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Thread: 3105, 3115 crossover questions

  1. #1
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    3105, 3115 crossover questions

    Hi,
    this is my first post
    please help me
    I’m 45 years old, and I have some lansing parts that came from my father.
    I’m restoring all my father equipment.
    sadly the speakers are trash but have some parts like 6 3115, 2 3105, pair of 2402 ,2404, 2405 , 2445 drivers and 2 pairs of woofers 15 and 18”
    almost everything needs to be rebuilt

    I have some questions

    3105
    16 Ohm driver ok
    what about the ohm for tweeter ?
    I’m confused hereand
    some 3105 info says 16 ohm other 8 ohm
    I need to change tweeters diafraghms then I can choose between 8 or 16
    reading some posts somebody says that genuine only came in about 10 ohm, my 2404 that are like news reads 7.2, and all my tweeter appears that are 8 ohms
    I cant found new original diafragm then I will buy the replacement aluminum or titanium ?
    The 3105 L pod is 8 ohm, then I supose that needs to be 8 ohm but I not sure about this
    then question is ,
    do I need 8 or 16 ohm diafragm for tweeters to be used with 3105 ?

    3115
    this is a 3115 not 3115a, a pair of this say clearly 3115 but the other 4 dont have the jbl plate
    on photos I saw that 3115a have an nextra gain switch that 3115 dont have, then I supose that all of this are 3115. but this other 4 can be other models, I supose that I need to open to look inside.
    I found some vintage info sheets that says that woofer needs to be 16 ohmm too, this is not a problem, woofer needs to be rebuilt
    I only want to be sure about this , I will ONLY use 1 woofer.
    is this correct 16 ohm on woofer with 3115 ?
    and finally

    I suposed that some capacitors need to be replaced, how can I determine this apart that have more than 40 years ?
    thanks in advance
    Last edited by Eduardocastrejo; 05-04-2021 at 08:31 PM. Reason: mispelinng

  2. #2
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    some photos
    thanks in advance
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  3. #3
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    3105

    2446J, 2350, 075 OR 077

    i will change to new capacitor, could be a good idea to change the value to increase the crossover frecuency from 7000 to 9 or 10,000 ?, is not pa use only indoor, house

  4. #4
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    As a matter of principle 40 years old capacitors you replace for gear safety and performance, considering this is usually a low cost.

    PA or home use has nothing to do in that specific case.

    Increasing crossover from 7khz to 9 or 10 khz is not a good idea here when you look at the horn response on the 2446 tech sheet. At 7 khz its still there, but at 9-10 khz response is down a lot. I wouldn't go more than 7 khz to avoid having a "hole" in system response.

  5. #5
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    THAKS A LOT FOR YOUR ANSWER, I will keep it at 7000 hz, only new capacitors (advice at brand ?)

    What about ohm at tweeter , change the frecuency of crossover ?, from 8 to 16 ?

    I read that all this tweeters have the same ohm with oem diapragms like 10 ohm (both 8-16 ohms)

    my 075 have oem diapragm ,with like 7 ohm , I opened and its on poor condition,

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    I have some new replacement not oem, I dont have the brand but I have with this replacements more than 20 years, ohm is like 7.8 ohm, also I recently bought 2 more at ebay that suposed to be 16 ohm, waiting for arrival
    I read some comments about if this tweeter dont have oem diaphragms are not anymore a jbl product and I supose its true but I cant found the originals, I have this tweeters and I want to use it

    the question and the reason to opened the 3105 crossover besides to change capacitors is to show and ask if is 16 0hm or 8 ohm tweeter model crossover ?, the L pad says 8 ohm (already bought new L pads too).
    some jbl info sheets says 16ohm other 8, but the 8 ohm model says 3105 with a small 3, then I suposed are diferent models.
    but if all the oem diaphragms 8 or 16 ohm models have the same ohm like 10, the crossovers are the same ?
    thanks a lot for your help

  6. #6
    Senior Member RMC's Avatar
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    Eduardo,

    Capacitors: Normally i use Solen brand (solen.ca). Their black ones (don't remember their exact model numbers) come in three voltages, 250V, 400V and 630V. The 250V ones should be more than enough for your project. I usually measure a sample of those i buy and their tolerances are very good. They are well made, nice quality and many members here use Solen capacitors. For lower power projects they also have some yellow ones having 160V rating.

