4x12 cab in stereo?

[cellardweller]

I'm curious what possible benefits running a 4x12 cab in stereo would have?

I don't have any stereo effects. Would the impedance be preferable (8 ohms as opposed to 16 ohms)???


BTW, this is one of those, "oh wow, I can do that with this thing I've had all of these years" questions.

-Thanks

 

[mshilarious]

I'm curious what possible benefits running a 4x12 cab in stereo would have?
-Thanks

I used to have a stereo 2x12 cab. It's pretty cool for rehearsal but I don't think it helps much live. And without stereo effects, I don't think it would do anything different at all.

 

[Farview]

If you don't have any effects, it won't do you much good. Even if you had effects, you would need 2 poweramps (or a stereo head) to get any benefit. I suppose if you used only 1/2 of the cab it would be easier to push the speakers a bit more.
There is no advantage to running 8 ohm vs. 16 ohm unless you are trying to match another cab.

 

[Imaduck]

There is no advantage to running 8 ohm vs. 16 ohm unless you are trying to match another cab.

*sigh*
Alrighty, yes, it is important to match impedance with other cabs that you are using, however, there is much more to it than that. What's really important, is matching your impedance with your amplifier.

See, "impedance" is the measure of the resistance your speakers give to the power being pushed out of your amplifier. This means that running your speakers at 16 ohms will significantly reduce the power pushed out by your amp compared to running them at 8 ohms (it almost halves the power on some amplifiers!). So, to answer a very common question, yes, a 16 ohm cab WILL NOT get as loud as an identical 8 ohm cab that otherwise has the same amp and speakers.

So then why would you ever want to run a cab at a higher ohmage? Well first off, and most importantly, is you have to match whatever your amp will support. It should say right on the back of your amp, and some amps will even have a switch. Most amps are either 4 or 8 ohms; some high-end or high-power amps go all the way down to 2 ohms, and a few rare amps are designed for 16 ohms (also, if you're using a stereo amp in bridge mode, you usually need to up the resistance). Now, you can always go over the resistance stated on the amp (though you'll have a power cut), but NEVER under it. Going under it will possibly mess up your amp, and very very likely mess up your speakers.

The other reason you would want to change your impedance is to match another cab, like Far mentioned. Most speaker outs on amps are parallel (it'll say on the back), meaning your total resistance is going to be (speaker 1 ohms + speaker 2 ohms) / 2. This number also cannot go below the number stated on the amp. Also, if the resistance of the speaker cabs is not equal, then you will have very uneven power distribution, so it's always good to make sure speaker cabs match.

Additionally, I should mention that some people simply prefer higher resistance because it cuts down on some line noise and lessens the risk of blowing your speakers.

Anyway, hope this helps!

 

[Imaduck]

Oh yeah, and about running in stereo. For the most part, it is pretty useless without a stereo amp and/or stereo effects. If you wanted to play softer or preferred only using two speakers, you could put it in stereo and use only one side, or if you wanted to share the cab for whatever reason with somebody else, you could put it in stereo and each use a side. Also, if you really wanted to, I guess you could use a Y-cable and put your guitar signal through two different amps, and use each amp to power a side of the cab. Granted, you'll probably never do any of these, but you could if you really wanted to.

 

[Farview]

*sigh*
Alrighty, yes, it is important to match impedance with other cabs that you are using, however, there is much more to it than that. What's really important, is matching your impedance with your amplifier.!

Yes but what I was refering to was if you have an 8 ohm cab and you want to have another one, you could match this up with that cab. Seeing as how ( with a tube amp anyway) you shouldn't mix cabs of different impedance.

*See, "impedance" is the measure of the resistance your speakers give to the power being pushed out of your amplifier. This means that running your speakers at 16 ohms will significantly reduce the power pushed out by your amp compared to running them at 8 ohms (it almost halves the power on some amplifiers!). So, to answer a very common question, yes, a 16 ohm cab WILL NOT get as loud as an identical 8 ohm cab that otherwise has the same amp and speakers.

Pure unadulterated Bullshit! It reduces the wattage, not the power. Speakers react to voltage swing, which does not change. The wattage changes as the impedance is changed because of the formula that is used to determine wattage. (look it up) The reason you have an impedance selector on guitar amps is to match the cabinet with the appropriate winding in the output transformer. (so you don't over heat it)

So then why would you ever want to run a cab at a higher ohmage? Well first off, and most importantly, is you have to match whatever your amp will support. It should say right on the back of your amp, and some amps will even have a switch. Most amps are either 4 or 8 ohms; some high-end or high-power amps go all the way down to 2 ohms, and a few rare amps are designed for 16 ohms (also, if you're using a stereo amp in bridge mode, you usually need to up the resistance).

