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Thread: JBL D131 "cone" number

  1. #1
    JBL Dog
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    JBL D131 "cone" number

    Question about a JBL D131:

    I know the early D131's were issued with the original cone stamped 131-404.

    If the number stamped on the cone is 21032, is that a later issue original or a recone?

    Thanks!

    This message comes from JBL Dog

  2. #2
    Senior Member Rudy Kleimann's Avatar
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    I got your number!

    Only thing is, it's not on a D131!

    The early (only?) D-series have a paper surround. I think they started out as plain paper, but at some point JBL began treating the paper surrounds with heavy oil, to increase linearity of excursion and (perhaps) power handling rating. The "1976 components" catalog in the JBL Library "catalog" section on this website, has a picture of a D131, but I can't tell for sure if it's paper surround or double-roll cloth surround. The 1974 Pro catalog shows the 2130; the 1976 Pro shows the K120. There is also a brochure of the 2130 in the "Pro components" section as well as plenty of old brochures on the D131 in the appropriate section. If your D131 frame/cone was an early version (the only version?), then the 21032 cone with a cloth double-roll surround would have to be a replacement. This cone/surround was used in the 12" K120 musical instrument speaker and the professional Series 2130, beginning around 1971.

    All of these models used AlNiCo magnets, although the 2130 had a slightly different shape to the magnet return pot- almost squared around the back edge, where your D131, the D120F and the K120 had a well-rounded edge.

    The only currently available JBL Factory replacement recone kit available for these is the C8RE120 8-ohm or C16RE120 16 ohm, which is the same kit used in the E120. "E" series drivers differ by using a ceramic magnet and use better glues and parts in the cone/coil assembly for even more power handling than all previously mentioned drivers. I don't know what the E120 cone is marked, but all the technical data I have read says it also has a cloth double-roll surround. I can only guess if it is the same as the surrounds on the 21032-marked 2130/K120 cones I have seen.

    I have never seen the front and back of any D131, nor a D120"F", but I would think the cone number on the D131 would have to be different due to the integral paper surround -whether it was treated or not. I have a pair of 2130's, and I just saw a K120 with good pictures front and back on ebay. My 2130 and the K120 cones, dust caps, and surrounds are identical, and both have "21032" on the cones. Only a good picture of a known original unreconed D120F and a known original unreconed D131 could shed some light on this. I don't know If JBL ever made a "standard" D120. I've never seen mention of one, but always that the D131 was identical to the D130 except for diameter, meaning that the coil and magnet "motor" are identical.

    I did a lot of homework on this and, thanks to forum members edgewound and Harvey Gerst (the man who designed the "F" variants of the D-series speakers at JBL) am confident this is accurate. Harvey says my cones definitely are not standard D-series cones. There is a currently active thread here titled "JBL D120 reproductions" that goes through all of this. There are pictures I posted in that thread pictures of the K120 and the 2130.

    Harvey Gerst has stated that the "F" ("F" for Fender) variants of the D-Series had a wider voice coil gap (and therefore have a slightly lower sensitivity) to prevent voice coil rubbing caused by overtightening the mounting bolts and warping the frame during installation into a cabinet. Seems the guys at Fender manufacturing were ruining a bunch of 'em this way. He also states here that as far as he remembers, all of the D120's were marked "F".

    Harvey also said in another thread here that failures from overpowering the standard D-series caused a need to improve the design and was another distinction of the "F" variants. In all the Old JBL catalogs and spec sheets I have checked, the "F" variants of the D-series components are rated to handle twice the power as the standard D-series, which is the same amount of power as the 2130 and the K120 were rated to handle.I am speculating that this could mean that a D120F is not the same as a D131. If I am right, then the D120F would most likely have the same 21032/cloth surround cone kit. Does this mean the coils are the same? I don't know... perhaps the coil could handle the power, but the old cone with paper surround couldn't. Perhaps more digging through old threads would reveal this. If anybody knew this and said it, I'd bet money on it being Harvey...

  3. #3
    Senior Member edgewound's Avatar
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    There is no difference in the original D131 and D120F cone/coil assemblies. The D120F had the added "goop" to bolster the paper surround and the .057" gap vs. the .053" gap in the D131.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  4. #4
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    Okay ;

    Some real trivia from a 1978 reconers' guide that I rescued from the trash .

