4 Ohm/200 Watt Head to 8 Ohm/140 Watt Cab

Walt-Dogg

New member
Will this work?

The head is a 1970's Sunn Concert Lead (200 watts and 4 ohms output). The cab is the matching cab for a Marshall G100RCD (140 watts and 8 ohms handling).

I know that it's okay to plug a head into a cab if the head has higher impedance than the cab does, but what about the wattage? I can't afford to blow out the cab.
 
If the head puts out 200 watts at 4 ohms, it will only put out 100 watts at 8 ohms. You will be fine. If it's a solid state head, it's all good.
 
Also, say I used the 8 ohm 140 watt Marshall cab with a Marshall 1960 Lead cab set at 4 ohms, both plugged into my 200 watt at 4 ohm Sunn head, how would that work out?
well .... you end up with mismatched cabs. the one at 4 ohms would draw more power and be louder than the 8 ohm cab PLUS, you'd have a little under a 3 ohm total load which is below your amps rating.
I'd set that cab at 16 ohms instead which would be safe for the amp but still mismatched with one cab taking a lot more of the power than the other.
I think you'd probably be best off with just one of the cabs.
 
well .... you end up with mismatched cabs. the one at 4 ohms would draw more power and be louder than the 8 ohm cab PLUS, you'd have a little under a 3 ohm total load which is below your amps rating.
I'd set that cab at 16 ohms instead which would be safe for the amp but still mismatched with one cab taking a lot more of the power than the other.
I think you'd probably be best off with just one of the cabs.
Yeah I was kinda just thinking that using just one cab would be better. Though if I were to set the 1960 Lead at 16 ohms and use the 8 ohm Marshall together with the head, how much power would be coming out of the head and what would the impedance become?


I see you're already losing your hearing. :)


I'm kidding with you.

140W...200W...you got enough power there to peel paint! :D
Haha. I use ear protection. Enough power to peel paint, break windows and melt hearts.
 
Yeah I was kinda just thinking that using just one cab would be better. Though if I were to set the 1960 Lead at 16 ohms and use the 8 ohm Marshall together with the head, how much power would be coming out of the head and what would the impedance become?



.
well .... it'd be around 6 ohms which would have the amp putting out maybe 125-150 watts.
 
well .... it'd be around 6 ohms which would have the amp putting out maybe 125-150 watts.
That's not too bad, I'm better off with just the Lead 1960 at 4 ohms to get the full 200 watts though. How does it work if I we're to run two Lead 1960 cabs at 4 ohms each? What would happen then.

Sorry for the questions, amp output has just been something I've never really been able to grasp.
 
That's not too bad, I'm better off with just the Lead 1960 at 4 ohms to get the full 200 watts though. How does it work if I we're to run two Lead 1960 cabs at 4 ohms each? What would happen then.
Well, your amp would put out 400 watts....for about 10 minutes before it started on fire.


When you have two matching cabinets, the impedance is cut in half. Two 16 ohm cabs will be 8 ohms, two 8 ohm cabs will be 4 ohm, etc...


AS the impedance goes down, the wattage goes up. 100 watts at 16 ohms will be 200 watts at 8 ohms, etc...

If you run an amp into a cabinet that has a lower impedance than it is designed for, you will blow up the amp.
 
Well, your amp would put out 400 watts....for about 10 minutes before it started on fire.


When you have two matching cabinets, the impedance is cut in half. Two 16 ohm cabs will be 8 ohms, two 8 ohm cabs will be 4 ohm, etc...


AS the impedance goes down, the wattage goes up. 100 watts at 16 ohms will be 200 watts at 8 ohms, etc...

If you run an amp into a cabinet that has a lower impedance than it is designed for, you will blow up the amp.
So in order to run a fullstack with my head, I would need two 8 ohm cabs, to make the impedance 4 ohms to get a full 200 watts coming out of each cab, am I correct? Also to get the full 200 watts I could use one 4 ohm cab.

