Sorry about the long title...wanted to make it as search friendly as possible...especially since Yahoo! crawls this place.
Couldn't really find any information on it, but do you build an 8th order active crossover by cascading two 4th order Linkwitz crossovers?
Couldn't really find any information on it, but do you build an 8th order active crossover by cascading two 4th order Linkwitz crossovers?
Linkwitz-Riley is just a filter slope characteristic. To make an 8th-order filter you just cascade 2 4th-order filters. The resulting Q will be filter_1 Q * filter_2 Q
If you want an 8th-order Linkwitz-Riley response, you need to cascade 2 4th-order Butterworth filters.
If you want an 8th-order Linkwitz-Riley response, you need to cascade 2 4th-order Butterworth filters.
I'd suggest doing a little research on Jon Marsh's Cauer Eliptical filters on the DIY portion of www.htguide.com. His filters typically exhibit 8th order LR slopes with less components.
Elliott describes the construction of a 36dB/octave filter (only the high pass section) cascading two 18dB/octave Butterworth filters. See http://sound.westhost.com/project99.htm, maybe some interesting info there!
Kind regards, Emiel
Kind regards, Emiel
I couldn't find the Project 99.
I found these active crossover filter circuit schematics. They cover;
I found these active crossover filter circuit schematics. They cover;
Look here: http://sound.westhost.com/articles/ntm-xover.htm
Also, if you want to go passive look at Jon Marsh's cauer elliptical crossover. Search for "cauer" on htguide.com. I like the transfer function better than the ESP crossover above. OTOH, implementing an active version is evidently challenging. You'll see something about that on htguide.
Also, if you want to go passive look at Jon Marsh's cauer elliptical crossover. Search for "cauer" on htguide.com. I like the transfer function better than the ESP crossover above. OTOH, implementing an active version is evidently challenging. You'll see something about that on htguide.
Hybrid fourdoor said:
Sorry, here's the correct link:
http://sound.westhost.com/project99.htm
Kind regards, Emiel
To make an 8th order Linkwitz Riley filter you have to cascade two 4th order butterworth filters to give you -6db at the cut off frequency. Cascading two 4th order Linkwitz riley filters would give you -12db at the cut off frequency which is obviously not wanted.
I think the question of "what is an 8th order Linkwitz-Riley filter" has been put to rest. Every LR filter is two Butterworth filters of half the order in series. This is why the LR filter type is called "Butterworth squared" and only even orders exist.
Here is some advice on "How" to do it:
There is certainly more than one way to construct an active 8th order crossover (don't try this as a passive filter!). One way that I would suggest is using two 4th order state variable filters in series. Look up "state variable filter" for more info. For a crossover you will need THREE SV filters: the first provides 4th order LP+HP. You then connect another SVF to the HP output and use its HP output to get 8th order HP out. Likewise you connect the third SVF to the LP output of the first SVF and this produces the 8th order LP out.
By the time you purchase and build all of these circuits and the required power supply you could buy a MiniDSP 2x4 and easily implement an LR8 and many other filter types (all at the same time) and it will cost less.
Here is some advice on "How" to do it:
There is certainly more than one way to construct an active 8th order crossover (don't try this as a passive filter!). One way that I would suggest is using two 4th order state variable filters in series. Look up "state variable filter" for more info. For a crossover you will need THREE SV filters: the first provides 4th order LP+HP. You then connect another SVF to the HP output and use its HP output to get 8th order HP out. Likewise you connect the third SVF to the LP output of the first SVF and this produces the 8th order LP out.
By the time you purchase and build all of these circuits and the required power supply you could buy a MiniDSP 2x4 and easily implement an LR8 and many other filter types (all at the same time) and it will cost less.
The question was never 'what is an 8th order Linkwitz Riley filter' it was asking how to build one.😀
Your best change is to use a dsp and multi-amping... because the required tolerances (and values) of the parts you need are almost impossible to produce and reproduce if you want to build a small series of those filters.
Even designing and building a "good" 2nd or 3rd order filter is a big challenge ...
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My cheap DMM has a capacitor value facility.
It is 2000 count.
If I want 5n6F I would use the 20.00nF scale and be able to read off 3 significant digits.
For comparison/matching, that would give me a tolerance of +-0.2% on capacitor values.
Similarly I can easily get +-0.2% tolerance on matching of resistor values.
Why would I need better than +-0.2% for a matched series of 4th order Butterworth filters?
It is 2000 count.
If I want 5n6F I would use the 20.00nF scale and be able to read off 3 significant digits.
For comparison/matching, that would give me a tolerance of +-0.2% on capacitor values.
Similarly I can easily get +-0.2% tolerance on matching of resistor values.
Why would I need better than +-0.2% for a matched series of 4th order Butterworth filters?
This is rubbish. Tolerances are NOT a problem for the DIYer making a few boards, especially when you can measure components. See AndrewT's comment above. Component tolerances are only a problem for mass production where you have to live with whatever you can get from the manufacturer. The DIYer can buy a batch of less expensive loose tolerance components and measure & match or measure (e.g. caps) and adjust other values (e.g. resistors) as needed.
Hey guys,
I'm trying to implement some L-R filters using APO Equalizer to do some active crossover. But APO doesn't have built in L-R filters. So I'm trying to create them using BW filters.
Can someone verify if this is correct? 1000hz is used in these examples.
#L-R2 12db/octave
Filter: ON HPQ Fc 1000 Hz Q 0.5
#LR-4 24db/octave
#Cascading 2 2nd-Order BW Filters
Filter: ON HPQ Fc 1000 Hz Q 0.7071
Filter: ON HPQ Fc 1000 Hz Q 0.7071
#LR-8 48db/octave
#Cascading 2 4th-order Butterworth
#4th-order BW is: 4th order -> 2nd with Q = 0.541 + 2nd with Q = 1.306
Filter: ON HPQ Fc 1000 Hz Q 0.541
Filter: ON HPQ Fc 1000 Hz Q 1.306
Filter: ON HPQ Fc 1000 Hz Q 0.541
Filter: ON HPQ Fc 1000 Hz Q 1.306
Q-values reference: http://csserver.evansville.edu/~ric...ynthesis/resources/handouts/ButterQValues.pdf
I'm trying to implement some L-R filters using APO Equalizer to do some active crossover. But APO doesn't have built in L-R filters. So I'm trying to create them using BW filters.
Can someone verify if this is correct? 1000hz is used in these examples.
#L-R2 12db/octave
Filter: ON HPQ Fc 1000 Hz Q 0.5
#LR-4 24db/octave
#Cascading 2 2nd-Order BW Filters
Filter: ON HPQ Fc 1000 Hz Q 0.7071
Filter: ON HPQ Fc 1000 Hz Q 0.7071
#LR-8 48db/octave
#Cascading 2 4th-order Butterworth
#4th-order BW is: 4th order -> 2nd with Q = 0.541 + 2nd with Q = 1.306
Filter: ON HPQ Fc 1000 Hz Q 0.541
Filter: ON HPQ Fc 1000 Hz Q 1.306
Filter: ON HPQ Fc 1000 Hz Q 0.541
Filter: ON HPQ Fc 1000 Hz Q 1.306
Q-values reference: http://csserver.evansville.edu/~ric...ynthesis/resources/handouts/ButterQValues.pdf
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