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The Speaker Page

FreeMind

Power User
Hi there.
Amp block speaker page.
The point of it is, that the Amp block has no idea what IR or real cab is connected, so the user has to set up Amp to cab interaction/Resonance manually to achieve authentic results.

1) Is it so, that each cab or IR has a single specific Speaker page configuration for all amps?
That is, if you keep the same Speaker page configuration and Cab/IR, then change only the amp sim, the results will remain authentic.
Or should the user change the speaker page settings each time he changes the amp?
That is, every Amp has a different interaction with the same cab.

2) Is it possible, that this part of the Amp block could be automated in the future?
The Axe has IR capturing capabilities, but maybe it could also capture the Authentic Speaker page settings for all amp sims too somehow? That would be cool.

Sorry, I am pretty ignorant on how this works and my questions may be stupid.
I am curious, though.
 

brianv4

Power User
this could be the last piece of the modeling puzzle. Having these parameters update with a specific IR would be great. But, I would think that data has to be embedded in the IR which means a huge task. I'd be happy if cab packs included that info in a pdf
 

aziz

Power User
A rough version could be a generic line of info in the .syx file: this cab is open/semi/closed, 1x10", 16 ohm, which would tell the amp block what to do. Or this could be a quick option dropdown list in the amp block speaker page? That'd get you "close enough" I guess?
 

mferrand

Inspired
I asked about this a couple of years ago and got shot down. Every speaker has a unique Impedance vs. frequency curve. The cabinet affects this curve as well by loading the speaker. This was some of the basis behind the Thiele-Small parameters for ported boxes. The measurements for impedance vs. frequency are taken an entirely different way then an IR and not so easily done at home.
 

Raab90

Inspired
Hi there.
Amp block speaker page.
The point of it is, that the Amp block has no idea what IR or real cab is connected, so the user has to set up Amp to cab interaction/Resonance manually to achieve authentic results.

1) Is it so, that each cab or IR has a single specific Speaker page configuration for all amps?
That is, if you keep the same Speaker page configuration and Cab/IR, then change only the amp sim, the results will remain authentic.
Or should the user change the speaker page settings each time he changes the amp?
That is, every Amp has a different interaction with the same cab.

2) Is it possible, that this part of the Amp block could be automated in the future?
The Axe has IR capturing capabilities, but maybe it could also capture the Authentic Speaker page settings for all amp sims too somehow? That would be cool.

Sorry, I am pretty ignorant on how this works and my questions may be stupid.
I am curious, though.
The speaker page's curve is a current/frequency response. This means that it controls how much current is drawn from the amp, to drive the speaker, depending on the signal's frequencies. However, note that this current is a product of the everything thats in between the amp's inner circuitry, you house's power, and the speaker's load characteristics.

Now, making the following considerations:

-Amp and speaker are 2 loads in series.
-There's a current from the amp to the speakers that's a product of the amp and cab being in series. This means that if you take one element out, there's no more current.** (by element I mean load)
-This current is the actual sound signal.
-Audible sound is created when this resulting series current, drives the cab's speakers.
-The curve at the amp's speaker page is this series current's properties, which are a product of the amp's aspects and impedance, and the speaker's load characteristic stage.
-All aspects from the amp are modeled, including it's own impedance..
-All aspects of a speaker cabinet are modeled:
-The load stage (inside the amp block) -Here lies the problem-
-and the filter stage (IR) -The actual cab block-

SO:

Becasue the the speaker's load characteristics are already included in the amp block, the taking the out the cab block would still prodce sound out of the amp, cos both loads would still be in series inside the amp.

To make that curve vary with each cab block, the load characteristic would have to be taken out of the amp's parameters, and put into the cab's. But this would also mean you would have to take independent meassurements of each speaker's components (The load characteristic stage), and combining them into a the same cab file along with the IR (woldn't be called IR anymore).

However, this would mean that if there's no cab block after the amp, there would be no sound from the amp, since you would be taking a load out of the series chain, and end up with an open circuit (no current). Amp's speaker curve would be blank.**

So what would happen when you would want to use a real cab with the AXE? You would usually remove the cab block, and by doing so, you are also eliminating any virtual series load with the axe, thus, having no speaker curve, and no sound.

