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Linkwitz or Butterworth?

12.9.186.2

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Hi, need some help.
The Magnepan manual does not specify which type (L-R or Butterworth) to use on the high pass crossover (12 dB @ 200 Hz) for MG3.5R for active/electronic crossover.
Do you know which? Gotta reply back to Phil soon.

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Re: Linkwitz or Butterworth? - neolith 13:10:15 11/22/06 (1)
The values I have for the crossover are C=115 mfd and L=8.5 mH and R=3.9 ohms which calculates to a Q=0.45 and -6db point of 180 hz which is fairly close to a L_R (Q=0.5). I would use and active 2nd order L-R at 180 hz to simulate the stock passive xo.
As AndyR points out Magnepan takes a fair amount of license with their published values and tend to use Q's lower than the standard L-R or Butterworth and they also tend to "round off" the actual corner frequency.

I may be an egoist but at least I don't talk about other people.
- Clarification to the above - neolith 13:20:02 11/22/06 (0)
  Usually corner frequencies are listed at -3db but L-R are better described at the -6db point (a symmetric L-R xo will cross at the -6db point so when the low pass and the high pass are summed the output curve is flat). For the MG-3.5 mid hi-pass, the -3db point is 300 Hz as stated by Magnepan but the -6db point is at ~180 hz.
  
  I may be an egoist but at least I don't talk about other people.
Re: Linkwitz or Butterworth? - andyr 12:42:40 11/22/06 (1)
I believe the stock passive mid HP slope on the 3.5R is 2nd order Butterworth. However, Magnepan normally engineer slopes which are less steep than the theoretical 12/18dB ... so I suspect that the stock slope is probably around 10dB per octave.
In fact I doubt Phil will hear the difference between 12dB Butterworth or L-R.
Regards,
Andy
- Re: Linkwitz or Butterworth? - rathbone 13:05:23 11/22/06 (0)
  Thanks Andy.
  Phil = P. Marchand :) (am in the process of ordering modules)
  I suppose the difference between the two types would be subtle at best, so perhaps that is why the types (L-R, Butterworth) are not specified in the manual.
  The MG3.5R stock passive XO's HP is reported to be 12 dB/oct quasi 300Hz, and the LP is 18db/oct 200Hz Butterworth. To be honest, I am not 100% sure what they mean by "quasi" other than is neither a true L-R or Butterworth.
  Again, thanks!
  Basil

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