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Thread: LE14A quandary

  1. #1
    Senior Member Donald's Avatar
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    LE14A quandary

    Just got a pair of LE14A. Still have intact, original surrounds but they have seen better days. Will have to get new surrounds. The serial numbers are 2858 and 2859. Very low numbers, no? The strange part is they are 16 ohms.

    Which means I can't use it in my L222 or Dorian S12. Time to build somthing, I think.

    Hmm, to build a cab all I need is a table saw, router, sander, clamps, etc, etc.
    Couple of grand for a box. :-)
    Don L25,L36,L40,L65,L100(4),L120,L222,L300,AquariusIV( 2),DorianS12,B380,S1,4401

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    RIP 2011 Zilch's Avatar
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    Well, I have the other two 16-Ohm LE14's you're gonna need, S/N 5429 and 5430. I already have another 4 8-Ohm ones set aside for this project. We're gonna build triple-chamber bandpass subwoofers based upon the Control SB-5 model, scaled up for LE14's.

    The drivers will mount in face to face isobaric pairs, wired inverse parallel, on the two interior panels dividing the box into three chambers. All we need is for the box-modeling gurus here to tell us the box dimensions and the sizes for the 3 ports. We're gonna build outta 1-1/8" Sturdifloor.

    Check it out HERE!

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    Hi: What is Sturdifloor?

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    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Alex Lancaster
    What is Sturdifloor?
    Structurally rated subfloor plywood or oriented strand board. Whichever the lumber yard has in that thickness, OSB preferred, probably.

    The thickest and strongest stuff we can buy without payin' a huge premium....

  5. #5
    Senior Moment Member Oldmics's Avatar
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    For Real Low End Lunacy

    Gentlemen,Gentlemen

    Why fool around with measley little 14 inchers when the big guns were already done by the pros.

    Follow this link and then when you are on that page-check out the 4688-4

    http://www.google.com/custom?q=4688-...www.jblpro.com


    Oldmics

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    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by Donald
    The strange part is they are 16 ohms. Which means I can't use it in my L222 or Dorian S12.
    Why not? Have you measured them, or is that what is labelled? Giskard has posted numerous times on this "labelled impedence" issue, and IMO, it may not preclude your planned project. Although, I too am intrigued with the replies you've gotten...
    bo

    "Indeed, not!!"

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    RIP 2011 Zilch's Avatar
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    Oldmics: 30 X 30 X 60 and 250 Lbs.? Naw, we're gonna build something PRACTICAL here. Those are just one channel.

    Do we have any details on 4685 and 4688? They CLAIM to be pushpull, and even TCB (?), but only use two drivers.

    Last made 1982, no exploded view Tech sheets.

    SB-5 is two-channel acoustically summed in the center chamber using four pushpull drivers.

    We can use up the surplus of LE14's floating around out there.

  8. #8
    Senior Member Donald's Avatar
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    Bo,

    I don't have a project. Although what is being talked about here is interesting.

    Anyone here have thoughts about using 123As in this setup?

    I have the speakers. I have sound deadening fiberglass. I can assemble circuits. No reason a xover can't be wired point to point. All I need is a box and a xover diagram. :-) And I just might have a cabinet builder that I could enlist. I guess I need dimensions.

    What I want to know is cone motion. Do all 4 move left and right in unison? Or do the left face to face pair mome left and the right pair mobe right?
    Don L25,L36,L40,L65,L100(4),L120,L222,L300,AquariusIV( 2),DorianS12,B380,S1,4401

  9. #9
    RIP 2011 Zilch's Avatar
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    Each face-to-face pair comprises a channel, left or right.

    The two speakers in each pair are wired in parallel, but one the reverse of the other, so that they move in unison, one pushing, one pulling, toward and away from the center chamber.

    The two pairs operate in phase, both "facing" the center chamber. Thus, given the same signal, the left pair moves left while the right pair moves right, and vice-versa, when the signal polarity reverses.

