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Old 25th July 2015, 12:06 AM   #1
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Default Crossover 2nd order Butterworth Questions

I'm curious if that in a 2nd order butter worth crossover that a speaker's voice coil inductance needs to be treated as part of the crossover. Any help and answers are appreciated. Im wanting to build a replica of the jbl everest dd67000. I'm just leaving out the uhf. so its a 2 way system. This is a photo of the actual one. Ive heard a real pair of them. the reason im replicating with modifications is because $75,000 is about over 10x my budget. Click the image to open in full size.
Im new to forums in general so my post won't be so great.
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Old 25th July 2015, 01:10 AM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by FellCrustacean8 View Post
I'm curious if that in a 2nd order butter worth crossover that a speaker's voice coil inductance needs to be treated as part of the crossover.
Yes, a series RC across the woofer terminals can compensate for its impedance rise at higher frequencies.
Then the crossover can be more textbook.
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Old 25th July 2015, 01:17 AM   #3
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I dont know if you understood the question correctly. Should the drivers inductance (L) be treated as a normal inductor in a crossover network.
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Old 25th July 2015, 01:22 AM   #4
rayma is offline rayma  United States
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Quote:
Originally Posted by FellCrustacean8 View Post
I dont know if you understood the question correctly.
Should the drivers inductance (L) be treated as a normal inductor in a crossover network.
No, because with the series RC network, the inductance can be balanced out so the woofer electrically looks more like a resistor.
That's how this problem is normally dealt with. See this article: https://www.trueaudio.com/st_zobel.htm

Last edited by rayma; 25th July 2015 at 01:27 AM.
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Old 25th July 2015, 01:41 AM   #5
djk is offline djk
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"Should the drivers inductance (L) be treated as a normal inductor in a crossover network. "

No.
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Old 25th July 2015, 05:53 AM   #6
system7 is offline system7  United Kingdom
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Voicecoil inductance Le does act as a coil in filtering terms. Usually around 0.5mH in PA speakers like the well-behaved and flattish Eminence Beta 8A.

Higher inductance tends to fight your efforts with simple filters and create an unwanted peak at crossover. Usually if the filter bafflestep coil is three times the speaker Le, a simple shunt cap will work, which is a quirk of 3rd order butterworth filters. So eminence often recommend 2.2mH and 10uF bass, and 3.3uF and 0.3mH tweeter with an attenuator for 2.5kHz crossover, simple as that.

If the speaker has very high inductance, like the Visaton W200S, your shunt element will be more like a Zobel, which is a similar capacitor and resistor around 7.5 ohms to correct impedance and control a tendency to peak badly.

It's a complex business best resolved by modelling. You might find interest in Pi Speakers which AFAIK, uses a Zobel. And some images below on the Jeff Bagby Fusion 8 Alchemy which uses the Eminence Beta 8A with a slightly more extended bass filter. In fact he adds to the voicecoil inductance with the second coil.

IMO, a good speaker is just an inspiration. You can interpret it in your own way. You are looking at high efficiency, high Qms drivers.
Attached Images
File Type: jpg Fusion_8 Alchemy.JPG (38.9 KB, 38 views)
File Type: png Eminence Beta 8A frequency response.PNG (19.7 KB, 39 views)
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