# Two 16ohm cabs = 8ohm from the head?



## Feathered Serpent

I have a jcm2000 tsl60 with 8/16 ohm selector if i hook it up to two 16 ohm cabs 
do i set the head to 8 or 16 ohms? do the tsl's have a parallel speaker output? btw the cabs are a carvin legacy 4x12 loaded with vintage 30s and a marshall 1960 with g 12s


----------



## Micky

Yes.


----------



## Feathered Serpent

wow that was fast and thank you


----------



## Adwex

Micky speaks wisely.


----------



## Wycked Lester

plus we've has alot of practice answering that question..... 

.... nevertheless,...welcome to forum man.


----------



## Feathered Serpent

thanks i have been looking on here for a while, and found similar topics but was not sure. the whole 16ohm plus 16ohm = 8ohm gets confusing


----------



## Adwex

Feathered Serpent said:


> thanks i have been looking on here for a while, and found similar topics but was not sure. the whole 16ohm plus 16ohm = 8ohm gets confusing



It's not confusing if you understand what "parallel" means, electrically speaking. Speaker loads in parallel, don't "add", speaker loads in series do.


----------



## Wycked Lester

so, technically speaking,... 

is 8 ohms MORE LOAD than 16 ?

I don't claim to understand it, I just know where to put my switch depending on how many cabs im running...

1- 16 ohm = 16 ohm
2- 16 ohm = 8 ohm
4- 16 ohms = 4 ohm

2 - 8 ohms = 4 ohms


----------



## Dogs of Doom

Adwex said:


> It's not confusing if you understand what "parallel" means, electrically speaking. Speaker loads in parallel, don't "add", speaker loads in series do.


yes, it's more of a multiple/division equation.

in this case instead of 16+16=32, it's 16(ohms)÷2(units)=8ohms I tend to think of series as 16(ohms)x2(units)=32ohms, in simplistic situations.

Parralell = ÷
Series = x


----------



## Wycked Lester

Adwex said:


> It's not confusing if you understand what "parallel" means, electrically speaking. Speaker loads in parallel, don't "add", speaker loads in series do.



fuck me, now im am confused,.... i thought the 2 speaker outs ARE PARALLEL??


----------



## Dogs of Doom

Wycked Lester said:


> so, technically speaking,...
> 
> is 8 ohms MORE LOAD than 16 ?
> 
> I don't claim to understand it, I just know where to put my switch depending on how many cabs im running...
> 
> 1- 16 ohm = 16 ohm
> 2- 16 ohm = 8 ohm
> 4- 16 ohms = 4 ohm
> 
> 2 - 8 ohms = 4 ohms


lower ohm # = more resistance.


----------



## Wycked Lester

Dogs of Doom said:


> yes, it's more of a multiple/division equation.
> 
> in this case instead of 16+16=32, it's 16(ohms)÷2(units)=8ohms I tend to think of series as 16(ohms)x2(units)=32ohms, in simplistic situations.
> 
> Parralell = ÷
> Series = x



ah, thanks,... thats what i thought.


----------



## Dogs of Doom

Wycked Lester said:


> fuck me, now im am confused,.... i thought the 2 speaker outs ARE PARALLEL??


they are.


----------



## Wycked Lester

Dogs of Doom said:


> lower ohm # = more resistance.



yea, right on, ..... its kinda like golf


----------



## Jethro Rocker

Uhhh, higher ohm is higher impedance therefore resistance. Parallel is running 2 loads parallel to one another so getting less impedance total but also less power to each speaker, sort of. Suffice to say, parallel total impedance with 2 speakers = 1/2 the impedance of 1 of the speakers. Series = twice the impedance of any one speaker in the same setup. At least just remember that part and stuff won't blow up!


----------



## Adwex

Wycked Lester said:


> fuck me, now im am confused,.... i thought the 2 speaker outs ARE PARALLEL??



They are, that's why two 16s in parallel = 8.


