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Thread: what goes wrong with the GTI subwoofers ?

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    Noob Lurch's Avatar
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    what goes wrong with the GTI subwoofers ?

    Hey guys,

    i finally own a JBL GTI MKII 12"

    BUT : something has gone wrong with it.
    The first enclosure was a 2.25 cuft ported that sounded
    ok till it blew apart, that's when the the GTI started to make
    mechanical " bottoming " sounds.

    So we tried it in free air before building a new sealed enclosure
    just to test it, it seemed fine running in the open so a sealed
    1.2 cuft box was built.
    It sounds amazing until a certain power level is reached and the awful
    noise rears it's ugly head again which has me turning down
    the bass control instantly because it is a LOUD scary " WHACK ".
    The amp is an Audison UNO and the gti runs at three ohms, so
    it is seeing approx one thousand watts.

    Im hoping someone out there has experience with the GTI's and
    can point me in the direction of what to inspect :
    - a separated spider ?
    - voice coil former separated from spider ?
    - something else ?

    i just hope that this amazing woofer is saveable.....

    thanks !

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    Seer Newby Hic's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    Lurch,

    New sub time
    "A dog is the only thing on earth that loves you more than you love yourself - John Billings

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    Noob Lurch's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    AAAAAUUUURGH !
    NOOOO !

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    Seer Newby Hic's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    Lurch,

    A subsonic filter with a vented/ported box. But the big boys just let it unload "rumblin" , then you buy another / another /
    Rinse and repeat
    "A dog is the only thing on earth that loves you more than you love yourself - John Billings

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    Noob Lurch's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    This turned out to be a bad power wire issue.
    The wire i was using just wasn't sufficient.
    Today i installed a dedicated 2ga. cable and the problem has " mostly " disappeared.
    The crapping sound is only there at very high SPL now.
    EVERYTHING sounds better.
    The next step is to inspect all the associated grounds, if that doesn't completely clear it up
    I will reduce the box volume ( 1cuft is recommended by the manual, the current box is about 1.2 ).

    This GTI is just fine, my own stupidity on the other hand ......

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    mental anomoly Hillbilly SQ's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    Glad you got it mostly straightened out. The GTI is an amazing sub in all variations. Sounds like your amp wasn't happy and still isn't as happy as it should be.
    There is a rose in Spanish Harlem...BLAT, BLAT BLAT BLAT, BLAT BLAT BLAT, BLAT BLAT...

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    Noob Lurch's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    Hi Hillbilly,

    i'll update with what i find with the ground, i used the closest seat bolt and im always in a hurry, i seem to remember
    sanding the paint off the seat rail but who knows ....
    i also wonder if I should be using a different bolt, something more conductive.
    Once i get the dremmel set up with a sanding disc the bolt will come out, the seat rail will get a PROPER sanding and
    i'll clean up the bolt threads + the hole threads, pretty sure this will clear the situation up for good.
    This poor Audison must have been going through hell in the last few years but it never complained, never got warm,
    never missed a beat. Gotta Wonder how much distortion it was producing though.
    ( it was driving a DC Audio level three in a ported box previously and got LOUD )


    BTW.... Love your sig, funny as hell ....

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    mental anomoly Hillbilly SQ's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    If sanding around the bolt doesn't work you might need to find a good area to run a bolt straight through the floor. That's what I always did when my battery was under the hood and never had an issue.

    And thanks for the compliment on the siggy. Spanish Harlem is an old SQ comp song that has been so overplayed it's ridiculous and it's to test sub to midbass transition. Used to joke that playing it in my truck would cause the seat to eject the listener out of there.
    There is a rose in Spanish Harlem...BLAT, BLAT BLAT BLAT, BLAT BLAT BLAT, BLAT BLAT...

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    Gold Subscriber chithead's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    JL Audio has a great lug I've used on many occasions for just this purpose.

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    Noob Lurch's Avatar
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    Re: what goes wrong with the GTI subwoofers ?

    ^^^ nice lug !

    Anyways..... Finally got around to ground inspection / upgrade, i had actually done a pretty good job the first time
    ( to my astonishment), paint was sanded off, bolt head & washer clean.
    I dremmeled the surface this time with a sanding disc, cleaned up the bolt threads on a wire wheel, pull tested the
    eyelet and reset. The ground cannot be better now.
    Did it help ?
    maybe by a very small percentage.

    This very could be the UNO crapping out, it is rated for 700 watts at 4ohm, the GTI is 3ohm, maybe it's time to
    find a class D that is capable, unfortunately it would require a large class D at that impedance.
    The voltage is good and steady, never goes below 13.2 at idle with the music cranked.

    So now a " spec " box will be built @ 1 cuft, this could help, but really, how much ? ( present box = 1.3-ish ).
    It's a minor annoyance now, not like it was at the beginning of this thread, i could live with it.

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