    --------- Frame # ---------Dome #---------Gasket #
    K120 : ---50409------------21060-----------21031
    D120F : --50409------------21060-----------21031
    D131 : ---21035------------21060-----------33924
    121a : ---21035------------50201-----------52806
    124a : ---21035------------50201-----------52806
    2130 : ---47384------------21060-----------21031
    2202a : --47384------------21042-----------21031
    2203a : --47384------------21042-----------21031

  5. #5
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    Quote Originally Posted by edgewound
    There is no difference in the original D131 and D120F cone/coil assemblies. The D120F had the added "goop" to bolster the paper surround and the .057" gap vs. the .053" gap in the D131.
    - According to my mid-70s' "Quality Assurance Notes" for JBL transducers ;

    Healthy DCRs' for the voice coils of these drivers ; 2130, 2135, 2150, D120F, D130F, D130, D131, "must" be in the 5.6 ohm to 6.8 ohm range to avoid being labelled as having a "suspect coil" .

    - The implication , is that these woofers, all had similar voice coils . ( for instance; the newer K120s & K130s were given a slightly different "healthy" DCR range ).

    - All the other listed drivers have their own DCR ranges ( some of the others seem to share voice coils, because they too share DCR ranges ) .


    - My 1977 gap gauge info gives the D131 gap width as .057" ( FWIW , since gap widths were prone to being widened ).

    Quote Originally Posted by Rudy Kleimann
    ,,,,snip,,, I don't know If JBL ever made a "standard" D120. I've never seen mention of one,,,,snip
    Actually, I have one mention of the D120 . By 1978 , the proper recone for that woofer was the C8RK120 . ( It had the same frame , dome and gasket as the D120F , according to my info ) .



  6. #6
    Senior Member Rudy Kleimann's Avatar
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    Post More good details

    Quote Originally Posted by Earl K
    Okay ;

    Some real trivia from a 1978 reconers' guide that I rescued from the trash .

    --------- Frame # ---------Dome #---------Gasket #
    K120 : ---50409------------21060-----------21031
    D120F : --50409------------21060-----------21031
    D131 : ---21035------------21060-----------33924
    121a : ---21035------------50201-----------52806
    124a : ---21035------------50201-----------52806
    2130 : ---47384------------21060-----------21031
    2202a : --47384------------21042-----------21031
    2203a : --47384------------21042-----------21031
    Earl, I failed to mention you... Sorry. Many thanks! You've been a good source here too. I'm sure there are others I haven't mentioned- can't get 'em all.

    Does this list of frame numbers mean frame AND magnet assemblies, i.e., same gap, top plate thickness, magnet slug, and return pot? Seems so, visually speaking.

    Seems pretty unlikely the same cone number would ever apply to a paper-surround cone and a cloth surround cone. So the "21032" cone in JBLDOG's D131 must be a replacement, right? He hasn't mentioned the surround yet... that should tell the story. Are the current E120 kits using the same 21032 cone/coil assemblies?

    The 1977 K-Series catalog states "...new mat'ls for for high stress areas of the cone and voice coil give K Series double the power handling capability of the F series... surround fatigue has been virtually eliminated by the use of new compounds and materials developed by JBL." I'm guessing this relates to the new cone/coil assemblies. And, the 1980 Pro Catalog states "New materials and design techniques allow the E Series to outperform earlier JBL loudspeakers..." I assume this is referring to the higher magnetic flux of the new magnet design and ferrite (ceramic) magnets' relative immunity to demagnetization at high power levels.

    So...One last Q: since the power ratings went like this:

    Cont. Sine/Continuous Program
    D131: 12 watts (very old catalogs) no Sine or program power statement
    D131: 25 watts (1964 cat.) D131F also shown here.No sine/program rtg
    D131: 25/50 watts (old catalogs)
    D120F: no/100 watts (1970 "F" series spec sheet)
    D131: no/60 watts (1976 components catalog)
    2130: 50/100 watts 101dB (1976 professional, others) 13 lb. magnet w/ more squared shoulder
    K120: 100/200 watts 101dB(1976 professional, others) 12 lb. magnet w/ rounded shoulder
    E120: 150/300 watts 103dB(1980 professional) ferrite (ceramic) magnet w/1.35T flux vs Alnico magnets' 1.2T; immunity to demagnetization from high input level.