----------



## Adwex

Jethro Rocker said:


> Uhhh, higher ohm is higher impedance therefore resistance. Parallel is running 2 loads parallel to one another so getting less impedance total but also less power to each speaker, sort of. Suffice to say, parallel total impedance with 2 speakers = 1/2 the impedance of 1 of the speakers. Series = twice the impedance of any one speaker in the same setup. At least just remember that part and stuff won't blow up!



Don't just "remember", it...."understand" it.

Think of it like water flowing in pipes...if you have two of the same pipes, the resistance to the water flowing is half. If you have 4 pipes, the resistance is 1/4.

I know alot of you guys are afraid of math, but this is actually the best way to think of it. If you understand this, you'll never be confused. Speaker loads in parallel combine (not "add") like this: 

1/Rtotal = 1/R1 + 1/R2 + 1/R3 +1/R4 ....and so on for as many loads there are. THIS is why two 16s in parallel = 8

1/Rtotal = 1/16 + 1/16
1/Rtotal= 2/16 which is the same as 1/8, so...
1/Rtotal = 1/8 and by the rules of algebra....
Rtotal = 8

THIS is the ONLY way to get it right.


----------



## Jethro Rocker

Indeed. I was trying to keep it simple. I like the water analogy, well done. You need to know the math - if you are running 2 different impedance speakers into say a SS amp, an 8 and a 16 in parallel = 5.3 ohms. You need to do the math to figure it out properly. Thanks for the great analogy!


----------



## Wycked Lester

Adwex said:


> Don't just "remember", it...."understand" it.
> 
> Think of it like water flowing in pipes...if you have two of the same pipes, the resistance to the water flowing is half. If you have 4 pipes, the resistance is 1/4.
> 
> .



I don't do math with letters in it..... but i do like this explanation 


its like more speakers is less resistance because there is more places of the electricity to go,... right?


----------



## Adwex

Wycked Lester said:


> I don't do math with letters in it..... but i do like this explanation
> 
> 
> its like more speakers is less resistance because there is more places of the electricity to go,... right?



Yes, that's exactly it, conceptually, but if you want to actually get the answer, you need to at least understand how the math works. For example, what happens if you have 3 speakers? I know you'll probably never have just 3, but....


----------



## Adwex

And don't be afraid of the letters, the R1, R2, etc. stand for the impedance of the first speaker, the impedance of the 2nd speaker, etc. It's 9th grade math.


----------



## Adwex

Jethro Rocker said:


> Indeed. I was trying to keep it simple. I like the water analogy, well done. You need to know the math - if you are running 2 different impedance speakers into say a SS amp, an 8 and a 16 in parallel = 5.3 ohms. You need to do the math to figure it out properly. Thanks for the great analogy!



There's more to the water analogy, if you're interested.


----------



## Wycked Lester

so now, back to the water hose.... 

if you were gonna hook up 2 hoses, you would want them EACH to put out as much water as just one did earlier,....

Say like you had one hose, and i'd fill a bucket in one minute,... now, if you just hooked 2 hoses to it,.. it'd still only fill 1 bucket per minute.....

.... if you wanted to fill 2 buckets per minute you'd have to turn up the pressure [ampres?] .....

so is that what the ohms switch on your head does? ....tell it how many ampres to push?

not really sure if ampres is the right word.... I know amps 'push' voltage, is this the same thing?


----------



## Wycked Lester

Adwex said:


> It's 9th grade math.



um, yea,... i flunked that.


----------



## Adwex

Then this could take a while to explain.

The short version is this...

In the water analogy,
voltage is like the water pressure pushing the water through the pipe
current is like 'how much water is flowing'
resistance (or impedance) is like the friction the water encounters from the walls of the pipe. If the pipe is larger, or there are more pipes, then less overall friction.

If we want to go into more detail, you kinda have to have at least a basic understanding of some physics.


