Amp Speaker Page matched to cab?

Why not just stick the recommended low res frequency on the IR name? Just look it up (or figure it out with the Q sweep), then add it in.

Hmm... Maybe I'll do this tomorrow.
 
barhrecords said:
A proprietary .syx file can store arbitrary data?
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Yes, a proprietary file could store any data you like. But an impulse response file can only store impulse response information.

There are pros and cons to deviating from that standard. For the record, I'd also like to see a way to load impedance data along with an IR.
 
Rex said:
The amp's speaker page models the impedance of the speaker...

To see an example of what a typical speaker impedance curve looks like, just go to the Speaker page in your amp block. That graph shows the speaker's impedance at different frequencies...
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Thanks, Rex, for your detailed explanation.

Am I correct in saying that the Amp block speaker impedance curve is an idealised curve? Or is it based on a particular speaker? What I'm getting at (and I think you've explained this but I'm still struggling a bit, lol) is that, ideally, the Amp block speaker impedence curve should reflect the impedence curve of the speaker represented by the loaded cab IR. As you mentioned later in the thread, the IR doesn't include this info, of course.

What does all this mean in terms of the authenticity of the modeled amp/cab combination, if the speaker impedence curve is quite different from that of the actual speaker? Or are these differences minute and don't have a significant, or even noticeable, effect on the sound? It could be interesting to experiment with this. Do speaker manufacturers publish this impedence data?

PS: I realise all of this is rather academic discussion which may have little bearing on the tones achievable with the Axe FX, but I'm curious. :)
 
Rex said:
Yes, a proprietary file could store any data you like. But an impulse response file can only store impulse response information.

There are pros and cons to deviating from that standard. For the record, I'd also like to see a way to load impedance data along with an IR.
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FAS already uses a non-standard file. But making the impedance data separate from the .syx and .ir files kind of makes sense if it was to be loaded into the amp block speaker page separate from the cab.
 
It probably would do just as well to have a "table" with res and imp for as many as possible cabs, speakers, etc. Surprised someone in the world has not done that yet.

Although I have never searched for such a thing.

The lo and hi res in the speaker tab works great for me for going from a Strat SC to HB's. And also on some amps I need to raise or lower one or both to get the tone I want. Just by ear, have no working knowledge of "particular speakers"
 
adew said:
Am I correct in saying that the Amp block speaker impedance curve is an idealised curve? Or is it based on a particular speaker?
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It's a typical curve of a typical speaker. It's a starting point, but not particularly "idealized."


adew said:
What I'm getting at (and I think you've explained this but I'm still struggling a bit, lol) is that, ideally, the Amp block speaker impedence curve should reflect the impedence curve of the speaker represented by the loaded cab IR.
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Yes, that would be ideal in terms of accuracy.


adew said:
What does all this mean in terms of the authenticity of the modeled amp/cab combination, if the speaker impedence curve is quite different from that of the actual speaker? Or are these differences minute and don't have a significant, or even noticeable, effect on the sound?
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It means that the amp/cab combination isn't perfectly modeled. But it's pretty close. The cab has its own frequency response that's completely independent of its impedance curve. That frequency response dominates, and is accurately represented in the IR. An accurate impedance curve would give a small but noticeable increase in accuracy.


adew said:
Do speaker manufacturers publish this impedence data?
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All cab manufacturers publish the nominal impedance of their cabs (a single number, such as 8 ohms). A few publish the cab's resonant frequency. I've never seen any of them publish an impedance curve.
 
I suspect Fractal will develop something to get at this at some point...maybe through Cab Lab. In reading another thread, Kevin at Ownhammer suggested a utility that can give you the eq curve of the IR where you can look at the high and low points in detail and use that as your guide. Ideally though, I would like to see something that would allow you to get at the real cab through the same method of IR capture...or...you can take an IR that was already made and have it extract the speaker page settings from there. What would be slick is if you could just load the IR and the speaker page will "read" the IR for the ideal settings. Not sure if it's possible, but that would be ideal in my eyes.
 
