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Upgrading GK 115T to bi-amp usable

Discussion in 'Amps and Cabs [BG]' started by AdamF, Jul 9, 2005.

  1. Hi
    I have a GK 700RB, 210RBH (has a horn) and an old 115T (no horn, 200 w 15 in speaker - bought to use with my 200MB). Has anybody out there experience of upgrading a 115T to have a horn, splitter and likely a 400 w 15 in)? Cheaper and lighter than the 67 lb GK 115RBH. And the existing 200 w 15 in is underrated for the 700RB (though :) it's a Mk I).
    Adam (Melbourne Australia)
  2. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    No, bit this should be pretty simple. The biamp capabilities of the 700 are delivered through a Speakon connector. So the speaker cable is 4 wires with 2 dedicated to the woofer and two to the tweeter. (I suppose they MIGHT be able to share a ground but I doubt that they do.) So you select the proper horn/tweeter. The Foster horn seems to be popular. Cut a hole and mount the horn. Run two of the connectors to the horn and two to the woofer. This assumes this assumes that you already have a Speakon connector on the cabinet. If not you'll need to add one. Then you need a properly configured Speakon to Speakon cable for your amp to the cab.

    2 additional thoughts.

    As long as you're going to upgrade the 15, why not drop in a JBL and skip the horn ? The JBL has a beautiful top end presence that makes a tweeter sound shrill in comparison. While the JBL doesn't have the power handling ability of something like an Emminence and is much more expensive, it is way better sounding and is more efficient to boot. The spec for the JBL driver call's for between 4 and 5 cubic feet in volume and about 24 square inches of port space. My experience has been that if you're even close to that, the JBL will sound very good. 1 JBL 15 can get pretty darned loud, 2 can get quite loud indeed.

    Last thing is my disclaimer. I'm a JBL bigot. There is no better sounding driver than the D or E or K 140 / 145 for a 15" in my opinion. They flat out rule!

    My other strongly held belief is that tweeters in bass cab's suck... The only reason that they exist is to add a little sparkle to an otherwise ho-hum sounding driver. The driver sounds ho-hum primarily due to the materials used in the cone and voice coils so that the driver can achieve high power handling characteristics. Those high power handling characteristics come at a cost of efficiency and tone. It requires more power to get them to the same relative volume level and tweeters to bring back the high end ...

    The manufacturer's do this 1. because naturally good sounding drivers are expensive and 2. Efficient drivers used with high powered amps by people who aren't paying attention will tend to smoke thereby driving warranty claims high. No fault of the mfgr at all.

    So using a really high quality driver isn't really in the mfgr's interest and might cost them market share as on paper their gear won't spec well. They will develop a rep for being 'boo-teek'. Expensive, finicky and underpowered. What mfgr want's to sign up for that program ?

    This is also why companies like Epifani, Bergantino and Accugroove exist. They make no apology about the cost and their business model doesn't appear to involve selling tonnage at Guitar Center...

    I hearby end my Sunday morning rant... Can I get an Amen!

    Seriously - if you got this far and you're still interested in the tweeter and bi-amp thing, then ping Daniel Elliot and get the proper pin-outs for the Speakon cable. That wil be a crucial step for you. It is easy enough but if you get it wrong that little horn is going up in smoke. Oh yeah - you don't need a divider network with that setup as the dividing is done by the GK head. Nice head by the way!
  3. Thanks for that.
    Food for thought. I had the impression that the divider network in the cabinet was needed to add to speaker protection. I guess you are indeed sure that it is all done by the head? I also had the impression that the Paragon 15 in. that GK install is made by JBL - maybe wrongly. and from what you say maybe a low end 15 in. at that?
  4. tplyons


    Apr 6, 2003
    Madison, NJ
    You posted this over at the GK forum right? If that wasn't you, I'll post my opinion:

    Sell it. Put the money towards a 115SBX-II. Power rating you want, horn you want, and the 115T wasn't a great cabinet to begin with.
  5. Thanks
    'It was me'
    For reasons I guess of our isolation from the Main Stream, the 115 SBX II is not on sale here (yet, I hope). The old one is only 200w. But this makes sense to me. I'll wait. What don't you like about the 115T?
  6. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge

    I could be wrong there but ... the new GK head has a cross over built in with 50 watts being directed to the tweeter. There is a tweeter level control on the front panel of the amp. It's actually bi-amped. If your's is the same, then no divider network is necessary.

    In a passive setup, where ther is no active corss over, the a passive cross over (divider network) is in place for primarily to protect the tweet from frequencies that will melt it.

    Never heard that the Paragon driver was made by JBL and I am pretty sure that is not the case. I've heard that Emminence actually makes some drivers for JBL today. If you look at the range of product available from JBL today it runs from some truly terrible hi-fi gear through consumer level sound refinforcement into pro level sound reinforcement.

    The drivers I refer to are a vintage design having been around since the 60's. They are pretty pletiful in the used market. I generally find them blown. Buy them for 25 bucks and then recone them for $125. Once in a while you'll find them in decent shape for less but that's hit or miss. At this point I actually prefer them blown so that after the recone, I know what I'm working with.

    Check over the GK. If you have that tweeter level control on the amp rather than on the cabinet, you don't need the divider network. If there is no level control. Then as I recall, Avatar was selling the Foster horn and a crossover for not much. If Dave is still not selling for export, I'm sure that someone over on this side of the world will provide and assist with the shipping. There are probably other sources and one in Oz would be a easier for you I would guess. If that doesn't work out then i'm sure we can find other approach.

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