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Dumb question..

Discussion in 'Cabinets & Speakers' started by Marcomel79, Sep 20, 2021.

  1. PelliX

    PelliX Well-Known Member

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    No, the internal speaker uses that jack. :)
     
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  2. Marcomel79

    Marcomel79 Well-Known Member

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    What @PelliX said...
     
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  3. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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    Ah, the manual doesn't show this,
    upload_2021-9-20_14-12-41.png
    and I didn't see anything about unplugging the internal to use an external.
    So, ok, never mind.
    But I did say another stupid question...

    No, you can't hook up 2 external 16 ohm speakers.
     
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  4. RLW59

    RLW59 Well-Known Member

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    Yes, it can do that. Plug the 16 ohm 412 into one of the amp's 8 ohm outputs. Plug the Z-Matcher into the amp's other 8 ohm ouput. Connect the 8 ohm 212 to the output of the Z-Matcher.

    The Z-Matcher has two knobs -- one for the amp side and one to the cab side. The speaker knob gets set to the cab's impedance (in this case 8 ohms), the amp side gets set to what you want the amp to see (in this case 16 ohms, so the amp sees two 16 ohm cabs).

    That will split the amp's power equally to the two cabs.
    -----------------------------
    You could also plug both cabs into the Z-Matcher and set the speaker knob to 5.3 ohms. Then set the amp knob to match whichever amp output you want to use.

    But that set up will send more power to the lower impedance cab. In this case, 2/3 of the power to the 8 ohm 212 and only 1/3 the power to the 16 ohm 412. That would be backwards of what you want (but if the 412 was the 8 ohm cab and the 212 was the 16 ohm cab, sending more power to the 412 would be good).
    ---------------------------
    If your Marshall has the modern 5 jack output set up, you can use an 8 ohm and a 16 ohm cab together without needing a Z-Matcher. Plug the 16 ohm cab into one of the 8 ohm jacks, and plug the 8 ohm cab into one of the 4 ohm jacks.

    That gives a perfect impedance match and splits the power equally between the cabs.
     
  5. LPMarshall hack

    LPMarshall hack Well-Known Member

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    I never knew you could just plug in each cab into the respective jack in the back of the amp!

    My JMD has the five jacks in the back. I'm gonna connect my 4x12 (16 ohm) and my 2x12 (8 ohm) up to it and destroy the neighbors. So you just halve the cabs' ohms....easy peasy! Thats why I love this place...learn something new every day!

    Thank you!
     
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  6. PelliX

    PelliX Well-Known Member

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    Come again? Regardless of the fact that a little higher impedance is absolutely fine up to about 2x the spec on the tap, the taps are intended to be used for that specific impedance. The modern layout provides multiple outputs for the 8 Ohm tap and others depending on model, but just use a/the 16 Ohm tap for your 16 Ohm speaker and an 8 Ohm tap for the 8 Ohm speaker.

    You have some fun cab matching ahead, then! :D
     
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  7. LPMarshall hack

    LPMarshall hack Well-Known Member

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    Wait....so this was bad advice? I should NOT do that?
     
  8. PelliX

    PelliX Well-Known Member

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    That's a black and white way of putting it. @RLW59 is correct in the sense that this will not damage your amp most likely - up to around 2x the impedance marked is 'OK'. That said, just use the taps as they're marked. Easy and yields the 'best' result. Now, plenty of people mismatch cabs and say it's "their tone, man". Feel free to try it, but it would be a case of 'doing it slightly wrong', honestly. :)

    I should also add that this does not work both ways - putting too little impedance on a tap can kill your amp. Will you kill a 16 Ohm tap with an 8 Ohm speaker? Not per se, but it's certainly not pleasant for the output. Going too far and for too long can damage the amp, no doubt about it, though.
     
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  9. LPMarshall hack

    LPMarshall hack Well-Known Member

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    Just re-read your post...so do NOT halve the ohms of the cabs. Just plug my 16 ohm cab into the 16 ohm jack and the 8 ohm cab into the 8 ohm jack?

    Thats the bad part about internet...you may get two diametrically opposed pieces of info. So now I am still confused.
     
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  10. PelliX

    PelliX Well-Known Member

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    Yes... and yes. :thumb:

    Indeed, never "under-Ohm" a tap. The higher the output power (wattage), the more likely and quickly you will cause damage if doing so, so a 5W seems relatively tolerant for a while. On the DSL1 for example you can run the whole thing without a load because of the low wattage (a no-no for bigger amps) - after all, 1W is not a lot to dissipate.
     
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  11. LPMarshall hack

    LPMarshall hack Well-Known Member

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    I'm talking about my 100 watt JMD. The OP has the 1 watt.

    I derailed....my apologies.
     
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  12. PelliX

    PelliX Well-Known Member

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    OP as a 5W, I believe. But yeah, be careful with the JMD. My rule of thumb is generally that never go further than -30%-ish or +100% of the rating on a tap. Never killed an amp, yet. YMMV.

    Also, note the markings on the jacks; if you see something like 2 jacks marked "1 x 8 Ohm or 2 x 16 Ohm", it means it's an 8 Ohm tap.

    [​IMG]
     
  13. LPMarshall hack

    LPMarshall hack Well-Known Member

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    I'll just stick with a single cab....
     
  14. RLW59

    RLW59 Well-Known Member

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    Santiago Alvarez designed the JVM, among other Marshalls. He posts here as "santiall".

    Mickeydg5 was the first to explain the "16 cab into 8 ohm amp jack plus 8 cab into 4 ohm amp jack" concept. Santiago agrees and explains the math/electrical theory.

    I mentioned Santiago first, because he doesn't post as much as Mickeydg5 so his posts about mixing impedances are easier to find. Plus, he's the one who started putting 5 jacks on Marshalls.

    Go ahead and search santiall, but here's a thread to get you started:

    https://www.marshallforum.com/posts/1525516/
     
  15. LPMarshall hack

    LPMarshall hack Well-Known Member

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    Wish Santiago would post more often. I see he mentions this in post #15. Thank you.
     
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  16. Marcomel79

    Marcomel79 Well-Known Member

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    UPDATE: just wired my two 16ohm speakers in series and plugged them in the 16ohm output of my dsl5. Works fine as im just playing at bedroom level...
     
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  17. PelliX

    PelliX Well-Known Member

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    I see the point here, but I don't quite follow - that is, I understand the effect of increased total impedance from the perspective of the primary, but I would not expect the difference to be large enough to warrant moving down taps. If I get time I need to bench test this for some numbers tomorrow. I don't have a 2555X, but a couple of other OTs. Thanks for the pointer, I'm intrigued.
     
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  18. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    Absolutelh you can run two different cabs.
    You were correct the first time.
    Run the 16 ohm cab from one of the 8 ohm outputs. That is half a load as amp is still expectkng another 16 in that tap.
    Run the 8 ohm cab from 4 ohm tap. There is also a half load.
    Two half loads equals 1 full load. No mismatch at all. Works with any amp that has separate outputs amd no impedance switch.
     
  19. LPMarshall hack

    LPMarshall hack Well-Known Member

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    Thanks Jethro!
     
  20. Chris-in-LA

    Chris-in-LA Well-Known Member

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    If it’s for night practice, you only need the one speaker.
     
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