Hi all,
Im looking for a conical stand alone horn for a JBL 2452, but I have some questions that im looking to answer before I go any further.
Im interested in the JMLC 350hz and ferguson horns that jzagaja sells, but I cannot find any graphs for FR or other data of the driver I have (or similar 24xx drivers) on this kind of horn.
The exit angle of the driver is 10 degrees (so im told), what would the throat angle be on the jmlc horn? Does it matter?
what is the T factor of the jmlc 350?
The 2452 is a 1.5" driver, Jzagaja only lists 1.4" not 1.5" as available mountings- Does he do a 1.5"?
http://www.autotech.pl/pdf/audio_en.pdf
Any help apperciated!
Thanks
Im looking for a conical stand alone horn for a JBL 2452, but I have some questions that im looking to answer before I go any further.
Im interested in the JMLC 350hz and ferguson horns that jzagaja sells, but I cannot find any graphs for FR or other data of the driver I have (or similar 24xx drivers) on this kind of horn.
The exit angle of the driver is 10 degrees (so im told), what would the throat angle be on the jmlc horn? Does it matter?
what is the T factor of the jmlc 350?
The 2452 is a 1.5" driver, Jzagaja only lists 1.4" not 1.5" as available mountings- Does he do a 1.5"?
http://www.autotech.pl/pdf/audio_en.pdf
Any help apperciated!
Thanks
The 2452SL is throatless ("optimize aperture" design), so a 0° angle would be ideal, but I guess any small exit angle will do.
www.jblpro.com/catalog/support/getfile.aspx?docid=298&doctype=3
www.jblpro.com/catalog/support/getfile.aspx?docid=298&doctype=3
thanks guys,
Obviously 0 degrees is ideal, but I cant see what other option I have unless I make it myself.
Is there a way around this? has anyone tried building up the first few mm of the horn with putty to graduate the transition between the driver and horn angles?
Obviously 0 degrees is ideal, but I cant see what other option I have unless I make it myself.
Is there a way around this? has anyone tried building up the first few mm of the horn with putty to graduate the transition between the driver and horn angles?
Use an Adapter
Buy the horn version with an Rt = 1" and design/build an adapter block to match driver to horn.
Use a cosh flare to match the tangent angle [Am] of the horn at the throat radius Rm = 1"
Formula to use to determin the profile:
Rm = Rt*cosh(m*Lm)= 1.0"
Tan(Am)= m*Rt*sinh(m*Lm)
Lm - Length of adapter
Rt - Radius (ordinal) where driver an adapter join
= .75"
m - Flare coefficient of the adapter
(Adapter Fc <= Horn Fc)
Regards,
WHG
Buy the horn version with an Rt = 1" and design/build an adapter block to match driver to horn.
Use a cosh flare to match the tangent angle [Am] of the horn at the throat radius Rm = 1"
Formula to use to determin the profile:
Rm = Rt*cosh(m*Lm)= 1.0"
Tan(Am)= m*Rt*sinh(m*Lm)
Lm - Length of adapter
Rt - Radius (ordinal) where driver an adapter join
= .75"
m - Flare coefficient of the adapter
(Adapter Fc <= Horn Fc)
Regards,
WHG
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Hi whgeiger,
Im having difficulty understanding your post. The driver is 1.5", so are you suggesting getting a 2" version of the horn and making an adapter piece that goes between the horn and driver to make a tighter angle transition?
jzagaja, what is the final throat angle on the 2" version?
Im having difficulty understanding your post. The driver is 1.5", so are you suggesting getting a 2" version of the horn and making an adapter piece that goes between the horn and driver to make a tighter angle transition?
jzagaja, what is the final throat angle on the 2" version?
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Yes!
From Driver:
Rt = 0.75", At = 0.00 deg.
To Horn:
Rm = 1.00", Am = (from jzagaja)
You adjust m & Lm to get a matching Rm & Am for the adapter.
If you want a design, once [Am] is known, I will send you a drawing.
Regards,
WHG
From Driver:
Rt = 0.75", At = 0.00 deg.
To Horn:
Rm = 1.00", Am = (from jzagaja)
You adjust m & Lm to get a matching Rm & Am for the adapter.
If you want a design, once [Am] is known, I will send you a drawing.
Regards,
WHG
Adapter Internals
L R A
0.00 1.905 0.00
1.00 1.910 0.58
2.00 1.925 1.17
3.00 1.951 1.76
4.00 1.987 2.36
5.00 2.034 2.98
6.00 2.091 3.60
7.00 2.160 4.25
8.00 2.240 4.92
9.00 2.332 5.61
10.00 2.436 6.33
10.89 2.540 7.00
Regards,
WHG
L R A
0.00 1.905 0.00
1.00 1.910 0.58
2.00 1.925 1.17
3.00 1.951 1.76
4.00 1.987 2.36
5.00 2.034 2.98
6.00 2.091 3.60
7.00 2.160 4.25
8.00 2.240 4.92
9.00 2.332 5.61
10.00 2.436 6.33
10.89 2.540 7.00
Regards,
WHG
Hey lbstyling,
I´m not so sure the talk of zero angle is true if we should believe JBL´s Technical note:
The driver is made for "fast flare rate" and this would mean the angle should be big.
So don´t mind any adapters. Just let Jack customize a pair for 1,5". We haved tried quite a few of the horns and they are great.
I´m not so sure the talk of zero angle is true if we should believe JBL´s Technical note:
.
