Any tonal difference between 4 or 8 ohm cabs?

[cfsporn]

The output side of the transformer is ( approximately ) paired to the expected load. The total forms an appropriate back loading to the front side of the transformer to get the rated power. Something like that, I think, one of the real tube guys may shoot me.

I'm sorry, but I don't quite understand.

 

[Yorin]

this seems perfectly reasonable to me, don't know why there's any fighting about it.

as for the OP, he's probably asking with the idea of "one cab to get all the watts". the answer to his likely actual question is, "if it's a big cab that you'd never need two of, make it 4Ω; if it's a small cab make it 8Ω so you can get another one and stack 'em."

Well the discussions started when i was looking for a new 4x10 cabinet. Normally i use a 4ohm since i dont stack them anyways and with 4 ohm i have more power. But some people said that 8ohm 'sounded' better even if you have less power. And since i have plenty of power even at 8ohm they recommended an 8ohm instead. It got me curious if there was any difference except volume.

 

[Downunderwonder]

I'm sorry, but I don't quite understand.

That makes two of us. The output transformer has a selection of windings on the output side, you know what a transformer is/does right? Low current high voltage tube signal on the input side windings excites low volt high current on the speaker side. A magnetic field is shared by the coils with the help of a big piece of iron. I forgot the maths but less coils on output equals less voltage higher current and within reason the power stays the same. The speakers form part of the balancing act in the transformer.

 

[cfsporn]

That makes two of us. The output transformer has a selection of windings on the output side, you know what a transformer is/does right? Low current high voltage tube signal on the input side windings excites low volt high current on the speaker side. A magnetic field is shared by the coils with the help of a big piece of iron. I forgot the maths but less coils on output equals less voltage higher current and within reason the power stays the same. The speakers form part of the balancing act in the transformer.

I am semi-aware of what a transformer is and what it does, but I am not at the point where I understand how it does it and the many applications of them.

What I am wondering, is if a tube amp is putting 200 watts through all of its taps (lets say 8Ω, 4Ω, and 2Ω), then wouldn't it be delivering 40V, 28.3V, and 20V into the voice coils of an 8Ω, 4Ω, and 2Ω speaker?

 

[agedhorse]

And yet it's funny to see some people SWEAR to hear the difference. I would love to see how they would do in a blind testing .

Depending on how well the matching of parameters is achieved, the difference may not be noticeable, or they could be pretty obvious. It really depends.

 

[agedhorse]

I am semi-aware of what a transformer is and what it does, but I am not at the point where I understand how it does it and the many applications of them.

What I am wondering, is if a tube amp is putting 200 watts through all of its taps (lets say 8Ω, 4Ω, and 2Ω), then wouldn't it be delivering 40V, 28.3V, and 20V into the voice coils of an 8Ω, 4Ω, and 2Ω speaker?

Yes, correct. The transformer steps the voltage down from the plate level voltages. The reason it's done this way is because the load (impedance) that the plate circuit sees needs to be relatively constant (for power transfer efficiency), so the 2 ohm load of the speaker is reflected at a different ratio than the 8 ohm speaker load. The speaker load divided by the transform ratio for it's load tap will all roughly equal the same plate load to the tube output stage.

 

[cfsporn]

Yes, correct. The transformer steps the voltage down from the plate level voltages. The reason it's done this way is because the load (impedance) that the plate circuit sees needs to be relatively constant (for power transfer efficiency), so the 2 ohm load of the speaker is reflected at a different ratio than the 8 ohm speaker load. The speaker load divided by the transform ratio for it's load tap will all roughly equal the same plate load to the tube output stage.

So then, on that tube amp, an 8Ω speaker would be louder than a 2Ω, no? Lets just assume that the 8Ω and 2Ω speakers are otherwise identical which is obviously impossible.

 

[B-string]

I am semi-aware of what a transformer is and what it does, but I am not at the point where I understand how it does it and the many applications of them.

