Axe-FX III Dyna-Cabs

[yeky83]

It appears that I am being misunderstood. Please note my original post on this subject:

"All the above is fine - it essentially adds to user-accessible IR parameters - but, in five pages so far, not one person has mentioned what is arguably the biggest development."

It is a challenge to implement a system that combines IRs of a cab with impedance data on the same cab in a format that can be used in the modeler's amp block. It appears to me that Cliff has made great strides in meeting that challenge, a feat that none of his competitors have yet accomplished.

If only it were actually IRs of a cab and not truncated IRs of a nearfield mic'ed cab in a room! But yes, a cool development indeed.

I wonder how it's combining and assigning cab impedances when you have several DynaCabs in a preset... and up to two amp blocks... @FractalAudio?

 

[jay mitchell]

Music Trades sales figures, internal company sales figures <snip>

You answered (sort of) the second question but not the first.

 

[Mongillo19]

You answered (sort of) the second question but not the first.

32.33 repeating of course

 

[ax84ch]

I wonder if you can attach controllers to the mic position controls

 

[Orvillain]

You answered (sort of) the second question but not the first.

Oh sorry. I was pre-occupied with cleaning my flaeshlight.

 

[Deadpan]

I wonder how it's combining and assigning cab impedances when you have several DynaCabs in a preset... and up to two amp blocks... @FractalAudio?

To the first slot only.

 

[norminal]

I wonder if you can attach controllers to the mic position controls

So that you could dial in your cabs with expression pedals while playing?

 

[Boudoir Guitar]

I hadn't been paying attention to this thread, seeing as how I don't own (nor do I anticipate owning) an AFXIII. It was clear that the FW introduced two elements: 1) a UI that facilitates navigation among several presumably related IRs, and 2) an interpolation algorithm that morphs IRs to "in-between" spots not represented by an actual IR.

All the above is fine - it essentially adds to user-accessible IR parameters - but, in five pages so far, not one person has mentioned what is arguably the biggest development. I quote Cliff:

"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block."

Discuss....

I did, I did, I did!!!!

Assuming it's using actual impedance curves of the cabs they measured, I think it's great and wish they had meta tags in n the legacy IR collection that could do this also.

 

[Greg Ferguson]

I've been saying for ages, a speaker sounds different in all 360 degrees from center.

Um… I'm not sure that's quite true. 90º from the cap to the edge on the front in either direction *SHOULD* be the same, just as it would be on the back, assuming the speaker is centered in the cabinet. Yes, a cabinet might have an asymmetrical sound because the speaker wasn't centered, or the cone wasn't glued correctly around its circumference, or was damaged somehow, but, in general, it's the same across the front surface or the back.

Shooting IRs across the cone from one edge to the other on the front, or separately on the back would overwhelmingly result in a terrible amount of redundancy that was not worth recording.

When shooting IRs, like modeling amps, they want to start with the best representation of the cab or the amp, they're not modeling something that's damaged or faulty, at least not that I know of.

 

[Greg Ferguson]

In your last video, you moved it a mm and your cat started crying. Coincidence?

Anyone who's had a cat knows it can make a major difference.

 

[Greg Ferguson]

That doesn't mean they couldn't also improve the regular IR management. All the file browser type views are not very good. Just too much stuff without proper grouping, tagging, search, sort, favorites etc features.

*I* look at it as FAS trying to meet the needs of both worlds.

Dyna-Cabs appeal to those who want to twiddle mics, said tongue-in-cheek, because they sound amazing and I look forward to knowing where they're going with the FM* units too. The Legacy cabs appeal to those who have single IRs and want to continue using them. FAS hasn't abandoned the "Legacy" camp, they've opened up their cab choices instead. It also means they can improve the regular IR browser at their leisure.

There might be a method behind the madness.

 

[BenIfin]

Showing my technical illiteracy here .... I always *thought* that "Speaker Ohm-age" and "Speaker Impedance" varied-fluctuated in real-time as the speaker is driven softer / harder / with different input signals etc ..... (?)

I don't know (?)

Ben

 

[Greg Ferguson]

Showing my technical illiteracy here .... I always *thought* that "Speaker Ohm-age" and "Speaker Impedance" varied-fluctuated in real-time as the speaker is driven softer / harder / with different input signals etc ..... (?)

I don't know (?)

Ben

The impedance does, but I think the ohms are steady.

 

[BenIfin]

The impedance does, but I think the ohms are steady.

Thanks ! :)

 

[DLC86]

The impedance does, but I think the ohms are steady.

I don't think so.
Anyone a bit into vaping knows that each material has its TCR (Temperature Coefficient of Resistance) which tells us by how much its resistance rises in percentage for each °C increase of its temperature.
For copper this value is 0.393 %/°C.
I don't know what kind of temperatures a speaker voice coil can reach, I guess it depends on various factors including the wattage applied and how efficient the cooling of the speaker is.

But, as an example, if the DC resistance of a speaker is 6 ohms at 20°C, at 50°C it will increase by:
(50-20) * 0.393% = 11.79%
Which means the DC resistance will go up to:
6 ohm * 111.79% = 6.71 ohm

 

[FractalAudio]

Showing my technical illiteracy here .... I always *thought* that "Speaker Ohm-age" and "Speaker Impedance" varied-fluctuated in real-time as the speaker is driven softer / harder / with different input signals etc ..... (?)

I don't know (?)

Ben

Speaker impedance varies with motor temperature and cone displacement. We model both. The speaker impedance curve represents the impedance with the speaker at rest.

 

[DLC86]

The speaker impedance curve represents the impedance with the speaker at rest.

But when you measure it it's not at rest though, the test tone will make it move and heat up.
Doesn't that throw off the measurement?

 

[FractalAudio]

But when you measure it it's not at rest though, the test tone will make it move and heat up.
Doesn't that throw off the measurement?

The test tone is low amplitude.

 

[jay mitchell]

But when you measure it it's not at rest though, the test tone will make it move and heat up.

Acquiring speaker impedance is done with a sweep signal like the ones that are used to acquire the impulse response. Two elements make temperature changes during the sweep negligible:

1) The sweep applies a constant current of very small magnitude (I use 1milliamp) to the voice coil.
2) The duration of the sweep is much shorter than the thermal time constant of the speaker's motor assembly.

Doesn't that throw off the measurement?

Given that normal operation of the speaker will elevate its voice coil temperature, a very good argument can be made for acquiring impedance data with the speaker at its normal operating temperature instead of room temperature. This would have the greatest effect when acquiring data to calculate a woofer's Thiele-Small parameters, which are needed to determine the optimum size and tuning of a ported enclosure. However, the effect can be modeled to a very good approximation by adding a series resistance, the value of which is adjusted depending on the modeled operating temperature and the TCR of the voice coil conductor (copper or aluminum). You could then easily model operating conditions that would destroy a physical speaker in short order.

 

[jay mitchell]

If only it were actually IRs of a cab and not truncated IRs of a nearfield mic'ed cab in a room!

There's nothing other than money, time, expertise, and an appropriate facility stopping a vendor from acquiring reflection free IRs at a suitable distance and importing them into this format. Well, there is one more thing: the mic robot would be useless; you'd need a rotation fixture for the cab.