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How is this 4 ohms ?

Discussion in 'Amps and Cabs [BG]' started by david_l_perry, May 28, 2004.

  1. I have an SWR goliath senior 6x10 rated at 1000w 4ohm
    Do the PAS drivers that come with the SWR have an odd rating

    I cant understand how 6 x 8ohm ( or 6x4ohm) drivers can be connected to make a single enclosure rated at 4ohms. :meh:

    I need to replace a couple of the drivers and am struggling to find the rating.

    The driver is labled as BG-1080-C8
    I assumed the C8 refered to 8 ohm drivers ?

    I have tried PAS and got nowhere fast.

    Can anybody give me any ideas

  2. Hurley


    Feb 12, 2004
    Cape Cod, MA
    Try looking in this thread. The Ampeg 6x10 is 4 Ohms as well.

    Here's an excerpt: (I hope BillyB doesn't mind :bag: )
    I don't know for sure what SWR uses, but that would make sense.
    I hope this helps. :)

  3. Cheers Hurley
    That would make perfect sense, but can anybody else confirm if the SWR/PAS Drivers are 6ohms..no sign of a number 6 on the speaker (the sticker on the driver says BG-1080-C8)...so not totally convinced yet..its got to be right..cant understand why PAS couldnt tell me
  4. Petebass


    Dec 22, 2002
    QLD Australia
    Most 6x10's use 8 ohm drivers for a nominal impedance of 5.4 Ohms. Most technical people tell you to treat it as though it's a 4 ohms cab. They've probably labeled it a 4 ohms to give people a hand working out how to configure their rigs.

    Have you got access to a multimeter. If so, measure the DC resistance of one of he speakers. An 8 ohm speaker will show a DC restiance of about 5 or 6 ohms. A 4 ohm speaker will show roughly 3 ohms.

    I've never seen a 6 ohm speaker. I'm sure they exist but I've never seen one.
  5. Funky Doctor

    Funky Doctor

    Aug 28, 2003
    I had this wierd idea that it went like this...

    2 speakers at 4 ohms in parallel = 8 ohms
    4 speakers at 8 or 32 ohms each in whatever configuration it takes to get 8 ohms.

    Put the 2 in parallel and you magically get 4 ohms. The 2 4 ohm speakers would no doubt be rated a tad higher.

    I don't know if this is how it's done, but it is the way I would do it.
  6. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    No, no this is way wrong!

    Wiring series:


    R = R1 + R2 + R3 + ...
    for example: 8 Ohm + 8 Ohm in series = 16 Ohm



    1/R = 1/R1 + 1/R2 + 1/R3 + ...
    For example: 8 Ohm + 8 Ohm in parallel = 4 Ohm

    This is the way of properly counting impedances
  7. OrionManMatt


    Feb 17, 2004
    You also have to factor in whether or not the speakers have single or dual voice coils. If they are dual 8's, that would result in a series/parallel connection of 4 ohms. From looking at their transducer.pdf it seems like they use 8 ohm configurations so the possibility is there but the likelihood doesn't seem to be.

    SVC options:

    Series wire 3 pairs, then parallel the pairs = 5.333 Ohm
    Or, probably the more sane thing to do would be to series two pairs and then parallel the rest for 2.67 Ohms.

    Here is a good link for stuff like this:


    I'll run some numbers later.
  8. Just had confirmation from PAS

    >The BG-1080C-8 is an 8 ohm speaker rated at 200 watts.
    > Allan Sohl
    > PAS Engineer

    So that puts the cab at either 5.33 or 2.66 ohms and 1200w

    Cheers guys

    But hold on a second....if the cab is rated at 2.66ohms, is that not way to low for my amps minimum rating of 4ohms mono bridged ?

    It would explain why the amp gets so damm hot...!

    Think I had better check the wiring out a bit closer...
    Cheers for all the input, Dave
  9. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    5.33 is likely. They would have blown out too many amps the other way. Probably your amp gets hot 'cause it's being driven hard. :)
  10. Can I check the cabs overall impedence with a simple multimeter ?
  11. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Yes. Generally the DC resistance will be around 70-80% of the nominal impedance. I'd guess if you used an ohm meter you'd measure right around 4 ohms. If you measure under 2 ohms then I'm totally wrong and you're very lucky to still have a working amp. :)
  12. I checked out the cab wiring last night.