What I am wondering, is if a tube amp is putting 200 watts through all of its taps (lets say 8Ω, 4Ω, and 2Ω), then wouldn't it be delivering 40V, 28.3V, and 20V into the voice coils of an 8Ω, 4Ω, and 2Ω speaker?

To add to agedhorse, the transformer is not a constant current device (or fixed voltage for clarity). Very basic when voltage drops, what happens to current to maintain the same wattage. The primary is the basic "load" for the tubes, the reason why the secondary should not be run open without a load.

 

[B-string]

So then, on that tube amp, an 8Ω speaker would be louder than a 2Ω, no? Lets just assume that the 8Ω and 2Ω speakers are otherwise identical which is obviously impossible.

I can assume my last post answered?
"Watts" is voltage (E) multiplied by current (I) if you change R in ohms law with a "fixed" wattage E and I are on a tetter toddler.

 

[agedhorse]

So then, on that tube amp, an 8Ω speaker would be louder than a 2Ω, no? Lets just assume that the 8Ω and 2Ω speakers are otherwise identical which is obviously impossible.

No, they would be the same volume because the delivered power would be the same. The 2 ohm speaker would have lower voltage delivered but the current would be higher. Ohm's law is important to understand here.

 

[Downunderwonder]

The power is ''transformed'' from high voltage low current to lower voltage at higher current. It's the same power ( less heat losses ). It would be better for one of the more knowledgeable geezers to further explain the implications of hooking up non spec loading.

Connecting 8 ohm to 2ohm tap is bad news. I can't figure the logic.

 

[DinoRock]

I apologize if this is off topic, but it seems like this is the right group of folks who could help me understand this. Further, it may be relevant to this thread, I'm just not sure.

In the Steve Luongo interview of Pete Townshend on John Entwistle, starting at about 4:20, Pete talks about the harmonics that John generated live in large rooms. He talks about the fact that these harmonics could not be re-created in the studio, which was a problem for the band. He talks about doing the '89 tour at a lower volume level, which meant that the band needed to be augmented in order to deal with the lack of harmonics that they would not get from John playing at a lower volume, which meant they needed many more musicians to fill in. Anyway, its a great interview concerning bass playing and all of JAE's contributions, all of the air that Pete has to fill live once John passes, the bass solo on My Generation, John's hearing, John and Pete dueling live, and so on.

 

[agedhorse]

In large rooms, the reflections will be more interesting and complex in general, and the time constants between reflections will be longer with more low pass filtering from the room. I suspect this is what he is referring to.

 

[seamonkey]

Get and IR response of a hall or large room and run your tracks through a convolution, and voila! - it's the same as being in the hall. Popular in recording, Convolution is even used in live performances these days.

Can't always afford a large hall and audience for recording.

 

[B-string]

The power is ''transformed'' from high voltage low current to lower voltage at higher current. It's the same power ( less heat losses ). It would be better for one of the more knowledgeable geezers to further explain the implications of hooking up non spec loading.

Connecting 8 ohm to 2ohm tap is bad news. I can't figure the logic.

Bares answering. If the expected load at the tube plates is say 2,000 ohms with a 2 ohm load on the 2 ohm tap, instead you hook up an 8 ohm load that will result in a 8,000 ohm load which is outside the desired plate loading.

Side note: Dude what did you do?

 

[Ric5]

How many ohms is this speaker?

 

[cfsporn]

No, they would be the same volume because the delivered power would be the same. The 2 ohm speaker would have lower voltage delivered but the current would be higher. Ohm's law is important to understand here.

Got it.

I think I took the idea that speakers are "voltage coupled devices" (I think Bill Fitzmaurice said that once so I assume it's true.) and ran with it way past the finish line.

Thanks to you and B-String!!

 

[B-string]

Many hate water analogies, but If you have 90 psi of water pressure (Voltage) it does not do anything till you open a faucet to start the flow (gpm~current).