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Is a 4-ohm cabinet 'Quicker' than 8 ???

Discussion in 'Amps and Cabs [BG]' started by Zapp, Nov 28, 2006.


  1. Zapp

    Zapp

    Sep 4, 2005
    Gruene Texas
    Gang
    don't claim to be an EE!
    pls explain. ... I'm wondering if I can over-stretch my ancient SWR WM 12 with an extension at 4-ohm instead of the common 8 ohm???? I have read in the past that the secret to "punch" is the power supply... how fast it can shoot a peak load then relent, then another. If 4-ohm presents less resistance, all other things being equal [i know.... this is theory], isn't a 4-ohm cab going to respond more quickly than an 8-ohm ?

    also, if you happen to know the answer: is the default/stock 12" inside the WM 12 cab a 4-ohm or 8-ohm?

    thx, and DON'T laugh me outta here :bag:
     
  2. AFAIK 4 ohm cab & 8 ohm & 2 ohm cabs are all the same as far as speed of reproducing the sounds. I dunno the impedance of yr combo, but You'd wanna find out if it was safe to plug in an extra spkr cab B4 doing so-so U don't possibly wreck yr transformer! If U can get into yr cab, U can measure yr impedance(ohms) by using a simple multi meter,volt-meter, Power can be off (safest??) & put one of the probes on the +ive & one on -ive- on the ohms setting-should tell U the impedance- likewise for the lead that plugs in the speaker!---ps I aint no E.E. eeeiiither!!!
     
  3. Jazzdogg

    Jazzdogg Less barking, more wagging!

    Jul 29, 2006
    San Diego, CA
    I seem to recall having read (here at TalkBass?) that, all other variables being equal, the loudspeaker with the higher impedance *should* be better damped. All other variables being equal, a well-damped speaker should sound "quicker" (have more tightly-controlled cone excursions).

    But what the heck do I know? I'm just an old bass player, not an electrical engineer.

    Hopefully, Bill FitzMaurice will chime in and share his abundant knowledge with us.
     
  4. Pickebass

    Pickebass Supporting Member

    Jul 12, 2004
    San Antonio, TX
    If this is an original WM12, you will get 20 more watts with a 4ohm speaker vs. an 8ohm speaker. The stock speaker is 8ohm.
     
  5. JGR

    JGR The "G" is for Gustav Supporting Member Commercial User

    Jun 29, 2006
    Maryland
    President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
    as a sort of side note, speakers wired in parallel vs. series will appear "quicker" or "tighter" than those in any sort of series arangement.

    when speakers are in parallel, the amp can "see" all of the speakers for lack of a better term, which allows for better control of damping. parallel is "looser" sounding.

    one of the secrets to the classic 810 design, in addition to separate compartments and a sealed design, is that all speakers are wired in parallel (8 32 ohm speakers) which help to give the cab such a tight, focused sound.

    JR
     
  6. Johnny Crab

    Johnny Crab ACME,QSC,Fame/Hondo/Greco/HELIX user & BOSE Abuser Gold Supporting Member

    Feb 11, 2004
    South Texas
    Neither is quicker as them dern electrons fall out the wire just as fast for both.

    If you don't "neglect" the "neglectibles"(i.e. voice coil inductance, magnet strength, cable capacitance, etc)...then I gotta dust off books I haven't looked at in 16 or so years. Most likely after scribbling, scratching, playing with equations for a few pages to solve for time(as in response time)....probably find it very minute if there is any difference at all. Next time by that 10 foot bookcase, I'll try to remember to pull the acoustics text, electromagnetics text, and whatever else looks needed to "prove" anything about this.

    Got the EE paper in 1989. Shame on Tulane for closing down electrical and civil programs. Ain't no biomedical engineers gonna fix THOSE levee fiascos(lived there from 1959~1989) or rework the electrical and telecomm systems.....

    This is probably the manual you need:
    http://www.swrsound.com/support/manuals/pdfs/wm10_12_15_om.PDF
    on page 8 it indicates that the internal speaker is 8 ohms and power out is 160 Watts RMS @ 4 ohms. Then it says the MINIMUM impedance of the extension speaker is 8 ohms....SO when you plug another cabinet in the internal jack wiring makes it parallel to the internal speaker. It might fry if you plugged a 4 in(plus the sound would be WAY unbalanced) as the impedance the amp sees would be about 2.67 ohms(YIKES!!).

    Here's some help: http://www.bcae1.com/spkrmlti.htm
     
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Maybe, the problem is one of semantics, as 'quick' and 'tight' are not technical definitions, so what they mean is up to each individual. In technical terms series wired drivers have a higher inductance than parallel wired, so they will roll off response at a lower frequency.
     
  8. Zapp

    Zapp

    Sep 4, 2005
    Gruene Texas
    Yes, in my case I was presuming on the question. I assumed that some speakers, especially if a long 'throw' would be slower than others. Then I assumed that what comes across as a jab, a punch, had something to do with the electrical specs.