    What would a currently available E120 recone kit do to the power ratings of older speakers like JBLDOG's D131? What would you say is a reasonable limit?

  7. #7
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    I don't know anything about the 4 digit models, but during the years I worked there, the D120F, the D130F, the D131, and the D130 ALL HAD IDENTICAL VOICE COILS.

    Howard Weiser made all the 4" voice coils by hand, and then they were all delivered on a cart to George Martin's speaker assembly area. If there was a call for any of the above speakers, he (or one of the people there) would just get a one of the coils on the table.

  8. #8
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    Quote Originally Posted by Rudy Kleimann
    Harvey also said in another thread here that failures from overpowering the standard D-series caused a need to improve the design and was another distinction of the "F" variants. In all the Old JBL catalogs and spec sheets I have checked, the "F" variants of the D-series components are rated to handle twice the power as the standard D-series, which is the same amount of power as the 2130 and the K120 were rated to handle.I am speculating that this could mean that a D120F is not the same as a D131. If I am right, then the D120F would most likely have the same 21032/cloth surround cone kit. Does this mean the coils are the same? I don't know... perhaps the coil could handle the power, but the old cone with paper surround couldn't. Perhaps more digging through old threads would reveal this. If anybody knew this and said it, I'd bet money on it being Harvey...
    Okay, lemme clear this up once and for all:

    The only reason I raised the power rating on the "F" series is because the program source material had limited range. Typically, electric guitars go down to around 80Hz, but most of the energy is an octave above that, around 160Hz. The "why" has to do with string length, tension, and diameter - let's just say there's not as much fundamental there as most people think.

    So, I knew that guitars were mainly putting out from about 160Hz to around 3kHz, with some harmonics probably going out to around 6kHz. Not exactly the hardest range to handle for a big ass 12" or 15" JBL speaker.

    When it was time to really rate them, I brought them into the lab, hooked them up to our "monster Mac" - our tube 200+ watts McIntosh, and started to play guitar, while we watched where they started to crap out.

    Everybody felt comfortable that increasing the published power ratings was a reasonable step. We weren't playing pipe organs or symphonies thru these things; they could handle more power simply because the instrument's range was severely limited.

    Hopefully, that should clear up some misconceptions.

  9. #9
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    Quote Originally Posted by Rudy Kleimann
    Does this list of frame numbers mean frame AND magnet assemblies, i.e., same gap, top plate thickness, magnet slug, and return pot? Seems so, visually speaking.
    - No, the list of frame numbers is specifically for the frame/basket only. It doesn't include the rest of the magnetic assembly.
    - I can say that with confidence , since this list shows the 2205 , 2215 , 2216, 2220, 2230 & 2231, as using the same frame/basket ( # 47063 ). This number obviously includes 3 completely different families of 15" woofers with 3 different magnetic assemblies ( though they all share a 22xx designation ) .
    - I've read the reason for the different frames was because the "collars" all had varying "heights" for structural strength & intended market reasons. The "collar", to varying degrees, obscures seeing the full thickness of the 7mm top plate.

    Quote Originally Posted by Rudy K
    Seems pretty unlikely the same cone number would ever apply to a paper-surround cone and a cloth surround cone. So the "21032" cone in JBLDOG's D131 must be a replacement, right? He hasn't mentioned the surround yet... that should tell the story. Are the current E120 kits using the same 21032 cone/coil assemblies?
    - I don't know real anwers to any of those questions ( I'm not a reconer ). I can only offer speculation that the newer E120 kit superceeded the older 21032 cone/coil assembly. That "21032" part number was at least a decade old when the switchover to Ferrite happened. The ferrite switchover, also "rationalized"/"retired" all the old alnico frames since their collars wouldn't fit over/around the broader , wider ferrite magnets .

