Slashdot Mirror
World's Most Powerful Subwoofer
dponce80 writes "This $13,000 subwoofer, the TRW 17 from Eminent Technology is billed as the world's most powerful due to its ability to reproduce sounds with frequencies as low as 1Hz. Typical subwoofers bottom out at 20Hz, and while the human ear can barely hear below that point, it is still possible to feel the sound. This particular woofer does not have an enclosure, instead relying on a fan-like design, wafting a cone of modulated air into the room, and effectively turning it into a resonating box, in its entirety!"
This is a confirmed myth. Was showed on muythbuster.
Digital audio is filtered to remove all sounds below 20Hz before going onto CD, as that increases the dynamic range of remaining frequencies, so unless you have access to the original high bit rate studio recordings, you won't tell much difference.
foo mane padme hum
Here's the source article: http://www.sonicflare.com/archives/eminent-tech-tr w-17-the-most-powerful-subwoofer-in-the-world.php
IIRC, they placed him in the middle of a circular arrangement of woofers, pointing towards the center. Depending on the frequency, number of speakers and radius, the soundwaves could very well cancel themselves, dampening the effect. Even then, he came exhausted from the experience as the soundwaves forced air in and out of his lungs.
Just pointing out the testing method perhaps wasn't the most adequate. According to Wikipedia, they only tested three frequencies below 20hz; a low sweep between 0-25hz would've been better.
This is because - on vinyl - the lateral deflection of the groove is proportional to frequency (as well as amplitude). So for the same volume, low frequencies cause a groove to take considerably more space on the disk than high frequencies.
This is addressed by attenuating low frequencies (and boosting high) before recording, and reversing this on playback. This is known as RIAA equalization because the RIAA equalization curve became the standard for recording and playback on vinyl.
No, you have it wrong. The artist's woofer wasn't large enough (and probably wasn't baffled properly). It wasn't a woofer at all, just a moving cone.
It's all about creating enough air pressure to be felt/heard. A 12" fan can move much more air than a wall full of 12" cones.
The limitation of most acoustical drivers is that by design, they need to reciprocate and most of the power is wasted in accelerating and decelerating mass. The best analogy I can think of is that of a modern helicopter compared to that old learning-to-fly contraption with the beach umbrella on top.
Most digital audio is not filtered below 20 Hz. That's a myth that persists for a variety of reasons. In the days of vinyl, audio was consistently high-pass filtered because even with the standard RIAA equalization, deep bass produced excessively large grooves. Microphones are sometimes filtered to remove rumble, but in cases where the lowest frequencies are important, such as movie soundtracks, the lowest frequencies are generally preserved, subject to limitations of the equipment, such as AC coupling capacitors. Placing a filter at 20 Hz also has potentially audible drawbacks since the phase shift of the filter will easily extend an octave higher (40 Hz).
I realize this is a joke, but there have been studies done of how the body is affected by music. I don't know about the "brown note," but the idea that bass "rattles your colon" is not far off. Interestingly a recent issue of Playboy (I, um, read the articles) had a brief note about this when somebody wrote in and asked what frequencies make women the horniest; it turns out someone did a study to determine exactly that. The frequencies were very much on the low end, though I don't remember. The study itself sounded pretty interesting though - they had various women sit on top of a subwoofer and played different frequencies while asking about their sexual response...
I'm the guy who originally dug up the Eminent over at http://www.sonicflare.com/ before I wrote the companion article on ohgizmo.com (which looks dead from a quick and painless /. death...).
I'm a blogger, not an engineer, so I really have no idea what I'm talking about (par for course, right) but I did talk to the creator Bruce Thigpen a few days ago about his crazy invention:
Yes, it's real. Yes, you can "hear" it below 20hz. No, it doesn't blow women's clothes off...yet.
The way the TRW 17 (Thigpen Rotary Woofer model #17) works is the fan spins at a constant speed but the fins themselves rotate back and forth to change the frequency. Also, you don't just set this up in your living room and crank up the volume. It has to be installed in an adjacent space like your attic or basement which then becomes the actual subwoofer enclosure, firing through a chainsawed hole into your main listening room.
The TRW was demoed at the Rocky Mountain Audio Fest a couple weeks ago and the reviewers from established audio publications were actually frightened as the walls started to pulse in and out at about 10Hz. Wimps. But the surprising discovery was the sound wasn't booming or nasty, just frighteningly "there." The TRW 17 is advertised with +/- 4dB of distortion which is awesome for any subwoofer, let alone one that covers 1Hz to 30Hz.