    It's quite amazing. You have the lid off with all the speakers exposed, playing. Sounds wimpy and terrible. Drop the lid on, and it's, "OMG, where is that BASS coming from?"

    WinISD has a bandpass mode, but I can't get it to produce reasonable numbers. It also warns that getting it tuned right is an art. We need the box-modeling gurus here to get us started with this, please....

    123A's should work. Extended bass woofs are probably better, but what the Hell, give it a try. 4688 used 2240H's down to 23 Hz (-10 dB) while 4685 and 4682 (specs unknown) used 2225H's and 2206H's, respectively.

    Control SB-5 uses a pair of CSB-5003 5-1/2" drivers on each side. They've got rubber surrounds, if I recall, but don't hold me to it until I open 'em up and look again.

    They're wired inverse-series, but that doubles the impedance, thought it's not reflected in the data sheet:

    http://www.jblproservice.com/pdf/Con...rol%20SB-5.pdf

    I guess they're "nominal 4-Ohms" when 8-Ohm satellites are connected. Whatever. I'm wiring inverse parallel with 8-Ohm drivers to get an actual 4 Ohms each side.

    Note shorter, larger diameter port in the center chamber....

  10. #10
    Senior Member Donald's Avatar
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    >>Extended bass woofs are probably better
    So 4 SUB1500 would be better? :-)

    I assume no internal xover would be needed if the amp feeding the box was being fed the low output from an electronic xover?
    Don L25,L36,L40,L65,L100(4),L120,L222,L300,AquariusIV( 2),DorianS12,B380,S1,4401

  11. #11
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Donald
    I assume no internal xover would be needed if the amp feeding the box was being fed the low output from an electronic xover?
    I assume the same. We don't want anything but wire in the path, and we're not doing "satellites" here.

    Maybe Niklas will build with Sub1500's.

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    Senior Member GordonW's Avatar
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    Quote Originally Posted by Zilch

    WinISD has a bandpass mode, but I can't get it to produce reasonable numbers. It also warns that getting it tuned right is an art. We need the box-modeling gurus here to get us started here, please....
    You rang?

    Did the box model, not in WinISD, but in BassBox. The 123A will work, but NOT easily in the type of bandpass JBL used in the described above (triple-chamber). The problem, is the ports in the two outside chambers... it works much better, with a high-Q woofer such as a 123A, with the outside chambers SEALED and the center chamber VENTED.

    I've included a line diagram of a proposed box, for 4- 123As in the push-pull isobaric configuration. Total box volume, is about 17 cubic feet. In the drawings, the measurements under the dividers are from the OUTSIDE of the end of the box, to the CENTERS of the dividers (ie, 3/8" into a 3/4" thick piece of wood). Also, the vent dimensions (and it needed them to be this big!) are 16.5" tall (full internal height of the box), 4" wide (internal dimension of the vent), and 26" long from the outside of the box to the very inside end of the vent. That's a 66 square inch vent!

    According to my calculations, this box should be able to exceed THX spec by about 5 dB- something like 110 dB max output- with a bandwidth of 25 to 70 Hz, f3 on both ends. That's with only a 200 watt amp running the WHOLE thing!

    BTW- the 123As should be wired in series-parallel... gets you back to about a 6 ohm load...
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  13. #13
    RIP 2011 Zilch's Avatar
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    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.

    Looks like, wired inverse parallel, with the two sides kept separate, a 100W/channel amp could drive the box you designed here nicely, too, then. We tend to think of subs being driven with summed mono. This configuration lends itself to being driven stereo; summing occurs acoustically in the center chamber....

  14. #14
    Registered User MJC's Avatar
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    The strange part is they are 16 ohms.

    All the 16 ohm LE14A I've seen are coax units, I have one in a L55. Are the pair you have coax, or just a single driver?

  15. #15
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    Quote Originally Posted by MJC
    All the 16 ohm LE14A I've seen are coax units, I have one in a L55. Are the pair you have coax, or just a single driver?
    Isn't the LE14C the coax version?

    John

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