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Vintage GMT/GK folded horn cab

Discussion in 'Amps [BG]' started by vistacruiser, Jan 14, 2014.

  1. vistacruiser

    vistacruiser

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    [​IMG]
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    Hey, I'm interested in any practical info or knowledge you can share about this GMT 118B folded horn enclosure. Serial # 73050242.

    Of particular interest would be, audio specs, other cabs and amps that were used in a system with this cab, artists who used or endorsed this cab. Anything you have that is specific to the GMT/GK 118B folded horn.

    I've had this cab for quite some time but it's never been my go to. Now you might say that is for the better, and I'm aware of the short-comings and strengths of the design. But now I've re-coned the Cerwin Vega 188c driver and I think this could be the basis for an impressive, if not menacing, outdoor set-up.

    Since reloading the driver, I messed around at low vol with a tweeter equipped 115 and my 800rb, the combination with flats & P bass was inspiring to say the least.

    GK support staff, while being prompt and courteous, so far have offered nothing that pertains to this model. I realize it's an older discontinued product, but I still have hopes.

    Any one have experience to relate?
  2. uglyrumor

    uglyrumor

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    Interesting. I have a similar Fender cabinet from the mid-eighties. What are your experiences with the sound of this one?

    can't get picture to load
  3. grenadilla

    grenadilla

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    Is it a Sunn copy?
  4. AdamR

    AdamR Supporting Member

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    You need an old 400B (not RB) to go with that. Cool cab
  5. The Nameless

    The Nameless

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    I also have an old Fender 115 cab similar, but not exact, in design. I'd been usin it with its hundred watt matching head for rehearsals, but out of curiosity ran it with my big rig. Wow! I am interested in this thread to find any design secrets. Searched online an found nothin. Jus another non-descript cab in Fender history. I'll definitely follow this thread. Curiosity, ya know...
  6. vistacruiser

    vistacruiser

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    Thanks for the thoughts on the cab and interest in this thread! I hope more info comes up.

    There may have been a similar Sunn cab, now that you mention it I recall a pic of a different brand cab that looked identical. Do you have info on the Sunn?

    I was able to crank it up a bit louder as wifey was out tonight.
    Two observations:
    A) anything that can buzz or vibrate in the area, will buzz and vibrate.
    B) the back panel needs to be mechanically refastened and re-glued, to a triangular internal brace that runs up the center, between the back of the cab and the speaker baffle.

    edit: Actually on closer inspection, the speaker baffle board has separated from the brace, not the rear panel.

    Through this triangular brace, the baffle is tied into the rear panel, stiffening the construction of both. But since the glue has let go, only staples remain. It's buzz city, I can't get a feel for the real sound it will have. I have a plan by which to epoxy and through-bolt the baffle, brace and rear panel. Wood screws/epoxy might do it, if the bolts are impractical. Probably will be a big improvement and breath some new life into it. I'll post some pics along the way.
  7. tjh

    tjh Supporting Member

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  8. vistacruiser

    vistacruiser

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  9. B-string

    B-string Supporting Member

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    Have you tried a PM to rag (Robert A Gallien)? He is a member here and IS G-K/GMT. If anyone would have memories Bob would.
  10. shoot-r

    shoot-r

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    Wasn't aware of these.......
    G.K. also had a 412 folded horn cabinet, I've only seen one, and that was MANY years ago.
  11. will33

    will33

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    PL Premium glue and a few screws to hold it while it sets. It's strong glue that will expand a bit as it sets, filling in any gaps. Airtight is extra important for horns. Can find it at Home Depot, comes in a caulk gun size tube.
  12. vistacruiser

    vistacruiser

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    Thanks for the tip will, I made the repair today already. I used a 2 part marine epoxy that I have a quantity of left over from when I had a wooden boat. It goes on as liquid, like a thick syrup, and capillary action pulls it into all the gaps. I applied it with a plastic syringe, and needed a mirror at times to see where I was putting the glue. Hardening happens slowly so there is plenty of time for it to seep in. Also, it's intended for use on exactly what this cab is made of...fir and mahogany plywood.:D

    I'll add some pics to show you all what I did today.