And here's the good news: Bruce told me there's a cheaper version in the works. Not cheap like free beer, but not 13 grand. Also, there is a car version in the works that, no doubt, has Luda all hot and bothered. A "normal" version is also planned -- normal like a subwoofer the size of a refrigerator but still better than converting the den into a boom machine.
So you know, no actual music was played at the RM audio fest. It was purely a proof of concept, though it's claimed to work perfectly for music and HT. I haven't talked to Bruce in a few days (no doubt rappers are all up in his biz after I posted it on Monday) but I'm sure we'll be seeing a lot more of the TRW 17 soon.
Pictures of installations and live reports: http://www.sonicflare.com/archives/eminent-tech-tr w-17-part-2.php
Josh
And *that* is what is special about this woofer. Here and here explain it all. Basically, its very hard to move much air at such low frequencies with cone subwoofers (as you saw), so they instead the fan pushes the air with the angle of the blades being adjusted to produce the frequencies.
Paul
MythBusters had an episode trying to recreate the brown note. They couldn't do it.
It's rare for an sound/recording/editing engineer to cut off low frequencies, after all this is where there's a lot of percussiveness (and the lowest note of the contra bassoon is actually lower than 30hz). Some used to use roll-off filters that 'shaped' the DC-20hz region, believing there was no information down there, but that's not true-- there is.
---- Teach Peace. It's Cheaper Than War.
As you pointed out, if you use several sources the soundwaves can reinforce or cancel eachother. To do a sweep from 1-25 Hz would mean you have to move your sources in accourdance with the frequency. Just a few points on the curve that you can calculate beforehand would be much simpler.
This space is intentionally staring blankly at you
The real challenge is improving the input, not the output. Audiophiles waste a lot of money on really high-grade amps and speakers just to buy cd's and dvd's recorded with industry standard mic's that don't come close to covering that range. There are very few recordings that use equipment that even come's close to the set up of a "real audiophile."
Why waste >$30,000 on you living room system if you're just going to pop-in a cd recorded with $150 worth of equipment? Or almost any CD, really, as the digitization eliminates these 'unnecessary' bands in the quest for more space on the CD (Which is not entirely unreasonable, given the quality of 99% of the systems on which they will be played and 99% of the ears that will listen to them).
Most of that "stuff you're missing" is really just distortion. Its just very expensive, 1334 distortion, for which "real audiophiles" will pay a great deal. Like caviar for other rich people. Or spoilers on Honda Civic's.
(BTW- IAAAE [I am an Audio Engineer])
Universally, everyone that works on or around submarines refers to them as "boats" though. At least in the U.S.
Please stand clear of the doors, por favor mantenganse alejado de las puertas
There are all sorts of reasons to shape sounds, and the use isn't empirical. If there's no information, then it cleans up the mix to use all kinds of equalization to cut noise, transients, and so on. But an overall mix can sound very AM Radio (e.g. bandwidth limited) if too much equalization is used. When I did masters, I'd use a 36db/octave slope starting at about 18hz, then check to see if there was something useful that I'd tamped down. Sometimes, there was useful percussiveness that was cut, and the only real way to detect that was by using a pretty loud playback with floor-mounted 3-ways or the best Sennheiser headphones that I had (which usually didn't help much at that freq).
A lot of LF energy tends to bottom out traditional woofers, no matter how good their inner compliance is. Add low-level DC, then add a kick-drum thump, and the voice coil bottoms, maybe damaging the woofer in some way-- usually voice coil cracking or distortion. So, I rarely changed the filter, but had to re-slope it to make the impact as realistic as was rational.
The point of the post is to connote that the final mix will have a lot of energy in some genres in the LF range. Individual channel feeds are commonly shaped to suit the needs of the mix. But you don't want to rob the overall mix of information to suit the problems with one feed, re-mix, etc.
---- Teach Peace. It's Cheaper Than War.
CD audio consumes 88,200 bytes per second.
Close, but off by a factor of two. There are 44100 samples per second, 2 channels, 2 bytes (16 bits) per sample. Total 176,400 bytes per second.
www.wavefront-av.com
Of the consoles I've used, they used open-ended DACs with only slight pull-up resistors and had 20-20K within a db. Overall system was 5-27K +2/-1, not counting tape. Tape was another disaster altogether.
An 18' horn... probably Cerwin-Vega...? C-horn? E-horn? That's a bunch of bass, buddy.
I don't know about Hollywood in general in terms of their spec, but it would be tough to believe that they didn't want lower freq energy recorded. My experience is southern and in NYC. But I'll probably catch hell for responding to an AC. Oh well.
---- Teach Peace. It's Cheaper Than War.