Axe-FX III Dyna-Cabs

[DLC86]

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)

Cool! Even though that wouldn't replicate the frequency shift on resonances which happens along with the temperature increase, I guess.

 

[jay mitchell]

Cool! Even though that wouldn't replicate the frequency shift on resonances which happens along with the temperature increase, I guess.

The only effect that temperature has on "resonances" is due to the increase in DC resistance of the voice coil. Adding a series resistance to a modeled impedance is a realistic representation of what the physical speaker would do.

 

[FractalAudio]

Resonant frequency is dependent upon displacement (which we model).

Our speaker impedance is an electrical model. The parameters of the model change based on virtual temperature and virtual displacement.

 

[jay mitchell]

Resonant frequency is dependent upon displacement

That statement reverses the roles of independent and dependent variables. Stated correctly, displacement for a constant voltage input reaches its peak at the frequency of mechanical resonance.

Resonant frequency depends on three parameters: the moving mass (including air load) of the speaker, the spring constant (including the effect of the air in a sealed enclosure when present) of the speaker's suspension, and the mechanical resistance (damping, mostly from friction in the suspension) of the motor assembly. All three of these parameters are, to an excellent approximation, constant. The resonant frequency of a transducer will not change with any amount of displacement that lies within the linear range of its suspension.

 

[DLC86]

The only effect that temperature has on "resonances" is due to the increase in DC resistance of the voice coil. Adding a series resistance to a modeled impedance is a realistic representation of what the physical speaker would do.

I recall Cliff saying that resonant frequencies also get shifted upward in frequency (I don't remember if due to temperature or some other variables), that's why I said that. But maybe I'm confusing it with some other phenomenon.

 

[TheTrueZoltan!]

That statement reverses the role of independent and dependent variables. Stated correctly, displacement for a constant voltage input reaches its peak at the frequency of mechanical resonance.

Resonant frequency depends on three parameters: the moving mass (including air load) of the speaker, the spring constant (including the effect of the air in a sealed enclosure when present) of the speaker's suspension, and the mechanical resistance (damping, mostly from friction in the suspension) of the motor assembly. The resonant frequency of a transducer does not change with any amount of displacement that lies within the linear range of its suspension.

 

[the swede]

So… the cabs sound good?

Y’all talking a bunch of bla bla bla… swede doesn’t understand all that.

Swede understand “it’s sound damn fucking good” and “yeah man rock on!” or “nah man, this sounds like poo poo”.

Swede is seeing himself out right now. Sorry. As you were.

 

[fretworn]

So… the cabs sound good?

Y’all talking a bunch of bla bla bla… swede doesn’t understand all that.

Swede understand “it’s sound damn f*****g good” and “yeah man rock on!” or “nah man, this sounds like poo poo”.

Swede is seeing himself out right now. Sorry. As you were.

Spoiler: Swedish Translation of DynaCab

When you say “Dynacab“… You got to say it in Mike’s voice. Don’t forget to mention the two pet 400 pound Tigers marking their turf.

 

[Greg Ferguson]

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

You're right, I forgot the effect that temperature has on resistance.

The coil can get hot enough to burn out. We used to do that out of perverseness by hooking up returned car speakers to a 700 watt stereo amplifier and turning it up until the speaker was hopping around, then smoking, then sparking, then sitting there sizzling. The opening to Dark Side of the Moon was especially efficient.

 

[jay mitchell]

The coil can get hot enough to burn out. We used to do that out of perverseness by hooking up returned car speakers to a 700 watt stereo amplifier and turning it up until the speaker was hopping around, then smoking, then sparking, then sitting there sizzling.

Ca. 1986, ML Procise did the same thing with sixteen 18" subwoofers (JBL 2245s) in the sound check before opening night of the ZZ Top Afterburner tour, on which he was mixing FOH. He used pink noise to "check the calibration" of the crossover overload LEDs. The venue was in Canada, and it cost a little to airmail him replacements. When we got the trashed ones back, the voice coils looked like blackened Slinkys and stank.

 

[Orvillain]

stank

 

[Greg Ferguson]

When we got the trashed ones back, the voice coils looked like blackened Slinkys and stank.

Ew! That's a major "stank".

 

[jay mitchell]

Conjugation verb stink

 

[Jarick]

So… the cabs sound good?

Y’all talking a bunch of bla bla bla… swede doesn’t understand all that.

Swede understand “it’s sound damn f*****g good” and “yeah man rock on!” or “nah man, this sounds like poo poo”.

Swede is seeing himself out right now. Sorry. As you were.

Yeah I think it sounds great.

I spent a day or two tinkering with dual mics (dynamic and ribbon) and got a pretty good sound, then decided to do a single condenser to see how balanced it would be and I haven't touched it in two days. I've got the mic basically halfway between center and edge and backed off a tiny bit.

Sounds as good as any aftermarket mixed IR I've tried IMO. Being able to sweep across the speaker is great to tame the highs.

I am doing a bit of a low cut but not as much as with most legacy cab IR mixes.

 

[BenIfin]

So .... is the Speaker Impedance Curve for any given speaker "fixed" / "static" at all volumes -or- does to change / vary as the Speaker is driven harder / softer / louder / quieter (?)

Ben

 

[jay mitchell]

So .... is the Speaker Impedance Curve for any given speaker "fixed" / "static" at all volumes -or- does to change / vary as the Speaker is driven harder / softer / louder / quieter (?)

Asked and answered earlier in the thread. A speaker's impedance vs. frequency changes with temperature. Playing louder makes a speaker hotter.

 

[FractalAudio]

Speaker resonance is a function of displacement. I'm away from the office and don't have access to my document library but a quick search yielded this:

There are several papers that cover the subject. Klippel et. al. IIRC has graphs of resonant frequency vs. displacement.

I have made my own measurements and guitar speakers, in particular, display this behavior no doubt due to their intentionally nonlinear behavior.

 

[DrewJD82]

Speaker resonance is a function of displacement. I'm away from the office and don't have access to my document library but a quick search yielded this:

There are several papers that cover the subject. Klippel et. al. IIRC has graphs of resonant frequency vs. displacement.

I have made my own measurements and guitar speakers, in particular, display this behavior no doubt due to their intentionally nonlinear behavior.

Why do I have the feeling you’re sitting on a beach in Hawaii posting this stuff?

 

[FractalAudio]

Why do I have the feeling you’re sitting on a beach in Hawaii posting this stuff?

Florida

 

[DrewJD82]

Florida

If you’re in the Ft. Lauderdale area, A) you’re crazy because it’s Spring Break and B) shoot me a PM if you want any recommendations!