Speaker compliance

T

Tpj1333

Inspired
I’ve been using the vox ac 30 hot and normal and I find that higher levels of speaker compliance add something good to the tone I have it on 22% I also have the saturation drive on authentic and set to 5 I feel like it adds a beautiful flavor to every amp block
I would love to know more about the speaker compliance parameter and how it should vary for each style of amp to get extra levels of realism
 
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https://forum.fractalaudio.com/thre...2-00-public-beta-2.144615/page-6#post-1711452

FAS say: "The easy way to understand compliance is to think of a spring. In Physics 101 we're taught that F = kx but that's an ideal spring. A real spring is nonlinear. Eventually you get to a point where compressing or stretching the string you run out of travel and the force goes nonlinear. A speaker is the same way. The suspension is essentially a spring and the greater the displacement the greater the force trying to restore the cone to its rest position. The compliance parameter controls how stiff that suspension is."

it sounds like increasing the compliance (making it stiffer) would be like new speakers, not broken in yet, very snappy. Decreasing compliance (making it softer) would be like worn in speakers, softer, less snappy. I don't know if it effects the frequency response like worn/new speakers would, maybe it does. FAS seems to like to compartmentalize parameters wherever possible.

EDIT 8MAR2019: i think i had it backwards up here. compliance meaning 'bend with force', increasing a compliance parameter would add compliance, make it softer. decreasing compliance would reduce compliance, make it stiffer.
 
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related question: compliance is it's willingness to fold. this is semantics but if the parameter is named 'compliance', wouldn't increasing the compliance make it...more compliant...softer?
 
shatteredsquare said:
related question: compliance is it's willingness to fold. this is semantics but if the parameter is named 'compliance', wouldn't increasing the compliance make it...more compliant...softer?
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Think of it as a "resistance to compliance" parameter. Higher value, higher resistance to compliance.
 
no it's labeled correctly...increasing the compliance parameter does make it more compliant (floppy.) It doesn't sound like it's affecting the frequency response though
 
shatteredsquare said:
no it's labeled correctly...increasing the compliance parameter does make it more compliant (floppy.) It doesn't sound like it's affecting the frequency response though
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What makes you say that? My reading of this always made me think higher values meant the "spring" would return to zero faster -- i.e. stiffer, more resistance. Maybe resistance is too flawed an analogous term to use here?
 
iaresee said:
What makes you say that?
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because "the compliance parameter controls how stiff that suspension is", and compliance meaning a 'willingness to bend'...so increasing the compliance amount would make it more compliant...more willing to bend...softer. I was blathering before, i hadn't even used the knob, i just now twiddled it and higher settings make the floppiness, lower settings make the clarity. No perceptible frequency response change though.
 
iaresee said:
What makes you say that? My reading of this always made me think higher values meant the "spring" would return to zero faster -- i.e. stiffer, more resistance. Maybe resistance is too flawed an analogous term to use here?
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I assume it is the former since setting it at 0 turns off the algorithm.

The stiffness of a speaker increases when the displacement increases (similarly to a spring), so I think the effect on the output waveform would be similar to a soft clipping, low amplitude signals will pass almost unaltered, high amplitude signals will get the peaks squeezed.

Now a doubt arises though:
Shouldn't this "soft clipping" be asymmetrical in a sealed or ported enclosure?
Cuz, when the speaker moves, there's a difference of air pressure outside and inside the cab, and the force needed to push in the speaker (so the pressure inside increases) to obtain a given displacement is always more than the force needed to pull out the speaker and obtain the same displacement in the opposite direction.
 
DLC86 said:
I assume it is the former since setting it at 0 turns off the algorithm.

The stiffness of a speaker increases when the displacement increases (similarly to a spring), so I think the effect on the output waveform would be similar to a soft clipping, low amplitude signals will pass almost unaltered, high amplitude signals will get the peaks squeezed.

