Shall I mount the Zobel at the speaker or on the crossover board? Also I have seen networks that use inductor, capacitor, and resistor instead of just the capacitor and resistor. I am not sure what use they would have.
An LCR vs a CR shunting filter are 2 very different things. LCR is a trap or notch that shunts to ground the nasties you have to avoid and/or remove. CR filters adjust the knee at the point of rolloff, smooth out the impedance of the driver on the upper end, or tilt down the response of a tweeter or mid.
A Zobel is a special-case CR filter. As defined, a zobel is used to flatten the inductive rise of the impedance in a driver. If the values differ from this method of use, then it is no longer acting as a zobel.
They both can serve differing purposes, but it depends on the method or place they are used.
Later,
Wolf
A Zobel is a special-case CR filter. As defined, a zobel is used to flatten the inductive rise of the impedance in a driver. If the values differ from this method of use, then it is no longer acting as a zobel.
They both can serve differing purposes, but it depends on the method or place they are used.
Later,
Wolf
Thanks Wolf. Does it matter where physically the Zobel is positioned? At the driver or on the crossover?
As long as the wire between the driver and the Zobel is of low enough resistance it will not matter.
I would put the zobel on the amplifier pcb.
A long speaker lead with have resistance and inductance.
A long speaker lead with have resistance and inductance.
Actually, you are trying to correct the driver's impedance curve, so, in an ideal world you would want it at the driver's terminals.
I would not expect any inductance in a speaker wire - unless you coil the wire.
On the contrary the amp is the thing you are trying to give a flatter load to.
I have seen quite resistive speaker leads and like you say sometimes people coil them up. I run a mobile disco and can have upto 50 foot cables.
If I am reading the original post correctly, the speaker has a passive crossover.
In this case it's the crossover that needs to see a constant impedance.
No, the zobel was designed to match the amplifier better to the load.
It gives a flatter load to the output transistors.
The crossover has to deal with speakers which are never a flat impedance.
Well, that is not how I understood it. I can cite this website as a reference. If he is wrong I would like to understand why because I am in the midst of designing a two-way passive crossover now.
The link:
Passive Crossover Network Design
Look for the following statement in section 3.1.1:
"Once determined, the Zobel network must be treated as part of the loudspeaker. All measurements or calculations for the crossover network must include the Zobel network and loudspeaker driver combined. If correctly done, the combination of the two will give an acceptably flat and very usable impedance across the entire crossover region. This will result in a crossover filter with the minimum error possible."
I am reading that as the Zobel must be between the driver and the crossover network, which makes sense to me.
Pretty much every amplifier design I have seen has the zobel on board.
Why not have a look around at amplifier designs and you will see what I mean.
If the zobel is put after the crossover then the function of it is masked by the crossover components.
The zobel damps down the high frequency load on the amplifier to stop it oscillating.
This is due to speakers having a higher impedance at higher frequencies.
Why not have a look around at amplifier designs and you will see what I mean.
If the zobel is put after the crossover then the function of it is masked by the crossover components.
The zobel damps down the high frequency load on the amplifier to stop it oscillating.
This is due to speakers having a higher impedance at higher frequencies.
Hi Swantzilla,
If you look at the impedance curve of a bass/mid-range driver (for example), you will see a peak in its impedance due to the loudspeakers low-frequency resonance. As frequency increases, there will be a point where the impedance starts to rise again, which is due to the driver’s voice coil inductance. The increase in the impedance due to the voice coil inductance can have a significant effect on a passive Xover that is designed to operate into a constant resistance load. To overcome this problem, a Zobel network is used to flatten the impedance curve in order that the Xover sees a constant resistance. So the Zobel network has to go across the speaker terminals.
You can also see a peak in the impedance of a tweeter as well, at its low frequency resonance. Unfortunately, this impedance peak is very often in the vicinity of the tweeters Xover frequency range and (as described above) affects the Xover’s performance, but to overcome this problem, a series LCR network is sometimes required.
