GK 115 RBH

Discussion in 'Amps and Cabs [BG]' started by Bluesbarrister, Mar 25, 2004.

  1. I'm trying to learn about my GK 115 RBH cab, which I run with an 800RB. I've had the amp for 5 or 6 years - just got the cab (used) a month ago. At the first gig, I fried the tweeter. I assumed it was because the cab's tweeter is rated at 50 watts (so far as I could tell) and I was pushing 100 watts through it in bi-amp mode. When I removed the tweeter, I see it was a PAudio 20 watt. Apparently, that is the OEM tweeter. Can anyone help me out with the following questions:

    1. What's up with the tweeter - is it 20 watts or 50?

    2. Shouldn't the bulbs have fried before the tweeter, or are the bulbs bypassed in biamp mode?

    3. I've ordered an X-Tealth (Foster-replacement) 100 watt tweeter to replace it. Freq. response 5Khz to 20Khz (if I remember correctly). It's only $50Cdn so if it's a dud - no great loss - but it seems to have better specs than the PAudio. Thoughts?

    4. Does anybody know at what frequency the passive crossover in the cab crosses over?

    4. In biamp mode, where should the crossover be set?

    5. Any other comments, ridicule, bad jokes?
  2. The crossover is at 5k. The fuses are mostly bypassed in biamp mode, so it is possible to blow the tweeter. If you are using the high amp from the 800RB to drive your tweeter, you're going to blow it everytime. Even if you set the crossover frequency to it's highest setting, which is 1k, you are pumping way too much power at frequencies below 5k, which the crossover is not capable of handling. You'll most likely blow your new 100 watt horn as well.
  3. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Yeah, the GK bi-amp mode is more intended for two separate cabs, like a 15 or 18 on the bottom, and a 2x10 or 4x10 on top. You're not really supposed to bi-amp into a tweeter alone. I'd use the GK in full range mode, and just go with the internal crossover in the cab.
  4. http://gallien-krueger.com/SUPPORT/Manuals/RBH_Owner_s_Manual.pdf

    This is where I'm getting my guidance. The manual specifically <b><i>recommends</b></i> using the rbh cabs in biamp mode, running a separate amp to the tweeter. I know it refers to the 700RB, which has a 50watt high end, but ... I'm thinking that 100 watts at low volume into a 50 watt tweeter shouldn't fry it. A 20 watt tweeter, however ...... Which is why I asked: "what's up with the tweeter - is it 20 or 50 watts?"

    Dan - you say I'll fry the tweeter every time - is that because the 800RB doesn't crossover at as high a frequency as the 700RB?

  5. Fred312b

    Fred312b What if I want to play jazz precisely? Supporting Member

    Apr 23, 2002
    Chicago, IL
    I'll admit I'm no amp expert, but I just went through an exhaustive "figuring out" of my gk 1001rb/210 combo, which has essentially a 210rbh cab. how are you using the 100 watt amp on the 800rb? the way i would understand you hooking up the 300 watt ouput of the 800rb to this cab is through the full range input, and the 100 watt amp wouldn't be used. my 1001rb uses the biamp with a 4 conductor speakon, but if i hooked my amp up to my swr cabs, my 50 watt tweeter amp wouldn't be used. :confused: nonsqtr is right in that the 800rb is designed for two seperate cabs, one for highs (a 2x10, etc) and one for lows (1x15, etc), the new gk heads are a different set-up and designed for use with the new cabs. you should run one cable from the 800rb to your rbh cab , swith the cab to full range and utilizethe cab's internal crossover and turn off the crossover on your 800rb.
  6. I've come to the same conclusion - unless I can get my drummer the amp wizard to design a mod to the x-over in the 800 to bring it up to 5Hz or more. Does anybody know of a such a mod??

    Fred: If you get a speakon wired to two 1/4" jacks, instead of speakon to speakon, you should be able to use your 50 watt high end into an ext. cab like a 2x10 (???)
  7. Fred312b

    Fred312b What if I want to play jazz precisely? Supporting Member

    Apr 23, 2002
    Chicago, IL
    i think you're not understanding what i am saying. outside of a gk 700rb or 1001rb, there's no way to get to just the tweeter in the rbh cabs. the problem is not in your amp's crossover. just because you're hooking up the 100 watt amp to your cab, doesn't mean that it's just going to the tweeter. i HOPE you're not hooking both the 300 watt AND the 100 watt amp up to the same cab, because that's just asking for trouble. the only way you are going to get "bi-amped" with your amp is to get 2 seperate cabinets. the rbh has a passive crossover built in, so if you just use the 300 watt side, you'll use your tweeter, just make sure your switched to full-range. :)

    and while you could use a 4 conductor speakon to 2 1/4" plug (in theory, if such a thing exists), there's really not much need- my swr cabs have a crossover in them at 3khz, and the 50 watt amp is only going to do 5khz and over. if i could get a horn box like trace elliot and hartke used to make, then maybe, but i'm not looking for all that glass shattering treble myself.
  8. You can get to the tweeter in the RBH by wiring to pins 2+ and 2- on the speakon connector, which is what I was assuming he was doing. It didn't occur to me that someone would actually hook both the 100 watt and the 300 watt amp to the same speaker. If that was the case, I'm surprised the amp isn't totally fried. If you're in biamp mode on the cabinet and you don't have anything wired to pins 2+ and 2-, then you would not get any sound out of the tweeter in which case someone might mistake that for a blown tweeter. Switch back to full range mode to see if the tweeter works before assuming that it's blown.

    If you did have it wired to pins 2+ and 2-, and you were feeding it signals below 5k, that will blow the tweeter.
  9. Thanks Dan.

    Yup. That's what I did. A little knowledge is indeed a dangerous thing. So, that takes me back to the question: Is there a mod that can be done to the x-0ver in the 800 that will bump the max x-over frequency up to 5Khz?:help:
  10. If you have a techie friend, they'll need to make some kind of mod to the preamp board. You can get a schematic emailed to you if you contact tech support, but they won't tell you how to do the mod because of liability issues.
  11. 'Tanks (and battleships)