    Tweeter impedance has to be taken into account when figuring crossover component values. I don't use 3105 or 3115, less familiar with these and don't want to potentially send you in a wrong direction, so i'll let other members answer in this regard.

    The JBL DC resistance specs for all versions of 075 and 077 is minimum 5.7 ohm and maximum 6.7 ohm. So your 075 at 7 or 7.8 ohm are a little too high it seems (assuming your multimeter is properly calibrated).

    If you can't find oem diaphragms, and you're not the only one, then you can only use what you find, it is what it is.

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    THANKS a lot !

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    Since one of your DC resistance numbers is not that far from JBL specs this trick might help you get better and closer multimeter readings.

    Put multimeter in ohm mode, hold the two test leads together and wait for number on readout to stabilize. Note that number. This is the meter's residual resistance which must be subtracted from driver readings when you test their DC resistance.

    Example: you tested meter residual resistance and you get 0.5 ohm. Well your 7 ohm measured tweeter minus 0.5 ohm meter residual now gives 6.5 ohm as real tweeter reading. And that 6.5 is within JBL specs (5.7 - 6.7). Bingo!

    Meter tolerance if not corrected can give wrong numbers. And wrong impression a driver is not good...

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    THanks for the tip !
    I need a better multimeter
    yes the residual is between .3- .5
    i have 3 tweeters here still with original diaphragms between 6,9-7.2 ohms minus -.3-.4 residual. all are in bad conditions, lot of years of no use
    the replacements that bought my father are 6.8 minus .3-.4, I can obtain locally more of this, I live in Acapulco and several disco uses this tweeters at 80īs, a friend of my father have a box with this replacements- no brand

    my 075 bullets tweeter have 21743 1979 sp silver diaphragms
    077 have 83752 blue sp diaphragms
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    You don't need to buy a better meter, no rush, all you have to do is remember the residual resistance and subtract it from your driver DC measurements. That's it. Save your money you'll have enough expenses already in rebuilding the speakers...

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    I received the 16ohm diaphragms
    reads at multimete 11.5 ohm

    then i have 8 ohm reading 6.5 and 16 ohm reading 11.5 at multimeter

    I already bought the capacitors for the 3105

    which diaphragm ohm is the correct one for my 3105 crossovers ?

    thanks in advance

  12. #12
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    Eduardo,

    2446J rated 16 ohm and the 077 is also rated 16 ohm. (The 075 is rated 8 ohm).

    2446J with JBL original diaphragm has DC resistance spec of 8.5 ohm +/- 10% . So your measured 11.5 ohm here is about 2 ohms too high vs spec, even with the 10% tolerance applied.

    The 6.5 ohm measured for the 077 would be within DCR specs (5.7 - 6.7). (Same spec applies to 075).

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    Quote Originally Posted by Eduardocastrejo View Post
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    It would appear that the phase plug was turned with the diaphragm in place when the screw was tightened, which left the "twist pattern" in the aluminum.

    When the tweeter is assembled, it is essential that the phase plug not move when the screw is tightened, or you will do the same to the new diaphragm.

  14. #14
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    MY mistake

    2446j have original and good condition diaphragms at 16 ohm, nothing wrong here

    my doubt its about my 3105 crossovers with tweeters ohm, 075 or 077
    some jbl brochure says 16ohm for tweeter othe brochure with number 3, 3105 3, small 3, I supose 3 version says tweeter at 8 ohm

    I opened my 3105 crossovers and have 1.5 uh capacitors, I dont know nothing about this, i already have the 8 and the 16ohm diaphragms to install on tweeters
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  15. #15
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    All vintage JBL ring radiator tweeters (pre-D2) are the same whether labeled 8 ohms or 16 ohms. JBL has confused thousands of people over the years with their changing labels. The 075/2402 tweeter which is the correct tweeter for the 3105 and the 077/2405 use diaphragms of different thickness aluminum, but they are all about 10-12 ohms.

    BTW: The 077/2405 tweeters use the 3106 crossover.

    Regarding your diaphragms with different impedance ratings, if they were made by JBL, they will be either for the 075/2402 or 077/2405, but they will not offer two different impedances. Diaphragms from other sources can be of any spec, and so far no one seems to have offered an alternative diaphragm that works properly in either of these JBL ring radiators.


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