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Giant Sub-Woofer
PuceBaboon sent us linkage to an amusing story about building a
gigantic custom sub woofer. I was about to yawn until I looked at the pictures of them excavating a 60 cubic meter hole, and laying bricks. This one might be a little outside the realm of reasonable, but it's damn impressive.
The horn is an acoustic transformer that links the cone to the air in the room very effectively. For good results, a bass horn has to be very large, on the scale of the wavelength of the notes it's reproducing.
The bass you hear on your home hi-fi is most likely produced by resonance, something you should avoid if you really want to hear what those bass notes are sounding like. But resonance is cheap! Large bass horns are neither cheap, nor easy, but they sound so much better...
-- oldthinkers unbellyfeel ingsoc
these guys build custom home cinema installations so this was either for a client or I think their own demo to show off what they can do....
The Hitch Hiker's Guide to the Galaxy notes that Disaster Area, a plutonium rock band from the Gagrakacka Mind Zones, are generally held to be not only the loudest rock band in the Galaxy, but in fact the loudest noise of any kind at all. Regular concert goers judge that the best sound balance is usually to be heard from within large concrete bunkers some thirty-seven miles from the stage, whilst the musicians themselves play their instruments by remote control from within a heavily insulated spaceship which stays in orbit around the planet - or more frequently around a completely different planet.
Their songs are on the whole very simple and mostly follow the familiar theme of boy-being meets girl-being beneath a silvery moon, which then explodes for no adequately explored reason.
Many worlds have now banned their act altogether, sometimes for artistic reasons, but most commonly because the band's public address system contravenes local strategic arms limitations treaties.
This has not, however, stopped their earnings from pushing back the boundaries of pure hypermathematics, and their chief research accountant has recently been appointed Professor of Neomathematics at the University of Maximegalon, in recognition of both his General and his Special Theories of Disaster Area Tax Returns, in which he proves that the whole fabric of the space-time continuum is not merely curved, it is in fact totally bent.
this might seem odd to you, but some people design listening systems for sound quality, not volume. if you'll RTFA, you find that the amp is only delivering 6W to each of 2 horns (despite total power handling capacity of 6400 watts).
full-sized church pipe organs are specially tuned. Each pipe plays exactly one note, and the pipe's length determines the wave length. The high ceilings in a church also help.
Why read the article when I can just make up a snap judgement?
The setup is designed for high sensitivity, not high power. He's only feeding them with 400W RMS signals, for 6.4 KW total; here in the UK that'd cost about 30p (about 50c) per hour to run. Not a huge problem.
Richard Clark's "Bread Truck" subwoofer
Here's a guy who designed and built a custom driver to compete in car stereo SPL competitions. The driver was built to be mounted in the box of an old bread truck. It was driven by 2 custom 10,000 watt amplifiers.
Unfortunately, one giant sub doesn't always work as well as several smaller ones, because he didn't win squat with this setup. However, it's not like he needed to prove anything to those in the car stereo world (check out some of the tech briefs on their Main Autosound2000 website)
Overrated / Underrated : Moderation
indeed, the response time of this woofer must be extremely slow negating any good effect it might produce on the frequency range. First you will need a very powerfull amp to drive it so that you actually hear something and even then all sounds will be muffled, bass and bass drums and explosions won't have any attack because even with the appropriate energy the size and weight of the cone will prevent any sudden movement of the cone. In effect the cone will react slower than the sound going in, providing natural compression.
It will just sound like an aural pool of mud. Subwoofer often need a lot more energy to drive than a tweeter, this is why on bi-amplified or tri-amplified system you will read that 250watt goes to the bass, and 70 watts to the tweeter, imagine what's needed to drive this correctly. Not to mention that at this size it nearly impossible for the cone to be even and solid (if part of the cone are moving before the rest it will just sound, well, disgusting).
Impressive to look at, disgusting to hear, funny to read!
Note that you won't get the full range of the subwoofer with a DVD or CD. Both have a bottom limit of 20 Hz, while the sub in question can allegedly output down to 10 Hz flat (and well below that with fall off).
