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Old 29th November 2013, 11:39 PM   #1641
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Quote:
Originally Posted by Jmmlc View Post
Iwata-JMLC and E-JMLC horns don't use such kind of diffraction to control directivity. Their directivity in the vertical plane is higher than in the horizontal plane. There is no pattern flip.

Best regards from Paris, France

Jean-Michel Le Cléac'h
Jean-Michel,

The E-JMLC-1000 has higher directivity in the vertical plane in the high frequency range, going to a lower directivity at 1000 Hz (nearly double the beamwidth) than the horn has in the horizontal plane.

In other words, the pattern flips.

Art
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Old 30th November 2013, 01:49 PM   #1642
Jmmlc is offline Jmmlc  France
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Hello Art,

I disagree. Such E-Jmlc 1000à is to be used over 2kHz and then you can see that between 2kHz and 3kHza, the horizontal and vertical directivity are the same and then above 3kHz, vertical directivity is higher than horizontal directivity.

Only at the lowest frequency range such horns can be modeled by a planar piston of the dimension of their mouth...

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 1st December 2013, 03:37 PM   #1643
pos is offline pos  Europe
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So that is exactly the same phenomenon as any other horn, there is no magic bullet:
you have to keep the crossover high enough to avoid the pattern flip range, which is dictated by the vertical dimension.
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Old 1st December 2013, 07:59 PM   #1644
pooge is offline pooge  United States
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Most of the LeCleac'h horn arrangements I am seeing in reality seem to have bass boxes other than bass horns.

This allows the mid horns to stick out ahead of the bass box to time align, yet have the mouth in free field where it belongs.

Yet, if using a longer bass horn, to time align without electronic delay, the mid horn has to be moved back over the top of the bass horn. I'm wondering what degree of vertical separation between the two horns is the minimal separation that allows the mid horn to be in free field and not affected by the top of the bass horn or other horizontal platform below the mid horn. I assume this is also dependent on the mid horn cutoff frequency, and that an absorptive padding on top of the bass horn would help regarding reflections, but what about the shape of the wave fronts from the mid horn? Low frequencies would not be absorbed that much by padding, and the acoustic load on the mid horn might be affected. Any rules of thumb regarding vertical separation to minimize this problem without resorting to moving mids forward and using electronic delay?
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Old 2nd December 2013, 08:58 AM   #1645
Jmmlc is offline Jmmlc  France
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Quote:
Originally Posted by pos View Post
So that is exactly the same phenomenon as any other horn, there is no magic bullet:
you have to keep the crossover high enough to avoid the pattern flip range, which is dictated by the vertical dimension.
Hello Pos,

I disagree again. pattern flip Inside the interval of frequency inside which the horn is used is for sure to be avoid. But in the case of both the Iwata-Le Cléac'h and the e-JMLC there is no pattren flip inside that interval of frequency inside which they are used.

Surely you can see horns having horrible pattern flip (Smith horn...) but this is not the case with both the Iwata-Le Cléac'h and the e-Jmlc as their
directivity is the same as a round horn near their acoustical cut-off frequencies (as predicted by theory) but as soon the ferquency is higher, both horizontal and vertical directivity decreases but with a higher directivity decrease for the horizontal one.

(Both horizontal and vertical directivity of the E-JMLC is somewhat smaller than the directivity of the axisymetrical Le Cleac'h horn of the same cut-off frequency which is a plus for the e-jmlc for people who want a large "sweet spot". The price to pay being just some equalization to be performed...)

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 2nd December 2013, 10:35 PM   #1646
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Originally Posted by pos
So that is exactly the same phenomenon as any other horn, there is no magic bullet:
you have to keep the crossover high enough to avoid the pattern flip range, which is dictated by the vertical dimension.


Quote:
Originally Posted by Jmmlc View Post
Hello Pos,

I disagree again. pattern flip Inside the interval of frequency inside which the horn is used is for sure to be avoid. But in the case of both the Iwata-Le Cléac'h and the e-JMLC there is no pattren flip inside that interval of frequency inside which they are used.

Surely you can see horns having horrible pattern flip (Smith horn...) but this is not the case with both the Iwata-Le Cléac'h and the e-Jmlc as their directivity is the same as a round horn near their acoustical cut-off frequencies (as predicted by theory) but as soon the ferquency is higher, both horizontal and vertical directivity decreases but with a higher directivity decrease for the horizontal one.
Jean-Michel,

I would agree that the pattern flip in the range of frequency you specify the horn to be used is not problematic, but the difference between the "horrible pattern flip" exhibited by the Smith horn and the pattern flip the E-JMLC 1000 polars show is just a matter of degree.

The pattern flip the JBL 2370 bi radial exhibits is similar to the E-JMLC 1000, though the 2370 has a larger vertical height, so the flip occurs at a lower frequency.

The Renkus Heinz complex conic horns have vertical heights similar or equal to the horizontal width, so do not exhibit the pattern flip common to all horns with vertical heights less than the horizontal width.

Any horn requires the vertical height to be a wavelength long to provide pattern control, simple physics determines that your horn with a vertical height of 115mm will begin to have progressively wider dispersion below 2260 Hz as the waves begin to diffract around the mouth.

There is nothing wrong with your horns obeying the laws of physics, but you seem to be disagreeing with those laws .

Art
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Old 3rd December 2013, 04:10 AM   #1647
soongsc is offline soongsc  Taiwan
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Having considered the horn designs, I am much convinced that curvature radius of horn walls should gradually decrease as do the LeCleach type horns. The main consideration of how depend on the driver involved. Considering the directivity characteristics and loading, I am looking at trying out these designs at the extreme ends of speaker spectrum in two way or three way designs. Would appreciate links to any experience in LeCleach based subs and back loading horns.
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Old 3rd December 2013, 04:36 AM   #1648
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Are you sure, Soongsc? LF horns must incorporate the floor reflection as part to the design. Maybe the JMLC could be truncated at the 90-degree point where it meets the floor, since there will be another (reflected) JMLC horn right under the floor. Below 100 Hz, the floor will be more than 90% reflective, even with heavy carpeting.
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Old 3rd December 2013, 05:17 AM   #1649
soongsc is offline soongsc  Taiwan
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For the extreme low, I think it makes sense to use the corners. Sure, we need good padding behind the speakers like Earl does. Also it is a goal to keep the final design reasonably small and flexible for an average user.
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Old 3rd December 2013, 05:29 AM   #1650
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Well, by using corners, you are committing to a folded horn like a Klipschorn (unless you are building them into the room itself). Then the response will be kind of funky from 250 Hz and above, so that implies a crossover to a straight-bass horn or a very large MF horn.

Klipsch cheated by pretty much ignoring the trouble in the 250 Hz to 500 Hz range; check out the unsmoothed response of a KHorn some time. When I was young, I remember seeing an extreme audiophile's system with a KHorn bass section and a very large wood multicell. In retrospect, it must have been a 300 Hz multicell, since it was one of the biggest ones I've ever seen. That's the most elegant solution for good response between the bad region of the KHorn and the LF region of the large-format compression driver.
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