We are talking about a guitar cabinet here. Marshalls always go to 16 ohms The cabs in mono mode are 16 ohms (so you can run 4 of them with 1 head at 4 ohms if you choose)

Now, you can always go over the resistance stated on the amp (though you'll have a power cut), but NEVER under it. Going under it will possibly mess up your amp, and very very likely mess up your speakers.

Never do this with a tube amp. Solid state is much more forgiving. You will not have a power cut. If you go under, you run the risk of melting the amp and sending DC to the speakers. (thus melting them)

The other reason you would want to change your impedance is to match another cab, like Far mentioned. Most speaker outs on amps are parallel (it'll say on the back), meaning your total resistance is going to be (speaker 1 ohms + speaker 2 ohms) / 2. This number also cannot go below the number stated on the amp. Also, if the resistance of the speaker cabs is not equal, then you will have very uneven power distribution, so it's always good to make sure speaker cabs match.

More bad info. (16ohms + 16ohms) /2 =16ohms. this is wrong
It is simply cab1/cab2=impedance
If the impedance (not to be confused with resistance) is not equal between the cabs, you will simply not come up with an even impedance between the 2 (therefore not be able to match it with the switching options on your head)

Additionally, I should mention that some people simply prefer higher resistance because it cuts down on some line noise and lessens the risk of blowing your speakers.

If you are getting line noise between the power amp and the speaker cabinet, you need to stop setting your rig up on top of a radio transmitter. There is almost no probable way to pick up line noise in a speaker cablethat would have enough power to move a speaker. Thats one of the reasons speaker cable isn't shielded. (the other is that shielded cable has an impedance of it's own that you would have to deal with)

Anyway, hope this helps!

I don't think so. BTW impedance is like resistance, but it changes with frequency.

 

[mshilarious]

It reduces the wattage, not the power. Speakers react to voltage swing, which does not change.

I'm bad at physics, but what is wattage except a measure of power? If the voltage is constant, changing the resistance does change wattage which is work done, no? Could you clarify?

More bad info. (16ohms + 16ohms) /2 =16ohms. this is wrong
It is simply cab1/cab2=impedance
If the impedance (not to be confused with resistance) is not equal between the cabs, you will simply not come up with an even impedance between the 2

Is the correct formula not (cab1*cab2)/(cab1 + cab2)?

 

[Farview]

I'm bad at physics, but what is wattage except a measure of power? If the voltage is constant, changing the resistance does change wattage which is work done, no? Could you clarify?

Wattage is the disipation of power, as you send voltage through the speakers, they turn the voltage into kenetic energy (sound) and heat. How far the speakers move is a function of how much voltage (and what direction the voltage is moving) you send to it.

The formula is: wattage (P) = voltage (E) squared/ resistance (Impedance)
So you can see that changing the impedance will affect the wattage without having anything to do with the voltage. The voltage is what makes the speaker move.

Is the correct formula not (cab1*cab2)/(cab1 + cab2)?

Yes you are right, but if you are using cabs with equal impedance, my formula is easier to do in your head

This is an over-simplified explanation. The fact is that impedance changes with frequency so the whole mess is dynamically changing as you play.

 

[cellardweller]

Well, that all was slightly confusing!

I suppose it is noteworthy to add that my cabinet has two inputs, and my amp has 5 or 6 outputs, rated from 4-16 ohms. I'm pretty sure it is 5 outputs, one for 16 ohms, two for 8 ohms, and two for 4 ohms.

The question for me remains, would the lower impedance result in more efficient usage? I've always used the 16 ohm output, as that is what my cab in mono position is rated at. I could use the two 8 ohm outputs as well, could I not? Would this benefit me at all?

Thanks
CD

 

[futurestar]

2 related questions:

1) How about running out of my head at 8 ohms into one side of a stereo Marshall cab (at 8 ohms as well). Is it ok to do this? I assume so ...

2) Running out of both 4 ohm outs of my head - left and right into my Marshall cab. (At 4 ohms of course).