You'd have to use vinyl to get frequencies that low. And have one hell of a damping system for the player to avoid it being shaken by the sound it's reproducing...
Not a vinyl snob (all of my music is on CD and ripped to MP3), but there are technical limitations. Of course, 20 Hz is far lower than most people's stereo systems can reproduce anyway. Below that you can't really hear it... but you can feel it.
This text is filler, because apparently my per line character rating is too low. Hopefully it's an average, so this fluff will bring it up. Please fix Slashcode so that this crap isn't a problem. I have sincere doubts that it does any good to stop the trolls (browse at -1 if you don't believe me). So why torture your other readers/posters by making them jump through the troll hoops?
Overrated / Underrated : Moderation
Negative feedback is used in transistor amplifiers to eliminate even harmonics (2X 4X 6X) that your ear hears as distortion. The downside is that it also eliminates odd harmonics (1X 3X 5X) that pianos and acoustic guitars produce naturally. Tube amplifiers don't generate the even harmonics, so they have no need for the negative feedback.
The early 70's Marketing pushed the THD (Total Harmonic Distortion) measurment as a indication of superior design of the trasistor amplifiers. A good tube amp may have as much as 5% THD compared to a 0.001% transistor amp, but any true audiophile would rather the tube.
Of course, if all you listen to is rock, the distortion is already in the recording, and you probably won't be able to tell the difference other than the transistor will be able to produce more Watts/$. I had to have this pointed out to me while working at a Hi-Fi shop (all I listened to was rock at the time)
uh, no, both are capable of DC output, what's wrong with you? Getting 10Hz out of vinyl (turntable rumble doesn't count :P) would be quite the feat, especially with anything other than a pure 10Hz test tone containing no other frequencies.
Forgive my naivete, but I cannot see how that can be. My understanding of acoustics and digital sampling suggests that a DVD or CD only has a top limit (of 22-24 kHz). Low frequencies, like 10 Hz, are easily represented by almost any digital sampling standard; they are all over the Nyquist frequency of 20 Hz.
Any problem with bass reproduction from a CD or DVD is purely a matter of the amplifier or signal reproduction circuitry between the CD/DVD player and the speaker, not of the medium itself. Or is there something in the Red Book standard that limits the reproduction after the signal is read off the disc?
Those who complain about affect & effect on
FYI, Church organs go to 32 foot pipes. The good ones go one rank further to 64 feet. These are the big folded pipes in back. You won't get to see these unless they have a viewing window to the real pipes. They are not the pretty pipes in front. The 64 footers are almost always folded double or triple (like most brass insturments) because the pipe loft isn't that tall. Due to the shape of the pipe, it's throat, and other attributes, most pipes don't play exactly one pitch. That's why they don't all sound like sine waves or have a flute sound. Some pipes have brass and trumpet sounds instead of flute sounds. This is due to the harmonics generated by many pipes to give them rich fat sounds by design.
The truth shall set you free!
Purity. Negative feedback is never quite phase coherent with initial signal, you get filtering effects and so on. AFAIR, Bob Carver's wonderful Phase Linear power ampflifiers ran on a similar principal - they sounded terrific, which is why Pink FLoyd's techs chose them as PA power for the Wall tour 25 years ago. We did an A-B test blindfold between these and some MOSFET power amps years ago - and could tell the difference in a matter of seconds. The Phasies won hands down, of course.
32 foot pipes are the largest commonly found, and even then only on very large instruemts. A 64' pitched rank is exceedingly rare. The only instrument I'm aware of (in the US) with real 64' pipes is the one at the Atlantic City Convention Hall (website: http://www.acchos.org/ ).
The Washington National Cathedral, in DC, has a 64' pitched rank, but if I recall correctly it's electronic (using speakers), not with actual 64' long lengths of pipe.
Bear in mind, a 32' pitch C is already below 20Hz, well below what most people can hear. A 64' pitch is more of an impressive "special effect" than anything else.
Actually, if anyone else can cite another pipe organ with a 64' pitch (US or otherwise), I'd love to hear about it, so I could hear that monster!
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