How to read/ translate a cabs frequency response ON a graph, which points I should pick to use in Axe Amp page?

image.jpg

It's a Mesa 4x12 Oversize Cab with Celestion Greenbacks
 
Ironwill said:
How to read/ translate a cabs frequency response ON a graph, which points I should pick to use in Axe Amp page?

View attachment 26604

It's a Mesa 4x12 Oversize Cab with Celestion Greenbacks
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This is a good question , I see no clear points to go by ! especially that the graphs show ex: somewhere between 100 and 200hz ? It's still all ears and guesswork . Plus the impedance curve will be totally different .
 
Ironwill said:
How to read/ translate a cabs frequency response ON a graph, which points I should pick to use in Axe Amp page?
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The Speaker page in the amp block represents the impedance curve of the speaker, not the speaker's frequency response. Those are different things, and you can't derive one from the other.
 
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barhrecords said:
I wish the IR suppliers could include the AMP block speaker page data along with the IR (either in the .syx file or in a new metadata file).

That way, we could load in the parameters that match the IR's original real cabinet / speakers.
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Yes... This seems to me to be the only "real" solution with the decoupled component model the AFX uses: metadata that is measured specifically for the cab measured and coupled with the IR.

I don't know if it possible but if the AFX IR capture utility could do it at capture time it would go a long way at least with AFX created IRs. Still there are so many legacy IRs you're just going to have to tune by ear. I suppose if there was this metadata feature we could create a db or lobby the kind folks like OwnHammer, TAF, et al who make commercial IR products to back fill it.
 
As a side question. Is there anyway to disable the Speaker Res page? I am trying out running the Axe as a preamp into the FX Return of my tube head and using just the power section of that, out to a cab. I presume the tube head is handling all the speaker interaction naturally, so there's no need for the Axe to simulate it?
 
Genome said:
As a side question. Is there anyway to disable the Speaker Res page? I am trying out running the Axe as a preamp into the FX Return of my tube head and using just the power section of that, out to a cab. I presume the tube head is handling all the speaker interaction naturally, so there's no need for the Axe to simulate it?
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If you are using a tube power amp, I would turn sag to zero. This effectively turns off the power amp modeling and you're in preamp mode with the AFX. I presume that disables all the power amp modeling related effects on the signal.
 
Yeah, I turn off power amp modelling in Global and turn the sag down to zero too (just to be sure). I wasn't sure if the Speaker Res page is still active, though?
 
How will the Oversize Mesa cab alter Frequency response of the Speakers (Greenbacks)then and Impedance curve, I don't get it fully

But nice to see the discussion and great suggestions to make IR's easier to dial in/match for users with the Axe maybe in future.
Sure most important is what I hear with my ears improving my tone, but maybe my ears trick ON me here and there, my head wants the realest, accuratest way to go just, mostly anyway, I know its a though piece in the line , in modeling Amp and cab generally, so glad we have this Speaker page for adjustments at any rate!
 
Genome said:
Yeah, I turn off power amp modelling in Global and turn the sag down to zero too (just to be sure). I wasn't sure if the Speaker Res page is still active, though?
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Speaker impedance only affects the power amp. If power amp modeling is disabled, there's nothing for the Speaker page to affect.
 
Ironwill said:
How will the Oversize Mesa cab alter Frequency response of the Speakers...
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Any enclosed space will change frequency response. Stick your head in a box and say something; your voice will sound different.


Ironwill said:
...and Impedance curve...
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A speaker is a transformer. Instead of transforming one electrical circuit to another, a speaker transforms an electrical signal into physical motion. It works backwards, too, transforming physical motion into an electrical signal. And just like an electrical transformer, it reflects the impedance of its physical "circuit" into electrical impedance.

A speaker's physical impedance is affected by physical things (the mass of the cone, the springiness of the spider...). That physical impedance is transformed into an electrical impedance which is presented to the power amp at the speaker's terminals.

One of the things that affects the speaker's physical impedance is the springiness (compressibility) of the air inside the cabinet. Change the cabinet, and you change the impedance of the air inside the cabinet, which changes the electrical impedance of the speaker.
 
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