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Re: an active (or passive)crossover is:

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In Reply to: Re: an active (or passive)crossover is: posted by Andre Linoge on March 22, 2001 at 11:56:23:

The crossover frequency is one piece of the puzzle when trying to replace an exixting passive speaker-level design with a line level active/passive approach. As Arbelos mentioned you really need to know the shape (Q) of the filter sections as well in order to duplicate the performance of the original. This information is hard to come up with unless you have access to the schematic diagram or have measuring capabilites which can monitor the actual drive voltages at the xducer terminals. Also, somebody above mentioned the cavity resonance trap that is required for the BG drivers. This part of the crossover response could also be taken care of at line level, but for a first cut design it is probably better left in place in the existing network.
The passive line level circuit I did for the Magnepan 1.6 works pretty well because of the straightforward and low order crossover slopes involved. I'm not sure what the characteristics of the 520 speaker system is, so I couldn't say if a similar circuit would work. Passive line level circuits have many limitations and IMHO a dedicated active circuit is the way to go in most applications.
The generic 24db/octave slope active crossovers that are available from Marchand and others are great, but they almost certainly have much steeper slopes and different Q's than the existing crossovers in most speaker systems.
I think you can definetely improve your setup by bi-amping, but it's not as easy as just popping in an active 4th order crossover at the same crossover frequency. This would most likely give less than optimal results compared with the original.
If you can come up with a schematic diagram of the crossover of your BG 520's I would be more than happy to take a crack at modeling a line level circuit to replace it.
Regards.
Davey.

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Re: an active (or passive)crossover is: Andre Linoge 15:08:30 03/22/01 (7)
Clyde posted this URL (scroll halfway down) with a BG ribbon XO schematic.
http://www.audio-x-stream.com/faqbase.html#FAQ Planar Magnetic Drivers
I made a quick drawing of what the XO board looks like and the parts. Here's the link for the drawing.

http://www.geocities.com/alinoge2000/bgxo.htm
- Re: an active (or passive)crossover is: Arbelos 19:27:20 03/22/01 (6)
  If you go to an active crossover, i'd obviously use the Audio X-stream crossover, which incorporates a tuneable notch filter for the B-Gs. I forgot about it. Better would be only a tube crossover IMO.
  I think that the passive notch filter ahead of the speaker is probably a severe limit on sonic quality - i prefer to implement such filters with a parallel 'sink' circuit, not a blocking 'tank' circuit - if i have to.
  It is probable that a text-book crossover will work quite well from the start on the B-Gs, because they have a rel. well behaved fundamental resonance at ca. 130 Hz, so the used crossover is about two octaves away, and the bass will be at least 2 octaves away from its upper limit. The used XO frequency sits nicely (and sensibly IMO) between both drivers lower resp. upper limit. A bit of tuning will probably still be necessary.
  What preamp and amp do you want to use?
  - Re: an active (or passive)crossover is: Andre Linoge 22:28:20 03/22/01 (5)
    Hi Arbelos, here's the link to my earlier post with the details about my system:
    http://www.audioasylum.com/forums/mug/messages/13002.html
    Where can I find about the Audio X-treme?
    Thanks.
    - Re:-> audio-x-stream.com Arbelos 11:53:12 03/23/01 (1)
      http://www.Audio-x-stream.com/cxrframe.html#Clearview Equalizing Crossovers
      - Re:-> audio-x-stream.com Doug 15:26:59 03/23/01 (0)
        
        In Reply to: Re:-> audio-x-stream.com posted by Arbelos on March 23, 2001 at 11:53:12:
        
        Audio-X-Stream is no longer. I tried for almost a year to buy a Clearview for my CALS Platinums. I have since given up and I'm building my own.

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