I'm a little confused with the Marshall 1960 Lead cab though, it has two jacks, one at 4 ohms and one 16 ohms, and the stereo switch to put it at 8 ohms? Which jack do I use then, if I had two 1960 lead cabs set for 8 ohms stereo?
 
So in order to run a fullstack with my head, I would need two 8 ohm cabs, to make the impedance 4 ohms to get a full 200 watts coming out of each cab, am I correct? Also to get the full 200 watts I could use one 4 ohm cab.

I'm a little confused with the Marshall 1960 Lead cab though, it has two jacks, one at 4 ohms and one 16 ohms, and the stereo switch to put it at 8 ohms? Which jack do I use then, if I had two 1960 lead cabs set for 8 ohms stereo?
well, if they're set for stereo they need 2 amps each right?
They separate the 4 speakers (that add up to 16 ohms) into two pairs which are 8 ohms each.
So does it have 2 jacks to plug into if you use it stereo?
Seems there'd have to be 2 or it wouldn't be stereo.
If it really is stereo then I'm guessing one jack would go to two speakers and the other jack will go to the other two.
 
If you want to use a full stack, you would need two of those cabinets set to 16 ohms.

If you have two amps and want to run the cabinet is stereo, you would set it to stereo and both sides would be 8 ohms each

If you want to just run one cabinet, you can set it to 4 ohms or 16 ohms and see which one sounds better. Even though 4 ohms will give you more wattage, it won't be significantly louder than 16 ohms. You need 10 times the wattage to get twice the volume.

Worrying aout how much wattage you are creating with different cabinet impedances is a waste of time. The impedance may affect the sound, but that normally isn't the case with solid state amps.
 
And just as an additional comment ..... it's not true that halving the impedance doubles the output.
It depends on the power supply. While there are amps that can do that, I also see plenty of amps that will be rated at say, 100 watts into 8 ohms and 150 into 4 ohms.
For example ... a Peavey CS800 is rated perchannel at:
180watts into 8 ohms
300 watts into 4 ohms
and 400 watts into 2 ohms

notice that it never doubles when the impedance halves.
This is pretty common ....... it's actually not super common for an amp to actually double power when the impedance halves because it takes a very robust power supply which costs money.

Farview is very correct ...... the difference between 100 watts and 200 watts isn't significant as far as volume goes. It'll make some difference in headroom and probably tone.
So use whichever combination sounds best without worrying about getting the most volume.
 
..For example ... a Peavey CS800 is rated perchannel at:
180watts into 8 ohms
300 watts into 4 ohms
and 400 watts into 2 ohms

notice that it never doubles when the impedance halves.
This is pretty common ....... it's actually not super common for an amp to actually double power when the impedance halves because it takes a very robust power supply which costs money..
Would the amp try (for lack of a better was to say it) to double but run out of supply or thermal capacity, so they derate it to reflect that?
 
Maybe I should stop being stupid and just get a single cab that will handle the head perfectly. No Jerry-rigging with random unmatched cabs.
 
Also, say I used the 8 ohm 140 watt Marshall cab with a Marshall 1960 Lead cab set at 4 ohms, both plugged into my 200 watt at 4 ohm Sunn head, how would that work out?
Not a good idea. With those cabs, you'd be run at 2.6 ohms. Not a good idea. But, I am surprised that a Sunn head doesn't go to 2ohms. My Bass Coliseum 300 (same vintage) will carry a 2 ohm load.
 
Not a good idea. With those cabs, you'd be run at 2.6 ohms. Not a good idea. But, I am surprised that a Sunn head doesn't go to 2ohms. My Bass Coliseum 300 (same vintage) will carry a 2 ohm load.
Yeah, we already went over that.

I'm not actually too sure as to what the ohms are on the head, as it only says it's rated at 200 watts on the back of the head and nothing else. And whenever I search for it I can't find that specific model. And there's no year on the amp itself.
 
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