frequency range.
As a practical matter, the human ear filters everything below about 20 hz and above 10-20 khz (depending on age, noise exposure, and genetics). A carefully-produced CD at 16 bit/44.1 khz can reproduce everything that's audible, and a more than adequate dynamic range, without the pickiness of vinyl regarding setup and equipment quality. Production is the key - and generally requires higher sample rates and bit depths while working to allow for the vagaries of the process. Just as production quality was and is important for vinyl.
There were vinyl LPs of a pipe organ in Sydney, Australia, that has a full-sized 64' stop (bottom octave: 8-16 hz). Not sure how that was accurately recorded on tape machines with odd response artifacts at low frequencies, let alone microphones that generally didn't go that low, but it got onto the record. You can't hear it, but with the right system you can feel it. Tends to cause feedback if the turntable is in the same room as the speakers, though. CDs produced from the original tapes produce a cleaner bottom end.
when i was back there in high school, a friend's dad had a McIntosh system with big Wharfedale speakers, the kind that came with good quality English sand to fill the cabinet with because local sand might not be of comparable sonic purity.... anyway, when you pushed that setup, you would reliably find that the vinyl of that era contained sufficient lows to punish your guts until you barfed.
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Nice understanding of RIAA equalization you have there! :eyeroll:
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No, they were cut at somewhere between 20-50 Hz so that you could have enough room for 20-35 minutes of audio per side. The RIAA eq curve was to reduce rumble (and hiss, by boosting the high end), and that was restored upon playback through the dedicated PHONO input of the amplifier. I think this flurry of antique-looking all-in-one turntables is lacking the proper equalization circuit, because they all sound raspy and weak to me.
That's why 12" singles really do have more punch. With an entire side for u
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Either you're incapable of taking care of your records, or you've only heard them sampled on 90's Hip Hop CDs.
Oscilloscope from a sound card (Score:4, Interesting)
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.
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That's old as shit. We had a program to do that with the voicemail cards my old company made way back in the 80s.
Windows Media Player or whatever they called it had a skin that did that and one that gave the frequency spectrum.
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Yes, but the title is "cheap and fun," not "new and interesting"!
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A couple of other posters have mentioned that this project is a very old one. Yes, I understand. I was thinking of it as an educational project for the OP's kids, in the context of his/her offer of "[b]onus points if [it] can be done with the assistance of a couple of smart children, without boring them too much." Of course, that could also mean he wants to employ his kids in the grunt-work for his hobby. I hope it's not just that.
An oscilloscope can expose a young, smart kid to a whole new understanding of
Surround Sound Decoder? (Score:2)
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.
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You won't get 4 independent channels though, but I think it still counts as an analog decoder.
More info: https://en.wikipedia.org/wiki/... [wikipedia.org]
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It's not, it's the old David Hafler/Dynaco circuit. It has interesting effects that mimic something sort of like environmental effects.
Note that virtually no other scheme replicates nor does the source material contain anything like true spatial effects anyway, they are always synthetic to one degree or another.
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Yup. Difference matrix. Been around for years.
i first encountered it in the late seventies, sony had a smallish radio (i don't recall that it had a cassette player; definitely no vinyl playback) which featured a big center speaker and two little side firing speakers that gave a really wide soundstage, and i was so intrigued I had to look at the schematic fo see how it was done; to my then childish mind, it was waaaay out of the box thinking.
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You don't seem to understand the terms decode and encode. They are not unique and new to the digital realm. Audio / Analog encoders and decoders existed before computers. I assure you, this circuit functions as a simple analog decoder.
decode is ib my node.
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Look carefully at the polarities.
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The only difference that's going to make is put the phase of the sound waves out 180 degrees
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Not quite, no.The surround channel is encoded as a net differential between the left and right channels.
SONAR (Score:1)
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.
Ultrasonic microphone... (Score:1)
... 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
Audio? Kinda (Score:3, Interesting)
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Broken smart phone (Score:2)
Theremin (Score:2)
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... [instructables.com]
http://www.thereminworld.com/s... [thereminworld.com]
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Plus you get to tell them, nobody touches my theremin!
Build your own O2 headphone amp (Score:5, Informative)
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 [blogspot.com]
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 [blogspot.com]
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 [ieee.org]
Aural bypass (Score:1)
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!!!
Re: Aural bypass (Score:1)
I don't think so because that still use the nerve hookup from the inner ear to the brain. My nerves in my left ear were completely severed so I would need a different approach. I wonder if some sort of haptic interface would produce aural cues that my brain could use to compensate. I can still hear in my ight ear so for now it is mono for me...
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I think a cochlear implant will do the job, provided that you still have enough nerve function to hook the device to. It's not cheap, requires professional adjustment after an operation, and the quality is poor. At most you get 22 narrow frequency bands and have to interpolate for intermediate frequencies.
The technology is improving, but progress isn't particularly rapid.
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There are brainstem auditory implants that are for people with actual nerve deafness (damage to the 8th cranial nerve, not the cochlea as is the case for most types of deafness)... Since this type of deafness is quite rare (they would only consider something like this for bilateral losses), very few people have them. They are only available via clinical trial in the US for children, but they are approved in Europe.
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"...no wires in my brain please!!!
Really? I'd love to be able to muck around with wires in my brain, stimulating this part, and that, just to see what happens. I would certainly do it to regain music! But from a practical point of view, I can understand your objection.
