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| Re: Basshorns - Pros and Cons [message #19076 is a reply to message #19074] |
Mon, 05 February 2007 17:27   |
DMoore
Messages: 58
Registered: May 2009
Location: Seattle
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Baron |
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Speaking of the reduction of reactance peaking in rear-loaded horns, here is an another example, although not as elegant in implementation as the ELENA, is the 1956 Glenn (General Electric) patent for a rear-loaded short-path-length folded horn this time with a purposely too-small mouth size for the Fc, US patent# 2,765,864. Dana
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| Re: Basshorns - Pros and Cons [message #19079 is a reply to message #19074] |
Tue, 06 February 2007 07:01 |
elena
Messages: 3
Registered: May 2009
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Esquire |
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Hi, thanks for replying.
Actually I'm abroad, as I'll be back home I'll start elaborating.
The .pdf document is totally missing the [twin] reflex operation above the cutoff of the horn, I'll give a practical perspective of the system, and all formulae sufficient to calculate and build a system. I feel we together may pursue this way further and get an even betetr result, for instance employing a hyperbolic horn at the throat and a tractrix at the mouth, along the line of the "rubber throat" of the Klipsch design.
This case the resonance frequency should be more better determined by empirical method, rather than from the theory, as a closed form to solve the integral of the formula could be missing.
Beyond the theory, there's the practice, so it's time to take the drawings, build the cabinet and test the system. We must not forget that the cabinet lodges a 55 Hz horn, with a optimum mouth on the eigth space, and due to reactance annulling and front reflex porting capable to go down to 30 Hz, as the [twin] reflex operates with a tuning frequency which coincides with the free-air woofer frequency, that is 29 Hz (half the cutoff of the horn). Even without porting along the horn pathway, the system would be worth making.
This is what I am willing to embark on, a 2.nd system with the hyperbolic horn to be the testbed of the approach. It is clear that this is a home system, as the PA and sound reiforcement don't need such an arrangement to best the performance. But for your home it could help to balance room availability and performance, reducing space requirement without affecting the transient ringing in the low bass band.
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| Re: Basshorns - Pros and Cons [message #19098 is a reply to message #19074] |
Mon, 12 February 2007 09:30 |
elena
Messages: 3
Registered: May 2009
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Esquire |
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Patent 4549631 of BOSE Corp. may be helpful to illustrate operation of multiple porting loudspeaker, what I call twin reflex.
It is clear from the patent document that, in case of equal frequencies porting tune, emissions cancel out each other, that is the practical principle of the horn reflex porting, by far forward and reflex waves damp out each other. This would achieve better than a pure Helmoltz's resonator operation does, in effect I forecast the use of both of them, but in my practical protoype I emploied the reflex principle solely (the cut-away viea of the system claryfies that, the top elevation view is somewhat misleading, find out the pictures at the Klipsch forum link posted by D-MAN).
The reflex technique is a feed-forward open loop, far better than a feedback closed-loop like an Helmoltz's resonator.
I shall explain better if anyone is interested.On the other hand, below the cutoff the half frequency reflex porting -in the system the woofer resonance is at 29 Hz and the cutoff at 55 Hz- ensures good operation, according to the design criteria of a twin reflex system. By the way, I am seeking for an oscilloscope on e-bay Italy, I hope to satisfy the commitment to myself to finally test it and ... cheer up, we have got something good! Good vibrations ELENA
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