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Thread: LE14A quandary

  1. #16
    MJC
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    Quote Originally Posted by johnaec
    Isn't the LE14C the coax version?

    John
    Ya, that's correct, I hadn't finished drinking my morning coffee when I wrote that reply.

  2. #17
    RIP 2011 Zilch's Avatar
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    LE14A Impedance

    4 ea. "8-Ohm" = 5.8, 5.8, 5.9, 6.1

    2 ea. "16-Ohm" = 5.8, 6.2

    The 16-Ohm units are the oldest ones; original Lansaloy surrounds, so not recones.

    Looks like the early numbers game is all.

    Still, I'd probably want to use 4 "16-Ohm" together, not mix them.





    Notes:
    A) Measured at the solder terminals behind the push terminals, which are oxidized and unreliable for DCR measurements.

    B) Gotta be quiet. Microphone effect is apparent. DCR is measured with low current. How low, I dunno. Itza Fluke 77 multimeter.

  3. #18
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    Quote Originally Posted by Zilch
    4 ea. "8-Ohm" = 5.8, 5.8, 5.9, 6.1

    2 ea. "16-Ohm" = 5.8, 6.2

    The 16-Ohm units are the oldest ones; original Lansaloy surrounds, so not recones.

    Looks like the early numbers game is all.
    Yep, we've hashed over this before but you've brought data to the hash.
    Data is our friend.
    Thanks!

  4. #19
    RIP 2011 Zilch's Avatar
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    Oh, mighty Giskard:

    Having played just about every subwoof game ever conceived, do you have any insight as to the design layout of 4682, 4685, and 4688? Or specs on the first two? They claim to be "Push-pull" Triple-Chamber Bandpass with two drivers. I also see reference to an "upper chamber" in the literature. I'm guessin' the triple ports are the center chamber "output." Also, can you tell us what happened to these products? It's been 20+ years since JBL made them, apparently.

    I've seen a design similar to what Gordon proposes here in a recent JBL subwoof product, no? At least from the exterior: no drivers visible, just a continuous wide slit in the center of the front? I'm thinking Gordon's design would make a good subwoof base under a widescreen home theater....

    While I'm rambling here, readers might be interested in seeing a new Vertec sub I came across in nosing around for info. Looks outstanding in a "relatively" small B380+ size box:

    http://www.jblpro.com/vertec1/new_vertec/vt4881.html

    See also:

    http://www.jblpro.com/vertec1/new_vertec/vt4882.html

    [Heh, heh.]

    Looks like them specs are with EQ, but similarly were B380/460....

  5. #20
    Senior Member Donald's Avatar
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    So, really 16 or mislabeled 8?
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    had L25,L36,L40,L120,L300,AquariusIV(2),S1,4408 have L65,L100,L222,DorianS12,B380

  6. #21
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    Mislabelling ? No! / Confusing ? Yes!

    Obviously, JBL used to use 2 different labelling methods to arrive at their "conclusion" for stating a nominal impedance. This impedance territory/story has been extensively covered in this or past forums . An impedance "curve" is just that, it's a curve, pick any point on it and one will get a differing conclusion about the working ( AC ) impedance .

    - Suffice it to say; people who want to "build something" according to "information" as superficial as what the foilcal label says - shouldn't use JBL in their projects.
    - Learning how to measure AC impedance is also useful for the project-minded.

    regards ,. Earl K

  7. #22
    Senior Member GordonW's Avatar
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    Quote Originally Posted by Zilch
    Woo-HOO, Gordon! That looks like one Helluva nice project. 123A's are plentiful, for sure.

    How about for LE14A's? Can you run them for us too, please? That's what I'm geared up to build here.

    Have you ever opened up a 4682, 4685, or 4688 to see how they are designed? They're called "Triple-Chamber Bandpass," as well, but with just two drivers.
    Your wish is my command...

    Box for LE14s. HOWEVER- note that this one is NOT isobaric/clamshell... it IS push-pull, but with EACH driver mounted FLAT on a baffle... so that ALL 4 drivers are directly accessing both chambers of their box.

    Note that this box IS a triple-ported bandpass (vents in ALL THREE chambers). The LE14, being lower Q than the 123A, lends itself quite well to this alignment.

    In this, due to clearances, I'd get driver access through panels into the OUTSIDE chambers of the box, NOT the center chamber... the two "front" drivers (near the vent) CANNOT go in through the center chamber- they'll hit the vent, going in, and the magnet will not clear. With all the air pressure THIS monster is going to generate, you want that center chamber to be built like a Brinks truck... so making access through the OUTSIDE chambers is MUCH better anyway.

    Box dimensions are: 56" wide, 36" deep and 20" high. This assumes 3/4" thick material (MDF or high-layer-count plywood). The internal chambers are 19" wide internal for the two outside chambers, and 15" wide for the center chamber. The vents are: 6.75" wide (inside width), full height of the box (18.5") and 18" deep for the center chamber vent, and 1" wide, full height of the box (18.5") and 18" deep for each of the two end chamber vents. Putting the vents near the outside wall, like shown, can reduce the parts count, by letting the outside walls act as one "side" of the vent...

