mono vs stereo amps

[dmakfan]

Hey,

Is there a tonal advantage of having a 2x12" pushing the same combined power out as a 1x12"?

The only thing I can really think of is that you'd be driving each speaker half as hard?

Thanks,
D

 

[Blue Bear Sound]

There IS a big tonal difference... a 2x12 sounds a lot beefier than a 1x12....

You're wrong for assuming the 2x12 is "stereo", though -- it isn't.........

 

[dmakfan]

Right, it's just two channels, but not really "stereo".

So do they typically have 2 spereate power amps, one for each speaker?

I guess when you crank it up, a 1x12 would be running at it's limits, whereas 2x12s at the same power would be half that.

 

[Blue Bear Sound]

It's not 2-channels - it's 2 speakers powered by a single-channel amp section (at least, that's the case in my Yamaha DG100-212, compared to my DG80-112.)

I'm not sure what the internal wiring is like, but the load the amp will see depends on whether the speakers are wired in series or parallel. The load would be lower if wired in parallel, but the amp will work harder.

 

[dmakfan]

Thanks for the info Blue Bear Sound.

I'm not sure if I agree that the amp would work harder though 'cause the amp will be providing some power P. If the load is haved because of the speakers being in parallel, then you can get the same power by having the voltage, or in this case the volume.

So to get the same total output, you can do it at half the voltage, but it will cost you twice the current => amp working just as hard.

But I guess at higher voltages, the amp may start to clip etc., and would distort the sound. by the way, I'm using a solid state amp, so the clipping is more obvious (and ugly).

But whatever the reasons is, all I wanted to hear is that 2-speakers is better than 1

Thanks again,
Dave

 

[Blue Bear Sound]

But whatever the reasons is, all I wanted to hear is that 2-speakers is better than 1

I don't think you can say that.... I bought the single speaker version of the amp because there were times when I wanted a thinner sound and the beefier 2x12 sound was too thick for what I was doing.

It's more about "what's approriate for a given context" than "2-speakers are better than one" in any given situation!

 

[dmakfan]

That's true too

I guess a lot of it has to do with the amp too. I'm using a Fender Princeton 112 Plus 65W right now, and once I hit about 2 on the volume dial (most of the power is between 0 and 2.5), I loose all the bass and I hear almost all mids.

I borrowed a Fender Princeton Chorus 2x10 60W last weekend, and the tone was immeasureably better. Granted there are probably other variations between the amps, but I just found that the tone (especially the drive channel) was a lot smoother and fuller, even with the smaller speakers.

Maybe it's more the amp difference than the speaker difference

 

[juststartingout]

Maybe it's more the amp difference than the speaker difference

It's actually the combination of amp and speakers. If you have the opportunity, try hooking your amp up to a 4x12 cab.

To see the difference in speakers, it's important to run the comparison at the same amp settings. The reason that you get more mids when turning the amp up is that the mid freq range is where the guitar is at, so it will be the first to come to life. Just turn the mids down on the amp. Each power setting will require different bass-mid-treble settings to keep the sound the same.

Speaker do make a difference. To see this, go down to your local shop. Grab one of the 15W Fender champs. Play it a little, then plug in a 4x12 cab and keep the settings the same and you will understand.

 

[Light]

I'm not sure if I agree that the amp would work harder though 'cause the amp will be providing some power P. If the load is haved because of the speakers being in parallel, then you can get the same power by having the voltage, or in this case the volume.

Sorry, you don't get to disagree on this one. It is not an opinion. It is physics, and it is a fact.


Light

"Cowards can never be moral."
M.K. Gandhi

 

[dmakfan]

I know it's physics... that's why I don't see how the amp shouldn't have to work harder. First of all, by definition, if the power is the same, the amps must be working just as hard (work = power * time). So the answer should be obvious right off the back. But if you want the numbers:

In the one speaker system, your amp will provide power as:
P=I1*V1 or P=I1*I1*R.

So if you put two identical speakers in parallel, if you want the exact same power, you get:
P=I2*V2 or P=I2*I2*(R/2)

so I2*I2*(R/2) = I1*I1*R, or I2=root(2)*I1.

Sub the values in for the 2 speaker system and you get:
P = (root2*I1) * (root2*I1) * (R/2)
= I1 *I1 * R
which looks exactly the same as the 1 speaker system. Kind of makes sense because we're saying that we want the same power output, so by definition they have to do the same amount of work (Work=P*time).

