Author Topic: RC filter experience?  (Read 1717 times)

Offline hope

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RC filter experience?
« on: December 23, 2017, 09:46:30 PM »
Hi DIYers,

Does anyone have any experience with passive line level RC filters for biamping?

VH

Offline Agaton Sax

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Re: RC filter experience?
« Reply #1 on: December 24, 2017, 12:21:21 PM »
Many years ago when I was bi amping Klipschorns I asked the highly regarded builder of my pre amp if he could include RC filters on the double ouputs. He,who is known to everyone here, tried his best (which is way out there excellent) but could not get it to work well . He refused to include the mod. Figuring that if someone like him failed it is not worthwhile pursuing .I quit the idea.

Having extensive experience with active crossovers I kept persisting with passive line levels settling on a cap /choke pllxo that has served me well for decades , finally settling on a quad amp configuration. There are rules,mainly regarding pre out impedance and a 1db insertion loss but otherwise it works exactly as specified. Tbe unit is the Marchand  XM 46. You can get it as a kit  and that includes Phil Marchandís experience with this somewhat black art form but if you insist on diying the coils yourself ,welll...

Offline hope

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Re: RC filter experience?
« Reply #2 on: December 24, 2017, 03:16:50 PM »
Thank you, but I understood the RC to stand for Resistor Capacitor and that inductors / chokes were only used in passive speaker-level XOs?

Offline Agaton Sax

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Re: RC filter experience?
« Reply #3 on: December 24, 2017, 04:25:17 PM »
Thank you, but I understood the RC to stand for Resistor Capacitor and that inductors / chokes were only used in passive speaker-level XOs?

Correct . This is what we could not make work repeatably and accurately. The Marchand way adds chokes to the c and r at line level,delivering precise results almost independent of pre amp output impedance (provided it is below 500 phms) and independent of power amp input impedance.my measured crossover graph here
https://flic.kr/p/GDneH9

That is only my experience. I am aware of a few horn fans who made rc work for them though.

Offline hope

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Re: RC filter experience?
« Reply #4 on: December 24, 2017, 07:00:32 PM »
Which active XOs did you try in all, before going Phil "RC"?

Does RC not seem less dynamic than active? In your case your horns might make up for a loss in dynamics, but more neutral / transparent sound?

Offline Agaton Sax

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Re: RC filter experience?
« Reply #5 on: December 24, 2017, 08:03:38 PM »
Which active XOs did you try in all, before going Phil "RC"?

Does RC not seem less dynamic than active? In your case your horns might make up for a loss in dynamics, but more neutral / transparent sound?

Luxman,Audio Research,Krell. In every case the system took on the sound of the crossover i.e my CJ premier 3 started sounding like an ARC keeping the negative cj traits and gaining the negative ARC ones. Pits was the beautiful Krell  that sounded as bad as those early Krell pre amps (not dissing the superb Krell power amps here)  . The little Luxman was probably best.

There was a long interim off passive speakers and radical system changes from planar to horn before multiamping again so I cannot really say about lack of dynamics  with pllxo Every component in my speaker system does 110db for 1 watt so dynamics is never an issue nowadays. Pre amp selection was also influenced as I was keen on either a cj ART or Kondo or the Italian Viva. All of these were deemed unsuitable for a passive line level xo so I settled for many happy years with Lamm before our own Doornpoort devil knocked the ball way out of the park with the sadly one-off Revelation.
« Last Edit: December 24, 2017, 08:14:06 PM by Agaton Sax »

Offline hope

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Re: RC filter experience?
« Reply #6 on: December 24, 2017, 08:57:52 PM »
So no experience with Phil Marchand's ACTIVE XOs then, valve or SS, for comparison?

I see Phil likes 4th order, it seems yours are not, except maybe your band-pass driver in the middle.

Offline hope

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Re: RC filter experience?
« Reply #7 on: December 25, 2017, 10:05:57 AM »
Dear Agaton,

Merry Xmas.

Thank you for your salient advice, I see Phil sells each mono board for only $100. Even a poor cheapskate like me can afford those prices. I will place an order after Xmas.

Offline Ampdog

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Re: RC filter experience?
« Reply #8 on: February 11, 2018, 04:22:49 PM »
I 'dialled' onto this by accident - late. If I may still add a few comments:

With due respect for all concerned, the design of cross-over filters is by now well documented, and several programmes are available, including some degree of Spice to view results. This is particulaly so for R.C types as used in bi-amping, as relevant impedances can be accurately determined and remain constant. (Design of cross-overs at the loudspeaker level remain a problem because of the mostly difficult/varying impedance of the load: the drivers. These cannot be developed successfully without including the loudspeaker characteristics.)

Thus, in this post I read that R.C. filters for use in the signal line of a bi-amping system are the subject. As said, several design programmes are available plus ease of analysis. There are also several modes of filter; 2nd, 3rd or 4th order to be decided on.  (In these, inductors are not normally used becaue they are large and relatively expensive, and stray fields can have an influence etc. The greater loss of R.C. types  is not relevant because of the amplification added.)

But in the meantime you might have succeeded, Hope. Kindly give information if the problem has been solved. Experience on this subject is always welcome!     
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)

Offline Ampdog

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Re: RC filter experience?
« Reply #9 on: May 17, 2018, 11:58:49 PM »
Hope,

Should I say "Bump"?

Have you progressed with this, and with what result? I think a number of members might be interested!
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)