    I guess what you guys are saying is that the Ohm-rating of either a driver or an extension cab is the least concern in trying to get a more solid punch out of the rig. Is that right?

    What about wattage ratings on cabs? If a cab is rated at 200w, I assume that is conservative, as they will surely allow for peaks that are considerably higher. But the question is: would a cabinet rated for 200w necessarily be any more responsive than a cab rated for say 500w. I'm talking about a 12" single or maybe a 210, nothing big and gnasty. I'm trying to narrow down what to look at and trial, in my quest to get rid of some of the "whooosh" on the low end and get a much tighter low.
     
  9. Jazzdogg

    Jazzdogg Less barking, more wagging!

    Jul 29, 2006
    San Diego, CA
    Am I misunderstanding you, or did you mean to say speakers wired in series sound "looser?"
     
  10. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    A cone must move at the precise speed in Hz as the signal applied to it. If it did anythng else the note you got out of it would be different than the one you put in. That doesn't occur with fundamentals, but it can occur with harmonics, and is one source of harmonic distortion.
    Impedance does not define tone, only the load the driver/speaker places on the amp.
    The power rating is what the manufacturer expects that the driver/speaker will handle without damage. That's all.
     
  11. RyreInc

    RyreInc

    May 11, 2006
    Kalamazoo, MI
    Um, where did you hear this?? I'm pretty sure 810s and 410s are wired in series/parallel configs, i.e. wire up, in parallel, 4 sets of 2 speakers each in series with each other. This would give, for 8ohm speakers, 16ohms per 2-speaker set, and 4 sets of these in parallel gives 4 ohms output.

    I've never seen 32 ohm speakers, that's for sure!
     
  12. My old svt-410he's had 32 ohm speakers, that's for sure. :)
     
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Ampeg uses 32 ohm drivers. The original SVT driver was probably the same driver earlier used by Fender in some production runs of the Super Reverb.

    However, just as four 8 ohm drivers in series will have more inductance than one, a 32 ohm voice coil will have a higher inductance than an 8 ohm coil with otherwise similar specs.
     
  14. JGR

    JGR The "G" is for Gustav Supporting Member Commercial User

    Jun 29, 2006
    Maryland
    President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
    good catch, gets confusing going back and forth.... :meh:

    yup, series wired seem to sound looser, parallel tighter...


    in addition to the ampeg 8x10, GK's 8x10 uses 32 ohm drivers... pretty sure the Bergantino 6x10 used 24 ohm drivers for the same effect...

    JR
     
  15. jondog

    jondog

    Mar 14, 2002
    NYC metro area
    Asking EE questions is good for learning, but in practical terms I think all you really need to know is "What 8 ohm cab will sound _________ with my SWR combo?" Tell us what style of music you play and list some tunes we know with tones you like and we can make some recommendations. Also, talking is fun but I'd recommend just bringing your gear to a big store and trying every 8 ohm cab until you find one you like!
     
  16. RyreInc

    RyreInc

    May 11, 2006
    Kalamazoo, MI
    re: 32ohm speaker

    I stand corrected!

    Are these speakers common though, or is what I previously described more common?
     
  17. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I don't buy any of this. :spit:

    What am I missing here? :confused:

    Series vs parallel: If you wire two identical drivers in series, symmetry dictates that each driver sees exactly half of the input voltage, across the entire frequency band. Therefore, neither frequency nor transient response will be affected.

    4 Ohms vs 8 Ohms: If "all things being equal" means that two drivers have the same frequency response curve, then they must also have the same transient / group delay curve.

    If two speakers sound different, look at the relative frequency response curves, both on- and off-axis. Also, make sure they are driven to the same SPL, otherwise your brain will pick the louder system.

    The problem arises from looking at a single parameter, when multiple parameters are changing. For instance when you wire two drivers in series, the inductance doubles, but so does the series resistance, total cone mass, BL product, mechanical resistance, and so forth. In the case of 4 vs 8 Ohms, the DC resistance is not the only thing that changes if you want the two versions of the driver to produce the same ultimate frequency response curve. You have to consider the total system.

    Once in a while, the "speed" of speakers comes up as an issue, but I think what we are really hearing is differences in frequency response or off-axis response.
     
  18. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    In this case the answer is deceivingly simple. Inductance in and of itself affects tone, the other parameters do not.
     
  19. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Any parameter that affects frequency response affects tone.
     
  20. Kael

    Kael

    Dec 26, 2004
    Oklahoma City
    I was intrigued enough by this to perform the following scientific experiment.

    I took two cabs, one 8 ohm and the other 4, and set them side by side. Then I yelled GO as loud as I could. I'll be damned if neither one moved quicker than the other....

    This is all a bit overkill on the picky front. Get the cab/combination that sounds the best and go with it. If it floats your boat, then get cabs that max the power output of your amp. Although, I'm getting to the point where I think that even that is silly.
     

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