The driver is made for "fast flare rate" and this would mean the angle should be big.
So don´t mind any adapters. Just let Jack customize a pair for 1,5". We haved tried quite a few of the horns and they are great.
Fast flare does not imply any particular initial angle.
Looking at the throat of a PT wave guide the initial angle is 0°, even if it rapidly increases in the first mm of the profile.
Looking at the throat of a PT wave guide the initial angle is 0°, even if it rapidly increases in the first mm of the profile.
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Hey Pos,
So true! But JBL doesn´t talk about waveguides. They use the 2352 family in their examples. By looking at their throats one could surely tell what JBLs intentions where. Have never studied them though, have you?
Still in the paper the drawing seems to be angled from the phaseplug through the plate. Anyone who have removed the mesh to see how it looks IRL?
The OS 375, 2441 etc. 2" JBL drivers where 38mm to 49mm with a 69mm long exponential "adapter" with a 180Hz flare. The newer 2447 etc. are surely the same but with the "adapter" chopped of.
So true! But JBL doesn´t talk about waveguides. They use the 2352 family in their examples. By looking at their throats one could surely tell what JBLs intentions where. Have never studied them though, have you?
Still in the paper the drawing seems to be angled from the phaseplug through the plate. Anyone who have removed the mesh to see how it looks IRL?
The OS 375, 2441 etc. 2" JBL drivers where 38mm to 49mm with a 69mm long exponential "adapter" with a 180Hz flare. The newer 2447 etc. are surely the same but with the "adapter" chopped of.
the 1.5"/2" adapter inside the 2" drivers starts with a 0° angle.
I have a p_audio adapter, but it looks like it is purely conical...
I've never has a 2352 horn in my hands, but I do have some H9800 clones (S9800, meant to be used with the 435Be which is a 1.5" throatless design similar to the 2452H), and the initial angles are not 0°:
The angle is quite wide on the horizontal plan (maybe 45°), and is something like 130° (!) on the vertical plan, forming a diffraction slot.
(look at the bottom of this page: FEBRUARY 2004 )
It is even worse with the 2332 (used in the DMS-1).
If the phasing plug is good and the wavefront is "coherent" (which is not the case witht he 2435 and 435, but certainly is with the 2452), then the initial angle is less an issue withe throatless drivers than with the one that have an integrated throat.
I have a p_audio adapter, but it looks like it is purely conical...
I've never has a 2352 horn in my hands, but I do have some H9800 clones (S9800, meant to be used with the 435Be which is a 1.5" throatless design similar to the 2452H), and the initial angles are not 0°:
The angle is quite wide on the horizontal plan (maybe 45°), and is something like 130° (!) on the vertical plan, forming a diffraction slot.
(look at the bottom of this page: FEBRUARY 2004 )
It is even worse with the 2332 (used in the DMS-1).
If the phasing plug is good and the wavefront is "coherent" (which is not the case witht he 2435 and 435, but certainly is with the 2452), then the initial angle is less an issue withe throatless drivers than with the one that have an integrated throat.
Good thinking! So no need for any adapters, think we agree on that.
Forgot to say that the OS 2" JBLs has close to 5° angle.
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Apple vs. Banana
The wave front emanating from the driver, by design, is that of a flat disk not that of a spherical cap. To match the plane wave condition, a tangent angle of 0 degrees is required for the initial boundary condition, not a diffraction edge with a 7 deg receding slope (discontinuity). If you examine the figures 1a and 1b of the referenced JBL document [1] closely, you will notice that they are drawn incorrectly. So inferences drawn from them are probably erroneous as well. Under the high pressure conditions present in the horn/driver throat, you want to gradually transform the flat wave front to a spherical one of declining radius of curvature. That is the purpose of the adapter that you say is unnecessary. Otherwise a different horn design strategy should be employed were diffraction edges are employed to affect beam spreading (banana). This is an design regimen contrary to that of the horn (apple) to be used.
[1] JBL’s New Optimized Aperture™ Horns and Low Distortion Drivers
http://www.jblpro.com/catalog/support/getfile.aspx?docid=298&doctype=3
The wave front emanating from the driver, by design, is that of a flat disk not that of a spherical cap. To match the plane wave condition, a tangent angle of 0 degrees is required for the initial boundary condition, not a diffraction edge with a 7 deg receding slope (discontinuity). If you examine the figures 1a and 1b of the referenced JBL document [1] closely, you will notice that they are drawn incorrectly. So inferences drawn from them are probably erroneous as well. Under the high pressure conditions present in the horn/driver throat, you want to gradually transform the flat wave front to a spherical one of declining radius of curvature. That is the purpose of the adapter that you say is unnecessary. Otherwise a different horn design strategy should be employed were diffraction edges are employed to affect beam spreading (banana). This is an design regimen contrary to that of the horn (apple) to be used.
[1] JBL’s New Optimized Aperture™ Horns and Low Distortion Drivers
http://www.jblpro.com/catalog/support/getfile.aspx?docid=298&doctype=3
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I am not so sure the 2452 is really suitable for the LeCleach, adapter or not and be a compromise what ever you do. I am also aware the JBL paper has faults, more than the one you pointed out.
About 7 deg we should also know what angle the horn will have if cut to 2". Should be a steeper angle if not much.
About your adapter, have you calculated what flare it will have?
About 7 deg we should also know what angle the horn will have if cut to 2". Should be a steeper angle if not much.
About your adapter, have you calculated what flare it will have?
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