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# WHAT'S THE IMPEDANCE OF MY BASS CAB?

Discussion in 'Amps [BG]' started by fernandobicho2, Nov 21, 2012.

1. ### fernandobicho2

Aug 30, 2011
Hello
I've bought a 2006 user SWR GOLIATH III (4x10), but I don't know the impedance. I want to use it with my EDEN WT-600 in bridge mode to have full power and the bridge mode minimum it's 8 Ohm. I don't know if I can use this cab or not..

Some people say we must multiply the multimeter result by 1,3 factor to know the impedance correct.
I did some measurements but I still don't know:

GOLIATH 4X10 = 4,3 ohm (if multiply by 1,3 = 5,59)

EACH DRIVER FROM GOLIATH 4X10 = 4,4 (x 1,3 = 5,72)

AN AGUILAR 12'' 8 OHM CAB = 6,4 (x 1,3 = 8,32)

A GAUSS DRIVER 8 OHM = 5 (x 1,3 = 6,5)

A 8 OHM DRIVER = 7,2 (x 1,3 = 9,36)

A 4 OHM DRIVER = 3,2 (x 1,3 = 4,16)

So, the question is: MY GOLIATH 4X10 IT's 4 Ohm or 8 Ohm?

Someone can help? Thank you in advance

2. ### lethargytartare

Sep 7, 2004
Chicago
I'm going to venture that it's 4ohm -- if it advertised itself as an 8ohm cab and was actually 4-5 ohms, people's amps would be getting destroyed.

And I'd say for sure -- if the amp says it's only rated for an 8ohm cab in bridged mode, do not play it through a cab that your meter is showing as 4.3ohms (even at 5.5ohms).

Got a serial number? Maybe there's a clue on the back panel. Worst case -- you could take it apart and check the individual drivers and the wiring...

Good luck!
ltt

May 25, 2011

Sep 7, 2004
Chicago
6. ### fernandobicho2

Aug 30, 2011
EACH DRIVER FROM GOLIATH 4X10 = 4,4 (x 1,3 = 5,72)

and yes, it has a serial number. I'll check it.

thank you

7. ### ThisBass

Aug 29, 2012
Germany
Emiminence Deltalite II 2510/2512

Re: 5 Ohm

* 1.3

= 6.5 Ohm

?????

So do that mean the Emminence enigineers are stupid people?

8. ### LowEZSupporting Member

Mar 29, 2011
Central NJ
Did you measure the individual drivers while they were completely disconnected from the wiring? It doesn't make sense because your measurements of other drivers and cabs appears proper. 4.4 ohm DCR I have never seen.

Aug 29, 2012
Germany
He told:

10. ### ThisBass

Aug 29, 2012
Germany
or even the "calculated" 6.5 Ohm for the Emminence Deltalite ...

11. ### lethargytartare

Sep 7, 2004
Chicago
So, if each driver is measuring 4.4, then they're 4ohm drivers.

With 4 x 4ohm drivers, you can't get an 8ohm total impedance:

4 in parallel = 1ohm
pairs in series = 8ohms each, in parallel = 4ohms total
all in series = 16ohms

But the core issue for you is simple: your amp is only rated to play in bridged mode through an 8ohm cab -- you definitely don't have that, so don't do it

May 25, 2011
13. ### ThisBass

Aug 29, 2012
Germany
What's about the 5 Ohm like the Emminence Deltalite?
These are then 4 Ohm or probably 6 Ohm Drivers?

so that means the Emminence Deltalite are garbage,
because of you can do nothing with 6 Ohm ...

So hope for yourself you'll never play Emminence Drivers ...

14. ### Bmorefoozler

Oct 9, 2009
Baltimore, MD
DC resistanse does not equal impedance. The correction factor listed *1.3 is simply a "guide". From what I've read, 4 ohm drivers generally read down below 4 ohms in DC resistance. Most of these speakers listed are likely nominal 8 ohm drivers.

15. ### Downunderwonder

Aug 26, 2009
New Zealand
The extra bridge power isn't necessary to get good volume out of that cab. A 300W amp is plenty powerful enough to stress it even if it was 8 ohms.

16. ### Jaco who?

May 20, 2008
I tend to agree with lethargytartare, but I'll add a few things to try -

Most dvms except maybe the cheapest most worthless models will have a way to "zero" the reading you get so that the resistance reading at that low of a value is eliminating the test leads from mucking up the reading. Usually you touch the leads together and push a button somewhere on the unit (zero, or calibrate) until the reading is zero.

http://www.colomar.com/Shavano/4x12wiring.html

You might be able to discern the wiring of your cab - (parallel, or series parallel) by tracing the wires to see if it matches any of the diagrams. Some cabs are wired pretty neatly, some can be a rats nest. Hope this helps.

17. ### NYCbassistSupporting Member

Sorry, I had to go back to school on this subject.

18. ### lethargytartare

Sep 7, 2004
Chicago
Agreed -- I assumed he did something similar to get the "overall" value he listed as

"GOLIATH 4X10 = 4,3 ohm"

19. ### noetical1

you can measure the impedance value yourself with a multimeter: plug a speaker cable into your cab, and measure impedance with positive and negative probes of your multimeter... oh wait...look! someone else already recommended this path...sorry for the repeat... good luck!

20. ### lethargytartare

Sep 7, 2004
Chicago
You're right -- and so are the mad rantings of ThisBass -- I got my 8ohm Deltalite IIs out and they have a DCR of 5ohms.

So back to the OP...personally, I'd still feel better if I had a clear confirmation that the cab was rated 8ohms -- probably IS, but before I risked my amp, I'd be over-cautious.

And as someone else noted -- you probably don't NEED to run bridged to be enough volume out of that setup, but I wouldn't presume to tell you what you need for your application.

Continued good luck!
ltt

21. ### Bassmec

May 9, 2008
Ipswich UK
Disclosures:
Proprietor Springvale Studios
Look if it reads > 4 OHMS DCR on a cheap meter Its an 8 ohm nominal Impedance cab.
Here is an expensive DCR meter measuring an expensive eight ohm driver.

Most hobbyist DCR meters are highly inaccurate especially at the low end of the range.