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I'm trying this tweeter in my GK MB150s, any tips?

Discussion in 'Amps and Cabs [BG]' started by gkintn, Mar 22, 2005.

  1. gkintn


    Mar 6, 2005
    I'm using my Rob Allen MB2 bass in a bluegrass band, and wanted to make my little GK amp a little more expressive sounding. I want just a bit more natural "air" to the tone.

    I have a nice heavy duty JBL bullet tweeter that I've used with the amp and it sounds great, however it is BIG and bulky. I'd prefer something "built in" for portability. Also the JBL is way more efficient than needed, so I thought maybe something smaller would do the trick.


    I just ordered a Peerless dome tweeter, and a 3.5k crossover from Parts Express. I may regret such a high crossover point, but I wanted to try something safe to begin with. This particular tweeter is shallow enough that I plan to suspend it inside the metal grill of the MB150, centered right over the 12" woofer. I'll then drill one small hole in the top corner of the front speaker "baffle" for the tweeter wire, just behind the GK logo. I wanted to make the mod as unobtrusive as possible, if I later put the amp back to stock.
    Anyway, I should be able to mount the crossover inside the aluminum cab, as there is plenty of room. I'm not sure this tweeter will be efficient enough, however the stock 12" speaker isn't all that high tech and is limited in it's efficiency by the totally sealed small cabinet. I also bought a 100 watt L-pad, but I bet I won't need it.

    Any tips? Here are links to the exact parts for the project:



  2. I tried the Dayton 3K crossover with my Foster Horn...not good enough to stop all the distortion. I went to a 3.5K and it did ok. It will probably do much better with the Peerless than with my Foster.
    Let us know how you like it.
    If you need the 3K I will mail you one for free as I am not using it or the 3.5K as I made my own 4th Order Linkwitz-Riley.

    By the way, if you put the reostat control on the output of the crossover between it and the horn..it will not get hardly hot at all.

  3. gkintn


    Mar 6, 2005
    Thanks for the offer on the 3k unit, appreciate it. I'll first try the 3.5 and see how it does. I don't know how the stock 12" specs out in the highs, but it appears to be more of a woofer than a full range guitar speaker or something. My guess is that it rolls off around 3-4k.

    I might try just running the crossover as a high pass unit with the woofer wired straight. Then I'll try the crossover wired the way it supposed to go.

    Might be an overkill effort for the little GK. Still, it has enough power for the gig just not much clarity.
  4. gkintn


    Mar 6, 2005
    Anyone else ever added a tweeter to their MB150?
  5. gkintn


    Mar 6, 2005
    It worked out great!

    The tweeter was just shallow enough (9/16" D) to suspend behind the grill using some small black pull ties. Instead of mounting it in front of the speaker, it fit nicely in the top corner of the grill just under the "GK" logo on the faceplate. The only hole required for the tweeter was for the tweeter wires. So basically the tweeter fits sandwiched in between the steel grill and the aluminum front baffle plate. On the opposite side of the front I mounted the L-pad, which is accesible through the front grill with a screw driver to adjust. I mounted the crossover inside the speaker part of the combo, up where the power trans protrudes downward.
    It took some carefull work to place the mounting screws for the crossover so that they cleared the PC board on the topside. However it worked fine with carefull measuring.

    The little Peerless dome tweeter is plenty efficient along with the stock 12" speaker, and I actually have the L pad cranked way back. I might someday try a 3k crossover, but my 3.5k one seems to be working pretty nicely.

    My Rob Allen MB2 now has the acoustic "air" it was lacking without the tweeter. Tha amp also sounds nice with my Fender Precision. The amp still is lacking in the deep lows, but I think of the rig as a monitor for the most part, since I'll run the DI out to the mains.

    As a bonus the amp now makes a great acoustic amp too with my pickup equiped Martin.