----------



## Adwex

Height plays the same role as pressure...if one end of the pipe is at a greater height than the other end, the water will flow due to gravity. If you want water to flow uphill, you need a pump to create a greater pressure at the bottom of the hill. The pump is like a battery or voltage source like the wall socket.


----------



## Marshall Mann

Wycked Lester said:


> so now, back to the water hose....
> 
> if you were gonna hook up 2 hoses, you would want them EACH to put out as much water as just one did earlier,....
> 
> Say like you had one hose, and i'd fill a bucket in one minute,... now, if you just hooked 2 hoses to it,.. it'd still only fill 1 bucket per minute.....
> 
> .... if you wanted to fill 2 buckets per minute you'd have to turn up the pressure [ampres?] .....
> 
> so is that what the ohms switch on your head does? ....tell it how many ampres to push?
> 
> not really sure if ampres is the right word.... I know amps 'push' voltage, is this the same thing?



I think the term you are looking for is wattage Les, not amps. 

Watts is the unit of measure for total power (figured via ohms law). Amperes only part of the equation of volts (V) resistance (R) and current AKA amperes (I). 

I'll let Ad finish....


----------



## Wycked Lester

Adwex said:


> If we want to go into more detail, you kinda have to have at least a basic understanding of some physics.



like whats in a black hole?


j/k - i pretty much get it now,... i was saying ampres and i think it should have been voltage. 

so setting the switch on the head is actually doing what? Telling the head how much voltage to output?

Then, if its set to put out a too much voltage [ohms set to 16 into a 8ohm cab] it'd be like flooring a car that sitting on ice which would redline the engine and make it blow??? is that close?


----------



## Adwex

Marshall Mann said:


> ...I'll let Ad finish....



I don't have time, it could be a while


----------



## Adwex

Wycked Lester said:


> like whats in a black hole?
> 
> 
> j/k - i pretty much get it now,... i was saying ampres and i think it should have been voltage.
> 
> so setting the switch on the head is actually doing what? Telling the head how much voltage to output?
> 
> Then, if its set to put out a too much voltage [ohms set to 16 into a 8ohm cab] it'd be like flooring a car that sitting on ice which would redline the engine and make it blow??? is that close?



No, setting the switch determines the impedance of the output transformer, which has to match the impedance of the speaker load. This part of the discussion has nothing to do with the water analogy, or ohm's law. It's a separate issue. Let's just understand how impedances combine, for now.


----------



## Wycked Lester

Adwex said:


> No, setting the switch determines the impedance of the output transformer, which has to match the impedance of the speaker load. This part of the discussion has nothing to do with the water analogy, or ohm's law. It's a separate issue. Let's just understand how impedances combine, for now.




and this is why i take my shit to a tech when i fuck it up...


----------



## Adwex

Forget WHY you have to adjust the switch, that's complicated, just know that it has to match the speaker load. It's complicated because there is no "direct" connection between the amp and the speaker, the signal is "transmitted" (actually the word is "coupled") through the coils of the transformer as a result of magnetism.

But you are capable of understanding how to determine the resulting load when you combine speaker cabs, it's not complicated.


----------



## Marshall Mann

Adwex said:


> Forget WHY you have to adjust the switch, that's complicated, just know that it has to match the speaker load. It's complicated because there is no "direct" connection between the amp and the speaker, the signal is "transmitted" (actually the word is "coupled") through the coils of the transformer as a result of magnetism.
> 
> But you are capable of understanding how to determine the resulting load when you combine speaker cabs, it's not complicated.



Excellent job Ad! 

Les, using the water analogy, think of it like this. 

If your pump (your transformer) was trying to push more water than the hose could handle, it would back up. You need to tell your amp what size hose it's dealing with.


