Different ohm tap, different sound?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by BenBo, Jul 28, 2008.

  1. BenBo

    BenBo Member

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    Will using the 8 ohm tap with an 8 ohm speaker sound different than using the 16 ohm tap with a 16 ohm speaker of the same make/model?
     
  2. Dexter.Sinister

    Dexter.Sinister Still breathing Gold Supporting Member

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    Depends on how OT is wound. If full winding used, not as much. If winding tapped, yes.

    IME.

    DS
     
  3. BenBo

    BenBo Member

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    I'm not sure what you mean. How can I tell?
     
  4. Dexter.Sinister

    Dexter.Sinister Still breathing Gold Supporting Member

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    The Output Impedance will depend on how many turns of wire are in there and on how thick the gauge of the wire is. When there are more turns, there is better coupling, but also more impednace. To have equal turns and different impedance, you need different wire. Most companies tap a single wind at differnt points for different impedance. For these OTs, the 16 ohm wind has more turns than a 8 ohm tap which has more turns than a 4 ohm tap. Under these conditions, to me, the 16 ohm tap sounds better than 8 and 8 better than 4. When the wind number is the same but the impedance is altered another way, like different wore gauge or type, then these differences are less noticible.

    Me...I try to stick with highest impedance. There are other reasons for this, too, but it late, I'm busy...you know...

    If in doubt, ask the manufacturer.

    Good night!

    DS
     
  5. SatelliteAmps

    SatelliteAmps Member

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    No, there won't be a major noticeable difference. There are people that claim that using the full windings affects what they hear, and for the most part, that is incorrect. I've never found anyone who could tell the difference in a blind test.

    There will be a difference if you are talking about multiple speaker setups, but that is more about how the speakers are wired together.
     
  6. pgissi

    pgissi Member

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    To slightly disagree and offer my opinion as to why, on some amps there is a difference and by some amps I mean amps of differing design, cleaner versus more dirty, non master versus non master amps, its not as apparent on certain amps especially with cleaner tones. Using an impedance mismatch reduces power which means, you may be more apt to run the amp harder which can get the amp where you normally would not take it. The nature of tube amps is somewhat dynamic and the amps response is altered with output since the nature of a tube amp is to be so some degree non linear, the response curve is not fixed through the power band. Running them harder can compress the tone more, maybe smooth the highs, this in itself can be a way to alter the tone.

    The imp mismatch I am talking about is a 100% mismatch using a speaker load that is higher than the OT tap, not lower, never more than 100%, and certain amps I just dont do it.

    For example, I use an impedance mismatch on my little Rivera R30 which is a stock 8 ohm output, I use a 16ohm cab with 2 speakers wired in series and there is a difference and I do agree that the series speaker wiring is probably the greatest influence in tonal alteration there but since I am throwing away some power, I run the master higher, getting more power tube into the tone.

    The highs are not as fizzy this way which was exactly what I was looking for but at the same time are thicker. Overall the amp is browner and there is slightly more compression albeit with less headroom and the response of the amp seems flatter, more balanced across the power band.

    At 8ohms the amp was ok, but at 16ohms its inspiring because it became tonally richer with more harmonic overtones.

    But once again, you wont hear/or will hear minimal difference on clean tones with mismatches especially on high power amps since when the tone is clean, the amp is working within its linear range. Pushing it harder of course takes it to non linear terrirtory and that where imp mismatches can provides something different, even on high power amps but the more power, the more heat is generated with the mismatch and this comes with increased risk.

    Doing a mismtach on a 30watt to maybe max 40 or 50watt amp (not on a marshall) is probably the limit. I would not do it on a anything more powerful especially a 100watt amp, could fry the OT if the higher relfected imp spike doesn't do it in.

    But here is another example of a mismatch and some tonal changes, I accidentaly ran a 200% mismatch on my 93 marshall slx 100watt many years ago and for some time with the amp set for 16ohms, I was using a 4 ohm cab for some months, duh :jo! The OT tolerated and survived but the amp ate the Bridge Rectifier, singed the board and killed the power tranny which I repaired.

