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Inflatable Loudspeakers
fm6 sent in an article running at New Scientist talking about new technology that allows Inflatable Loud Speakers. The technology is apparently patented and there's not a lot of technical details, but I have to say the concept amuses me. And I somehow doubt that this technology will ever be used in high fidelity home systems.
thats correct, the tech. details are disclosed in an american patent(can't speak for other countries, but its probably the same)
If this is a patented item, as opposed to patent pending, you should be able to go th the US Patent and copyright website and look them up.
The Kruger Dunning explains most post on
The audio world is crawling with hopeful inventors who don't understand much about sound and electro-accoustics. I've had the privilege of seeing many of these "inventions" first hand. The article failed to address the key issue behind "inflatable speakers": rigidity. In a vented box, which is the most common type of low-frequency and very-low-frequency system, the walls need to be pretty rigid to prevent distortion and energy loss. If these inventors have some way to make a balloon as rigid as 3/4" birch plywood with closely spaced transverse braces, the article doesn't mention it.
The only kinds of speaker enclosure that aren't concerned with rigidity are those that simply enclose rigid horns made of fibreglas, plastic or wood. In these situations, the enclosure merely protects the components from dust, water and damage and does not serve an accoustic funciton. JBL among others has realized this and is making a series of touring speakers which are simply frames of metal tubing with no side walls. Again, inflatable walls would add nothing to such a system.
As for the "beach ball" idea, this can be interpreted in two different ways, due to the lack of detail in the article. If you make a conventional (sealed or vented box) speaker system with spherical form, it will have a sharp resonant peak related to the diameter of the sphere. This peak can be reduced by increasing the absorbent material inside the enclosure, but still reflects a design mistake. A sphere is the worst possible shape for a conventional speaker enclosure. A second application of a sphere is to place it in front of a speaker (possibly a tweeter) creating in effect a radial horn. By careful positioning, two or even three transducers could share one sphere. An inflated beach ball could work for high and even mid frequencies. As the frequency gets lower, however, the need for rigidity of the sphere increases. In general, the sphere should be hard and rigid.
Such a system will never work as well as separate, properly designed horns for the separate transducers. Its only benefit is visual gimmickry and possible cost savings.
Anyways, don't discount the inflatable speakers as things that wouldn't work... these guitars worked really well. I saw them first in the Boston Museum of Fine Arts...