| Horn gain - directed sound or acoustic transformer? [message #16985] |
Thu, 16 September 2004 15:49  |
Groove Tube
Messages: 4
Registered: May 2009
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Esquire |
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I was told that horn gain is caused by directed sound focused to a small spot. That is what I always thought about horns. Just the other day I heard it called an acoustic transformer. Is there more going on than aiming the sound? Is it two ways of saying the same thing?
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| Both! [message #16986 is a reply to message #16985] |
Thu, 16 September 2004 16:45  |
Magnus
Messages: 32
Registered: May 2009
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Baron |
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The magic with horns is that they are not merely focusing the sound like a parabola antenna compared to an omnidirectional antenna, but actually acoustically matches the driver to the air making it more efficient (acoustic transformer). These are two very different mechanisms. If you want an electrical analogy, again think of an antenna. Some gain comes from narrowing the dispersion pattern ("antenna gain") some comes from more closely matching the acoustic impedances (lowering back-reflected power i.e increasing SWR for an antenna). /Magnus
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| Re: Both! [message #16989 is a reply to message #16988] |
Fri, 17 September 2004 18:17 |
Oberon
Messages: 20
Registered: May 2009
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Chancellor |
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"the horn still can easily exhibit 10dB or more of gain over the direct radiator using the same driver." A direct radiator in 1/8th space exhibits 9dB gain over the same radiator in open space so the directional aspect is significant. Just an observation. This is not to say the impedance matching aspect is not also significant for its own reasons.
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| Re: Both! [message #16992 is a reply to message #16991] |
Sat, 18 September 2004 17:40 |
Bill Fitzmaurice
Messages: 335
Registered: May 2009
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Grand Master |
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I've never bothered to measure a mid horn corner loaded, but much of what's happening with a LF horn is that corner loading increases the effective path length and mouth area. However, if both the path length and mouth area are already at a full wavelength additional extension isn't going to make any difference, so the increase in SPL is frequency limited; the average bass horn won't see corner loading having much effect, if any, above 200 Hz or so. Your average mid or HF horn is going to have both the path length and mouth cross-section at least a wavelength through most of the passband, so additional length or mouth area will have little or no effect. Yes, the directivity aspect of both wall and corner loading is there, but here again that's only part of the equation, the rest being an improvement of the horn function itself.
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