 

[futurestar]

2 related questions:

1) How about running out of my head at 8 ohms into one side of a stereo Marshall cab (at 8 ohms as well). Is it ok to do this? I assume so ...

2) Running out of both 4 ohm outs of my head - left and right into my Marshall cab. (At 4 ohms of course).

Disregard question #2 - I forgot that the cab is 8 ohms a side in stereo! I need to grab a cup of java and wake up!

 

[TexRoadkill]

The question for me remains, would the lower impedance result in more efficient usage? I've always used the 16 ohm output, as that is what my cab in mono position is rated at. I could use the two 8 ohm outputs as well, could I not? Would this benefit me at all?

There would be no benefit unless:
1. You are doing some type of stereo fx on the guitar signal (delay, chorus, reverb,etc)

and

2. Your amp is putting out a stereo signal.

 

[Farview]

Well, that all was slightly confusing!

I suppose it is noteworthy to add that my cabinet has two inputs, and my amp has 5 or 6 outputs, rated from 4-16 ohms. I'm pretty sure it is 5 outputs, one for 16 ohms, two for 8 ohms, and two for 4 ohms.

The question for me remains, would the lower impedance result in more efficient usage? I've always used the 16 ohm output, as that is what my cab in mono position is rated at. I could use the two 8 ohm outputs as well, could I not? Would this benefit me at all?

Thanks
CD

What all that meant was that it makes no difference (sound, volume, or efficiency in your case) what impedance you run at as long as the cabinet matches the output of the amp. Yes, you could run out of the two 4 ohm outputs into the two sides of the cabinet, (because two 8 ohm loads hooked together this way would make 4 ohms) but why would you bother.

There is one 16 ohm output on the amp for running one 16 ohm cabinet
There are two 8 ohm outputs for running two 16 ohm cabs (that makes 8) or one 8 ohm cab
There are two 4 ohm outputs for running two 8 ohm cabs (that makes 4) or 1 4 ohm cab.

I will try to find a better way to explain my earlier post and post it later

 

[cellardweller]

I appreciate the patience, but yes, I think I get the gist of it, as far as calculating the correct impedance/ohms for a cabinet/amp (two @ 16 ohms would equal 8 ohms, etc.).

I was mainly curious if there was an advantage to different impedances, so I would officially consider this question answered .

Thanx again.

 

[Imaduck]

Pure unadulterated Bullshit! It reduces the wattage, not the power. Speakers react to voltage swing, which does not change. The wattage changes as the impedance is changed because of the formula that is used to determine wattage. (look it up) The reason you have an impedance selector on guitar amps is to match the cabinet with the appropriate winding in the output transformer. (so you don't over heat it)

Allow me to clarify. IF you have an amp that allows you to select the impedance ON THE AMP, then yes, matching them will result in the same power and loudness (well, close enough at least).

However, he was talking about switching it ON THE SPEAKER, so if you simply switch it on the speaker, and you do not have an amplifier that supports variable impedance, then using a higher resistance on the speaker will result in a less powerful sound (I do realize that it's still technically the same amount of "power" being output, but the wattage is halved, and when most people think about "power" and "loudness" in these situations, they're thinking "wattage).

Never do this with a tube amp. Solid state is much more forgiving. You will not have a power cut. If you go under, you run the risk of melting the amp and sending DC to the speakers. (thus melting them)

As I said before, you WILL have a wattage cut and volume cut. If you don't believe me, go use a 4 ohm amplifier with a 16 ohm cab and crank it. Then change the cab to 4 ohms and be marveled at how much louder it gets.

More bad info. (16ohms + 16ohms) /2 =16ohms. this is wrong
It is simply cab1/cab2=impedance
If the impedance (not to be confused with resistance) is not equal between the cabs, you will simply not come up with an even impedance between the 2 (therefore not be able to match it with the switching options on your head)

Well the actual difference is that Resistance is DC, and impedance AC. I'm sorry I did goof up here, anyway, to get it straight, people need to worry about resistance, and the proper formula for all that is:
Total resistance = (R1*R2)/(R1+R2)
I appologize for this mistake.

If you are getting line noise between the power amp and the speaker cabinet, you need to stop setting your rig up on top of a radio transmitter. There is almost no probable way to pick up line noise in a speaker cablethat would have enough power to move a speaker. Thats one of the reasons speaker cable isn't shielded. (the other is that shielded cable has an impedance of it's own that you would have to deal with)

I do realize that, for the most part, speaker cables are pretty much foolproof against line noise, however, some people will contend it is still there, and in theory higher resistance would lessen this, along with certain types of hum.