    This box will give a bandwidth of about 24 Hz to 89 Hz (f3 points), with a calculated max output of between 112 and 117 dB throughout that range. It'll take 400 watts total power (100 watts per driver) to do it, but it WILL be probably 4 db louder than the 123A box, or so...

    Regards,
    Gordon.
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  8. #23
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    Very Nice Work! Gordon

    <. Earl K

    PS ; Next Magic Trick

    Can You - turn a le15b/2216 into a usable le15a ( maybe Fs of 27hz ) ?

  9. #24
    Senior Member GordonW's Avatar
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    Box for TWO Le14As. Basically, the above quad box, cut in half. But, with a little "gimmickry" to make the vent work right...

    The problem was, to get enough area for the center vent with the reduced box volume/depth, it was necessary to "bend" the port... to make it turn a couple corners. This is done by using the back wall and a couple of "internal director" plates to extend the vent length.

    The center vent width is 4"; the "auxilliary extensions" on the center vent should be 2" wide. The center vent plates should end 2" from the back wall. This can be done, if a vent plate 18.5" high and 14.5" deep, from 3/4" thick wood, is used for the center plates, mounted to the BACK of the front wall of the box (where a 4x18.5" rectangular hole is cut in the front of the box to open the vent to the outside, mating to the plates). Then, space the "side auxilliary vent plates" 2" away from the outside of the center plates. The auxilliary vent plates should be 18.5" tall x 8.25" deep, mounted to the back wall of the box.

    The outer vents are only 3/8" wide... the internal plate is mounted 3/8" from the outside wall. The overall outer chamber vent lengths should be 14.5"; this can be accomplished by mounting 18.5" tall x 13.75" deep plates to the back of the front wall, and cutting a 3/8" wide slot into the front of the box to open the vent to the outside.

    Again, this box assumes 3/4" thick wood everywhere. The woofers should again be accessed through the OUTER chambers... with this complex center chamber, it should be PERMANENTLY SEALED, to avoid leaks...

    BTW: In case you want to play around with the center vent, the overall vent should be 18.5" tall, 4" wide and 26.25" long. When you add the 15.25" center, 2.75" across the back, and 8.25" back towards the front, you get 26"...
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  10. #25
    RIP 2011 Zilch's Avatar
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    THANKS, Gordon!

    I can hear them table saws buzzin' aready!

    What's the predicted performance of the dual LE14A box?

    Seems clamshelled LE14's would yield a smaller box than the quad push-pull you propose as well, since the Vas of the compound pair is half that of the individual drivers, no? Can't configure an alignment for that, as originally proposed? I mean, that's the big plus of isobaric, I assume.

    [It's clear this is beyond my expertise here.]

    Quote Originally Posted by Earl K
    Suffice it to say; people who want to "build something" according to "information" as superficial as what the foilcal label says - shouldn't use JBL in their projects.
    Now, Earl, no need to be HARSH with us hackers here. We'll GET it, eventually. Them 16-Ohm LE14's aren't rare, they're CHEAP, 'cause nobody want's 'em. Nobody but US now, heh, heh....

  11. #26
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    - Sorry if I sounded "Harsh" ( I intended something else )

    - anyhow,, its' you "Hackers" who were able to get Gordon to cough-up some neat designs ( for free ! ) .

    ( & yeh - so much for cheap and cheerful "16 ohm" le14s flooding the market )

    <> Earl K

  12. #27
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    Here is an interesting 18" isobaric sub, uses four 18"s per cabinet:

    http://cls.audiogon.com/cgi-bin/cls....ubw&1108139256

  13. #28
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    Cool. Those 18's appear to be in "back to back" isobaric configuration. I think "face to face" couples them more closely, since the intervening air column "spring" between them is minimized.. Those are not bandpass boxes, of course.

    While these below are not isobaric OR bandpass, JBL Precision Directivity products provide a suggestion as to how isobaric might be easily accomplished in conventional alignments:

    http://www.jblpro.com/pages/pd_series/pd162.html

    http://www.jblpro.com/pages/pd_series/pd125.html

    I guess it IS some kinda bandpass box when you array 8 of them together as shown in the .pdf there. Heh.

  14. #29
    Webmaster Don McRitchie's Avatar
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    Quote Originally Posted by Zilch
    While I'm rambling here, readers might be interested in seeing a new Vertec sub I came across in nosing around for info. Looks outstanding in a "relatively" small B380+ size box:

    http://www.jblpro.com/vertec1/new_vertec/vt4881.html

    See also:

    http://www.jblpro.com/vertec1/new_vertec/vt4882.html

    [Heh, heh.]

    Looks like them specs are with EQ, but similarly were B380/460....
    Here's a picture of a stack of 2256G's from the new Vertec sub. The look to be relabelled, or maybe reconed, W15GTI car subwoofers.
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    Regards

    Don McRitchie

  15. #30
    RIP 2011 Zilch's Avatar
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    Hmmmm,

    Quote Originally Posted by Don McRitchie
    They look to be relabelled, or maybe reconed, W15GTI car subwoofers.
    There's certainly the suggestion of synergy between the car audio and pro lines, of late. Are they using "Differential Drive" technology in mobile? I should go look, maybe....

    Apparently so:

    http://www.jbl.com/car/products/prod...er=GTI&cat=SUB

    They're no cheaper, tho. The "Boxes & Parameters" links there are kinda interesting.....

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