    Now I run the amp with the proper 16ohm load and the tone is creamy, the response is dynamic where as before, the amp lacked punch and dynamics, sounded like an overgrown op-amp based od box that does not clean up, which is uncharacteristic for this all tube tone path (except the op-amp fx loop and dual master stages) of an amp that goes to 20.

    Once again this tonal difference is only really apparent for OD aka non linear tones.


    I follow this when it comes to marshalls, the nature of their tone seems to prefer the higher impedance.
     
  7. pgissi

    pgissi Member

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    You mean series versus parallel speaker wiring, correct?

    Absolutley. Series wiring has increased mutual branch inductance due to the output from the OT having to pass through more than one voice coil in a series manner.

    Using this aspect along impedance matching or mismatching can be useful tweaks and can transform an amp from lacking that certain something to finding it.

    I agree with the Fender Marshall example, Marshall more OD in general, especially pre-amp derived, likes high impedance

    Fender BF, less OD, especially pre-amp derived type but rather more power tube seems to be complemented by lower imps.

    But that is a simplistic explanation and it should not be correlated as pre-amp od/high imps and power amp od/lower imps better since its not accounting for other factors that differ in these amps designs which would be more relavent to why this is.
     
  8. SatelliteAmps

    SatelliteAmps Member

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    pgissi: Impedance mismatches are a whole different issue, and will affect tone.

    A lot of people claim differences in the speaker ohms that is matched to the transformer, without really testing it. The way that Fender and Marshall each wired their cabinets is very different. If you try this out with all things being equal, and the exact same speaker with only a different ohm rating, and a transformer that has taps for both ohm ratings, you will not be able to significantly tell a difference. Try it with all things being equal.
     
  9. pgissi

    pgissi Member

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    I see what you are saying and duh on my part, the OP is saying just that, sorry the coffee was weak this morn.

    The street theory if you will is rooted in the commonly held belief that using the 16ohm tap is using all of the OT windings hence max efficiency/coupling occurs while disregarding the theory that states that max efficiency occurs as long as the OT secondary matches the load, whether its 4, 8 or 16.

    But that is about efficiency and your point was that there is no tonal difference. If we express efficiency as being the same in an 8 to 8 or 16 to 16 ohm coupling we express it as a ratio with the same value but that disregards additional the tonal effects on ac currents in higher impedance couplings, at least that my theory.

    I am leaning toward your argument to some degree that the difference could not be audibly differentiated in a blind test and by that I mean 2 participants, 1 playing and 1 switching settings with the player unaware of the setting, but this occurring at practice or slightly louder volume, so I would totally agree there.

    But I do have some suspicion the differences would be more apparent at live stage levels, how apparent is the question and its probably been done but at higher outputs where core saturation takes place my gut says the tonal difference should be apparent and maybe less as tone but say more as sensitivity or the way it feels if you will.

    I am in the high imp=smoother highs camp for high gain tones though, my ears hear it that way.

    Technically it should not be so though (no tonal difference) so your point is solid and I will regard the street theory as just that until it could be proven to where its audbile while allowing that voice in my head thats says coupling a signal to a speaker at 8ohms should sound different than 16ohms.

    And of course all things need to be equal, same amp, cab and speakers, just of 2 different impedances for this testing.

    But once again, using differenty impedances that are matched is simply preserving the ratio that delivers the same amunt of coupling expressed as efficiency disregarding all that extra wire in those additional windings to obtain the higher imp output and as you know, that means increased inductance but imo is only audibly apparent at higher levels.

    But the OP should know its probably the least dramatic change if a change at all (same speaker, different ohms making sure the OT Sec imp is matched to the other speaker).
     
  10. Dexter.Sinister

    Dexter.Sinister Still breathing Gold Supporting Member

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    Agreed. And more so in "Marshall" than in "Fender", but still, yes.

    And I have done experiment with different winds. Seemed pretty obvious to me and clients at time. So I go with what my experience showed and others can go with what their experience show or thoughts rationalize.

