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Mismatched Ohms Question

E

eno50

Jan 31, 2009
566
23
North of Memphis
#1
Hello fellow players, I have a question about mixing two cabs with different ohms . I have several different cabs that I'am trying out with my new Carvin B-1500, as you all know the b-1500 can go down to 2 ohms,so I was hooking up two 15 " cabs ,one is 4 ohms and the other is an 8 ohm cab,now that would bring the total load to 6 ohms right? But would one cab sound louder than the other? It seem so to me.
Most of the time your hooking up two cabs there the same ohms ,for me anyways but since I got the carvin with 2 ohm capabilty,i'am experimenting different combinations with the cabs I have and I seem to notice a volume difference.
I guess I need the 101 on Ohms law...
Eno
 
#4
....And from your Carvin B1500 manual; you DID read it, right? ......

"SPEAKER COMBINATIONS and OHMS (Ω):

Four x 8Ω cabinets = 2Ω (OK)
Three x 8Ω = 2.66Ω (OK)
Two x 8Ω = 4Ω (OK)
Two x 4Ω = 2Ω (OK)
One 8Ω and One 4Ω cabinet = 2.66Ω (OK)
Two 8Ω and One 4Ω = 2Ω (OK)
One 2.66Ω and One 8Ω = 2Ω (OK)
Two x 2Ω = 1Ω (no)
Three x 4Ω = 1.33Ω (no)
Two x 4Ω and One 8Ω = 1.6Ω (no)"


Regards,

Mike
 
#10
as long as you know what you are doing...whenever someone says mismatched ohms the hair on my neck stands up. Alot people think "hey know big deal!" and do it without any research into it. Ive had several friends with dead equipment. I should have know the talkbassers would be eduMUHcated though! it always best to match IMHO.
 
#17
brian nec said:
wire it in parallel? forgive my ignorance....
Click to expand...

Let's look at simple examples:

If it is a single driver cab - only choice is to change drivers


If it is a 2 speaker cab, to have a 4 ohm cab means there are 2 speakers wired in either series or parallel.

For a 2 speaker cab wired in series to be able to total a 4 ohm load, that would mean you have to using two 2 ohm speakers (which is very rare). If you take those rare 2 ohm speakers, and now change the wiring to parallel, you would have a 1 ohm cab.

Now lets say our 4 ohm cab is a cab that contains two 8 ohm speakers wiring in parallel (most common configuration). Changing the wiring in this cab to series would result in a 16 ohm cab.

When dealing with cabs that have 4 or more speakers, they are wired in combinations of series and parallel.

The same results apply. Therefore, you cannot go from 4 to 8 (and vice versa) by changing the wiring configuration.
 
#18
Bass_Pounder said:
Let's look at simple examples:

If it is a single driver cab - only choice is to change drivers


If it is a 2 speaker cab, to have a 4 ohm cab means there are 2 speakers wired in either series or parallel.

For a 2 speaker cab wired in series to be able to total a 4 ohm load, that would mean you have to using two 2 ohm speakers (which is very rare). If you take those rare 2 ohm speakers, and now change the wiring to parallel, you would have a 1 ohm cab.

Now lets say our 4 ohm cab is a cab that contains two 8 ohm speakers wiring in parallel (most common configuration). Changing the wiring in this cab to series would result in a 16 ohm cab.

When dealing with cabs that have 4 or more speakers, they are wired in combinations of series and parallel.

The same results apply. Therefore, you cannot go from 4 to 8 (and vice versa) by changing the wiring configuration.
Click to expand...

CURSE YOU OHMS LAW!!!!
 
#19
Think of it this way; connect an 8 ohm and a 4 ohm cab to the same head and you'll get one third of the output power through the 8 and two thirds through the 4. I used to do it without any problems but it still makes me feel guilty somehow!
 
#20
RickenBoogie said:
One 8 ohm cab, one 4 ohm cab = 2.6 ohms. Use the 2 ohm jacks.
Click to expand...
I'm splitting hairs a bit here, but with a tube amp, if you can't match perfectly, it's usually recommended to use the taps with a higher rating than the actual load, but as close as possible. This is of course contrary to solid state rules. So, stefandisgust really should use the 4ohm taps, since his actual load will be 2.6ohms with his cabs.
And no, as stated you can't rewire an 8ohm cab to 4ohms, or vice-versa. The odd exception to this are the D.I.S.T. cabs from Epifani, which have two voice coils per speaker.
 

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