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Thread: JBL B212 Sub Energizer Help

  1. #1
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    JBL B212 Sub Energizer Help

    I need to take a closer look at the sub but it appears to have stopped working. In my initial research it appears that it is something that happens fairly often. A couple of questions...
    1-I would like to keep the sub original as the L212/B212 I have is in very nice condition. Is there a good place to send the energizer to have it repaired?
    2-On the other hand I have heard the amp is under powered and may be better served by something like a 150w amp vs the 75w amp in the energizer. I'm a bit torn on locating a place to repair it or taking it out and placing something like the the dayton sa230 in thee underneath cavity.

    Any direction on getting it repaired or opinions on which way to go?

    I use the L212 system daily in our living rooom system and am really missing the sub and need to start the process of getting it fixed.
    Thanks.

  2. #2
    Senior Member SEAWOLF97's Avatar
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    I'm in the same boat with a UB212.

    When I acquired mine, the original amp had been repaired. worked great for a while.

    Then it started motorboating and I've taken it out of service since there are other subs
    sitting in storage. It's not a priority to me, but would be interested in seeing whatever solution you find.

    Have run across some L212 owners who now use M&K subs (Volkswoofers).
    They kinda match the original styling, but they seem to eat amps too.
    “If you think that’s the dumbest thing you’ve ever heard,
    just wait a couple minutes!”

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    Administrator Robh3606's Avatar
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    Hello In you have not seen it checkout the brochure it gives you the bass EQ curve used. If you do go with a new amplifier be careful not to overpower it that 12" 121 A has limited x-max and would be almost impossible to replace.


    http://www.lansingheritage.org/html/.../1977-l212.htm

    Rob
    "I could be arguing in my spare time"

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    Sounds like a fairly common thing unfortunately. I wish I had the skills to fix something like this but that just isn't an option for me. Hopefully someone will chime in with thoughts on fixing it. I would love to find someone to rebuild it. In the meantime, I will probably pull out the energizer and try to put in an external amp that has a crossover/eq like the Dayton SA230. Another option I was thinking about is using a BX63a and and a 150-200 mono amp. I am guessing set the BX63a to crossover around 70?
    I still like the idea of repair best but that may take some time to locate someone to fix it.

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    Quote Originally Posted by Robh3606 View Post
    Hello In you have not seen it checkout the brochure it gives you the bass EQ curve used. If you do go with a new amplifier be careful not to overpower it that 12" 121 A has limited x-max and would be almost impossible to replace.


    http://www.lansingheritage.org/html/.../1977-l212.htm

    Rob
    Thank you for that link. I hadn't seen that. Would a 6db boost around 30hz be about right if I am reading it correctly?

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    Administrator Robh3606's Avatar
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    Maybe a little more, close enough though I doubt you would hear a difference.
    "I could be arguing in my spare time"

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    Heather [Senorita member] hjames's Avatar
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    The pair of L212s I bought 2 years back did not have the Bass module -
    so I am using an old Volkswoofer with mine - its a perfect match.
    I already had a Volkswoofer, based on a tip from Seawolf years ago, and I'd heard enough about
    the instability of the amp in the B212 bass module to not bother chasing one down.
    (Mine are offlined temporarily while I sort out other speakers)

    Volkswoofers can be had for a reasonable price - and you just dial them up slightly to fill in the bottom end.
    And keep your B212 for the collector value.

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    2ch: Oppo, JoLida 502CRC, JBL L212, 18ti,240ti; Heath AS101, Von Schweikert VR4
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    Quote Originally Posted by hjames View Post
    The pair of L212s I bought 2 years back did not have the Bass module -
    so I am using an old Volkswoofer with mine - its a perfect match.
    I already had a Volkswoofer, based on a tip from Seawolf years ago, and I'd heard enough about
    the instability of the amp in the B212 bass module to not bother chasing one down.
    (Mine are offlined temporarily while I sort out other speakers)

    Volkswoofers can be had for a reasonable price - and you just dial them up slightly to fill in the bottom end.
    And keep your B212 for the collector value.

    Name:  L212_6011.jpg
Views: 203
Size:  229.3 KB
    Appreciate the tip on an alternative sub. It really is a nice looking sub and looks very nice with the L212. I am going to go down the road to either use an external amp/crossover with it, or try to find someone to rebuild the energizer.

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    I am ready to take apart the sub/energizer. Not a lot of experience with this kind. Does anyone have any experience taking one apart to remove the energizer? Do I need to remove the woofer first? I am having a hard time figuring out how to remove the energizer. Any help would be greatly appreciated.

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    I've sent you a PM with the service manual and a few people that may be able to work on it.
    The amplifier has some output transistors that I wasn't able to find (RCA 8203B)and there may be a suitable substitute. Knowing this, you will need to find someone proficient with substituing parts.
    Let's hope it's something simple.

    The Dayton amplifier will work. I think the internal crossover is fixed at 18dB. If you find that it doesn't sound quite right, you may need to find a 1st or 2nd order crossover slope.

    Some ideas would be a Marchand xm9, minidsp, Harrison FMOD(fixed at 12dB).

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    Quote Originally Posted by grey View Post
    I've sent you a PM with the service manual and a few people that may be able to work on it.
    The amplifier has some output transistors that I wasn't able to find (RCA 8203B)and there may be a suitable substitute. Knowing this, you will need to find someone proficient with substituing parts.
    Let's hope it's something simple.

    The Dayton amplifier will work. I think the internal crossover is fixed at 18dB. If you find that it doesn't sound quite right, you may need to find a 1st or 2nd order crossover slope.

    Some ideas would be a Marchand xm9, minidsp, Harrison FMOD(fixed at 12dB).
    Appreciate the PM on the service manual and a few ideas on who might fix it. Thanks for pointing out the crosover slope of 18 on that amp.
    My latest plan:
    1.Dayton APA102 with the dimensions of 16.9" W x 7.65" D x 2.15" H should fit nicely in the cavity under the sub. It would provide 160w in bridged mode.
    2. Minidsp 2x4 to set crossover point of 70/slope of 12. Measure in room response and apply eq settings in minidsp
    Both the mini dsp and amp should fit under the sub nicely.

    Is 160w about right for the amp around what I should be looking for?

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    Quote Originally Posted by dj7675 View Post
    Appreciate the PM on the service manual and a few ideas on who might fix it. Thanks for pointing out the crosover slope of 18 on that amp.
    My latest plan:
    1.Dayton APA102 with the dimensions of 16.9" W x 7.65" D x 2.15" H should fit nicely in the cavity under the sub. It would provide 160w in bridged mode.
    2. Minidsp 2x4 to set crossover point of 70/slope of 12. Measure in room response and apply eq settings in minidsp
    Both the mini dsp and amp should fit under the sub nicely.
    You have a good starting point and it may be spot on. The manual shows that it starts rolling off ~45hz and the slope is ~10 dB.
    You will want to avoid boosting the signal until you have a decent grasp. Robh3606's post expresses what can go wrong. I'm on the side of keeping it modest.
    Keep in mind that documented measurements were performed while attemting to eliminate the environment. In-room measurements will make a mess of comprehending the crossover point if that is your goal.

    You will have the tool to address a nasty in-room rise and a mild adjustment there may be a good thing.

    Quote Originally Posted by dj7675 View Post
    Is 160w about right for the amp around what I should be looking for?
    It is more than sufficient according to this.
    http://www.audioheritage.org/vbullet....php?4555-L212

    Monoprice has a tiny 100w and 200w amplifier that may be worth a look. As much as I like the idea of a tidy retrofit inside the chassis, they need to breath and vibration can kill too.

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