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Horn Throat Constriction [message #81378] Thu, 04 June 2015 18:59 Go to next message
PointSource is currently offline  PointSource
Messages: 28
Registered: May 2009
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I wasn't sure whether to post in Speaker, or in Pro Audio, because the loudspeaker in question was intended for a live-sound pro audio application. Please move if required.

Anyway, I'm hoping to get some Horn Guru input about a project prior to any expenses.

I'm attempting to load a pair of cone drivers into the same midrange horn with predetermined dimensions. For both speakers to fit, the passages leading from each square throat to where they meet will gradually collapse to almost half the throat area in (only) one dimension. At the narrowest point, the passage width is about 1/4 WL of 1500Hz. Both passages will feed a common horn flare & mouth. I'm aiming for an upper Xover of 1.6kHz. What kind of harmonic distortion & cancellation might I expect from this arrangement?

Any input appreciated....

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Re: Horn Throat Constriction [message #81384 is a reply to message #81378] Sat, 06 June 2015 07:00 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

It's really hard to say without measurements or even modeling. But I would expect that front volume to act as a low-pass filter, limiting HF.

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Re: Horn Throat Constriction [message #81385 is a reply to message #81384] Sat, 06 June 2015 22:13 Go to previous messageGo to next message
PointSource is currently offline  PointSource
Messages: 28
Registered: May 2009
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I got the idea that it might work from some old Altec Mantaray HF horns, which would collapse in the horizontal before expanding again. If such can pass HF, then why not midrange / midbass? The total throat area is just under 20in^2 for each 10" cone, so the front chamber area isn't too large (was also thinking about filler). The passage collapses to 2.25" horizontally while the vertical remains the same as the throat height.

Of course, the Mantarays are expanding in the vertical thru the point of constriction, and the mid horn doesn't.

I'm exploring theoretical plausibility for the time being. If the negative responses outweigh the positive, then I've saved time & resources.

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Re: Horn Throat Constriction [message #81386 is a reply to message #81385] Sun, 07 June 2015 08:20 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

It's just hard to say without measurements. If there is area expansion in the throat, I would expect it to act differently than if there is no expansion or if there is constriction. You also have the matter of two sound sources combining in the throat. This is a case where I think you'll want to make some physical models and test them.

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Re: Horn Throat Constriction [message #81387 is a reply to message #81386] Sun, 07 June 2015 14:05 Go to previous messageGo to next message
PointSource is currently offline  PointSource
Messages: 28
Registered: May 2009
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I knew in the back of my mind what your answer would be: model, build & measure! I have to decide whether the concept is worth the effort & expense.

The 2 sources don't actually combine at the throats; the 2 passages combine in parallel at the start of the common conical flare section. Either way, the 2 wavefronts will expand & impinge upon each other.

The goal is to achieve the longest path length within the given enclosure dimensions, including the use of 180-degree rounded curves. In order for the wavefronts to arrive at the conical flare relatively intact, I've surmised (guessed) that the passage width needs to be about a quarter of the upper frequency's wavelength. I'm concerned that the initial narrowing may pervert the waveform too much.

I'm working on a preliminary mechanical drawing (the old-fashioned way on 1/4 scale graph paper). I can post a photo in the near future if there's any interest....


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Re: Horn Throat Constriction [message #81388 is a reply to message #81387] Sun, 07 June 2015 14:43 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Absolutely! Keep us posted!

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Re: Horn Throat Constriction [message #81395 is a reply to message #81388] Thu, 11 June 2015 22:29 Go to previous messageGo to next message
PointSource is currently offline  PointSource
Messages: 28
Registered: May 2009
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Attached is one of 3 conceptual drawings for a pair of 10" drivers in a midhorn (chuckling wryly not permitted during presentation). This variation yields the longest path length of the 3. My concern is with possible effects of narrowing the passage width just after the throat (passage height remains same as throat height).

Convenient here would be a BF-style "W" horn, wherein the throat is divided into 2 narrow & equal passages, without the need to compress the wavefront. I would stack the 10s vertically, in that case. Avoiding copywrite infringement, we move on....

index.php?t=getfile&id=1738&private=0

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Re: Horn Throat Constriction [message #81396 is a reply to message #81395] Fri, 12 June 2015 10:58 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Two possible suggestions:
    1. Use push-pull drive. If you're going to have two drive units, you might as well take advantage of this configuration.

    2. Mount the drivers sideways to reduce (or possibly eliminate) the curve needed to feed the throat.

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Re: Horn Throat Constriction [message #81397 is a reply to message #81396] Sun, 14 June 2015 16:57 Go to previous messageGo to next message
PointSource is currently offline  PointSource
Messages: 28
Registered: May 2009
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I thought the throats were in the baffles where the drivers were mounted, while the curved sections contributed to the overall horn path length. Is this not the case?

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Re: Horn Throat Constriction [message #81398 is a reply to message #81397] Mon, 15 June 2015 10:40 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Yes, the throat is really just the entry point, the place of smallest area. Behind the throat is a front chamber, which is the area between the diaphragm and the throat. Beyond the throat, the horn flare makes a continually expanding area.

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