    Three pairs of 8ohm drivers wired in series and then the three pairs connected in parrallel

    Net result is a 5.33ohm cab rated at 1200w

    Why SWR list it as 4ohm 1000w is beyond me.

    Anyway, I have just sent off one of the drivers for analysis to a speaker specialist in London after the paper cone falling apart for a second time in my 18month old cab....remeber the last time petebass...SWR replaced all 6 drivers as they said it was clearly a manufacturing defect in batch control...can one man be this unlucky for it to happen again... :crying:

    The amp is never clipped, the lows are never boosted, the speakers always blow...some things remain constant. One of them is that my peavey back up cabs never break ;)

    Cheer for all the input chaps
  13. Funky Doctor

    Funky Doctor

    Aug 28, 2003

    Hmmm. Something tells me you cannot get 4 or 8 ohms out 6 8 ohm speakers, no matter which way you hook them. What I was getting at was hooking it all up so you had the equivalent of a 2x10 and a 4x10 stack. But yeah, 5.33 ohms it is...
  14. Petebass


    Dec 22, 2002
    QLD Australia
    Is this the same cab but with "new" speakers? Oh man, something's not right here. And you seem to know what causes speakers to blow so I doubt it's you.

    I think SWR replaced those initial faulty 6 drivers with another driver from the same darn batch.
  15. HI Pete
    Yep same cab...exactly the same visable fault...
    SWR replaced ALL of the drivers 13 months ago, just before Fender bought them out.

    I have sent one of the drivers down to an indipendant specialist in London to be checked out.

    I am pretty sure it is not overexcursion through user error (ie bad eq / clipping)...but will await the full diagnosis from the speaker pro...

    I want to know if it points toward fualty materials agian..possibly the same batch of dodgy PAS cones...if SWR knew the buy out was coming then I suppose new stock purchase may have stopped..but I am eager to hear from the speaker guy....before I have the drivers reconed / replaced I need to get to the bottom of the cause.

    Cheers Pete, will keep you informed

    PS My sister emigrated to Oz last year...maybee you know her, dark hair, small place Oz isnt it mate :D
  16. Petebass


    Dec 22, 2002
    QLD Australia
    I think I do know her. Has she got 2 legs? :)

    Definitely keep us posted on these speakers. I'm ver curious.
  17. OrionManMatt


    Feb 17, 2004
    What is easier to say:

    4 ohm @ 1000w


    5.33 ohm @ 1000w

    If each speaker is rated at 200w, feeding them at at a true 4 ohms would result in overpowering the speakers. Since they are seeing a 5.33 final load, they should be receiving enough wattage without overpowering them.

    Perhaps the voice coils were crap. ::shrugs::

    That is so, so unfortunate, man. So to hear that. All the best.
  18. 5.3 ohms @ 1200w sounds better than 1000w at 4ohms to me.....but more importantly its correct..
    It would stop fools starting threads like this asking dumb ass questions about ohms :D (I am that fool :p )
  19. OK Pete Here we go....
    I have just talked to the tech at Wembley Speakers in London (Wembley Speakers have been repairing and building speakers for 37years and came highly recommended) who was checking out one of the SWR drivers..This is what they say..at last the explanation I have been waiting for !!

    "The driver has failed due to a build up of air pressure behind the dust cap. This has occured due to the wrong type of material being used for the dust cover itself. Most speakers have vents in the magnet assembly (the little hole at the back of the speaker) which allows the air to escape when the speaker is moving in and out. The SWR drivers are solid cast magnet assemblies and should be fitted with linen dust caps which look identical, but allow the air to esacpe as the linen is porous. As the driver is working hard, the air pressure has simply popped the dust cap off the driver cone as the air has knowhere to go."

    I am having the dust cones replaced at a cost of about £10 per driver with Porous cones which should sort it out.

    Apparently they have repaired many drivers with the same fault.

    So goes a long way to explain the damage....

    Cheers, Dave
  20. Petebass


    Dec 22, 2002
    QLD Australia
    That's interesting. I find it strange that a company as big as PAS or SWR would allow that to happen. And to be honest, I can't see this defect doing any more than popping off the dust cap. The first lot of speakers had torn cones didn't they?