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3 ways active crossover
3 ways active crossover
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Old 6th June 2011, 04:29 AM   #1
bizicafe is offline bizicafe  Viet Nam
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Default 3 ways active crossover

Hi everyone,

I am moving towards a 3-way system and really in need of building one active crossover, preferably tube-based. I have been searching for schematics of such XO but unfortunately found nothing. Could anyone help out?

Thanks,
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Old 6th June 2011, 05:38 AM   #2
mashaffer is online now mashaffer  United States
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This will get you started.

http://greygum.net/sbench/sbench101/Crossover/xover.gif

It is two way but cascading a HP and a LP will give you the third BP filter that you need.
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Old 6th June 2011, 06:26 AM   #3
bizicafe is offline bizicafe  Viet Nam
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Thanks, Mashaffer,

I built an op-amp based XO with 3-way outputs but was not happy with what it brought to my tube-based systems, then came the reasons for the searching...

Could you help explain a little more how I can make the 2-way version given a 3-way one?

Thanks,
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Old 6th June 2011, 02:24 PM   #4
Evenharmonics is offline Evenharmonics  United States
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Here are couple.
Tube Active Crossover
Tube Crossover (Page 1): January's Circuit of the Month

But, what's wrong with SS active crossover?
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Old 6th June 2011, 02:42 PM   #5
bizicafe is offline bizicafe  Viet Nam
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Thanks, Evenharmonics.

I am working on the schematic for my XO using 6N1P tubes, and will post here for your comments and review

Don't know what was wrong with my SS XO exactly, maybe because I am a tube addict.
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Old 6th June 2011, 11:20 PM   #6
mashaffer is online now mashaffer  United States
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In the schematic listed you will see a chart of R and C values for various crossovers. You can kind of work out ratios for other cut off frequencies from studying that chart. Using a spice simulator like LTspice can help you to confirm/tweak the values. Use the HP section at a suitable crossover for the top, use the LP section also at a suitable (different) crossover.

The middle will be a cascade of a HP and a LP at the above crossover frequencies to create a bandpass. So if the upper crossover was at 7kHz and the lower at 150Hz then your mid band would have a HP at 150Hz and a LP at 7kHz.

As an example my woofer output in this simulation is a band pass. Note I tweaked the values somewhat to get an over all slope that would compensate for open baffle losses but the topology is essentially the same.

3 ways active crossover-crossoversectionbufferedinput-jpg
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File Type: jpg CrossoverSectionBufferedInput.jpg (194.7 KB, 1217 views)
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Old 6th June 2011, 11:22 PM   #7
mashaffer is online now mashaffer  United States
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Sorry for the size there.
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Old 7th June 2011, 01:26 AM   #8
bizicafe is offline bizicafe  Viet Nam
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Hi Mashaffer,

After a while delving into the theory, it seems a little clearer for me. Now the fun part is selection of R and C values, which is not easy as expected.
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Old 7th June 2011, 06:56 PM   #9
john dozier is offline john dozier  United States
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Is anyone producing boards for the 24db/octave two way? I would love to build it, but do have the software or knowledge to produce pcbs. Thanks
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Old 24th June 2011, 06:31 PM   #10
Mikewong is offline Mikewong  Italy
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Quote:
Originally Posted by mashaffer View Post
This will get you started.

http://greygum.net/sbench/sbench101/Crossover/xover.gif

It is two way but cascading a HP and a LP will give you the third BP filter that you need.
I am thinking of going active for my ATC SCM20SL Pro.The built-in passive cross-over is a simple 12dB/octave LC filter with the cross-over frequency at 2.8khz.
Using the aboved tube cross-over to start with,what are the components` values should I changed so that it could be used?
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