This is probably a dumb question but the "speaker" setting on the amp blocks...

Surrealistic Brillo

Surrealistic Brillo

Inspired
...what is the difference between the "speaker" setting on the amp block and the cabinet block?

I hadn't messed with the speaker setting on the amp block because I don't use the cab blocks since I use traditional guitar amps, but out of curiosity I was donging around with some of the "speaker" settings on the cab block and noticed a difference in the tone that I liked.

In a real world amp example (if there is one), what is the "speaker" setting doing that a real cab or cab block doesn't do? Is there an apples to apples example that will help me understand what is happening beyond just being an EQ?

Thanks in advance for your help. :)
 
Hellbat said:
The speaker tab is settings that affect the interaction of the power amp with a speaker load. Lots of good info in this thread...

http://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003/
Click to expand...


This is AWESOME information. Thanks, Hellbat.

So I guess the only question that remains in my mind is is the speaker tab of the amp block more of a theoretical area that simulates the response of the way the amp's output section interacts with the speaker or cab block, or does it model an actual part of an amp...like the output transformer but unlike a real output transformer it's tunable...like a "build/modify your own output transformer" function?
 
The interaction between a tube power amp and the speaker is very real, and it is not simulated by the cab IR in the cab block.

On the speaker page of the amp block, you more or less describe the impedance curve (frequency dependant impedance) of the speaker. So you could say that unlike a real speaker, you can tune the impedance curve. In a perfect world, we could just tell the amp block, which speaker we are modelling in the cab block, and then it would choose the right impedance curve. But the reality that the physical cab also affects the speaker impedance curve, so you would have to measure it for each cab (could be done). Instead we have the opportunity to tweak the impedance curve by ear, which is probably lots faster than a measurement.

Does it make sense?

If you are running into the FX loop of a tube amp, one could probably argue that you are getting a double dose of speaker interaction, but if it sounds good, it is good ....
 
Smittefar said:
The interaction between a tube power amp and the speaker is very real, and it is not simulated by the cab IR in the cab block.
Click to expand...

Right...I guess my confusion is that an "interaction" requires two or more components to interact with one another. My understanding is that on a real amp it's the interaction between the amp's output transformer and the speaker. So if this feature set isn't clearly defined as say, "output transformer" on the amp block or "speaker coil" or "speaker impedance" on the cab block then is more like what I think of as a "theoretical feature set" like the ability to have a Fender Twin with EL84's and a Hiwatt tone stack?

So I guess I'm wondering why this "interaction" setting isn't on the cab block, for example? Or why the amp block was chosen to host these settings over the amp block?

I'm sorry if I'm appearing obtuse here...just trying to understand whether it makes more sense to view the "speaker" tab on the amp block as a virtual/tweakable transformer or some other way of controlling the interaction between an amp's output section and the speaker cab that doesn't have a real world example.
 
I would say that in a real amp, it is the tubes interacting with the speaker through the output transformer. The power amps ability to apply a voltage/current in the speaker coil depends on the impedance of the speaker. Most speakers have a nominal impedance of 8 or 16 ohms, but that is not the full picture. The impedance of the speaker depends on the frequency. Usually there is a resonant peak, and the impedance goes higher at high frequencies. This affects the frequence response of the amp (an extra EQ you could call it), but it will also give rise to a frequency dependant compression in the output stage, which is more complicated than just EQ.

This interaction needs to be in the amp block, because it is part of the amp modelling. But it would also be OK to call it speaker coil impedance modelling - although the cabinet (the wood of it) actually influences the impedance curve of the coil.
 
Smittefar said:
I would say that in a real amp, it is the tubes interacting with the speaker through the output transformer. The power amps ability to apply a voltage/current in the speaker coil depends on the impedance of the speaker. Most speakers have a nominal impedance of 8 or 16 ohms, but that is not the full picture. The impedance of the speaker depends on the frequency. Usually there is a resonant peak, and the impedance goes higher at high frequencies. This affects the frequence response of the amp (an extra EQ you could call it), but it will also give rise to a frequency dependant compression in the output stage, which is more complicated than just EQ.