And franky, I'm sorry if I didn't clarify all of my stuff, but there's no need to be a jerk about it, especially when you're not a 100% accurate yourself.

 

[boingoman]

Cellardweller-No. As Farview stated, tube amps like to be run at a specified impedance. They don't like to be mismatched. The different impedance settings on your head are there so you have some more flexiblity with cabinet choices.

 

[mshilarious]

Sort of back on topic, if I had a 4x12 cabinet and I was bored, I think I'd put four different speakers in it for more options when recording. That's lots more interesting than stereo.

 

[cellardweller]

Cellardweller-No. As Farview stated, tube amps like to be run at a specified impedance. They don't like to be mismatched. The different impedance settings on your head are there so you have some more flexiblity with cabinet choices.

By "specified" impedance I'm not sure what you mean.
If there are dedicated speaker outputs, wouldn't you consider this a "specified impedance"?

And just so I understand, and am sure we are on the same page, let me more clearly try to describe this

My amp has 5 outputs, rated from 4-16 ohms
one for 16 ohms, two for 8 ohms, and two for 4 ohms.

My cabinet has two 1/4 inputs, labeled "left/input" and "right/output". There is a two position switch labeled "mono 16 ohms" and "stereo 8 ohms".

Does this indicate to you that in "stereo" that each individual input would be 16 ohms, and I should then run from the two 8 ohm ouputs from my amp???

I promise I will put this to bed once I understand this...

 

[Sonixx]

... Wattage is the disipation of power, as you send voltage through the speakers...

Not so Dr Watson...

Votage is applied across a load (Speaker) and the Current runs through the speaker... This is not a distinction without a difference.

The formula is: wattage (P) = voltage (E) squared/ resistance (Impedance) So you can see that changing the impedance will affect the wattage without having anything to do with the voltage. The voltage is what makes the speaker move.

Sorry but... your formula is only good for DC... not AC... the transfer of AC power is very complex, but maximum power is transferred when the load and source impedances match. Impedance and restistance are not the same thing. While a speaker may measure around 4, 8 or 16 ohms resistance, the transformer will see an entirely different load. For an 8 ohm load the amp's output transformer will see anything from < 4 to > 16 ohms based on frequency. The transformers impedance also varies with frequency. Both the speaker and transformer are inductive in nature... but, when the amp's ouput load is mismatched, this plays havoc with the transformer and output circuitry in the amp. The power has to be delivered somewhere and usually the transformer ends up eating it by dissipating it as heat. While you may get away with a mismatch for some time, it's damaging your amp (output transformer and power tubes) in the long run. Also, the frequency response is not optimum. Shit, this way to technical...

Now, what was the question:

I'm curious what possible benefits running a 4x12 cab in stereo would have?

I don't have any stereo effects. Would the impedance be preferable (8 ohms as opposed to 16 ohms)???

None from an impedance standpoint... unless you're doing it to match the cab and head. The load and amp need to match... if your cab is 16 ohms, then set the head to 16. If your amps output stage is solid state, refer to the manual.

Here's where a stereo cab works... you have a stereo out effects processor, you have two guitar amps, each amp will drive half the cab. You mic the two different amps speakers (two mics) and run the guitar into the house PA in stereo.

 

[Sonixx]

By "specified" impedance I'm not sure what you mean.
If there are dedicated speaker outputs, wouldn't you consider this a "specified impedance"?

And just so I understand, and am sure we are on the same page, let me more clearly try to describe this

My amp has 5 outputs, rated from 4-16 ohms
one for 16 ohms, two for 8 ohms, and two for 4 ohms.

My cabinet has two 1/4 inputs, labeled "left/input" and "right/output". There is a two position switch labeled "mono 16 ohms" and "stereo 8 ohms".

Does this indicate to you that in "stereo" that each individual input would be 16 ohms, and I should then run from the two 8 ohm ouputs from my amp???

I promise I will put this to bed once I understand this...

I don't think the amp is designed to have a load on each output connection. Pick an output connector and match the load to it. Refer to the manual concerning the two 8 and two 4 ohm connectors. I would think the amp is designed to handle one 16 or two 8 or two 4 ohm loads.

I would run the cab in mono 16, and plug it into the 16 ohm amp output.