If you are using a solid state amplifier where their output impedance is typically in the region of 0.08 to 0.04 ohms at low to mid frequencies, a zobel network will have no effect if placed across the amplifier's terminals. However, if you are driving your speaker with a vacuum tube amp, you may want to consider a zobel type network that is effectively wired across the amplifier’s terminals to flatten the impedance of the speaker as seen by the amplifier. This is simply because their output impedance can be much higher than a solid state amp.
Finally, most modern solid state power amplifiers have a series output inductor of about 10–15uH, which is more than any good quality speaker wire will have in normal consumer installations. So to conclude, I would recommend that if a zobel network is required, it is best located at the speaker end.
Best regards
Peter
If you look at the impedance curve of a bass/mid-range driver (for example), you will see a peak in its impedance due to the loudspeakers low-frequency resonance. As frequency increases, there will be a point where the impedance starts to rise again, which is due to the driver’s voice coil inductance. The increase in the impedance due to the voice coil inductance can have a significant effect on a passive Xover that is designed to operate into a constant resistance load. To overcome this problem, a Zobel network is used to flatten the impedance curve in order that the Xover sees a constant resistance. So the Zobel network has to go across the speaker terminals.
You can also see a peak in the impedance of a tweeter as well, at its low frequency resonance. Unfortunately, this impedance peak is very often in the vicinity of the tweeters Xover frequency range and (as described above) affects the Xover’s performance, but to overcome this problem, a series LCR network is sometimes required.
If you are using a solid state amplifier where their output impedance is typically in the region of 0.08 to 0.04 ohms at low to mid frequencies, a zobel network will have no effect if placed across the amplifier's terminals. However, if you are driving your speaker with a vacuum tube amp, you may want to consider a zobel type network that is effectively wired across the amplifier’s terminals to flatten the impedance of the speaker as seen by the amplifier. This is simply because their output impedance can be much higher than a solid state amp.
Finally, most modern solid state power amplifiers have a series output inductor of about 10–15uH, which is more than any good quality speaker wire will have in normal consumer installations. So to conclude, I would recommend that if a zobel network is required, it is best located at the speaker end.
Best regards
Peter
Yes they (amplifiers) usually do include a Zobel network on their output but the OP is talking about Zobels as applied to drivers. And as per post #2 these need to go after the (passive) crossover network so it sees a flat impedance curve.
Wait, you are both right. As nigelwright7557 says, a Zobel is used as he describes, however in the context of the OPs original post, the Zobel he is wanting to use is to present a constant impedance to the crossover. In this case the Zobel is treated as part of the speaker and is placed between the crossover and the speaker.
By the way, I have used the sound.westhost.com method to design a 2-way 2nd order crossover and I can attest to the accuracy of his documentation and the results obtained.
I suppose I was typing as you posted. I did not intend to post a redundant reply.
Three Zobels ideally
A Zobel on the output of an amplifier assists the amplifier drive a speaker lead ( not the speaker ) Amplifiers: Amplifier parameters
a second Zobel with a shunt resistor and resistor /cap is suggested by Cyril Bateman here: Capacitor Sounds, Speaker Cables and Crossover Inductors.
see article cables at AF, this one is placed at the speaker end of the speaker lead, and is calculated relative to the resistive characteristics of the cable.
A third zobel then is possibly found after the crossover prior to the speaker driver, and is described here: Speaker Zobel / Impedance Equalization Network Circuit Calculator
Cheers / Chris
A Zobel on the output of an amplifier assists the amplifier drive a speaker lead ( not the speaker ) Amplifiers: Amplifier parameters
a second Zobel with a shunt resistor and resistor /cap is suggested by Cyril Bateman here: Capacitor Sounds, Speaker Cables and Crossover Inductors.
see article cables at AF, this one is placed at the speaker end of the speaker lead, and is calculated relative to the resistive characteristics of the cable.
A third zobel then is possibly found after the crossover prior to the speaker driver, and is described here: Speaker Zobel / Impedance Equalization Network Circuit Calculator
Cheers / Chris
Nigel is referring to an amplifier output Zobel.
A very different animal.
This is a speaker enquiry asking about Speaker Zobel.
Chris is correct.
Three different Zobels each with a different function and as a result located in three different positions.
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