----------



## Feathered Serpent

Dogs of Doom said:


> yes, it's more of a multiple/division equation.
> 
> in this case instead of 16+16=32, it's 16(ohms)÷2(units)=8ohms I tend to think of series as 16(ohms)x2(units)=32ohms, in simplistic situations.
> 
> Parralell = ÷
> Series = x



that makes sense thanks

i like what you said adwex about the water in pipes it finally makes sense


----------



## Adwex

Wycked Lester said:


> so, technically speaking,...
> 
> is 8 ohms MORE LOAD than 16 ?
> 
> I don't claim to understand it, I just know where to put my switch depending on how many cabs im running...
> 
> 1- 16 ohm = 16 ohm
> 2- 16 ohm = 8 ohm
> 4- 16 ohms = 4 ohm
> 
> 2 - 8 ohms = 4 ohms



See, here's the problem with memorizing things without understanding.
Just because you have four 16 ohm speakers, doesn't mean the total impedance is 4 ohms. It depends on how they're wired...all 4 in parallel, or two pair in parallel with the pairs wired in series (this is how almost all cabs are wired). It's also the key to how the two input jacks (4 or 16) work on modern Marshall cabs that have the jackplate with the mono/stereo switch.

*edit* Oops, you were talking about cabs, not individual speakers IN a cab. In that case, you're correct. But why?


----------



## Adwex

Dogs of Doom said:


> lower ohm # = more resistance.



Uh, no. An "ohm" is the unit of resistance, so if you have less ohms, you have less resistance.


----------



## Micky

Less resistance = more load


----------



## Jethro Rocker

Especially with possible awkward loads on a PA amp with multiple speakers. Learned that one in around 1980 when we toasted the output transistor by hooking up lotsa stuff willy nilly.


----------



## Crichy

HI my first post...So if I have 4 quads and a 9200 stereo power amp I run the quads at 16 ohms and the amp in 8 ohms .2 quads per side.


----------



## blues_n_cues

Adwex said:


> Don't just "remember", it...."understand" it.
> 
> Think of it like water flowing in pipes...if you have two of the same pipes, the resistance to the water flowing is half. If you have 4 pipes, the resistance is 1/4.
> 
> I know alot of you guys are afraid of math, but this is actually the best way to think of it. If you understand this, you'll never be confused. Speaker loads in parallel combine (not "add") like this:
> 
> 1/Rtotal = 1/R1 + 1/R2 + 1/R3 +1/R4 ....and so on for as many loads there are. THIS is why two 16s in parallel = 8
> 
> 1/Rtotal = 1/16 + 1/16
> 1/Rtotal= 2/16 which is the same as 1/8, so...
> 1/Rtotal = 1/8 and by the rules of algebra....
> Rtotal = 8
> 
> THIS is the ONLY way to get it right.



"be like water"-Bruce Lee.


----------



## Dogs of Doom

Crichy said:


> HI my first post...So if I have 4 quads and a 9200 stereo power amp I run the quads at 16 ohms and the amp in 8 ohms .2 quads per side.


welcome to the forum - yes, you are correct.


----------



## Marshallhead

Micky said:


> Less resistance = more load



No, less resistance is less load.


----------



## Micky

Marshallhead said:


> No, less resistance is less load.



I should have said less ohms=more load...


----------



## Marshallhead

Micky said:


> I should have said less ohms=more load...



No, still not right! Less ohms = less load. No ohms (I.e. a short circuit) is no load at all.


----------



## Adwex

Micky said:


> I should have said less ohms=more load...



That's the same thing.

I know what you're thinking though....more "load" because the current source has to work harder to supply more current due to the lower resistance.
As opposed to "load", simply meaning the resistance in the circuit. More semantics than engineering, I think.


----------



## B.Gloob

This is more confusing than a pussy-fart?


----------



## anitoli

Micky said:


> I should have said less ohms=more load...


 
But now we need to clarify if the amp is transformer coupled ( tube) or direct coupled (SS ) load for both is very critical but not the same animal......


----------



## lowinput

Well I've just got a 3 ohm cab (6x12 with a Hf horn) can I run that with a 4 ohm setting on the amp? 
It's a 1974 P.A. cab by peavey.


