It will flatten the phase from an amplifier standpoint, but will not correct the phase from an audibility standpoint.
The amplifier will see something closer to a resistor, but it will not make the tweeter sounds better.
Often, I wonder why we are using Zobel in typical transistor designs... it only simplify slightly crossover designs at the expense of even more components.
I could be wrong, I'm not a professionnal, but that's how I see it.
The amplifier will see something closer to a resistor, but it will not make the tweeter sounds better.
Often, I wonder why we are using Zobel in typical transistor designs... it only simplify slightly crossover designs at the expense of even more components.
I could be wrong, I'm not a professionnal, but that's how I see it.
Hi,
One of the reasons (rather than blindly) for using zobels or partial
zobels is to manipulate the phase response of the crossover.
The crossover for a zobelled bass/ mid driver will be very different
to a non-zobelled driver, phase and amplitude are affected.
Driven directly the zobel will not affect a drivers phase or response
for a typical transistor low source impedance voltage amplifier.
/sreten.
One of the reasons (rather than blindly) for using zobels or partial
zobels is to manipulate the phase response of the crossover.
The crossover for a zobelled bass/ mid driver will be very different
to a non-zobelled driver, phase and amplitude are affected.
Driven directly the zobel will not affect a drivers phase or response
for a typical transistor low source impedance voltage amplifier.
/sreten.re:'phase and amplitude are affected' -
I guess I need to refine my question, how predictable is the phase change of a zobel ?
i.e. can you say for an xover of given order, you will get a given amount of phase change, plus so much extra from the zobel (presumably above it's knee freq)?
( there will assumedly be some divergence between theory and reality, let's just consider it theoretically first...)
I guess I need to refine my question, how predictable is the phase change of a zobel ?
i.e. can you say for an xover of given order, you will get a given amount of phase change, plus so much extra from the zobel (presumably above it's knee freq)?
( there will assumedly be some divergence between theory and reality, let's just consider it theoretically first...)
It depends on how it is used.
The idea of a zobel separate from the crossover is a "cookbook" technique. Easy to explain, but only a small part of the story.... From professional designers you will see few "zobels" that merely cancel inductive rise - it is only another crossover component...to be manipulated like any other.
The idea of a zobel separate from the crossover is a "cookbook" technique. Easy to explain, but only a small part of the story.... From professional designers you will see few "zobels" that merely cancel inductive rise - it is only another crossover component...to be manipulated like any other.
PeteMcK said:
Hi,
The short answer is that it is not.
It depends and the load impedance and the source impedance.
A directly driven driver (low source impedance) it has little effect.
Via a crossover it does have an effect related to the crossover.
As stated often the crossover is fine without a full or partial zobel.
/sreten.
sreten said:
Hi,
The short answer is that it is not.
It depends and the load impedance and the source impedance.
A directly driven driver (low source impedance) it has little effect.
Via a crossover it does have an effect related to the crossover.
As stated often the crossover is fine without a full or partial zobel.
The impedance of the speaker varies widely with frequency.
It would be impossible to complete negate the impedance at every frequency.
Re:'Why are you asking?' -
So I can think about the above question - 'can you say for an xover of given order, you will get a given amount of phase change, plus so much extra from the zobel' - or whether I should think about them separately -
I don't usually use zobels, but I have a driver which I'm thinking about using a 3rd order (don't use those either) + zobel on...
Of course, I won't know until I try, but just want to get a feel for how others approach this; - most advanced designers seem to use a zobel (if they use them at all) to tweek the response, rather than as a simple impedance correction. But my question is about phase, not impedance.
I guess from a theoretical viewpoint, Sreten has answered my Q. :- 'Driven directly the zobel will not affect a drivers phase or response for a typical transistor low source impedance voltage amplifier', and from a practical viewpoint, you have: 'It depends'
I appreciate your responses.
So I can think about the above question - 'can you say for an xover of given order, you will get a given amount of phase change, plus so much extra from the zobel' - or whether I should think about them separately -
I don't usually use zobels, but I have a driver which I'm thinking about using a 3rd order (don't use those either) + zobel on...
Of course, I won't know until I try, but just want to get a feel for how others approach this; - most advanced designers seem to use a zobel (if they use them at all) to tweek the response, rather than as a simple impedance correction. But my question is about phase, not impedance.
I guess from a theoretical viewpoint, Sreten has answered my Q. :- 'Driven directly the zobel will not affect a drivers phase or response for a typical transistor low source impedance voltage amplifier', and from a practical viewpoint, you have: 'It depends'
I appreciate your responses.
PeteMcK said:
Impedance has a phase
SPL has a phase
Both are "complex quantities", they have a real and imaginary part.
say z=6+2i is the impedance of a loudspeaker at some point.
z has a magnitude:
|z|=sqrt(6^2+2^2)=sqrt(40)=6.32 ohms
and a phase:
phi(z) = arctan(2/6) = 18.43 degrees
Calculation for SPL goes similarly.
The degree the SPL phase is modified depends on the degree to which impedance is modified and whatever else is in the circuit. You cannot use some rule of thumb to design a zobel or a crossover.
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