Working on some vintage Jensen P15LL woofers/midrange 15" drivers and doing re-cones. They are designed for peak performance from ~50 - 3000 Hz. 40 Watts. Commonly found in Leslie speakers ~1955 - ~1964.
I've noticed that the top plate is thicker across the surface, but down in the gap it is notched back some. So the top plates are ~0.6" thick, but it is notched back so that the part closest to the voice coil windings is only 0.54" thick. As originally built, the voice coil is centered on this 0.54" height and not the overall thickness of the top plate.
See the attached drawing.
Is it common to have an area notched out like this in the gap? Does the thickness of the plate closest the windings dominate the magnetic field location?
I've noticed that the top plate is thicker across the surface, but down in the gap it is notched back some. So the top plates are ~0.6" thick, but it is notched back so that the part closest to the voice coil windings is only 0.54" thick. As originally built, the voice coil is centered on this 0.54" height and not the overall thickness of the top plate.
See the attached drawing.
Is it common to have an area notched out like this in the gap? Does the thickness of the plate closest the windings dominate the magnetic field location?