There are differences in how loud and clear the different combinations will sound (because of dispersion of sound, how much air it is moving etc. etc), as well as possible clipping effects etc. because of the op-amps crapping out.

But to me, it looks like the amps work exactly the same amount. I'm open to being corrected, 'cause I don't know much about guitar amps. And you seem to indicate you understand this stuff, so maybe you can explain why one will work harder than the other.

 

[Blue Bear Sound]

The amp with the speakers in parallel will draw more current to drive the lower load than the same amp whose load is higher with the speakers in series.

The amp has to work harder to accommodate the increased current requirements of the low load.

 

[dmakfan]

It will draw more current, but at a lower voltage to get the same power. Therefore the work is the same.

Obviously if you drive it at the same voltage and twice the current, you'll get twice the work, but you're also getting twice the volume But that's not what I was asking about.

 

[Blue Bear Sound]

No - the voltage is the same in both cases....

 

[dmakfan]

I think we're dancing around a moot point here

I originally said that IF the power output was the same, both amps would have to work as hard. Therefore, since you half the impedance by putting the two speakers in parallel, you double the current. So to get the same power, you have to half the voltage.

If you keep the voltage the same, and put both speakers in parallel, you'll double the current, and would in theory be playing through two identical 1x12 amps (in theory). Sounds superimposes, giving you twice the volume.

So to get the same volume, you have to half the voltage too.

But maybe I don't know what I'm talking about... seems to make sense to me

 

[Blue Bear Sound]

You are setting up 2 different load conditions keeping the voltage the same.

A lower load causes greater current draw for the same voltage than a higher load does for the same voltage.

The higher current draw may be beyond the amplifier's ability to deliver in low load situations. That's where the amp has to work harder....

 

[juststartingout]

Bottom line here.

Your amp will work just as hard running 1 speaker who's total impedence is 8 ohms or 100,000,000 speakers who's total impedence (at the amp) is 8 ohms.

The 100,000,000 speakers will be louder than the 1 speaker. It has a lot more area that is pushing the air, so it will be louder.

A 100 watt amp is not 10 times louder than a 10 watt amp. Decibals climb at an expotential rate to the power and geatly depend on the speakers you are using, mainly the efficiency of the speakers.

If you are trying to decide between 1, 2 and 4 speakers, go down to your local shop and try each and see what you like. I can tell you from experience that a 15 watt amp can keep up to a drum set if it's run through a 4x12 cab. With the 1x8 that it comes with, will not even come close.

You can run all the equations you want, but it won't tell you anything. Once you run a test and listen to the actual sounds in different configurations, you will have a much better understanding.

 

[dmakfan]

Hey Juststartingout,

I agree with you, and I was just getting finicky because it was contradictory to say that at the same output power, one configuration should have to work harder than another.

All said and done, I'll just go to my local store and play with a few amps and see which ones sound best I just like to have an understanding WHY one might be sounding better than another.

 

[Sky Blue Lou]

http://www.guitarnuts.com/amps/index.php

Somebody posted this link the other day. Sorry - I forget who.


lou

 

[faderbug]

Bottom line here.

Your amp will work just as hard running 1 speaker who's total impedence is 8 ohms or 100,000,000 speakers who's total impedence (at the amp) is 8 ohms.

The 100,000,000 speakers will be louder than the 1 speaker. It has a lot more area that is pushing the air, so it will be louder.

????????

when the amp delivers the same amount of energy to the speakers 100.000.000 speakers will each recieve 1/100.000.000's of the energy one speaker would recieve. the total energy output of the speakers remains the same, wether it's one speaker or 100.000.000.

so how can 100.000.000 speakers be louder then 1?

correct me if i'm wrong.

 

[juststartingout]

so how can 100.000.000 speakers be louder then 1?
correct me if i'm wrong.

It's because of the efficiency of the speakers. Without getting into a lot here, at lower volume the speaker will use the energy much more efficiently (to a point). Just go down to your local shop and take a practice amp with 1 - 8 inch in it, and play it. Then plug a 4 speaker cab into it. At the same volume setting the 4 speaker cab with be substantially louder.

Think about it, a 20W amp driving 2 - 4x12 cabs will keep up to a drummer. But a 100W amp driving 2x10 inch speakers doesn't stand a chance of being heard. That's why the speakers are a more critical choice than the amp is for a given venue.