----------



## Valvelust

lowinput said:


> Well I've just got a 3 ohm cab (6x12 with a Hf horn) can I run that with a 4 ohm setting on the amp?
> It's a 1974 P.A. cab by peavey.



No by "Rule of thumb", your speaker/cab should always have more resistance than you amp is putting out otherwise it is overworked.


----------



## Jethro Rocker

I thought generally with tube amps a higher impedance is harder on the OT and less impedance (within reason) is harder on the tubes.


----------



## lowinput

I have phoned 2 amp industry guys and they say that the impedance varies in opperation and a valve amp should be able to handle it, but a solid state amp won't. 
the cab was made for transistor amp.


----------



## Jethro Rocker

Solid state will NOT like lower impedance! Turn it up for awhile and cook an output transistor. It does depend on which valve amp as well. Ultimately, match impedance with both amp and speaker. BTW, the PA speaker might sound gnarly cool or very shitty with a guitar amp. Try it!


----------



## Valvelust

lowinput said:


> I have phoned 2 amp industry guys and they say that the impedance varies in opperation and a valve amp should be able to handle it, but a solid state amp won't.
> the cab was made for transistor amp.



Not what all the old time valve amp guru's will tell you. It will tax the OPT and valves.

"Never pour more into the hole than the supply will handle"


----------



## lowinput

the 6, twelve inch, 16ohm speakers are wired parrallel, the horn is connected to the blue (negative side) the yellow (positive side) isn't connected to the horn.
the horn has no ID on it. I'll try searching the net for it. 

does anybody know whats happening here? how do they get the 3ohm's?

would you put 4 speakers in another box instead? (I have an empty 4x12 box)


----------



## Jethro Rocker

Put 4 - 16's in another cab, 2 in parallel to each other (8 ohms per pair), each pair then in series for 16 ohm total or parallel all for 4 ohms. Why dick around with the horn? What speakers are they? All 6 in parallel would be 2.7 ohms, close enough to 3, perhaps the horn is a piezo which doesn't count.


----------



## Ken

Marshallhead said:


> No, still not right! Less ohms = less load. No ohms (I.e. a short circuit) is no load at all.


 
Yes; a short circuit has zero load because everything passes. And an open circuit is an infinite load. I think it makes better sense to explain it in this context because I also had it backwards at first.

Ken


----------



## mickeydg5

What ?????


----------



## Jethro Rocker

A short circuit has NO load, all of the signal passes with nothing to impede it (as in impedance). An open circuit has no where for the energy to go thus being an infinite impedance to signal flow and an infinite load.


----------



## Ken

Jethro Rocker said:


> A short circuit has NO load, all of the signal passes with nothing to impede it (as in impedance). An open circuit has no where for the energy to go thus being an infinite impedance to signal flow and an infinite load.


 
That's what I was trying to say!

Ken


----------



## lowinput

The speakers are eminence 'man 'o'war' drivers (150 watt, 16 ohm) and the cones are CTS paper type (british tone type) the speakers are CTS brand made for ampeg by eminence and peavey used them. 
They sound really good, if you want vintage tone and really cheap, get some of these and try them!
(If 4 big companies have a hand in making them, they MUST be GOOD!)


----------



## lowinput

All USA made as well! top quallity assured!


----------



## mickeydg5

lowinput said:


> The speakers are eminence 'man 'o'war' drivers (150 watt, 16 ohm) and the cones are CTS paper type (british tone type) the speakers are CTS brand made for ampeg by eminence and peavey used them.
> They sound really good, if you want vintage tone and really cheap, get some of these and try them!
> (If 4 big companies have a hand in making them, they MUST be GOOD!)


That is confusing.
Can you show us pictures of the speakers including codes on the frame and cone?


