Diodes in passive crossover

hi_im_sean · 13th December 2004, 06:31 PM

My boss and I were looking at some crossover disigns from some very high end speaker cabinets, and noticed that there were diodes in the circuit. Can anyone tell me what the hell diodes are doing in a passive crossover? I have seen diodes in crossovers before and I cannot figure out why. And I have only seen them in very expensive speakers. Any insight or answers will help me sleep at night.

kelticwizard · 13th December 2004, 11:56 PM

Quote Greg Weaver, from Soundstage! magazine:

Quote:

The crossover is nothing more than a specialized filter, consisting of coils, capacitors, resistors and diodes.

Well, Greg Weaver seems to feel they belong in passive crossovers as well. If you get no answers, consider Emailing him.
http://www.soundstage.com/synergize/synergize031998.htm

kelticwizard · 14th December 2004, 12:04 AM

Those diodes you saw in the speaker crossovers. By any chance were there also electrolytic capacitors in that circuit?

I am wondering if the speaker manufacturers decided to take two polarized electrolytics and added diodes instead of using non polarized electrolytics, for high value capacitance.

My next guess is that since diodes have a logarithmic characteristic, the expensive speaker designers have some sort of circuit where a high slope is achieved by the diodes, and is by passed by other components to make up for the 0.6 volts requirement.

Just guessing.

hi_im_sean · 14th December 2004, 08:11 PM

Yes of course there are caps in the circuit, along with resistors and inductors, your idea of creating a steep slope may be correct, i think ribbon tweeeters were used (which require a fairly steep slope depending on the driver and crossover point). Good explanation... any others?

leadbelly · 14th December 2004, 08:19 PM

Hard to have any insight without at least seeing the portion of the schematic with the diodes, can you post or describe it? Either protecting polarized caps as KW suggested or used as a high value resistor in reverse bias is all I can think of.

ScottG · 14th December 2004, 09:36 PM

diodes are sometimes used in powersupply to reduce noise.

after thinking a bit more about it the term to search for on the web is "snubber".

Timn8ter · 14th December 2004, 09:56 PM

I only find them in active crossovers.

Bill Fitzpatrick · 14th December 2004, 10:09 PM

Why do I think that a diode, unless an LED, in a crossover is ridiculous?

tomi · 14th December 2004, 10:12 PM

Hi there guys.
It does indeed seem bizarre to put diodes in a crossover network. As preveous contributors have said, it's hard to know what they are supposed to be doing without seeing the exact configuration; Still, I can't see how adding the non-linear characteristics of a diode can possibly alter to the frequency response (to give a steeper roll-off).
My best guess is that they might be (hefty) zener diodes, in place to shunt the drivers or caps in case of overload... but even that's a long shot!

And for the record, I've never seen a filter, active or passive, with diodes in the signal path.

Cheers!

Timn8ter · 14th December 2004, 11:01 PM

Quote:

I've never seen a filter, active or passive, with diodes in the signal path

Yup, not in the signal path.

13th December 2004, 06:31 PM	#1
hi_im_sean diyAudio Member Join Date: Jan 2004 Location: az	Diodes in passive crossover My boss and I were looking at some crossover disigns from some very high end speaker cabinets, and noticed that there were diodes in the circuit. Can anyone tell me what the hell diodes are doing in a passive crossover? I have seen diodes in crossovers before and I cannot figure out why. And I have only seen them in very expensive speakers. Any insight or answers will help me sleep at night. __________________ sean

14th December 2004, 12:04 AM	#3
kelticwizard diyAudio Member Join Date: Sep 2001 Location: Connecticut, The Nutmeg State	Those diodes you saw in the speaker crossovers. By any chance were there also electrolytic capacitors in that circuit? I am wondering if the speaker manufacturers decided to take two polarized electrolytics and added diodes instead of using non polarized electrolytics, for high value capacitance. My next guess is that since diodes have a logarithmic characteristic, the expensive speaker designers have some sort of circuit where a high slope is achieved by the diodes, and is by passed by other components to make up for the 0.6 volts requirement. Just guessing. __________________ "A friend will help you move. A really good friend will help you move a body." -Anonymous

14th December 2004, 08:11 PM	#4
hi_im_sean diyAudio Member Join Date: Jan 2004 Location: az	Yes of course there are caps in the circuit, along with resistors and inductors, your idea of creating a steep slope may be correct, i think ribbon tweeeters were used (which require a fairly steep slope depending on the driver and crossover point). Good explanation... any others? __________________ sean

14th December 2004, 08:19 PM	#5
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Hard to have any insight without at least seeing the portion of the schematic with the diodes, can you post or describe it? Either protecting polarized caps as KW suggested or used as a high value resistor in reverse bias is all I can think of. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

14th December 2004, 09:36 PM	#6
ScottG diyAudio Member Join Date: Feb 2003 Location: US	diodes are sometimes used in powersupply to reduce noise. after thinking a bit more about it the term to search for on the web is "snubber". __________________ perspective is everything


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14th December 2004, 09:56 PM	#7
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	I only find them in active crossovers.

14th December 2004, 10:09 PM	#8
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	Why do I think that a diode, unless an LED, in a crossover is ridiculous?

14th December 2004, 10:12 PM	#9
tomi diyAudio Member Join Date: Dec 2004 Location: Aberystwyth and Manchester, depending upon term times.	Hi there guys. It does indeed seem bizarre to put diodes in a crossover network. As preveous contributors have said, it's hard to know what they are supposed to be doing without seeing the exact configuration; Still, I can't see how adding the non-linear characteristics of a diode can possibly alter to the frequency response (to give a steeper roll-off). My best guess is that they might be (hefty) zener diodes, in place to shunt the drivers or caps in case of overload... but even that's a long shot! And for the record, I've never seen a filter, active or passive, with diodes in the signal path. Cheers! __________________ The Geek shall inherit the Earth.

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