2x12 in a 4x12 Cabinet

Discussion in 'Amps and Cabs' started by backwater, Jan 15, 2006.


  1. backwater

    backwater Member

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    I am rebuilding a 75-ish Marshall 4x12 which has a motley selection of speakers (2 1965 celestion G12S' and 2 Goodmans Audiom 70's). I am going to remove the existing speakers and replace them with Celestion century vintage speakers. I was considering only fitting 2 speakers diagonally across the cab for just now as I generally gig with one 50W head and an 8ohm attenuator so 2 16ohm speakers will give the correct load. It would also allow me to add another two speakers later.

    My question is simple. Can I leave the two unused holes open or should I cover them with ply circles or something else? Any thoughts? :angel
     
  2. rockon1

    rockon1 Member

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    They call it a "detuned" cab- using only 2 speakers and leaving the holes open. I think you might put them in the top spots. Some do this on purpose.Might have interesting results.:)
     
  3. propska

    propska Member

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    I tried this a couple months ago with my 4x12. I took out the bottoms two speakers. It made the cab really loud and added a boominess in the lower mids that I didn't really like. However, I'm sure results will vary with different amps. I was running a route 66 which is plenty thick in the mids already. I thought about making the holes smaller more like a thiele/ported design to control the mids more, but never really got around to it and went back to the 4 speakers. I recall (don't quote me on this) reading that smaller ports (i.e. bass cabs) allows low frequencies to pass through and blocks the higher frequencies. So, I think that the larger the port, the more mids and highs are allowed through. Some one correct me if I'm wrong here because I may very well be. Anyway, I say try it. If you don't like it, you can always put all four speakers in or cover up the open holes entirely.
     
  4. Chiba

    Chiba Gold Supporting Member

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    You could hook up 2 and leave 2 unconnected. If you did that, I'd go with a top-and-bottom setup rather than diagonal - you'll never remember which diagonal is the right one :)

    Or, if you wanted to eliminate the weight, put in the two speakers and spray-paint the inside of the cabinet black - that way it won't look weird from the front.

    --chiba
     
  5. SecretAsianMan

    SecretAsianMan Member

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    How about a passive radiator?
     
  6. 908SSP

    908SSP Member

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    I tried the the Detuned thing with two speakers on the top of a Marshall 4 x 12 and it sound very good. I could see leaving it that way but didn't but it wasn't because it sounded bad just different. It had bit of natural echo and kind boxiness it was a cool sound just not one I wanted or needed. Saving weight wasn't an issue and I had more speakers then I knew what to do with. Try it, it won't cost anything.
     
  7. mccreadyisgod

    mccreadyisgod Member

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    Try it open, and maybe get a sheet of 5/8" ply to try covering the holes... but the interesting option would be to try to fabricate a couple ports using some 4" PVC pipe. Maybe a 6" or 8" depth. Could be interesting.
     
  8. Roe

    Roe Member

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    cover the holes or make them smaller. If you use only 2 of 4 speakers in a closed cab, the 2 connected speakers will move or make a sound first and then the 2 disconnected speakers will move and make a little sound afterwards - not recommended
     
  9. SecretAsianMan

    SecretAsianMan Member

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    Then that also means that passive radiators (as I posted above) are not a good idea, as they would be doing essentially the same thing as a disconnected speaker, just with less weight. You're right; it would probably sound like a phasing problem.
     
  10. Roe

    Roe Member

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    the 2 big holes will give you a massive resonance problem
     
  11. 908SSP

    908SSP Member

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  12. Roe

    Roe Member

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    yes, but two 12" holes will give you a resonance problem i a closed cab.
     
  13. johnspeck

    johnspeck Member

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    If the cab is closed-back and a slant, leaving the two bottom holes open ('detuning') causes phasing issues internally in the cab and it sounds boomy and undefined. 'Detuning' a 4-12 straight is a much better sound. 908SSP mentions a boxiness to the tone. This is true, although you may like it. I do. Listen to what an open back combo sounds like from the back, up close. That tone is being presented forward out of the two open bottom holes. Another great byproduct is that you don't have as much an issue with the 'directionality' of a typical closed-back 4-12, it really fills a stage, yet it still has that great push of a stock cab.

    As always, depending on the tone you're after and the amp/speakers you use, YMMV...
     

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