----------



## lowinput

That horn is REALLY good at putting out top quality trebles! 
What they physically do is keep the air around the cone in the right pressure for the next speaker 'push' movement.
Normally after the first 'push' of the air, a speaker has 'less air' to push the next time it pushes the air. This results in much less trebles being heard by the listener. 
The cone changes the air that the speaker is pushing (it's very complex) so that trebles are maintained. 
From my test, I was VERY impressed with the sound comming from the horn. 
I used the DSL to 'do all the distortion'. Every channel sounded like 'hendrix tone'.
Turning the amp up, the sound was similar to early eric clapton. (I haven't used that tone, so I might research that tone next) It also compared to utube clips of cranked vintage JMP's (from a DSL!) 
If you're not happy with the sound, don't buy a new amp, change speakers!


----------



## lowinput

CODEs on frame - 121638 G, 1377449, cone 63512109

121638G- is man'o'war, 12 inch 16 ohm 
137 is CTS maker, 74 year, 49 week

Hyperbolic Horn
(Electro voice drivers. I've written this down but forgotten what it is reference to)

SVT cabinet (ampeg)

I don't know the rest.


----------



## lowinput

If you look at peavey web site for 612H they have pics there, these speaker look the same, they have the aluminium caps in the middle of the cones.


----------



## lowinput

The frames Look exactly like the Man'o'wars, but these are metallic brown. NO LABELS! only black numbers and letters stamped.


----------



## lowinput

the cones have smooth paper with wide ribbed pattern all across the surface.


----------



## Jethro Rocker

Ken, I got ya! I was trying to re-word your post in hopes of it getting through. This stuff can get confusing!!


----------



## mickeydg5

lowinput said:


> If you look at peavey web site for 612H they have pics there, these speaker look the same, they have the aluminium caps in the middle of the cones.


I could not find them.
Did you measure 3 ohm or is that indicated on the cabinet (tag)?

I have seen CTS model 121638G and 12838G speakers.


----------



## lowinput

That is what is on the tag. I can't find the speakers on the net, only the whole cab at peavey site.


----------



## AbelsKeepeR

So, my Factory Stock 1960A 4x12 cab has the mono/stereo switch, 4 16 ohm 75 waters. In mono (1-4x12) is 16 ohms, so I use the one 16 ohm output on my DSL head, correct? If I run 2 4x12 16 ohm Marshall 1960A cabs, I would run each cab in the Heads 2 8 ohm outputs, right? And if running one 16 ohm cab in stereo mode, I would also use the 2 8 ohm outputs on the head. Have I got this right?


----------



## damienbeale

AbelsKeepeR said:


> And if running one 16 ohm cab in stereo mode, I would also use the 2 8 ohm outputs on the head. Have I got this right?


The rest is right, this part is wrong.
If connecting the two 8ohm sides of the cab to the amp, the total load is 4ohm.

Also, it is pointless. Might as well just use the 16ohm mono jack, and one lead.


----------



## FFXIhealer




----------



## AbelsKeepeR

Hmmmmmmmmmmmmmmm......then what's the point of putting a mono/stereo plate on a cab, when the head only has two 8 ohm jacks, and a 16? But I guess that was your point huh? lol

edit here------------------. But i thought, (I know, here he goes) shit, forget it, I'll just plug in an rock out! lol


----------



## AbelsKeepeR

Adwex said:


> See, here's the problem with memorizing things without understanding.
> Just because you have four 16 ohm speakers, doesn't mean the total impedance is 4 ohms. It depends on how they're wired...all 4 in parallel, or two pair in parallel with the pairs wired in series (this is how almost all cabs are wired). It's also the key to how the two input jacks (4 or 16) work on modern Marshall cabs that have the jackplate with the mono/stereo switch.
> 
> *edit* Oops, you were talking about cabs, not individual speakers IN a cab. In that case, you're correct. But why?