Furthermore, I'm assuming taking these cab measurments are not really easy, since there's also more complicated things to meassure than just the speaker's reactance, such as the driver's hysteresis characteristics and so on.

Things get a tad complicated.

Hope I made sense, I usually don't.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
People over-think this. The speaker's impedance is largely decoupled from it's IR. IOW, the frequency response of the speaker + cabinet is not very related to the driver's impedance curve. What does this mean? Pick an IR that you like. Adjust the amp block speaker impedance curve as desired. You're never going to see IR producers publish speaker impedance data because most don't know how to measure it and there is no standard format for the data.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
The speaker page's curve is a current/frequency response. This means that it controls how much current is drawn from the amp, to drive the speaker, depending on the signal's frequencies. However, note that this current is a product of the everything thats in between the amp's inner circuitry, you house's power, and the speaker's load characteristics.

Now, making the following considerations:

-Amp and speaker are 2 loads in series.
-There's a current from the amp to the speakers that's a product of the amp and cab being in series. This means that if you take one element out, there's no more current.** (by element I mean load)
-This current is the actual sound signal.
-Audible sound is created when this resulting series current, drives the cab's speakers.
-The curve at the amp's speaker page is this series current's properties, which are a product of the amp's aspects and impedance, and the speaker's load characteristic stage.
-All aspects from the amp are modeled, including it's own impedance..
-All aspects of a speaker cabinet are modeled:
-The load stage (inside the amp block) -Here lies the problem-
-and the filter stage (IR) -The actual cab block-

SO:

Becasue the the speaker's load characteristics are already included in the amp block, the taking the out the cab block would still prodce sound out of the amp, cos both loads would still be in series inside the amp.

To make that curve vary with each cab block, the load characteristic would have to be taken out of the amp's parameters, and put into the cab's. But this would also mean you would have to take independent meassurements of each speaker's components (The load characteristic stage), and combining them into a the same cab file along with the IR (woldn't be called IR anymore).

However, this would mean that if there's no cab block after the amp, there would be no sound from the amp, since you would be taking a load out of the series chain, and end up with an open circuit (no current). Amp's speaker curve would be blank.**

So what would happen when you would want to use a real cab with the AXE? You would usually remove the cab block, and by doing so, you are also eliminating any virtual series load with the axe, thus, having no speaker curve, and no sound.

Furthermore, I'm assuming taking these cab measurments are not really easy, since there's also more complicated things to meassure than just the speaker's reactance, such as the driver's hysteresis characteristics and so on.

Things get a tad complicated.

Hope I made sense, I usually don't.
Pretty much every thing posted is wrong, LOL.

The voltage at the output of a tube amp is a function of the speaker's impedance curve. The impedance curve is set in the SPKR tab of the amp block.

Real speakers respond to the VOLTAGE at their terminals, not the current. The amp block creates a virtual voltage which is a function of the amp model and the impedance curve.

The cab block uses IRs which represent the measured sound from the speaker vs. an applied voltage at the speaker terminals. The aforementioned virtual voltage is sent to the cab block which then produces an audio signal by convolving the virtual voltage data with the IR.

As I said in my previous post the IR is largely independent of it's impedance curve. The impedance curve can then be seen as just another tone and feel shaping tool. Bass too prominent? Turn down LF Resonance. Want more midrange? Lower HF Res Freq. The degree to which the impedance curve affects the output of the amp block is a function of the power tube type and the amount of negative feedback. The less negative feedback the more the impedance curve influences the output. Since Presence and Depth work by reducing negative feedback at high and low frequencies respectively, increasing them will also increase the influence of the impedance curve at those frequencies. The dynamic impedance of the power tubes also affects the output. A power triode, for example, has a much lower plate impedance than a tetrode or pentode and, therefore, the output will be mostly independent of the speaker impedance.
 

Raab90

Inspired
Pretty much every thing posted is wrong, LOL.
You said that the voltage at the output of a tube amp is a function of the speaker's impedance curve. The impedance curve is set in the SPKR tab of the amp block. Doesn't this mean that each cab would produce a different impedance curve?

