Hello Bear,
On one of my JA6681, opened for verification, I could measure 35mm for the main throat and for the smaller which appears after removal of the front part (throat part) I could measure 27,5mm (so not exactly 1 inch)
See attached pictures.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Attachments
Hello,
Here are 3 screen copies (from Arta audio analysis software) showing the beautiful shape of an unequaized JA6681 on 3 different horns :
- AH550 horn (an axisymetrical Le Cléac'h horn with Fc = 550HZ, built by Martin Seddon in Australia and sold under the brand AzuraHorn),
- J321 horn (an axisymetrical Le Cléac'h horn with Fc = 320HZ, built by Marco Henry and used to be sold under the brand Musique Concrète )
- E-JMLC 600 horn (a non axisymetrical Le Cléac'h horn with Fc = 600Hz, built by Autotech in Poland).
If a better adaptation was provided between the JA6681 (27,5mm throat) and those horns (25,4mm throat) may be the treble will extend at 20kHz, but still the extension in treble is excellent.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Here are 3 screen copies (from Arta audio analysis software) showing the beautiful shape of an unequaized JA6681 on 3 different horns :
- AH550 horn (an axisymetrical Le Cléac'h horn with Fc = 550HZ, built by Martin Seddon in Australia and sold under the brand AzuraHorn),
- J321 horn (an axisymetrical Le Cléac'h horn with Fc = 320HZ, built by Marco Henry and used to be sold under the brand Musique Concrète )
- E-JMLC 600 horn (a non axisymetrical Le Cléac'h horn with Fc = 600Hz, built by Autotech in Poland).
If a better adaptation was provided between the JA6681 (27,5mm throat) and those horns (25,4mm throat) may be the treble will extend at 20kHz, but still the extension in treble is excellent.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Attachments
Hello 3GGG,
I would recomand to remove the throat cast metallic front part of the JA6681 and to start from the plane at the apex of the phase plug inserting some annular part in the 27,5mm throat and prolongating then in a Le Cléac'h horn. (an angle of 0° or lesser than 5° can be considered).
Myself I intend to use one of my pairs of JA6681 with an E_Jmlc horns and will just introduce an annular part at the exit of the driver after to obtain a 25,4mm throat.
Best regards from Paris, France
Jean-Michel Le Cléac'h
I would recomand to remove the throat cast metallic front part of the JA6681 and to start from the plane at the apex of the phase plug inserting some annular part in the 27,5mm throat and prolongating then in a Le Cléac'h horn. (an angle of 0° or lesser than 5° can be considered).
Myself I intend to use one of my pairs of JA6681 with an E_Jmlc horns and will just introduce an annular part at the exit of the driver after to obtain a 25,4mm throat.
Best regards from Paris, France
Jean-Michel Le Cléac'h
How would you attach the horn without the cast? The surface underneath is shiny metal without holes, and I don't want to drill so close to the magnet.
I used a digital dial caliper.
The smaller measurement was to the bottom of the pole piece, not the exit of the pole piece. I can do this since I have one driver that is truly completely disassembled. Pole piece removed from the magnet. Do not fear, I did not destroy a useful driver - it was submerged in salt water and was corroded and covered with salt deposits.
3GGG, if you have a lathe, there is enough "meat" in the casting to move the angle a few degrees. Otherwise you have to machine a new piece for the job.
Rewind, how is the present front held on? You could work off those holes with a new piece/adapter to mount the horn?
The smaller measurement was to the bottom of the pole piece, not the exit of the pole piece. I can do this since I have one driver that is truly completely disassembled. Pole piece removed from the magnet. Do not fear, I did not destroy a useful driver - it was submerged in salt water and was corroded and covered with salt deposits.
3GGG, if you have a lathe, there is enough "meat" in the casting to move the angle a few degrees. Otherwise you have to machine a new piece for the job.
Rewind, how is the present front held on? You could work off those holes with a new piece/adapter to mount the horn?
Hello Rewind,
There is 2 screws that you can remove and use to fix the horn.
See picture :
http://www.diyaudio.com/forums/atta...compression-driver-ja6681_smaller_throat_.jpg
Best regards from Paris, France
Jean-Michel Le Cléac'h
Those screws are too tight. And the driver is so beautiful with that fake alnico extension.
I managed with a method I have come to call the pen-trick!
If the pen is pushing away your new horn throat, when it is aligned with the drivers throat, then you still have some more grinding left to do.
I managed with a method I have come to call the pen-trick!
If the pen is pushing away your new horn throat, when it is aligned with the drivers throat, then you still have some more grinding left to do.
Attachments
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Hello Rewind,
I don't care of anything fake and never take in consideration cosmetics, so I used to modify many drivers I have...
You have to use some solvent before they seem glued But i succeed to remove them on one of the pairs of JA6681A I possess and I could mount them on my E-Jmlc 600 horn (see the obtained frequency response in a recent message).
Bestregards from Paris, France
Jean-Michel Le Cléac'h
Cosmetics mean everything to me, so I built the horn around the drivers extension throat. Seems to be good for a horn that can play down to 500-600Hz. The bigger half should be identical to a Avantgarde Trio when I am done with it.
Below it another pair of yammies will be playing to around 340Hz. I was looking at the JMLC 200 horn foe this. Is this the best option to reach 340Hz?
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I measured one of my drivers with a plastic ruler tonight. The diameter of the exit of the throat section is 35 mm, that of the entry is 27 mm. The length of the throat including the two thin gaskets (cork at the entry and rubber at the exit) is 52 mm. Doing the math gives an angle of 4.4 degrees per side.
Jean-Michel measured 27.5 mm at the entry of the throat. On such a short distance, half a mm makes a difference. Using his figure yields 4.1 degrees instead of 4.4.
I discovered that the phase plug in both of my units has corroded. I purchased them from eBay and don't know in what conditions they were used or stored. Wondering if this is a common problem and if it will affect the sound... I have not tested them yet.
Pierre
Jean-Michel measured 27.5 mm at the entry of the throat. On such a short distance, half a mm makes a difference. Using his figure yields 4.1 degrees instead of 4.4.
I discovered that the phase plug in both of my units has corroded. I purchased them from eBay and don't know in what conditions they were used or stored. Wondering if this is a common problem and if it will affect the sound... I have not tested them yet.
Pierre
greetings just an inquiry i got 4 of these driver units and my problem is the diaphragm and coils which are already busted when i got them i thought we could rewind them but the diaphragms are already torn is there any way possibly for me to acquire replacements? did radian already produced replacements?
thanks for your help guys
thanks for your help guys