 
I've been slightly confused, so I read, and reread this thread over and over, and this last time, I got to this post, and "BAM" it just clicked....I finally got it! lol, took me long enough. lol


----------



## AbelsKeepeR

damienbeale said:


> The rest is right, this part is wrong.
> If connecting the two 8ohm sides of the cab to the amp, the total load is 4ohm.
> 
> Also, it is pointless. Might as well just use the 16ohm mono jack, and one lead.


 
or have I? the total ohm load may be 4 ohms, but still I would use the two 8 ohm output jacks on my head, which would be 8 ohms for each side of the cab. Correct?


----------



## damienbeale

AbelsKeepeR said:


> or have I? the total ohm load may be 4 ohms, but still I would use the two 8 ohm output jacks on my head, which would be 8 ohms for each side of the cab. Correct?



No. That's not how it works. Those two jacks are for the TOTAL load to be 8ohms. Whether you use one, or the other. The jacks are simply wired in parallel. They do not have their own dedicated winding from the transformer.

Again, though, unless you are specifically feeding different things into each side of the speaker (which you are not since you are connecting them up at the same point) it is a wasted exercise, and you may as well use the 16ohm and one lead. Or the 4ohm if you really prefer )which technically is connected in EXACTLY the same way but using only one speaker lead), but the 16ohm will be using ALL of the secondary winding of the output transformer, and theoretically have better coupling and an extended frequency response.


----------



## damienbeale

FFXIhealer said:


>



Well that was useful


----------



## BobV

Ok but isn't a myth that "less power is going to each speaker"? If you change from 16 to the 8 ohm tap on the transformer it accounts for that, no?


----------



## damienbeale

Yes. The transformer is merely a matching device between tubes and speakers, so that the correct load is presented to the tubes. Assuming same versions of 16 and 8ohm speakers used on the correct tap, the voltage difference will be non-existent.

Add more speakers and it will add more volume though for various reasons. Not least the increased cone area moving more air, per same power draw. There are diminishing returns with this though.


----------



## Hvymtlrednek

Same scenario for me in a sense. Running a axe fx2 mark2. Into a Samson servo300. 4 ohm min. On back of fx. Into a 1960 vintage Marshall 4x12.Switchable on the back. Which way to switch?


----------



## mickeydg5

Hvymtlrednek said:


> Same scenario for me in a sense. Running a axe fx2 mark2. Into a Samson servo300. 4 ohm min. On back of fx. Into a 1960 vintage Marshall 4x12.Switchable on the back. Which way to switch?


The Servo 300 is solid state.

If using in mono then the cabinet has to be connected at 16 ohm because the amplifier cannot go below 8 ohm. The amplifier will output about 150-200W at 16 ohm.
Two cabinets set up for 16 ohms in parallel would be 8 ohms. Amplifier outputs 300W mono.

In stereo operation the amplifier can go down to 4 ohm each channel but that would require two 1960 cabinets each at 4 ohms. Amplifier outputs 150W per channel.
You can run the stereo operation with two speaker cables into one 1960 cabinet set up for STEREO at 8 ohms each side. Amplifier outputs 100W per channel.


----------



## Shawn Martin

Dogs of Doom said:


> lower ohm # = more resistance.


Ohm means resistance. the HIGHER the number, the higher the resistance.

"*Ohms*, simply stated, is a *resistance* to the flow of electricity. It has nothing to do with volume, only the amount of "*resistance*" to the current that flows. The *larger* the *ohm* value, i.e. *16 ohms* versus 8 *ohms*, the *more resistance* is offered."


----------



## SkyMonkey

Old thread I know. But...

Yes, ohms are a measure of resistance.
Higher ohms = higher resistance.
For AC currents in guitar amp speaker circuits, the resistance is referred to as 'impedance' to differentiate from DC resistance.
Load resistance affects the current draw of the power amp if the voltage is (near) constant, according to Ohm's Law.

V = I x R, where V=volts, I=current, and R=resistance.
or 
I = V/R, when transposed for current (Amps).

