Fibonacci Spiral for Horns

[TN Allen]

Setting aside the complexity of building a horn based upon a Fibonacci spiral, or perhaps another exponential spiral, would there be an acoustic advantage to such a horn?

If so, and if building it were not a serious impediment, would anyone want to collaborate and be willing to provide the mathematical data to define the horn shape?

[clydethecat]

Re: Fibonacci Spiral for Horns

[Sydney]

Re: Fibonacci Spiral for Horns

...Would there be an acoustic advantage to such a horn? ...

One aspect of various horn flair rates is what Beranek called Radiation resistance ( particularly near cutoff ).
For practice reason large horns are usually made with flat wooded panels, not curved.

[TN Allen]

Re: Fibonacci Spiral for Horns

Do the practical reasons result from Radiation resistance or construction difficulty?

[Sydney]

Re: Fibonacci Spiral for Horns

Construction difficulty - Most bass horns I have seen ( that used curved panels ) were made from a molded/sprayed or formed material like fiberglass.
Here is a "classic" examination.

http://p10hifi.net/planet10/TLS/downloads/Dinsdale-Horns-3parts.pdf

[dlr]

[randyohoh]

Re: Fibonacci Spiral for Horns

Here are a couple of links on ebay to sellers touting the benefits of the fib horn

http://www.ebay.com/itm/AUDIOPHILE-F...item417e4f8eb7

http://www.ebay.com/itm/FIBHORN-4tbb...item3f335cb098

http://www.ebay.com/itm/FIB-HORN-4tb...item417e5f7978

bare cabinets for $299 a pair, with a TB 3" 881 SIF $378, and in a "stone" cabinet $999. Here is some of the hype.

How do we do it? By placing a superb full-range TANG BAND 3" driver into our unique FIBHORN 4 speaker cabinet, with four FIBONACCI (exponentially expanding) chambers that together form almost 36" of perfect horn for the back wave of the driver. It yields a flat bass to 38hz PLUS accurate equalization of all frequencies to 20,000hz.

[billfitzmaurice]

Re: Fibonacci Spiral for Horns

Setting aside the complexity of building a horn based upon a Fibonacci spiral, or perhaps another exponential spiral, would there be an acoustic advantage to such a horn?

Not really. It has the advantage of being easier to lay out than conic sections, as it consists of a series of constant radius bends. I use it in my DR horns for that reason.
As for this:
How do we do it? By placing a superb full-range TANG BAND 3" driver into our unique FIBHORN 4 speaker cabinet, with four FIBONACCI (exponentially expanding) chambers that together form almost 36" of perfect horn for the back wave of the driver. It yields a flat bass to 38hz PLUS accurate equalization of all frequencies to 20,000hz.
A 36 inch long horn will only load to 94Hz. A horn mouth that small won't even go that low. It may appear to be a horn to the uninformed, but between the short length and mouth area it will actually operate as a tapered port.

[clydethecat]

Re: Fibonacci Spiral for Horns

Not anymore, J-M Le C has died.

[weinstro]

Re: Fibonacci Spiral for Horns

Not anymore, J-M Le C has died.

He frequently requested features and model enhancements from Dave McBean, the author of HornResp. If this is a direction you'd like to explore, HornResp probably has the calc models.

Regards,

Rob