Switchable series to series-parallel

Discussion in 'Amps and Cabs [BG]' started by rockness monsta, Sep 27, 2022.

  1. JimChjones

    JimChjones

    Aug 6, 2017
    SE England
    Wouldn't something like this be more appropriate with 4 ohm drivers? But I must admit I tend to the general opinion its an undesirable complication. If my amp required 4 ohm I'd wire it for 4 ohms, and if 16 ohms 16, and live without the switch. I can too easily image some careless 'helper' knocking the damn switch off during the load in.

    upload_2022-9-27_21-30-39.png
     
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  2. Wasnex

    Wasnex

    Dec 25, 2011

    There companies that make this sort of product.
    Palmer CAB M | Signal Splitter & Switcher | Palmer (palmer-germany.com)
    Cab-Link - Radial Engineering

    Check the specs if they are posted. I don't think these are really designed for a 800W bass amp. They will work fine at a modest power level.

    I have a wiring diagram that does series parallel (I think). I believe this is how my Hiwatt DR201 was originally wired.

    upload_2022-9-27_15-49-43.png

    Here are the proofs I worked through...let me know if I missed something.

    upload_2022-9-27_15-50-46.png

    When no speaker is attached, I believe this configuration shorts out the output. This would be very bad for a solid state amp, but it's desirable for a tube amp. By bad I mean possible destruction of the amp.
     
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  3. hennessybass

    hennessybass Supporting Member

    Oct 11, 2008
    Bayou City
    Old Ampeg tube amp with a 16ohm output -- sounds like a B-25-B to me.
     
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  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Beware of those switch boxes where there is a connection to the enclosure, on a bridged amp this will place the box enclosure at above ground, so if the box touches ground, 1/2 of the amp will be shorted and damage can occur.

    I do not recommend using anything like this with most class D amps since they are usually internally bridged.
     
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  6. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    FWIW, every time I've contacted Eminence directly regarding replacement drivers I've been happy with their recommendations.
     
  7. rockness monsta

    rockness monsta

    Sep 27, 2022
    Wow! My mind is completely blown! What I thought was a simple problem is ridiculously complex and clearly I did not understand the variables. I think it is entirely fine to do some more research since I’ve already blown almost $500 on for new speakers and I wanna make sure they’re the right ones! I’m on my way to practice so I’ll send you guys some pictures of what I’ve been talking about.

    Regarding the switch I think I’ll take everybody’s advice and wire it for 16 ohm for now and just rewire it later on for 4 ohm.

    Thank you to everybody for your well thought out and insightful responses. I have really learned a lot and clearly have more to learn
     
  8. rockness monsta

    rockness monsta

    Sep 27, 2022
    Here are some pics: front and back of amp, PN of original speakers, and model of cabinet
     

    Attached Files:

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  9. So......

    if the speaker out is requires 16 ohm, and there's an extension speaker output available that is also 16 ohm... the amp is good with 8 ohms?

    Last pic above
     
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  10. JeezyMcNuggles

    JeezyMcNuggles Supporting Member

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    Woah! That thing is made for some serious abuse dude.

    600w, tilt back stand, and 122lbs

    My God, you're going to love everything but moving it. Especially since it's so low to the ground.


    I would simply take one set of leads going to the second input on the cab. Wire them in reverse order. Top, - +. Then, you'd have yourself one parallel port, and one series port. You would need to run in to that cab from the parallel out on another cab.


    That's my guess. I've never done it. Never needed to anyway. But, it makes sense right? That is how I would try it.

    Now, my question is...wouldn't that just put the entire cab out of phase?

    When one speaker is out of phase, you fix it by reversing the leads. If you have a whole cabinet taking a signal in reverse, wouldn't the whole cab just immediately be out of phase with the other cab?
     
    Last edited: Sep 27, 2022
  11. hennessybass

    hennessybass Supporting Member

    Oct 11, 2008
    Bayou City
    I believe the speaker out is for a 16 ohm cab,
    and the “ext” speaker out and speaker out are wired in series — you would use two 8 ohm cabs and the amp would make 16 ohms.
     
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  12. Possibly, some amps switch impedance automatically when an extension jack is plugged in. I have a peavey deuce guitar amp that does that between 8 and 4.
    That particular amp I have no idea about though.
     
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  13. It looks that way to me, too.
     
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Doesn’t work that way unless I’m missing something.
     
  15. Bassamatic

    Bassamatic keepin' the beat since the 60's

    When I built my first speaker cabinet back in the late 60's with a pair of Altec 421As, I worked out a series/parallel switch so I could use my only bass amp at the time, a B-15, with it, using the 16 Ohm capability. When I bought a dedicated head (a Super Beatle 1143) I used it in the 4 Ohm position.

    By the way, there is only a very small SPL difference when you switch it from 4 to 16 Ohms, but there is some tonality change.
     
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  16. JeezyMcNuggles

    JeezyMcNuggles Supporting Member

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    Okay.

    My thought was that the 8ohm cabinet, with all the speakers wired in parallel, would be the same as adding 1 8ohm speaker in series, if you were to reverse the input leads. Made sense to me. Just like, purchasing a "series wired cable"

    Except that the cable would just simply be the other input jack. Know what I mean?
     
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I don’t think so.
     
  18. anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    rockness monsta Do a search here on this forum using the term 'B-25B Dummy Plug'