In a simple theoretical single speaker example: 1.25 A = 10v / 8 ohms
Change the load: 2.5 A = 10v / 4 ohms

Lower resistance increases the current draw and increases the output (in Watts).
A power amp will have a maximum current draw rating, above which you can damage the amp.
That current draw rating is inversely related to the load (in ohms).
Halve the load = double the output. And vice-versa. (that is the inverse relationship)
i.e. 100W @ 8 ohms would equate to 200W @ 4 ohms, or 50W @ 16 ohms.
An ideal amp would react to different loads uniformly. 
Inefficiencies intrinsic to amp architecture skew this ideal ratio.
As the speaker load is the variable for most musicians, minimum impedances are stated on an amp with speaker output jacks.
Also the differently rated speaker outputs compensate for correctly connected speaker loads.
Using a 8 ohm into the 8 ohm jack is NOT twice as loud as 16 ohm into the 16 ohm jack.

References
https://geoffthegreygeek.com/speaker-impedance-changes-amplifier-power/
http://www.prestonelectronics.com/a...e speaker is simple,2.5 amperes equals 4 ohms.


----------



## scozz

Dogs of Doom said:


> yes, it's more of a multiple/division equation.
> 
> in this case instead of 16+16=32, it's 16(ohms)÷2(units)=8ohms I tend to think of series as 16(ohms)x2(units)=32ohms, in simplistic situations.
> 
> Parralell = ÷
> Series = x


Well done DOD!

Very easy way to understand the basics with that explanation. You know when someone says something very simple that just connects in your brain to see clearly how something works?

Well, that’s just what happened when I read your post.

Thanks for that!


----------



## Dogs of Doom

scozz said:


> Well done DOD!
> 
> Very easy way to understand the basics with that explanation. You know when someone says something very simple that just connects in your brain to see clearly how something works?
> 
> Well, that’s just what happened when I read your post.
> 
> Thanks for that!


well, it is the simplified version & should work for most typical/simple applications. When you have 2-4 speakers that all match, it's not that hard to estimate using this.

If you do series-parallel or parallel-series, you do the x & ÷, so it cancels it out & the resistance stays the same.

glad it helps...


----------



## uselessoldman

3 speakers raises an interesting question. Lets say you have a 4x12 cab. On one side you have a single G12T at 8 ohms and on the other you have two Vintage 30s 16 ohms. Could you parallel the 16s to make 8 and then series wire the two together to make 16? 

Marshall suggest a 2 to 1 ratio for valve amp/cabs so that would be 100 head into 200 watts cab and for the trannies 1 to 1 is ok but 1 to 1.5 better. What if any benefit is there then to a full stack depending on speakers this could be as high as 400 watts per cab or 800 watts in total ?? I guess every valve amp would have a different output ceiling depending on its components, unlike a power amp as they increase in output depending on the cabs ohms rating. A 100 watts valve amp is just that 100 watts, no matter what the ohms and power rating? 100 into 800?? or even 300 for that matter, what is the point when your speakers could be potentially running at a absolute max of 50% or less. 

By adding another cab are they going to just share the original output as it will not increase from the amp side would it? Even if a 100 watt rated valve amp had 2 outputs, its not 2x100 is it? its 50/50=100.

Believe it or not i got A at Maths A level (pure applied) but that was over 30 years ago and since then a lot of Beer has past my lips and my brain decided to retire. Maths hurts its complicated, like women... a law unto themselves beyond the comprehension and understanding of any sensible male.


----------



## Jethro Rocker

To simplify all that. 
Yes, the total power is shared. 100 watts into 2 speakers is 50 watts per speaker. It could be a 3000 watt cabinet amd amp will put out 100 watts. Most tube amps, granted, put out more distorted power at full bore thus the 2x cab ratings. 

Yes you can run 2x16 ohm parallel for 8 ohms and run that is series with a single 16 to get 16 ohms total. 
A full stack should give 3dB more output technicallynthan a half stack. Gives more oomph amd obviously raises the sound up higher to behind your head.


----------

