Parallel or serial notch filter in a crossover?

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Notch filter to flatten frequentie respons or impedance of speakers can be serial or parallel.
Parallel: L C and R parallel in serial witch the driver

Serial: L C and R in serial and parallel over the driver

I've seen crossover networks with both of them but what is the reason to prefer a serial version over a parallel one or a parallel over a serial?
 
Jonathan thanks for posting.;)

So you say that a notch filter in the signal path is not so good because you have more components and loses, before the signal gets into the driver.

But why don't everybody uses serial notch filter then in parallel with the drivers? There are many many crossover filters with the components of the notch filter in the signal path.:whazzat:
 
If I want to deal with a cone breakup hump above a woofers crossover frequency, I like to use a parallel notch filter. The parallel filter needs the series impedance (which the main crossover inductor is providing) or else it wont work.

If the notch filter is the only crossover part on the driver, a series will have to do otherwise (for a parallel to work) you'd need to add a series resistor to take the energy within the filter band.

All this is very generalised. I find filters are situation specific but I tend to prefer the parallel where possible. One reason might be that the drivers seem an easier impedance target to work with than the entire crossed over segment (if you look at where the respective filter's effects lie)
 
Indm's usage is in conflict with how the original poster defined series/parallel.

The main difference is in whether or not you can tolerate a rise in impedance (parallel notch) or a dip in impedance (series notch) The parallel filter will also have an insertion loss below the filter frequency due to the inductor DCR.
 
So, as I understand:
A serie notch filter in parallel with the driver is used for cone breakup. Cone breakup is mostly in the take-over region between woofer and tweeter. Both must be in phase. Is there no risk that the signals are not in phase anymore after inserting the notch filter?

A parallel notch filter (with components of the notch filter in parallel) is used in the passband of the crossover filter. Am I right?

I still don't see the reason why a parallel notch filter is better in the passband of the crossover? Can a serial notch not do the work. :bawling:
 
Jonasa said:
Both must be in phase. Is there no risk that the signals are not in phase anymore after inserting the notch filter?
The phase will be altered. Was it right to begin with? Matching phase is often a challenge and this is just one part of it. Using the right values and the right resistor is also fairly important.
A parallel notch filter (with components of the notch filter in parallel) is used in the passband of the crossover filter. Am I right?
It can be. If there is little series impedance from the inductor (for example) then the series notch (in parallel with the driver) can't work well. It really depends on the unit in question.

Are you able to sim the crossover?
 
One more question:
Why is a serial notch filter always used refered to the negative to remove bumps?
Is it not possible to use a serial notch filter to remove dips in the frequency when the filter is refered to the positive amplifier point.

I mean one side of the filter on the speaker + and one side on the amplifier + to remove dips in FR. At resonance frequentie of the notch impedance is zero and the speaker gets more energy from the amplifier to remove the dip in FR.:rolleyes:
 
If I understand you correctly, you are describing a bandpass filter. This is the standard way to cross over a midrange driver. This way, you can do the same as boosting a dip, by dropping everything on either side of the dip.

Actually increasing the level at some frequency is more tricky. For that, you'd either need to use a very high Q filter segment to cause a bump (if this is possible in your case) or use an active filter.
 
re:'Is it not possible to use a serial notch filter ' if used on a 'fullrange' driver with no other crossover components, this could cause a short circuit for the amp at the notch freq, hence the use of a parallel filter in this situation.

re:'Should a paralell notch filter be placed before or after the crossover?' - it depends how they interact, if far enough apart in freq it probably doesn't matter, but calculations will probably be easier if the notch is placed before the crossover
 
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