GordonW
09-13-2003, 09:24 AM
OK, I'm trying to track down a solution for my guy here, with the blown 122A woofer (L65A)...
Since the 122A kit (C8R122A) is long gone, and the JBL recommended retrofit 129H kit (C8R129H) is out of stock for the forseeable future, at the advice of Giskard, I've been looking at putting a 128H-1 kit (C8R128H1) into this basket. I even looked up the T-S parameters, and discovered that if I was to engineer a 10-11 gram "mass ring" onto the 128H-1 kit, it would be almost a DEAD RINGER in in-box performance to the 122A (Bl is identical on both, and Mms = 100g on the 122A, 90g on the 128H/H1)...
HOWEVER...
I did some research. As expensive as these kits are, two things make me hesitant to order this kit sight-unseen:
1) the voice coil gap guage is DIFFERENT in the 128H/128H1 basket. The 122A has a gap guage of .053", the 128H has a .057 gap. My question is: Does the 128H use a thicker voice coil winding (ie, bigger wire, more layers, etc), or is it just opened up for power handling or manufacturing ease, due to the increased flux density available from the ceramic magnet on the 128H??
2) Apparently, according to one lookup book I was referred to by our local JBL parts guy (Image reconing book), the voice coil FORMER LENGTH (ie, distance from the cone apex to the top of the voice coil winding, specifically) on the 128 may be DIFFERENT than the 122A, making the voice coil NOT center properly, vertically, in the gap at rest! Is the 128H basket made with a different magnet gap placement WRT the cone, compared to the 122A??
Can anyone directly address these issues? Is the 122A basket that much different from a 128H basket , that the 128H-1 kit won't work???? I can't find any "officlal" dimensions to tell me one way or the other!!!
:banghead: :banghead: :banghead:
Regards,
Gordon.
Since the 122A kit (C8R122A) is long gone, and the JBL recommended retrofit 129H kit (C8R129H) is out of stock for the forseeable future, at the advice of Giskard, I've been looking at putting a 128H-1 kit (C8R128H1) into this basket. I even looked up the T-S parameters, and discovered that if I was to engineer a 10-11 gram "mass ring" onto the 128H-1 kit, it would be almost a DEAD RINGER in in-box performance to the 122A (Bl is identical on both, and Mms = 100g on the 122A, 90g on the 128H/H1)...
HOWEVER...
I did some research. As expensive as these kits are, two things make me hesitant to order this kit sight-unseen:
1) the voice coil gap guage is DIFFERENT in the 128H/128H1 basket. The 122A has a gap guage of .053", the 128H has a .057 gap. My question is: Does the 128H use a thicker voice coil winding (ie, bigger wire, more layers, etc), or is it just opened up for power handling or manufacturing ease, due to the increased flux density available from the ceramic magnet on the 128H??
2) Apparently, according to one lookup book I was referred to by our local JBL parts guy (Image reconing book), the voice coil FORMER LENGTH (ie, distance from the cone apex to the top of the voice coil winding, specifically) on the 128 may be DIFFERENT than the 122A, making the voice coil NOT center properly, vertically, in the gap at rest! Is the 128H basket made with a different magnet gap placement WRT the cone, compared to the 122A??
Can anyone directly address these issues? Is the 122A basket that much different from a 128H basket , that the 128H-1 kit won't work???? I can't find any "officlal" dimensions to tell me one way or the other!!!
:banghead: :banghead: :banghead:
Regards,
Gordon.