4 ohm vs 16 ohm observation...

Discussion in 'The Squawk Box' started by Ginger Beer, Aug 26, 2014.

  1. Ginger Beer

    Ginger Beer Senior Member

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    So last night I was working on a pedal mod (where I could toggle back between "original" and modded sound) when I started thinking about this Marshall 4x12 cabinet that I traded for a while back. It's my first 4x12 with switchable impedance. Up to last night I have been playing it exclusively at 4 ohms.

    I decided to perform an unscientific comparison of 4 ohms vs 16 ohms sound differences using my Marshall JMP 2203. As I didn't have an assistant to switch both the amp's and the cab's settings between 4 and 16 ohms, I left the amp and guitar settings alone and tried to always return to listen from the same spot that I marked on the floor. Here's what I found...

    The sound between the two settings was "almost" identical but I noticed some differences. It seemed that the sound with the amp running at 4 ohms into the 4 ohm cab input was just a tad louder/ more powerful and slightly more defined with a smidge more lows and highs.
    Running the amp at 16 ohms into the 16 ohm input sounded very similar but the signal was a little more smeared with a very slight decrease in the lows and highs and just a touch less presence / power. For lack of a better descriptive term, I would describe the sound as "rounder" at the 16 ohm setting and "bolder" on 4 ohms. But I must emphasize again that these differences were very slight.


    The closest comparison I can draw is that it was like a very high quality copy of a photograph where the edges become just a little softer. This was not a bad thing at all and I might start running the amp at 16 ohms for live use. I went back and forth several times to try to confirm what my initial impressions were and each time I reached the same conclusion.

    I was wondering if it was simply due to the differences in the output transformer taps or is there some physics at play. IDK.

    Either way, I thought I would share my findings and wondered if others have found the same thing.
     
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  2. babatube

    babatube Senior Member

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    i tried it also with my 2204.
    to my ears the 4 OHM was more loose with a touch more of low end.
    a bit less clarity.
    the 16 OHM sounds tighter and has faster attack.
    overall i dig the 16 OHM input more.so 16 OHM input it is for me.
    the difference is really minor once you crank the volume.
     
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  3. Ginger Beer

    Ginger Beer Senior Member

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    Interesting. I would say that my findings were the opposite of yours with the 4 ohm being slightly more "forward" and defined - tighter. The 16 ohm seemed slightly softer or blurred with a tad less low end and high end. This makes me think that the difference might simply be due to the transformer windings. :hmm:
     
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  4. babatube

    babatube Senior Member

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    it depends on the transformer winding and the type of speaker and connection in the cab.
    as always it is best to let your ear judge:slash:
     
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  5. THDNUT

    THDNUT Senior Member

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    I have tin ears so I just leave my Metro JTM45 and my 1960A cab set on 16 ohms. :lol:
     
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  6. Ayton

    Ayton Senior Member

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    Presumably that switch on the cab is also making some parallel/series changes to get those numbers. I've experimented with this before in a2x12 and it's hard to figure out which has the greatest effect because both OT tap and cab wiring have to change at the same time.
     
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  7. Ginger Beer

    Ginger Beer Senior Member

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    True enough. Too many variables.
     
  8. Ayton

    Ayton Senior Member

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    My results were like yours, for what it's worth. Tighter and clearer at 4 Ohms (two 8 Ohm speakers wired in parallel), warmer and spongier at 16 Ohms (same speakers in series). Wrote it up here if anyone has too much time on their hands. The upshot was that I wished I could have 4 Ohms/parallel for rhythm and 16 Ohms/series for lead! :rolleyes:
     
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  9. KenG

    KenG Senior Member

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    The amps output will change depending on the load. Assuming same power output in watts. A higher impedance, properly matched, will draw less current and the output voltage will be higher, & a lower impedance load (properly matched) will draw more current with as lower output voltage. Just a law of electricity.
     
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  10. JCM900MkIII

    JCM900MkIII Senior Member

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    Keep in mind that the amp set @ 4 Ohm wants to see 2 (two) 8 Ohm speaker cabinets in parallel (according to Jim's official manual).

    " if the amp is running into a single 16 Ohm cab, the amp should accordingly be set to 16 Ohms. Etc."

    Using a single 4 Ohm cab.... oops not recommended.


    Jus' saying
     
  11. Ginger Beer

    Ginger Beer Senior Member

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    I had a friend over last night and repeated the test. He said the 4 ohm load was "punchier". He liked 4 ohms better.
     
  12. Ginger Beer

    Ginger Beer Senior Member

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    I just read the 1960a manual online and I didn't see anything about this. Do you have a link?
     
  13. hbucker

    hbucker Senior Member

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    I did this kind of comparison with a PV Classic 100 head and a 410 cab.

