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Ways to run to 8ohm cabs in series to get 16ohms

Discussion in 'Amps and Cabs [BG]' started by webmonster, Dec 19, 2013.

  1. webmonster


    May 19, 2013
    New Zealand
    I have two valve amps that have 8 and 16 ohm output options, another that can do 4,8 and 16ohms and a solid state head that has max. output into 4ohms.

    I (will soon) have two 1x15 cabs that are 8 ohms each.

    For the 8/16ohm valve amps to run both cabs I'll need to run them in series somehow to get 16ohms.
    Two options spring to mind:
    1. I've heard some talk here of a 'series box'. Are they commercially available? (I imagine that I could make one)

    2. The new cab I'm building... in addition to the regular input (will be XLR like my existing cab) could I sensibly have a 1/4" switched jack socket in the circuit in series to run to my existing cab when plugged into this socket?

    Any other suggestions gratefully accepted.
  2. Wire up a series box. That way you can't accidentally flip the wrong switch on a cab and wind up no load one day using one cab.
  3. mbelue


    Dec 11, 2010
    Why on earth would you use XLR for a speaker cabinet?
    I realize some companies made this mistake in the dark ages but there are vastly superior choices and standards now.
  4. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    I put 3 jacks in a plastic utility box to put two Bage End 4 ohm cabs in series for 8 ohm yers ago. That worked fine.
  5. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I would recommend that you use Speakon connectors. You'll need to get a 15/16" drill to make the holes. Per Mbelue's post I would replace the XLR on your existing cabinet with a Speakon too.
  6. webmonster


    May 19, 2013
    New Zealand
    I'm not thinking of using a switch that I flick (I agree - almost inviting disaster!) - I mean a 1/4" socket that includes the switch. Plugging in the jack flicks the circuit.
  7. Even more dodgy.
  8. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Read post #6 again. The use of 1/4" phone connectors is very limiting and not all that much cheaper than using the vastly superior Speakons.
  9. webmonster


    May 19, 2013
    New Zealand
    I'm certainly not against replacing the XLR ends, but it is easy to be lazy :bag:

    One end will always be 1/4" - all my amps have these connectors and I've never had any sort of problem with the XLR end. What benefits will speakon sockets in the cabs give me?

    Sell 'em to me :)

    Can a speakon socket be switching like a 1/4" socket can be?
  10. Speakons are high current. XLR isn't, not that it matters for oldschool power levels. However, you're relying on integrity of little soldered joints which can get stressed and fail over time so you might want to inspect.

    I wouldn't go near auto switching phone plugs with a 10ft pole. They tend to fail open with no warning.
  11. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com

    Use solder, too, but easy enough to make one yourself. it won't matter which cable you plug into the boxes, so make both ends speakon, and the end that plugs into your amp, leave 1/4".
  12. Primakurtz

    Primakurtz Registered Nihilist Supporting Member

    Nov 23, 2011
    Denver, Colorado
    I can't draw very well, but:

  13. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I don't have to, it's not my responsibility! Do a search on the subject, there's reams of information on this site

    You don't need switching jacks. Build a series box as suggested, total price in the range of $20. To use both cabinets use the box. To use one, wire straight to the amp.

    A caveat to the series connection is that if your cabinets have internal crossovers you may experience some negative interactions between those crossovers. If the cabinets are identical you might be OK if not it's a crapshoot.
  14. webmonster


    May 19, 2013
    New Zealand
    OK - switching cabs over to speakon - you've convinced me :)
    Series box - sounds v. sensible and leaves cabs as standard, so I'll do that too.
    (as long as I leave the box *in* the gig bag...)

    Thanks for all the input - this is a fine forum :)
  15. I recently built a friend of mine a cable for his cabs and it worked out great. I messed it up initially but realized my error mid build and rectified it. What ever you do make sure to get a multimeter and test your load before connecting to an amp just to be sure it is working correctly. I went for the cable route becauae we had left over ends from years of old junk.

    I am not and may never be sold on speakons.
  16. will33


    May 22, 2006
    Just make a series cable or series box. 1/4" is fine, they've worked for about 100 years. The increased contact area/current capacity of Speakon's doesn't matter until you get an amp bigger than about 500 watts AND crank it up to where you're actually using all that power. It's more of an "idiot-proofing" consumer safety thing than it is any current flow/tone/heat thing. I have both on various pieces of gear, no sound difference at all and my 1/4" plugs never get hot.
  17. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    i have no fear of the switching jacks (to choose between 4Ω and 16Ω) in my marshall 4x12 guitar cab, and i think they're probably fine for valve bass amps, since the max there is pretty much the 300 watts of an SVT.

    not sure how you'd rig that with two separate bass cabs, though. a nice solid "series box" with speakon in and outs seems like a pretty gig-worthy way to go. don't think i would trust a series cable over the long haul.
  18. webmonster


    May 19, 2013
    New Zealand
    My valve amps are 50W, 75W and soon I'll have a 200W one.
    I'm now thinking a good solid series box is what I will build. Keeps both cabs standard this way. Pretty idiot proof too ;)
  19. i like the cable but building it takes some thinking. i labeled the ends to make it dummy proof for my buddy. box is simpler and allows you to use regular cables, but finding some where to put it would be annoying. could velcro it to the side of your cab.