Gaps and bigger gaps in knowledge...
OK - time for the first posting...
I have a sheet of paper on the wall in the shop with measurements of a LOT of jbl magnets taken over the decades and notes on what combinations are possible.
I will attempt to compile it and post next week???? it is however limited to the 12-15-18 older magnet types.
I've created many "oddballs" over the years and the one thing that is common to any variance is the magnets with the deeper gaps ( 2220, E145/2215/LE15 ) will never work right with any other kit, unless you actually mill DOWN a frame 1/2 the difference in mag gap depth.
However this will weaken it to the point of instability.
The problem is voicecoil offset which prevents linear use and some of the overhang/underhang issues result in very high efficiency but limited linear travel.
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Hmmmm....speakers I guess
Hey there one and all - been 2 busy with 2 ( now ) teenage daughters to do much surfing / reading / posting / etc.....
Been selling on ebay for awhile but that gets kinda old paying FOUR TIMES to ebay ( listing, ending, paypal and CC ) so perhaps offering to the REALLY dedicated JBL crowd should be an improvement over the occasional ebay wannabe.
Remember, you grandad might of said that "what doesn't fit in your mouth is waste" wasn't referring to speakers / livingrooms / spouses ..:o)
enjoy
E145 is it's own beast....
Hey guys - the idea of plopping a 2225H kit into a "ring removed" E145 won't work correctly....
The E145 magnetic gap depth is MUCH MUCH deeper than the 2225 and the "center" of the gap will *not* be centered on the coil windings ( this the offset problem ).
This would make it very non-linear at anything above 50 watts or so.
Unfortunately it's not possible to mill down the frame enough - the mounting plate is too thin....
BUT you CAN put the LE15H kit into that frame and it would become a LE15H-1 NOTE: the LE15A kit will NOT work due to different frame depth!
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The list - gaps and all..
OK guys - here is the accumulated info...A few caveats:
(1) measurements were made in a dusty woodshop with an old set of ( now magnetized ) calipers
(2) Some variations of magnet structures ( bolt thru vs plate screws ) *might* be found.
(3) MOST magnets have a casting number that may or may not match others?? I'd bet JBL would know...:)
(4) JBL has a "goes into" checklist that applies to 10% of their items so use with a grain of salt...
(5) Some magnet structures use a thicker ring of ferrite - these WILL allow longer excursion ( wow - a whole 1/16 in.... )
(6) The earlier Alnico magnetic gap depths are the same as the ferrite if the model number is the same.
(7) Some variations of magnetic intensity are found in the published JBL literature - no attempt was made to confirm.
(8) The vented gap types are in a different league - NOT interchangeable.
(9) There are TOO MANY variations of magnets + cones on the smaller / consumer sizes so little info was compiled
(10) The 18 ferrite magnet structures are larger in diameter than the others
(110 Yeah I probably missed a bunch but I needs da sleep...:)
MODEL NUMBER GAP DEPTH FERRITE THICKNESS
E120 / 130 / 140 9 / 32 7 / 8
E145 19 / 32 7 / 8
E155 / 2240 / 2245 11 / 32 7 / 8
2220 11 / 32 3 / 4
2205 / 2230 / 2231
2135 / 2202 / 2130
2203 / 2204 / 2234
2235 / LE14H / etc 9 / 32 3 / 4
( most common type by far )
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Gap Width on Vented Gap Type ?
Hi
JBL published ( fairly accurate ) gap widths on their pre 1990 Alnico and Ferrite magnet types. This was relevant for those older model types until the introduction of the vented gap style of woofers.
- Does anyone have the gap width for the 1990s type of "Vented Gap & SFG 4" voice coil woofers ?
ie ; 1400 pro, 2206, 2217, 2226, 2227, 2241, 2242
- And how about the gap width for the later 90s' - 2000 series of 3" voice coil woofers ? - ie; the 2012, 2020, 2022/3/5/, 2032, 2035, etc. ( the cut sheets are quite clear for the 2012 & 2020 about top-plate and voice coil winding depths - but I've never seen those other models speced. )
regards <> Earl K :)