    DS
     
  11. rockon1

    rockon1 Member

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    This must be the case with my Supersonic and Peavey Ultra. Both these amps sound progressivly duller/darker when the 8 or 4 ohm tap is used(with the coresponding loads). They sound brightest/liveliest with a 16 load on the 16 ohm tap. Much prefer them both with a 16 ohm load on 16 ohm tap. Bob
     
  12. pgissi

    pgissi Member

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    Its strange isnt it, it defys conventional theory, but other than mathematical calcs when have tubes been about convention. When run clean they are theoretically capable of being eniac, can run logic so to speak since the linearity is predictable but when run into the non linear, that all breaks down.

    It was my confirmation of the same for my marshall, lower imps were darker and seemed to be less responsive and at the time I thought coupling is coupling as long as its matched for max efficiency and energy transfer. I blamed the amp for not being able to jump out of the mix and feeling as if it was ignoring my input. I soon realized I was applying the wrong treatment for my amp and that 16ohms would be the cure and it was a dramatic difference with the same speakers. I had 4 16 ohm G12M70's at that point and had wired them first for 4 then 16.

    Why I went for 4 ohms at the time I dont remember, was feeling adventurous but after a few shows I was ready to dump the amp but stopped myself and did 16ohms and there it was.

    But the key for me is the tone used for comparison, if its a clean tone, it was not as noticeable since the tubes/ot and speakers are not being driven hard at all.

    Piling on gain at both loads though revealed the difference with this marshall.
     
  13. rockon1

    rockon1 Member

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    I live on my dirty channels. Couldnt even tell you if the difference was as noticable on the clean channels of my amps. Its definately noticable on the dirty channels though! Bob
     
  14. SatelliteAmps

    SatelliteAmps Member

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    People that are comparing 4, 8 and 16 ohm multiple speaker cabinets are not taking into account the wiring differences of the cabinets. Those sound qualities are all indicative of differences in wiring styles.

    Wiring four speakers to get 4 ohms or to get 16 ohms will result in a different tonal quality, because of how they are wired. That is different than what is being discussed as it isn't everything being equal. Parallel, series, and parallel/series (or series/parallel) are all differences that add to the tonal qualities.

    The only way to find the answer is to use exactly the same wiring setup, with the same amp, same transformer, with the only difference being the speaker impedance, which has to be matched to the amplifier. Even running different cabinets affects the sound.
     
  15. pgissi

    pgissi Member

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    Agreed, so the best test is just comparing 1 speaker at a time of different value. Thats something I can do on my Rivera 1x12 combo since I have some model speakers in both 16 and 8 ohms although I have run it as a combo with at both 8 and 16 but using different speakers in the past
     
  16. rockon1

    rockon1 Member

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    This I have done. The Ultra is a 112 combo. Along the way Ive tried both 8 and 16 ohm versions of the same speakers in it.The 16 ohms models always sound better- brighter(in a good way). I cant say Ive done the same with the Supersonic but I know it reacts the same way with a 2x12 wired for either 4 or 16 ohms. Bob
     
  17. SatelliteAmps

    SatelliteAmps Member

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    This is my point. You can't compare a 2x12 wired for 4 or 16 ohms as a comparison for this because they have to be wired differently, an that will affect the sound. So it won't react the same way with two differently wired cabinets.
     
  18. rockon1

    rockon1 Member

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    I understood your point. Series vs parallel does affect it but not to the extent Im talking about. At any rate the difference is obvious when using a single speaker which Ive done on the Ultra. I would be willing to bet money the Supersonic will react exactly the same way if I took the time to try 16 and 8 ohm versions in one of my 1x12 cabs. I wish these two amps didnt react this way though. It limits my options. Bob
     
  19. SatelliteAmps

    SatelliteAmps Member

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    It will affect it to the extent you are talking about though.
     
  20. hasserl

    hasserl Member

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    Blind tests?!?!?! We don't need no stinkin blind tests.

    What would we do with all our prejudices? What about all our favorite mustard or orange caps? What about our favorite popular brands of transformers? What if we couldn't actually hear a difference? Worlds would collide, we'd have to completely change our way of thinking. No thanks! :hide :) :banana
     

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