    I agree that the tone was similar enough to not lose too much sleep over. I chose 16 ohm wiring because the tone seemed more "driven" sounding.It was a little less open and more focused - almost slightly compressed compared to the 4 ohm sound.

    The 4 ohm sounded a bit more open with some headroom. Bottom line, I was wanting the driven sound. Had I been going for more of a Fender type of tone, the 4 ohm would have been fine. Ultimately the 16 ohm is more versatile too.

    This was 10+ years ago, and these differences were VERY subtle. I dare say that in the mix, they would have been unnoticeable. In the long run, the functionality of a 16 ohm cab compared to a 4 ohm cab was the biggest payoff.

    fwiw
     
  14. martin H

    martin H Senior Member

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    Two things are essentially different in this situation

    The number of turns in the output transformer coil is different when using a 4 Ohm Load versus a 16 Ohm load. This raises a possible tone issue because of the different inductance of this winding. (a higher inductance presents a greater resistance to high frequencies than to low frequencies )

    The inductance of the the load presented by the cab is different too Assuming it uses 4 X 4 ohm speakers to get either 4 or 16 ohm load, it will be wired differently for 4 and 16 ohms

    All the inductances are in series in one configuration, but in series parallel in the other, presenting a different inductance to the amp.

    I can confirm from specs that, of two speakers that are identical in construction except that one has a 4 ohm coil and the other a 16 ohm coil, the 4 ohm unit is usually a little bit brighter on the high end.
     
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  15. martin H

    martin H Senior Member

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    Originally Posted by JCM900MkIII View Post
    Keep in mind that the amp set @ 4 Ohm wants to see 2 (two) 8 Ohm speaker cabinets in parallel (according to Jim's official manual).

    " if the amp is running into a single 16 Ohm cab, the amp should accordingly be set to 16 Ohms. Etc."

    Using a single 4 Ohm cab.... oops not recommended.


    Jus' saying


    The general rule for an amp with 4, 8 ,and 16 ohm output taps is

    Single 4 ohm cab - amp set to 4 ohms
    Single 8 ohm cab - amp set to 8 ohms
    Single 16 ohm cab - amp set to 16 ohms
    Two 16 ohm cabs - amp set to 8 ohms
    Two 8 ohm cabs - amp set to 4 ohms
    Two 4 ohm cabs - not recommended (total 2 ohm cab impedance cannot be matched by the amp)


    I don;t recall any Marshall warning about specifically using a single 4 ohm cab. Marshall used to warn against running a 100W top with a single 4X12 of any impedence

    This comes from the fact that the early 4x12 Marshals had greenbacks in them rated at 25w rms each. The max power the cab could take was therefore 100w rms

    A 100w Marshall in full output tube distortion produces a good deal more than 100W rms, so you could blow a single cab using it with a 100w top.
     
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  16. KelvinS1965

    KelvinS1965 Senior Member

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    I'm taking this at face value that you're being serious, so forgive me if it was tongue in cheek, but it makes no odds to the amp: If two 8ohm cabinets are connected in parallel then the amp 'sees' a 4ohm load. Absolutely NO different to connecting the amp to a single cabinet that is wired to present a 4ohm load to the amp.

    Granted the two may well sound different for other reasons as the OP has shown even with a single cab wired two ways, but the amp still 'sees' 4ohms in either case. So long as the speakers are rated to match (or exceed) the amp's wattage output then either version is OK electrically.
     
  17. Ginger Beer

    Ginger Beer Senior Member

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    When you say "driven" could you substitute the term "compressed"?

    And i agree - the difference is very subtle. I doubt anyone who was not particularly paying very close attention could hear it and maybe not even then. I just found it interesting that there was any difference. Had i not been toggling the modded pedal back and forth, it would not have even occurred to me to toggle the impedance back and forth.

    Ultimately, the a/b of the pedal made far more difference in the sound than the effects of 4 vs 16 ohm.
     
  18. Ginger Beer

    Ginger Beer Senior Member

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    What is the effect of this increased current draw on the perceived sound?
     
  19. hbucker

    hbucker Senior Member

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    Yes, in fact I stated so in my post. :hmm: It's all good.

    Great minds think alike.
     
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  20. JCM900MkIII

    JCM900MkIII Senior Member

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    Nope, I wasn't kidding.
    It is exactly what the manual says. Hence my confusion.
    I should have added my virtual dilemma (probably wouldn't be if I was an electromagician instead of a carpenter)...

    I was wondering if you are running with just half a load, in the case of 4 Ohm setting on the amp, with just 1 speaker/cabinet connected.

    4 Ohm = 4 Ohm (yep)

    In other words, are the outputs ALWAYS in parallel in an unmodded Marshall (2203 even)?
     

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