Isn't that exactly what i said?

I think my only error there was not being technical enough and talk about current, not voltage, but since current is the final product that creates the force to drive the speakers F=ilxB, which connects both devices, it would be easier to understand.

Otherwise, please correct everything I said wrong, for the sake of learning.
 

FreeMind

Power User
You're never going to see IR producers publish speaker impedance data because most don't know how to measure it and there is no standard format for the data.
Well... Fractal could just have it's own standard...
Just a written list of settings for the Speaker page is sufficient. The user can dial them in manually. These settings would result in an authentic Amp through that cab tone.
Or maybe a button "Load Authentic settings". The user is free to adjust from there according to taste.
Note: By "authentic", I mean - This is how the real amp would actually sound like through that cab.
Using real amps, the user has no access to these parameters, and they are fixed in a one specific way.

I think people often skip over the speaker page. For example, when people A/B a real amp versus an amp sim through the same cab, they will hear differences, because the speaker page is set up for a different cab, so they say "Nope, the amp modelling is not there yet. It sounds/feels too different on same settings". Also, they may be using one amp sim and browse around for a cab IR. He may get faulty results, because the speaker page is not set up to work with most of the IR's...
 
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rodzimguitar68

Fractal Fanatic
+1 This. I have always thought the Speaker tab's settings would change, according to the CAB that was downline from the amp. But for that to happen, the Cab block would have to contain a database of the performance characteristics of the IR, and recall the correct one. I think I just used up too much of processor #2......
 

Rex

Legend!
You said that the voltage at the output of a tube amp is a function of the speaker's impedance curve. The impedance curve is set in the SPKR tab of the amp block. Doesn't this mean that each cab would produce a different impedance curve?
Every physical speaker cab has an impedance curve. But IRs don't contain any impedance information. The Axe gets around that limitation by giving you a place (the Speaker page in the Amp block) where you can specify whatever impedance curve you wish. But that curve is not contained in the IR or in any other aspect of the Cab block.
 

brianv4

Power User
Thanks Cliff. I kinda glazed over towards the end but a lot of it made sense and will be very helpful to me.
 

StickMan

Experienced
I tried the settings recommended in the "Hot Kitty is nasty" thread, and I was surprised at how dramatic the change was (and how much better the amp model sounded). What I really learned is that this is definitely not a page that you want to skip, even if you're not at the "final tweaks" stage of setting up an amp block.
 

guitarmike

Experienced
To add another kink to the mix, if your using a FRFR speaker source, please realize, that with very few exceptions, this is mostly a generic term and does not necessarily really mean that the speaker source is truly flat. Most Pa type speakers will, at the very least, have some tilt to them, usually with the treble side being down a bit because a true flat response is very harsh to most ears. And if there is a bump in the low frequency response of your FRFR, and there may very well be, this further upsets the low freq res paradigm. For example, my Yamaha hsm8's are fairly flat and extend down pretty low. Being fairly flat, the treble can be very pronounced and even harsh, especially higher volumes. On these speakers the low frequency resonance "frequency" parameter usually sounds better set lower than the preset and the high frequency "Q" needs to come down a little. This seems to work "for me" in general with other systems that are relatively flat, also.

These parameters effect the tone and feel of the amp and the degree to which they do depends on certain other parameters. I think it would be great if we would learn all of the interactions of the parameters and stuff, but in the end, it is just like Cliff said, "The impedance curve can then be seen as just another tone and feel shaping tool. Bass too prominent? Turn down LF Resonance. Want more midrange? Lower HF Res Freq." And, if I may be so bold as to add to the mans comment, want a less "feathery" treble under your fingertips, lower the hi freq "resonance".

With great power comes great responsibility!!!! I have thought about creating some kind of chart or diagram that would represent what the parameters do and how they are connected; a sort of visual schematic or flow chart for easy reference. Would something like that be helpful?
 
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barhrecords

Axe-Master
Information about what amps (models) use negative feedback and how that affects things like the speaker page parameters would be useful.

How all the settings work together and interact is something I struggle with. I tend to shy away from most advanced parameters because of lack of knowledge of the implications of one parameter in regards to the others.
 
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