This interaction needs to be in the amp block, because it is part of the amp modelling. But it would also be OK to call it speaker coil impedance modelling - although the cabinet (the wood of it) actually influences the impedance curve of the coil.
Click to expand...

Excellent. Thanks so much for your help. :)
 
To put it shortly, as I understand:
There is a natural amp to cab interaction in real amps. A connected cab makes the amp sound different.
Axe has no way of knowing what cab is connected or how it affects the amp (Neither a cab block (IR), nor a real cab is recognised), therefore you have to dial these things manually.
Currently, by default, the speaker page is set up for the most common cabs used for the particular amp.
 
FreeMind said:
To put it shortly, as I understand:
There is a natural amp to cab interaction in real amps. A connected cab makes the amp sound different.
Click to expand...

This is exactly it!

And this is why it makes a big difference, which kind of load box you use with a tube amp rig.

In this video, taps a signal from the speaker output of an amp with a DI. The DI signal is then processed with the same IR for all clips. The only difference between the clips is the load on the other side of the DI box. He loads the amp with 1) a speaker 2) old school resistive loads, and 3) moderne reactive loads. Everything is processed with the same IR and amp, but the load that the amp sees makes a big difference for the sound.

 
No dumb questions, it's a powerful feature.

Hellbat said:
The speaker tab is settings that affect the interaction of the power amp with a speaker load. Lots of good info in this thread...

http://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003/
Click to expand...

This article from Cliff is gold, I keep this 2 sentences:
1. Altering the frequency (Low Freq) will change the frequencies at which the power amp resonates and tuning this to the key you are playing in can be an effective strategy, e.g. set it to 82 Hz if playing in E.
2. So there is a relationship between LF Res, MV and Transformer Match.

If you want to go deep:
http://forum.fractalaudio.com/threads/about-matching-your-cabinets-resonant-frequency.79816/

http://forum.fractalaudio.com/threads/about-negative-feedback.79697/

http://forum.fractalaudio.com/threads/simulating-speaker-impedance-mismatch.77944/

http://forum.fractalaudio.com/threads/the-secret-weapon-transformer-match.98527/

http://www.sengpielaudio.com/calculator-AmplifierLoudspeakerAndOhm.htm

http://www.roger-russell.com/wire/wire.htm

http://www.roger-russell.com/wire/dampaugs.htm

http://www.roger-russell.com/wire/damptoole.htm


Lot of food here...
 
I found this in the wikipedia:
https://en.wikipedia.org/wiki/Damping_factor

In loudspeaker systems, the value of the damping factor between a particular loudspeaker and a particular amplifier describes the ability of the amplifier to control undesirable movement of the speaker cone near the resonant frequency of the speaker system. It is usually used in the context of low-frequency driver behavior, and especially so in the case of electrodynamic drivers, which use a magnetic motor to generate the forces which move the diaphragm.

Speaker diaphragms have mass, and their surroundings have stiffness. Together, these form a resonant system, and the mechanical cone resonance may be excited by electrical signals (e.g., pulses) at audio frequencies. But a driver with a voice coil is also a current generator, since it has a coil attached to the cone and suspension, and that coil is immersed in a magnetic field. For every motion the coil makes, it will generate a current that will be seen by any electrically attached equipment, such as an amplifier. In fact, the amp's output circuitry will be the main electrical load on the "voice coil current generator". If that load has low resistance, the current will be larger and the voice coil will be more strongly forced to decelerate. A high damping factor (which requires low output impedance at the amplifier output) very rapidly damps unwanted cone movements induced by the mechanical resonance of the speaker, acting as the equivalent of a "brake" on the voice coil motion (just as a short circuit across the terminals of a rotary electrical generator will make it very hard to turn). It is generally (though not universally) thought that tighter control of voice coil motion is desirable, as it is believed to contribute to better-quality sound.

A high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone, particularly in the bass region near the resonant frequency of the driver's mechanical resonance. However, the damping factor at any particular frequency will vary, since driver voice coils are complex impedances whose values vary with frequency. In addition, the electrical characteristics of every voice coil will change with temperature; high power levels will increase coil temperature, and thus resistance.
 
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