Now a doubt arises though:
Shouldn't this "soft clipping" be asymmetrical in a sealed or ported enclosure?
Cuz, when the speaker moves, there's a difference of air pressure outside and inside the cab, and the force needed to push in the speaker (so the pressure inside increases) to obtain a given displacement is always more than the force needed to pull out the speaker and obtain the same displacement in the opposite direction.
Click to expand...

this man is thinking both inside and outside of the box simultaneously...
 
iaresee said:
What makes you say that? My reading of this always made me think higher values meant the "spring" would return to zero faster -- i.e. stiffer, more resistance. Maybe resistance is too flawed an analogous term to use here?
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It’s about reactance, not resistance. Compliance in the loudspeaker transforms into inductance at the amp’s output. (Loudspeakers are actually transformers. They transform electrical signals into physical movement, and vice versa. The physical properties of of a loudspeaker get transformed into reactance (resistance, capacitance and inductance) at the speaker’s terminals. This affects the impedance that the amp sees at its output.) Compliance = the opposite of stiffness.

If you reduce a speaker’s compliance, you raise its resonant frequency. If you mount a loudspeaker in a cabinet, the cab reduces compliance, and raises the speaker’s resonant frequency.

Things get interesting at the extremes of the physical movement of the speaker cone, where the speaker runs out of room to move, and compliance takes a nonlinear nosedive.
 
@iaresee probably wasn't talking about electrical resistance but a speaker more resistant to movement, IOW stiffer (more power needed to obtain a certain displacement).

Rex said:
If you mount a loudspeaker in a cabinet, the cab reduces compliance, and raises the speaker’s resonant frequency.
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Wouldn't a cab also make it "asymetrically stiff" as I wrote in my previous post?
 
Rex said:
Nope. Tha cab changes compliance in a very linear way.
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Well, that question came to my mind a few days ago actually, and I asked it to a dear friend of mine who has a PhD in theoretical physics (we call him Sheldon :D ).
He basically told me that when we pull the speaker out the delta between external and internal pressure can be 1 atm at most (assuming the speaker had no physical displacement limits, that means vacuum inside and normal atmospheric pressure outside).
When we push it in instead there's no limit for the internal pressure (until we create a black hole at least) and the delta can be much larger than 1 atm.
This also means that the force needed to push in the speaker by, let's say, 1 inch is more than the force needed to pull it out 1 inch. Pressure basically changes with a different trend so the delta will be larger in the first case.

The question though is if this difference of pressure delta is appreciable for typical speaker displacement range and cab internal volume, we didn't have the chance to do the math and discuss it in detail.

Maybe @FractalAudio can think about this, even though he probably already did it long time ago :)
 
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DLC86 said:
@iaresee probably wasn't talking about electrical resistance but a speaker more resistant to movement, IOW stiffer (more power needed to obtain a certain displacement).
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A yup. That's precisely what I meant. My follow up about resistance being the wrong word to use seems on point now.
 
Rex said:
It’s about reactance, not resistance. Compliance in the loudspeaker transforms into inductance at the amp’s output. (Loudspeakers are actually transformers. They transform electrical signals into physical movement, and vice versa. The physical properties of of a loudspeaker get transformed into reactance (resistance, capacitance and inductance) at the speaker’s terminals. This affects the impedance that the amp sees at its output.) Compliance = the opposite of stiffness.

If you reduce a speaker’s compliance, you raise its resonant frequency. If you mount a loudspeaker in a cabinet, the cab reduces compliance, and raises the speaker’s resonant frequency.

Things get interesting at the extremes of the physical movement of the speaker cone, where the speaker runs out of room to move, and compliance takes a nonlinear nosedive.
Click to expand...
Yea, I should not have used the word resistance.
 
Here's a question: Is Compliance a speaker property, or is it an amp property?
In other words: If I used a real cab, why should it be not zero, and how do I know the correct value?
 
Compliance in this context is a speaker property, how stiff the surround and spider is. Rex was making comments on the electronic effect that it has on the power section, a loser speaker vs a stiffer speaker. But the parameter (compliance) is simulating how stiff the speaker surround+spider is.
 
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