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2 amps 2 cabs 1 amp 2 cabs

Discussion in 'Amps and Cabs [BG]' started by matzingerz, Sep 11, 2019.

  1. MarkA

    MarkA In the doghouse. Supporting Member

    Sep 26, 2008
    I've never agreed with the idea that taking something plus or minus 3 dB in a mix (live or recorded) is "barely noticeable". Try that with any track in a halfway decent mix in your DAW and you will notice a substantial difference. Even going +/- 1 dB will yield a clearly discernible difference. A few dB, live, can make the difference between feeling relaxed or dynamically frustrated through the night.

    If you have a bad mix (problems other than relative levels) or other, acoustic difficulties, though, turning up often won't help (and you still might not be able to hear yourself or be heard clearly in the audience).
    As for running one or two amps with two cabs yielding more volume or not (re. the OP), I think that's been covered pretty well -- depends on where the bottleneck is. Some amps feel different running at different loads (or running closer to their output limits), so that might be a factor for some.
    ThisBass and HolmeBass like this.
  2. You and another poster have brought up how amps can feel different at different loads. I noticed this most with my Eden going down to 2 Ohms, where it felt “spongy” as the other poster mentioned.

    That Eden also felt really underpowered at 8 Ohms and really great at 4 Ohms. But that was a +6 dB jump as I was adding another 8 Ohm cab to a SS amp, and maybe that’s what felt so good?
  3. Yeah, when mixing very small volume adjustments can have a big effect. The noise level of the other tracks makes slight differences more noticeable.

    Check out the recording on the site with good headphones. They use white noise in their samples.
  4. MarkA

    MarkA In the doghouse. Supporting Member

    Sep 26, 2008
    Hard to say with certainty, as there's rarely one isolated factor at play. If I notice consistent differences in feel when an amp is run, well within its volume capabilities, at different loads (or notice marked differences in how different amps behave when moving from, say, an 8 Ohm to a 4 Ohm load), I'm likely to attribute it, at least in part, to that. If running at 8 Ohms means I'm close to maxing it out and running at 4 means I have some headroom (particularly if adding another cab), then it's hard to say it's just due to running at an 8/4/2.7/2 Ohm load.

    Another factor to consider: Nominal "8 Ohm" (or whatever) speaker loads vary both in their DC resistance and in how the impedance changes with frequency (not to mention all the other ways in which cabs can vary). Some will interact better with some amps than others.

    That said, I believe you about your experience.
    HolmeBass likes this.
  5. Wood and Wire

    Wood and Wire

    Jul 15, 2017

    Yeah, with a recording there are no variables - the exact same performance is repeated perfectly - and you are observing relative differences in level.

    I wouldn't expect everyone to notice a 1dB difference in an isolated white noise signal (even if it were measured as RMS), as it's random noise, with no context.

    Pink noise would be a fairer test for most folk, but even then, headphones aren't the best way to judge (side-presentation) ; near, or midfield monitors in a controlled environment are much more natural (frontal presentation).

    Of course, most of the time we're listening to conversation, or music, in less than perfect environments (rather than random noise, in a control room), but all of the most important information falls in the ears most sensitive frequency range ; and with that type of source most healthy ears should be able to detect a 1dB SPL difference.

    I think maybe here on TB, we ought to ditch talking about Watts, and Decibels, and instead start using the phon.
    HolmeBass and ctmullins like this.
  6. BogeyBass


    Sep 14, 2010
    obviously to make things realistic youd have to understand. To double the effective area of a 8x15 youd need a 16x15
    so anyone that feels 3 dB is no big deal...well uhhh ok, sure no big deal

    Actually very realistic is a 1x10 double that for 3dB would be a 2x10. that is very common. For everyone that quickly found out a 2x10 is not enough.
    They would have to double the area again and find out a 4x10 is just about right. make more sense now.

    likewise if you have run the 8x10 and you doubled that to 2x 8x10 you will quicly realize what a big deal it is.
  7. sowilson


