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Thread: Need some technical help / advice JBL 4627

  1. #1
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    Need some technical help / advice JBL 4627

    Hello to all,
    I started a thread over in general information but have not gotten any response, so I will try here. I have acquired a pair of JBL 4627's, caravan series. I was not able to hear anything from the tweeters so I dismounted everything to check them.
    Inside I found that The woofer is a E140 8 ohm (is supposed to be a 145 in this series).
    I tried to measure the Ohmage on the tweeter but got no reading.
    I suppose this means that it is blown!! So buying and installing a new diaphragm will solve
    this problem, right?
    The tweeter is a 16 Ohm 2410 driver with the 2301 "Potato masher" horn. These horns do not seem to be greatly appreciated in this forum and I was wondering why??
    Anyway I read that the original diaphragm was Aluminium. There are some originals available "D16R2410" but they cost over $300 each!! The aftermarket 2425 would apparently fit the 2410, is made out of Titanium, and only costs $75.
    So what should I get??
    Oh, and when I do get new ones how do I replace them?? I don't want to damage something else because of my ignorance!
    The question came to mind, why did they blow in the first place?
    Before I got them they were being used for music production, mostly synthesizer. Maybe some deeper frequencies were not being filtered out properly??
    The crossover circuit is in a sealed riveted box.
    How do I open this to check the elements?
    When I turn the L-pad I measure from 0 Ohms to about 5 Ohms in the middle and then goes back to zero. Is that the correct behavior for the L-pad??
    I have only checked one speaker so far so I don't have a comparison between the two, but the other one is surely blown as well since I was hearing nothing out of the tweeter.
    I hope someone can help me out,
    many thanks

  2. #2
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    Quote Originally Posted by analogean View Post
    Hello to all,
    I started a thread over in general information but have not gotten any response, so I will try here. I have acquired a pair of JBL 4627's, caravan series. I was not able to hear anything from the tweeters so I dismounted everything to check them.
    Inside I found that The woofer is a E140 8 ohm (is supposed to be a 145 in this series).
    I tried to measure the Ohmage on the tweeter but got no reading.
    I suppose this means that it is blown!! So buying and installing a new diaphragm will solve
    this problem, right?
    Could be, but could be a loose wire inside I guess.

    The tweeter is a 16 Ohm 2410 driver with the 2301 "Potato masher" horn. These horns do not seem to be greatly appreciated in this forum and I was wondering why??
    I don't know, I'm guessing that there have been inprovements in horn design since the 2301 was introduced? If you like it, then that's what matters.

    Anyway I read that the original diaphragm was Aluminium. There are some originals available "D16R2410" but they cost over $300 each!! The aftermarket 2425 would apparently fit the 2410, is made out of Titanium, and only costs $75.
    So what should I get??
    You seemed that the woofer wasn't stock, but seem open to slapping a $75 aftermarket diaphragm in there? What are you going to do with the speaker, listen in your home or play it in a nightclub? JBL aluminum diaphragms aren't cheap, and will likely sound different than a titanium aftermarket. So it boils down to what you want out of the speaker, and how you want it to sound.

    Oh, and when I do get new ones how do I replace them?? I don't want to damage something else because of my ignorance!
    Maybe start a new thread then.


    The question came to mind, why did they blow in the first place?
    Wore out? Played too loud/too long?

    Before I got them they were being used for music production, mostly synthesizer. Maybe some deeper frequencies were not being filtered out properly??
    Again, hard to say. That's the real problem with buying used equipment, even used drivers. You never know what they have been exposed to before you got them.

    The crossover circuit is in a sealed riveted box.
    How do I open this to check the elements?
    When I turn the L-pad I measure from 0 Ohms to about 5 Ohms in the middle and then goes back to zero. Is that the correct behavior for the L-pad??
    Somebody else will have to step in here.

    I have only checked one speaker so far so I don't have a comparison between the two, but the other one is surely blown as well since I was hearing nothing out of the tweeter.
    I hope someone can help me out,
    many thanks
    Good luck!

  3. #3
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    Thank you for your reply JeffW,
    Unfortunately your answer was not much help, but it was kind of you to try.
    I was hoping to learn from the expertise and experience of the folks on this forum, that is what forums are for, no?
    That it could be a loose wire is a good tip and one should always check for the obvious first, but that both tweeters should have loose wires would be quite a coincidence.
    I don't know if I like the the horn because I have never heard it!
    I was surprised to find a non stock woofer (but still a very good woofer) inside and my first thought was that maybe JBL released some with the E140-8 instead of the E145-8. My second guess is that the previous owner changed them or ordered them that way.
    I have read that the titanium and aluminum diaphragms sound different, and I have also read that some prefer titanium and other aluminum. I have also read that the aftermarket diaphragms can be just as good as the originals. I have no way of comparing them myself unless I buy both and try them out, but since many of you here have already had the chance to compare them, I thought I would ask what peoples experiences have been with the original/aftermarket titanium/aluminum issue. I am ready to pay what is necessary but am always happy to save money as long as the product is as good.
    I will be using the speakers for studio/practice room applications, probably as control speakers to listen to the playback. If it turns out that they are not good for that purpose and I have no other use for them then I will sell them and buy others, but either way I want to get them working properly.
    Once again i am hoping that the in-exhaustible experience and expertise of the forum members here can help me make the right decision.
    many thanks...

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    OK, take them apart and see if it's a loose wire. I have no way of knowing half a world away. If it's not, and the voice coil is open, you'll need a new diaphragm.

    You'll find little love or respect for most aftermarket diaphragms here. If you want it to sound like a JBL, put JBL parts in it. If JBL parts are too expensive, sell it and buy a cheaper speaker you can afford to operate.

    If it was for a sound reinforcement application for drunks in a club, you could run aftermarket diaphragms and nobody would notice. If it's for your home, then restore it as it should be.

  5. #5
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    Quote Originally Posted by analogean View Post
    I will be using the speakers for studio/practice room applications, probably as control speakers to listen to the playback.
    Those speakers were not meant for critical listening applications, the E140 is a musical instrument speaker.
    Not to say that it won't work, but it was not designed for this.

    The aluminum dias. are more expensive than the titanium and they sound different, depends on your taste.

    And about the aftermarkets, I never tried them... why would I?

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    Thanks,
    I will take them apart and inspect them for loose wires.
    I know this going to cause a storm but which speakers are good for critical listening??
    Maybe I will use them for organ.
    I will take your advice Jeff and buy the original JBL replacement.
    I have read that the titanium are "tighter" sounding and handle more power as compared to aluminum.
    Just for fun, which would be better for lets say a 70's string ensemble organ sound coming through a tube(valve) amplifier?
    My gut feeling tells me go with the loose sounding aluminum..more bucks though
    Cheers

  7. #7
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    I'd go with aluminum, personally. I think the main reason JBL went to titanium diaphragms was for longer life in high SPL sound reincorcement applications, not because it sounded better.

    I'm listening to aluminum JBL diaphragms right now, playing jazz vinyl, and it is superb.

  8. #8
    Senior Member Eaulive's Avatar
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    Quote Originally Posted by JeffW View Post
    I'd go with aluminum, personally. I think the main reason JBL went to titanium diaphragms was for longer life in high SPL sound reinforcement applications, not because it sounded better.
    I agree with that.
    Aluminum has the nasty habit of exploding in pieces when driven too hard.

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