    Quote Originally Posted by Rudy K
    What would a currently available E120 recone kit do to the power ratings of older speakers like JBLDOG's D131? What would you say is a reasonable limit?
    - Again, I don't really know . I hear that the flatter/thinner ferrite magnet does a better job at heat-sinking/dissipating heat, when compared to the alnico magnet. That makes sense to me. Even the older Gauss speakers ( with alnico magnets ) had high power ratings. They of course had a multitude of fins built into the cast return pots enclosing the magnet . ( Ironically, I've burned up more Gauss 18" woofs than I care to remember .)
    - I have a few 2225H kits installed in older alnico assemblies. I have always used them as if they were a bona-fide 2225H for 2 decades now, without any problems. So I'm left to wonder what percentage the magnetic assembly contributes to the overall cooling of a transducers voice coil. Knowing that "percentage" would help one properly "derate" the power going into an older alnico assembly .

    - Sorry, I'm out of answers for now .
    - ( I played guitar in another lifetime. ) This is where my "interest" stems from for the minutae of detail revolving around your conversation on the D120/K120 family of speakers. I used to own 2 Twin Reverbs back in the seventies. What was I thinking ??? Now I prefer "lifting" math equations. So much easier on the back ! )



  10. #10
    Senior Member edgewound's Avatar
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    EarlK,
    Thanks for that added bit of info from the 1970's manual. My D131 .053" gap width comes from early models...late 50's early 60's before Harvey came in and intro'd the D120F, et.al....and increased the gap to .057" for durability. Since then, the standard gap for all 4" voice coil low frequency transducers was .057". The VGC drivers have a wider gap and aren't interchangeable with SFG drivers. Most likely any early D130's, D131's that have been reconed with newer factory kits have had the gap machined out to .057"

    Rudy,

    To answer power handling question...The power handling is whatever the new kit will handle.

    For instance...a D120F frame/motor core with a C8RE120/C16RE120 kit will have the same power rating as the E120...albeit slightly less efficiency due to the 1.2T alnico magnet.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  11. #11
    Senior Member Rudy Kleimann's Avatar
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    Thumbs up Thank you, Sir!

    Right on, edge. That's about what I figured. Just didn't know how many watts the AlNiCo magnets could take without demagntetization, and if that would be a limiting factor to power handling. I thought this was a bigger factor than the heat dissipation. So, the Alnico could take 150/300 watts with the E120 cone kit!

    I have a Urei 6290 Amplifier (rating: 300RMS/8, 600RMS/4) and a pair of JBL L166's that I'm afraid to use together for this very same reason. Wouldn't want to demagnetize these woofers just trying to enjoy the speakers...

    I've read many threads, articles, and tech docs that comment about AlNiCo magnets becoming demagnetized from overpowering. in fact, on another thread, white paper, or article, someone here jokingly recalled an incident in the JBL lab where Greg Timbers says (something like) "I think this (AlNiCo) driver is a little overdamped... (applies full power to the driver from the test amplifier for a few moments, then retests) that's about right."

    So, I wondered how much is too much power in this case.

    As far as the frame thing, I just noticed that the same frame numbers had the same weight and shape of magnet i.e. the "squared" pot of the 2130,2202, and 2203, and the "rounded pot" of the D120F and K120 and was trying to see if their was anything to this. If it were the case, then I would be inclined to think the cone kits would interchange and give the same performance i.e., my 2130's could be made into a "true" 2203. I know that there are some cases where this is true, as well as some "homebrew hybrids" you guys have dreamed up where the cone fits a basket, but the magnet -and performance- is different than anything JBL made.

    Doesn't really matter; I am simply observant and quick to pick up on common patterns. Usually, but not always, correlates. That's why I ask, rather than make ignorant assumptions. Hope I didn't wear you guys out on it!

  12. #12
    Brivmora
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    D131 Repair

    Anyone know who is best to recone a 12 in. D131? I have an original but deteriorated cone on mine. By the way, the cone is stamped 21032 and I believe it is original if that helps resolve some earlier questions on this.

  13. #13
    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by Brivmora View Post
    Anyone know who is best to recone a 12 in. D131? I have an original but deteriorated cone on mine. By the way, the cone is stamped 21032 and I believe it is original if that helps resolve some earlier questions on this.
    Depending on the cause of your cone problem, you may also want to have the motor remagnetized. It seems to me there is a reconer in your neck of the woods with a machine to do that, but I don't recall the name. Maybe one of our New England members will chime in with it. You also might find it by doing a search here for "remag" and variants, but pour your coffee first, since there will be quite a number of threads to plow through.

    David

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