    Jul 5, 2013
    One of the reasons you might want 4 SVT tube heads into 2 cabs is to have more control over your tone. A single SVT head into a cab may result in more grit (distortion) or less headroom than you want. In my younger days I liked a very loud, clean tone which led me away from SVT's and towards PA cabs for my bass (in my day you needed 2x8x10 flat backs per SVT head). Today I would give 2 SVT's into a 8x10 a try as 600 watts of tube goodness would probably get me where I wanted. As a reference I used 2 SWR SM900's into 2 4x10 and 2 2x10 Goliath III cabs and liked that sound.
  8. ThisBass


    Aug 29, 2012
    You'd double the power on just the same cabinetry which would give you a plus of +3dB of loudness.
  9. ThisBass


    Aug 29, 2012
    The OP asks a question for just the same cabinetry.
    If I'd ask a question about the color of gras I don't wan't to read answers about the color of the sky.
    Sorry for off topic.
  10. buldog5151bass

    buldog5151bass Kibble, milkbones, and P Basses. And redheads.

    Oct 22, 2003
    OP was talking about doubling cabs v. doubling amps.
  11. ThisBass


    Aug 29, 2012
    I'm pretty sure your English grammer is way better than mine,
    the bold letters let make me believe he is asking the question for a difference of

    one svt 2 pro powers two 810


    one svt 2 pro powers one 810
    while simultaneously another
    svt 2 pro powers one 810

    so we have got in total

    300 watt versus 600 watt
    the cabinetry is just the same
    the difference will be +3dB for 600 watt total
    Last edited: Sep 18, 2019
  12. ThisBass


    Aug 29, 2012
    Uhm, I don't think its only an industry standard.
    In a rather science consideration we get everywhere +3dB for twice the power.
    RF applications would not work properly anymore in real practice if we would have to be more carefull with the common (and aproved) wisdom that we get +3dB more of signal by doubling the power.
  13. ThisBass


    Aug 29, 2012
    you may be right but, as long as just the same cabinetry is powered within linear limits then a doubling of power will always provide +3dB of loudness.
    We get +3dB of loudness if the cabinetry was powered with 2 watt instead of 1 watt.
    And we will get another +3dB if the cabinetry was powered with 4 watt

    A svt amplifier might push about 80 watt average without generating audible distortion respectively audible artifacts.
    So why the heck should we consider power compression or similar artifacts for about 160 watts (two svt) on a cabinetry (two 810) that can handle in total way more than 1000 watts average.
    ctmullins likes this.
  14. ThisBass


    Aug 29, 2012
    for same cabinetry the considerations are of no concern, that's valid as long as the cabinetry was powered within linear limits.
    I think that two 810 provide plenty of robustness versus two 300 watt svt amplifiers.
    Just the same way as one 810 was robust enough to handle the power of one svt amplifier
  15. ThisBass


    Aug 29, 2012
    Most of the time the benefit is less than +6dB cause the bigger part of SS amplifiers does not double the power on 4 Ohm load versus 8 Ohm load.
    btw, as long as an SS amplifier was played within headroom limits then the amplifier does immediatelly double the output power but, the headroom might NOT be doubled just the same way!
    Last edited: Sep 18, 2019
    MarkA likes this.
  16. ThisBass


    Aug 29, 2012
    just link preamp out of amp 1 to power amp in of amp 2,
    and its all well done.
  17. ThisBass


    Aug 29, 2012
    not neccessarily,
    I wouldn't suggest a pairing like this as a manufacturer but in real practice, as long as you know what kind of signal you feed to your system its even possible to "overload" the system at some content without damage.
    Nope, I don't suggest a general overpowering a bass guitar system too much!
  18. ThisBass


    Aug 29, 2012
    if amplification runs out of juice than smallish +3dB can be a big resorvoir of headroom.
  19. I am pretty sure you are dead right!
    ThisBass likes this.
  20. el murdoque

    el murdoque

    Mar 10, 2013

    This has to be a purely theoretical question/debate.
    an 8x10 cabinet with a 300W tube head should be enough for anything. There is no reason to add another 810 cab, let alone another head. Lugging around two full stacks - you're either playing stadiums and have your bass tech worry about these things or you're doing something fundamentally wrong.

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