    Tomorrow, after the glue sets, I'll jam some watts into her and hear the results!
  13. vistacruiser

    vistacruiser

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    [​IMG]

    This is what you'd see if you stuck your head into the front opening of the cab, looking down. At the top of the pic is the inside of the rear panel, at the bottom is the speaker baffle, the driver of course mounts to the other side, and the vertical piece between them is the triangular brace. The baffle and rear panel form a "V" with the brace ties them together.
    If you look close you can see a hairline crack in the joint of the baffle and brace, (foreground) there is also one at the far joint. Those failed joints I believe, are responsible for a horrendous vibration and I will show my attempt to fix that.

    [​IMG]

    I decided to place 2 bolts from through rear panel into the baffle, one above and one below the speaker frame and use nuts and washers inside to hold it together. Yea, screws and glue might have worked as well, but there should be no doubt this is permanent.
    Here I measure the location of the upper bolt hole, 20.5 inches from the bottom. The lower hole will be about 2 inches up. I intend to drill right through the center of that brace with some mad ninja skills and a foot long bit, and come in just over the driver.:ninja:

    [​IMG]

    Here is the set up, the foot long bit is starting it's way in, the 2 squares are helping me keep it perpendicular. But let's back up a bit, first I checked to see if the brace was centered in the cab... it wasn't. It was off by 3/8" at the top and centered at the bottom, so I marked the exact locations before drilling. While I was at it, I marked pilot holes for 2 long wood screws to help secure the back to the brace, between the bolts.

    I'm using 1/4 inch threaded rod for the bolts, (the top one is 9 inches) because you cant find 9 inch by 1/4 carriage bolts. And because I'm all about using what you have if possible, and I already had the 1/4" rod (brass) and a 1/4" foot long bit. I purposely mushroomed the threads a little on one end and tightened a nut in place with a drop of loctite for good measure. Then I drilled a shallow countersink for the nut with a 7/16 spade bit. The nut/head should pull in flush when tightened up from inside.

    [​IMG]

    After white knuckling it through a staple, here we are about an inch from the driver mounting hole...Yes!
    The screw hole is centered in the cab, so here you can see how the brace is slightly "off".
  14. vistacruiser

    vistacruiser

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    [​IMG]

    With holes drilled and fasteners positioned...

    [​IMG]

    ...about time to mix some epoxy.
  15. vistacruiser

    vistacruiser

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    [​IMG]

    After filling this syringe, I spread the gap a tiny bit with a putty knife and made several applications of epoxy. Turning the cab over every which way to get the stuff to run in where I wanted it. Drove home the screws and bolts, and left it sit....

    [​IMG]

    ...but not for long.

    Since I'm using sloooowwwwww hardener and don't know when to quit, I decided to drill some new pilot holes and refasten the upper edge of the speaker compartment to the baffle, it looked like a possible trouble spot for leaks/vibrations.

    This 90 degree attachment came in handy here.:cool:
    The wooden dowel is taped to the baffle face, to indicate the angle for drilling pilots into the edge of the baffle.

    Epoxy is applied to the joint and allowed time to seep into any cracks, then the 5 brass screws are tightened.

    [​IMG]

    If all goes well, this will be the "Rig of Doom" at rehearsal later today.:bag:

    [​IMG]
  16. vistacruiser

    vistacruiser

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    This cab is way over-kill inside a house...wow.
    It actually works pretty darn good, I'm not disappointed at all. But my basement acoustics are terrible.
    The cab buzzing is gone I think, just everything out side the cab (like walls & ceiling) vibrates.

    Playing through just the18" horn, an old p bass with GHS flats was the best sounding. The horn, even by itself, has no trouble with the range of my 4's. There is a tendency to accentuate certain freq's, or diminish others, probably the room doing that more than the cab itself. Even my 610hlf is too much for my paneled basement.
  17. uglyrumor

    uglyrumor

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    I was going to send the link from craigslist, but couldn't figure out how to do it. Look under Charlotte, N.C. musicical instruments, search "Sunn 115RH"; there are two cabinets for sale. A bit pricey, maybe, but look good.
  18. Cirk

    Cirk

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    I like the blatant overkill in your repair work. That cab is a tank. Great job!
  19. will33

    will33

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    +1

    Might be considerd a bit "obsessive", but that's a solid repair right there. Ought to make the journey to the new world. :D
  20. Jim C

    Jim C Supporting Member

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    Nice cabinet and restoration.
    I remember this style of bass cabinet to be boomy without much top end and were really meant for a bi-amp applications.
    Am I wrong?

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