Ohms always confuse me...

togglehead · #1 06-02-2010, 02:33 AM

This should be a quick one...sorry if its been answered already. I couldnt find it by searching the (probably incorrect) terms.

I have a 200w 8ohm 4x10 cab....and an amp that puts out 200w at 4 ohms...and 100w at 8ohm.

I want that cab getting all of the watts the head can put out. How can i do that? If i ran straight series on 4 speakers....wouldnt that bring it down to 2 ohm?

thanks in advance....

Jo6Pak · #2 06-02-2010, 02:55 AM

no. speaker impedance in series is ADDITIVE. 4+4 in series = 8 ohms. 4+4 in parallel = 2 ohms. to get the max (safely) out of your amp, match the load (combined impedance of the speakers in the cab) to the minimum rated load of the amp. in your case, run the amp with a single 4 ohm cab or two 8 ohm cabs (if the amp has TWO output jacks).

http://www.caraudiohelp.com/ohms_law/ohms_law.htm

togglehead · #3 06-02-2010, 03:02 AM

Oh youre right....my mistake.

But...ok, i cant afford another cab right now....so is there a way for me to wire these speakers in my current cab in a way that i can draw 4 ohms?

For example, if i naturally assume that each of my speakers draws 2ohms...with 4 of them will it equal 8 ohms? And...if so, is there a way for me to wire TWO of the four speakers in parallel, drawing 2 ohms...then again for the other two. Then, wiring those halves together in series to equal 4 ohms?

Or...have i gone totally nuts?

Jo6Pak · #4 06-02-2010, 03:13 AM

if your cab right now is 8 ohms, then it is likely wired series/parallel (probably 8+8 in series = 16 (two of these), then those two pairs of 8s (which equal 16) are wired in parallel to drop it down to 8 (16 +16 in parallel = 8). this is one example. how your cab can be wired depends entirely on the impedance of EACH speaker.

togglehead · #5 06-02-2010, 03:15 AM

I suppose i could test that with a meter....no?

Jo6Pak · #6 06-02-2010, 03:26 AM

if your cab is 8 ohms total, it almost certainly contains four, 8 ohm drivers, wired in series/parallel. you need to either replace the drivers with 4 ohm in series/parallel or add a second 8 ohm cab.

toggle: not only is it very early here, but i also have a lot of other s~*t on my mind at the moment. perhaps someone else can provide you with alternatives, once more people get logged on.

coreyfyfe · #7 06-02-2010, 04:36 AM

Quote:

Originally Posted by togglehead

But...ok, i cant afford another cab right now....so is there a way for me to wire these speakers in my current cab in a way that i can draw 4 ohms?

No. As Jo said, they're likely four 8 ohm speakers in series/parallel (or potentially four 32 ohm speakers in parallel) so the only way to get more volume would be to replace the speakers with 4 ohm speakers. Honestly you probably wouldn't notice the difference in volume. You'd get more of a boost by adding a second 4x10 cab.

jtc_hunter · #8 06-02-2010, 08:35 AM

Just save your money until you can get another 8 ohm cab. If you are looking for more volume, speaker surface area increase with get you there better than increasing your wattage by 100. In fact, believe it or not, by using the same cab and speaker surface, in this case a 410, to double your volume from 100 watts, you would have to pump 1000 watts (or 10x the wattage) thru that 410 .Doubling your wattage from 100 to 200 will not double your volume. You would hardly notice it at all thru one cab.. Wouldnt it be better to add another cab, like a 115? I have seen decent 115 , 8ohm cabs, on Craiglslist for $100+. That will make a noticeable difference.

BassmanPaul · #9 06-02-2010, 09:21 AM

To put it simply: There is no way to rewire an 8Ω cabinet to make it 4Ω.

Paul

togglehead · #10 06-02-2010, 09:30 AM

Quote:

Originally Posted by BassmanPaul

To put it simply: There is no way to rewire an 8Ω cabinet to make it 4Ω.

Paul

Gah, thanks.

Im not looking for more volume...i was looking to see if the amp had a better tone at its 200w rating, really.

The 410 is an old Guild/Hartke original free air cab, and i probably cant find another one. To be honest...its the head that needs replacing i feel. Acoustic B200h. GREAT price...and got me through some gigs...but im looking to make my rig SMALLER if anything, as i gig frequently.

Time to look for a 400rb or something like that. Thanks guys.

thisSNsucks · #11 06-02-2010, 09:34 AM

Quote:

Originally Posted by BassmanPaul

To put it simply: There is no way to rewire an 8Ω cabinet to make it 4Ω.

Paul

This.

You'd have to replace the speakers in the cab which would cost a decent amount of $.

You'd be better off either saving up for another 8ohm cab, buying a 4ohm cab, or getting a more powerful head.

jtc_hunter · #12 06-02-2010, 10:07 AM

Quote:

Originally Posted by togglehead

Gah, thanks.

Im not looking for more volume...i was looking to see if the amp had a better tone at its 200w rating, really.
------but im looking to make my rig SMALLER if anything, as i gig frequently.

Sell the entire rig and buy a brand new GK MB115. 200 loud watts , a 4ohm 15" speaker and only 35lbs. Try one, i think you would be impressed. You might be able to sell your 410 and that amp for close to enough to pay for the MB115. I got mine for $359 delivered.

togglehead · #13 06-02-2010, 10:20 AM

Quote:

Originally Posted by jtc_hunter

Sell the entire rig and buy a brand new GK MB115. 200 loud watts , a 4ohm 15" speaker and only 35lbs. Try one, i think you would be impressed. You might be able to sell your 410 and that amp for close to enough to pay for the MB115. I got mine for $359 delivered.

Ugh...i do NOT need excuses to go on a gear hunt now...thanks a lot!!!! haha

Good reco, though....thanks. Id love something like one of those micro rigs...but they just dont put out enough sound for the price. =\

Bass_Pounder · #14 06-02-2010, 10:34 AM

Quote:

Originally Posted by togglehead

Ugh...i do NOT need excuses to go on a gear hunt now...thanks a lot!!!! haha

Good reco, though....thanks. Id love something like one of those micro rigs...but they just dont put out enough sound for the price. =\

Hard to beat the Carvin BX500.............5lbs, 500 watts, stable down to 2 ohms, $399

jtc_hunter · #15 06-02-2010, 10:49 AM

Quote:

Originally Posted by togglehead

Ugh...i do NOT need excuses to go on a gear hunt now...thanks a lot!!!! haha

Good reco, though....thanks. Id love something like one of those micro rigs...but they just dont put out enough sound for the price. =\

In regards to the mb115, I think you would be surprised at how loud it can get. I have gigged mine w/ 3 guitar players and a loud drummer, and my wife later told me I was almost drowning them out.

These new GK ultra-light combo amps are very impressive.

Pilgrim · #16 06-02-2010, 11:15 AM

Quote:

Originally Posted by togglehead

Gah, thanks.

Im not looking for more volume...i was looking to see if the amp had a better tone at its 200w rating, really.

No, it won't have any different tone. It sounds the way it's going to sound through that cab. To change the sound you'd need a different cab.