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4 Pi crossover questions [message #52463]

Fri, 15 August 2008 12:10

jimbop
Messages: 60
Registered: May 2009
Location: Colorado Springs, CO

Viscount

In the 4 Pi crossovers, which caps have the greatest effect on the quality of the high frequencies? What brands of caps are people using in these positions?

Wayne, can you explain the function of the various caps, and which caps will benefit most from upgrading from the stock components?

Thanks,
JD

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Re: 4 Pi crossover questions [message #52464 is a reply to message #52463]

Fri, 15 August 2008 16:14

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

Importance from most to least:

C2, C3, C4, C1, C5

C2 and C3 are actually equal importance, being series capacitors. These pass the signal to the tweeter. C4 is a shunt filter cap, and it's important because it ultimately affects midwoofer response. C1 is a bypass capacitor, and only provides a tiny bit of signal at the extreme HF. C5 is part of the Zobel, which sets the load for the midwoofer crossover. This part has a very large tolerance, but if it's way off, upper midrange response is adversely affected.

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Re: 4 Pi crossover questions [message #52465 is a reply to message #52464]

Fri, 15 August 2008 16:51

jimbop
Messages: 60
Registered: May 2009
Location: Colorado Springs, CO

Viscount

Ideally, should C2 and C3 be the same brand of capacitor?

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Re: 4 Pi crossover questions [message #52466 is a reply to message #52465]

Fri, 15 August 2008 22:56

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

I suppose that would be a matter of preference, but I would use the same type and brand.

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Re: 4 Pi crossover questions [message #52468 is a reply to message #52466]

Sat, 16 August 2008 01:56

jimbop
Messages: 60
Registered: May 2009
Location: Colorado Springs, CO

Viscount

After posting my question, I did some searching and had a hard time finding many 22uF caps, especially in higher quality brands. Do you have any suggestions? I know you don't like to recommend specific parts, but perhaps you know of a couple of lines that others have used.

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Re: 4 Pi crossover questions [message #52469 is a reply to message #52468]

Sat, 16 August 2008 02:07

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

I use polypropylene capacitors from Solen, Erse, Jantzen and/or Audience (Auricap). Capacitor C1 is 0.47uF, C2 is 6.8uF, C4 is 10uF and C3 and C5 are 20uF or 22uF, depending on the manufacturer.

http://www.pispeakers.com/fourPi_schematic.gif

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Re: 4 Pi crossover questions [message #52476 is a reply to message #52469]

Sat, 16 August 2008 15:30

jimbop
Messages: 60
Registered: May 2009
Location: Colorado Springs, CO

Viscount

Is this crossover universal for all models. I think mine is the Theater 4 - it has the Eminence 15 woofer. The original caps are 8 uF and 22 uF.

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Re: 4 Pi crossover questions [message #52477 is a reply to message #52468]

Sat, 16 August 2008 18:12

Matts
Messages: 359
Registered: May 2009

Grand Master

an excellent bargain in a quality cap is the Obligato from diyhifi in Hong Kong. They ship 'em here very fast and reasonably. I used them for 22uF's, and Auricaps for the 8uF (now 6.8), although I wouldn't hesitate to use them for all. Very nice caps for the $$.

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Re: 4 Pi crossover questions [message #52479 is a reply to message #52476]

Sat, 16 August 2008 23:46

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

I'm not making the Theater four π speakers anymore, so the new crossover hasn't been tested on them. But it has been tested with the Eminence Omega 15 and Delta 12LFA woofers and it works well with those. The main difference is matching sensitivity, which you do with the proper selection of components R1 and R2. So I expect this crossover would work pretty well in a Theater Series four π, using 16Ω resistors in positions R1 and R2.

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