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Bypassing Crossover Capacitors

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Posted on June 22, 2016 at 17:13:53
Randal P
Audiophile

Posts: 33
Location: NYC Area
Joined: August 19, 2004
 I'm putting together a two way system with Altec 414/802/32A. I'm taking Joe Roberts' advice and letting the 414 run wide open and using a first order on the 802 at 6-8,000khz. I'm going to use an autoformer for HF attenuation.

Since the remainder of the crossover comprises a single capacitor, I can spend a bit more on higher end components, such as Jupiter or Audyn True Copper. My target value will be about 2.7 - 3.0 uF. These are not typically available values.

My question is if paralleling capacitors to get the desired value is a positive, negative, or neutral from a performance perspective? Any input would be greatly appreciated.

 

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RE: Bypassing Crossover Capacitors, posted on June 22, 2016 at 18:06:25
Cleantimestream
Audiophile

Posts: 7551
Location: Kentucky
Joined: June 30, 2005
 Neutral to positive I posit. I have mixed dielectric as well with synergy @ times. Paper in oil sound excellent with compression drivers
The Mind has No Firewall~ U.S. Army War College.

 

RE: Bypassing Crossover Capacitors, posted on June 22, 2016 at 22:30:47
horny
Audiophile

Posts: 745
Location: holland
Joined: October 17, 2003
 One good quality capacitor is for me always better sounding then parallel caps
i try it many times but like one cap always more

 

RE: Bypassing Crossover Capacitors, posted on June 24, 2016 at 19:51:12
Rod M
Web Geek

Posts: 16245
Location: So. California
Joined: March 1, 1999
Contributor
  Since: March 1, 1999
 I'd agree with Cleantimestream, a single paper in oil is hard to beat. I use some old military surplus caps that are wonderful.

-Rod

 

RE: Bypassing Crossover Capacitors, posted on June 25, 2016 at 09:23:53
tomservo
Manufacturer

Posts: 8210
Joined: July 4, 2002
 Bypassing caps is necessary when your dealing with caps that have significant series inductance and when operated at high frequencies.

At audio frequencies, a decent polypropylene cap (no need for boutique caps) is darn close to theoretically idea capacitor and doesn't benefit from being bypassed. If your looking at Mouser, Digikey, Newark, Allied or other electronic parts catalogues, look for caps rated for switching power supplies and or low ESR.

Of vastly greater importance is having the ideal value of capacitance and a circuit topology which accounts for the load's actual impedance which is nothing at all like a resistor.
Making a passive crossover for a horn driver is more complicated than it might appear as the impedance varies quite a bit and is reactive.

 

RE: Bypassing Crossover Capacitors, posted on June 25, 2016 at 13:43:30
bwaslo
Manufacturer

Posts: 245
Location: Portland, OR USA
Joined: September 10, 2006
 Watch out, though. Some crossover designs are engineered expecting the ESR of the capacitors they use Nonpolar electrolytics in the 10 to 100uF range can have "built-in" series resistance on the order of about a half an ohm, sometimes more. If you think the original designers were choosing things very critically (probably not in older designs!) then you might want to use a small series resistor with film capacitors that you replace into the networks.
_

Make easy high performance diffusors:-->http://www.libinst.com/diffusers/Depot_Diffuser.html

Horn Design Spreadsheet:--> http://libinst.com/SynergyCalc/

SmallSyns:-->http://www.diyaudio.com/forums/multi-way/292379-s

 

RE: Bypassing Crossover Capacitors, posted on June 26, 2016 at 07:23:29
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Truth is, no one cap " does it all " and plays in ALL ranges with the utmost of energy, color, vividness.

If, however, I was going to go the " one cap" route, I would suggest the Mundorf M Cap Supereme, Silver, Oil and Gold at the 1200 VDC rating !! No doubt in my mind.

I personally don't have the budget for the best caps, so, I multiple-bypass every cap in every position, in amps and speakers. BUT, it has to be done carefully, on a high quality system, and by your EAR - as the final arbitrator.

The bypass VALUEs you select are critical - to avoid overlap and loss of coherency. Usually, with all else equal, higher-voltage-rating-caps do sound better on my highly optimized A7-800 crossovers !! I'm " into " 1,000 VDC and 1,600 VDC rated caps in my crossovers these days. No contest to my ear, versus SAME cap in, say, a 250 VDC rating.

One other important thing I easily hear on my A7s, a TIP :

I find that whatever I do in the 12 dB realm, bypass-cap-wise for the tweeter, the SAME EXACT bypass VALUES and VDC ratings MUST be applied to the other driver's cap bank, ie : for the woofer's film cap bypassing !!!!!!!

Have FUN !!

Jeff Medwin

http://www.hostboard.com/forums/f700/279373-using-higher-voltage-rated-film-caps-altec-crossovers.html

 

RE: Bypassing Crossover Capacitors, posted on June 29, 2016 at 09:10:21
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Those remind me a lot of the capacitor that I installed in my house air conditioner compressor.

Dave

 

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