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This high-end audio loudspeaker consist in a array of N=2^k resonators; each one tuned to a specific frequency and a quality factor according to N.
For resonator I mean a device capable to make a single audible tone.
Process audio, do a FFT (Fast Fourier Transform) of 2*N samples length, and get
the power spectral density (PSD). Now feed the resonators with the N components of the PSD. One may consider this step as an "acoustical" inverse FFT.
An array of 4096 resonators should be fine for most people, exigent users could go up to a 65536 resonators.
Actually only N-1 resonators are needed, just removing the DC component.
For the really enthusiastic audio lovers, the DC component must be connected to a fan.
A rudimentary version
http://bobbyowsinsk...-wall-of-sound.html
The Wall of Sound: 439 independently amped narrow-band cones on eleven channels, including one tone generator and a host of mids and woofers for each string of Phil Lesh's bass. Clear as a bell at a 1/4 mile in 1972. Grandiose indeed. [Alterother, Mar 07 2013]
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frequencies aren't discrete, so you're actually saying "between frequencies x and y". |
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Sound systems accomplish this already, in a less grandiose format: a "3-way" speaker system has a big speaker, a medium sized speaker and a small speaker, which are fed low, mid and high frequencies respectively. |
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your 4,000 speakers are going to take up a rather large bit of the wall. |
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// 4,000 speakers // These aren't speakers, are tone generators. Big difference. |
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// less grandiose format: a "3-way" // I'm aware of 3-way systems. But as you said, it's less grandiose ;-) |
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Why the transform, if using a digital file as the audio source, can the digital data itself not be used directly to drive the resonators? |
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Passive resonators, like tuning forks, will reproduce the sound when excited poperly from a sound source like a digital file or any other format. It's an interesting aproach, but this one it's about active devices. May be I should said "tone generators" instead of "resonators" to achieve an electromechanical way to go from the digital spectrum to temporal and physical domains. |
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I mean that there isn't just whole number freqencies. |
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Is this supposed to be an instrument ? |
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Or, to make a long story short, I don't get it at a basic level. |
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//I don't get it at a basic level.// |
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No me. But it seems to be a proposal to have
one speaker for each discrete frequency. In which
case it will fail in several ways. |
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(1) Resonators resonate at their resonant
frequency. Thus, if you have a resonator
resonating at 440Hz, and you feed it sound at
441Hz, you're going to get some weird beat effect. |
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(2) See (1) because it's a big problem. |
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(3) Your music will sound like it's been through a
comb filter. |
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[MB] What I would expect from feeding a resonator with a frequency near the resonance frequency it's an amplitude drop depending on Q instead of a beat effect. |
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Regarding the sound.... until someone out there doesn't bring it to life we'll never know :-) |
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//You'd surprised about FFT's - you could get away
with as few as 128 frequencies.// |
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Yes, I'd be surprised. Try playing a trombone slide
using 128 fixed frequencies. Or a human voice. |
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//What I would expect from feeding a resonator
with a frequency near the resonance frequency it's
an amplitude drop depending on Q instead of a
beat effect.// |
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Sadly, your expectations would not be met. If you
drive a resonator slightly off its resonant
frequency, beats is what you get. Next time
you're standing next to a metal lamp-post (which
will have a nice clean resonant frequency), give it
a go. |
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What'd be cool is, if you have a few thousand speakers, assign a sine wave to each based on the thousand highest power frequencies. They'd be speakers though, not resonators since you'd almost certainly be changing frequencies as the song/program progressed. |
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Of course how you're going to determine what those thousand pure frequencies are in real time is beyond me. |
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If you push a swing regularly at just off its natural
frequency, it will alternately slow to a standstill and
swing higher. |
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However, it's entirely possible that my reasoning is
impaired due to Merlot. |
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