Amp ohms question

[bassoniac]

Hello everybody,

I play my Gallien-Krueger 700RB head through a 2x10 eminence beta 10 cabinet (4 ohm). The sound is fantastic, and most times loud enough. But for some occasions would like to add an 15'' cabinet.

Now, here's the thing.
My trusted salesman, told me, because my cabinet is 4 ohm, that he could add a 4 ohm 15'' cabinet and reconnect it through the 2x10 speaker. The overall impedanz would be 5,3 ohms.

Will that hurt/affect the amp, or should I go for it?

Thanks!

 

[chaotick]

Two 4 ohm cabs make a 2 ohm load.

Do not do this unless the GK can handle a 2 ohm load.

EDIT: My bad, I jumped the gun. I didn't realize upon first read that he was rewiring your stuff. I am not sure how that would make it 5.3 Somebody check this?

 

[herndonbassist]

The only thing that I could imagine doing, would be to run the 1x15 in SERIES with the other cabinet, but this would yield an 8 ohm load NOT 5.3. I'm not exactly sure what your salesman has in mind, perhaps he could explain and you could post the reulsts?

FWIW, you should check this out: http://colomar.com/Shavano/speaker.html they've got TONS of good information on that site. There's also a section on creating a series box to connect multiple speakers.

... peace ...

- EDIT: -
To clarify, I went through the calculator several times. The only way that you could add a 15 and get the 5.3 ohms that he's referring to would be if the 15 was an 8ohm cabinet and you were to rewire your cabinet to be in series (which would change it to a 16 ohm cabinet) then connect up the new 8ohm cabinet in parallel. Keep in mind tho, with all of this, that if you go from 4 ohm to anything higher, you will be dropping the output of your amp. This MAY NOT result in a volume drop, but it certainly could. From my experience, you'd be MUCH better off selling your 4ohm 2x10 and picking up an 8ohm 2x10 along with an 8ohm 1x15.

 

[bassoniac]

my bad.

I rechecked.

He would wire a 8 Ohm 15'' in series with my 4 ohm 2x10 cabinet. That would be 5,3. It's logical now.
He built my first cabinet, and I trust him.
But my concern is (beacuse the amp manual only speaks about 4 or 8 ohm load) will this 5,3 ohm load somehow affect the amp. I'm an ignorant regarding power/electricity etc, so I apologize if this is a stupid question.

Thanks!

 

[12bass]

Something still sounds incorrect. Wiring an 8 ohm cabinet in series with a 4 ohm cabinet gives 12 ohms, not 5.3.

 

[herndonbassist]

see my edit...

AND FWIW a 5.3 load will not have a bad affect on your amp, its just considered to be kinda odd that's all.

 

[bassoniac]

Now I'm totaly confused.
My cab is definitely 4 ohm, and the I know he uses the 8 ohms driver for the 15'' cabinet.
So, perhaps he would wire them parallel.

???


Thanks anyway

 

[bassoniac]

Now I get it.

Thanks RobertUI!

 

[herndonbassist]

Maybe this will help clarify more. Your existing 2x10 has 8ohm speakers in it (based on what eminence makes). They are currently wired together in parallel. If you were to wire them in series this would make it a 16ohm cabinet. At that point if you went with standard convention and hooked up the NEXT speaker (the 8ohm 15") via a parallel configuration it would result in a 5.3ohm load.

Hope this helps

 

[herndonbassist]

glad i could help!

 

[Espidog]

I think I know what your salesman may be suggesting. Your 4 Ohm 2x10 contains two 8 Ohm drivers. Currently they are wired in parallel. If he re-wires them in series, the cab will be 16 Ohms.

If we now take that 16 Ohms and put it in parallel with the 8 Ohm 15", the result will be 5.33 Ohms.

Just one thing to keep in mind, though: because it is now wired to be 16 Ohms, your 2x10 will only get one third of the amp's available power, while the 8 Ohm 15" will get the other two-thirds. Might make your rig sound very unbalanced.

Oh! I've just seen RobertUI's edit. It seems we agree!

 

[bassoniac]

hmmm, that's not good.

One more question. How much of a job would be to replace the eminence 8 ohm drivers in my cabinet, with 16 ohm drivers. Is that a simle driver replace job, or does it involve some electronicaly changes also. That way I would get a 8 ohm 2x10 cabinet (that pairs up nicely with the new 15 cab). Beacuse I really love the sound of the cabinet. Also it's hand made, and I would not get any decent price for it.

 

[herndonbassist]

a question for YOU... does your 2x10 have a tweeter in it? if it does, then you're going to have a problem changing out the wiring OR the speaker due to the fact that there'd be a crossover in place. as far as swapping out speakers, it'd be better to put 4ohm speakers in the 2x10 and wire them in series (making it an 8ohm cabinet) then you wouldn't have any trouble adding another 8ohm cabinet AND you'd get the full power out of your amp.

 

[herndonbassist]

one other thing that i wanted to mention:

take a look at this thread http://www.talkbass.com/forum/showthread.php?t=167733 it goes into a pretty good explanation of the difference between series and parallel. pay attention to billfitzmaurice, i've said it before, but the man KNOWS what he's talking about

 

[bassoniac]

No tweeter, just a plain 2 10 inch drivers.

 

[herndonbassist]

based on all of this: if the cost were feasible, i would swap the 8ohm speakers for 4ohm ones, and then add an 8ohm 15" cabinet

 

[bassoniac]

Great thread RoberUI, I learned a lot today.

Think that I wont do any changes. Basically the 2x10 is enough for the rehersals, some small gigs, and the large ones - where there's always some PA. Especially, because I get some really nice lows from my 2x10.
It was an idea, but now it's gone - it would be to much trouble/money spent, for a result that persaps would not satisfy me.

Greetings to all of you, from Croatia, Europe.
(and sorry for the bad english)

 

[herndonbassist]

Great thread RoberUI, I learned a lot today.

Think that I wont do any changes. Basically the 2x10 is enough for the rehersals, some small gigs, and the large ones - where there's always some PA. Especially, because I get some really nice lows from my 2x10.
It was an idea, but now it's gone - it would be to much trouble/money spent, for a result that persaps would not satisfy me.

Greetings to all of you, from Croatia, Europe.
(and sorry for the bad english)

Hey no need to apologize AT ALL... the thing that's great about this site is the fact that we can all learn so much. I came here with MANY of the exact same questions, and have learned from those before me. Best wishes to you!