I don't know if this counts or not... (Score:4, Interesting)
...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! ;-)
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Mr. Grantner's physics class?
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Dynamic range compression (Score:3)
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Dynamic range compression is one of the audio effects I use most often.
You, and every producer/engineer lately.
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I'm not sure what their reasons are. Mine used to be that I had to deal with various non-trivial levels of background noise -- turn the volume up loud enough to hear the quiet parts over that noise and the loud parts were enough to knock you over. These days, it's more that aging ears have greatly narrowed the spread between loud enough to understand and loud enough to hurt.
just add a little high freq distortion and gated white noise. http://www.aphex.com/products/... [aphex.com] in the initial days of solid state audio, everybody was so thrilled with how much better the highs sounded compared to tube amps. then people noticed listener fatigue setting in. then the observations of high freq distortion. then the next generation of much improved amps. then repeat when digital audio becomes a thing.
Laser speaker (Score:4, Interesting)
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
Vacuum tubes. (Score:2)
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'
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Vacuum tubes are the best. They saturate with only even-n harmonics, making them sound 'warm' or 'natural', unlike the random things you can do with digital audio streams.
It's the same idea as the harmonics of a guitar string.
Look up "Fourier Decomposition of a Wave" on Wikipedia for more details.
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Ah, that old wives' tale. Now I know you're a troll. :-P
I'm not an audiophile, but do know some. They are idiots. Wooden knobs, pyramids, and so on...
But really, what I said is true, based on basic audio engineering a& the physics signal-processing. Saturation of a vacuum tube (over-driving) produces a different set of harmonics than does saturation of a digital signal (which simply clips, introducing ALL harmonics). Go to Wikipedia like I told you.
That said: If you have both a high bit-rate A/D converter with a high sampling rate, when you can process
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Not a hack, per se -- but to do tubes and wrench on 'em yourself pretty much means you're a hacker.
Beat me to it. I built a GainClone amp a few years back, and while it was impressive, something was missing. On the pure hunch that the single ended triode (SET) zealots were actually onto something, I decided to build a Tubelab [tubelab.com] SSE. Best thing I have ever built, bar none. The side-by-side comparison with my chip amp was astounding, even with the cheap Chinese 6L6VG tubes I used while shaking down the new build. The typical SET tube amp is not the best fit for ballz-to-the-wall rock or full symphony materia
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Not a hack, per se -- but to do tubes and wrench on 'em yourself pretty much means you're a hacker.
Beat me to it. I built a GainClone amp a few years back, and while it was impressive, something was missing. On the pure hunch that the single ended triode (SET) zealots were actually onto something, I decided to build a Tubelab [tubelab.com] SSE. Best thing I have ever built, bar none. The side-by-side comparison with my chip amp was astounding, even with the cheap Chinese 6L6VG tubes I used while shaking down the new build. The typical SET tube amp is not the best fit for ballz-to-the-wall rock or full symphony material, but Steely Dan, Diana Krall, Nora Jones, or Cowboy Junkies? Yeah, way worth the time.
you can build fine IC amps, or fine discrete transistor amps, or fine tube amps, or fine digital amps. however, the kinds of errors that occur in imperfect tube amps are less irritating than the kind of errors that occur in imperfect solid state amps, which are less irritating than the kind of errors which occur in imperfect digital amps, as a generalization. which seems to correlate with the prevalence of similar kinds of distortion in "natural" sound, as my halfbaked observation.
Flame speaker (Score:2)
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One of the hacks I always wanted to do ( and still looking for parts for) is a flame speaker. [swtpc.com] I plan to do it outside maybe even in a bonfire if I can keep the wires from melting.
you can get plenty of flame speakers on the /. comments.
Just curious (Score:2)
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 als
Elekit TU-879s (Score:3)
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.... [vkmusic.ca]
Amazing cheap loudspeakers (Score:4, Interesting)
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.
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http://www.head-fi.org/t/49829... [head-fi.org]
Where entry level orthos/isos are in the range of $100 they can get as high as $3000 so not only your kids can wear what they have created, maybe they can start a local "business" Are they worth that much money? IDK I have some vintage Fostex monitors and yes the electrostatic technology is as good as it gets for a
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A project? (Score:2)
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 move
Don't do it. (Score:1)
"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.
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"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.
Seriously? Wow. One egregious error per sentence.
So, back to the origi
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whoosh?
https://en.wikipedia.org/wiki/... [wikipedia.org]
Spike Mic Project (Score:2)
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!)
Bootlegmic (Score:2)
http://www.openmusiclabs.com/p... [openmusiclabs.com]
Useful and you couldn't get simpler.
Whether you want to bring your kids to loud concerts is another story though.
Cheap Bluetooth 4.0 module (Score:1)
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
Crosstalk Cancellation (Score:1)
Use measurements to EQ your stereo better (Score:2)
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... [foobar2000.org]
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. Downlo
Play any instruments with Line Out? (Score:2)
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 mismat
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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.
i used to fool around with that stuff, more from the electronic standpoint than the musician, so caveats. anyway, you could do some fun effects by using an opamp with a power supply that supplied too low a voltage. and/or for an amp that required positive and negative supplies relative to ground, providing asymmetric voltages.
fun with clipping!
dangerous fun with ac (Score:2)