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.
Quote Greg Weaver, from Soundstage! magazine:
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
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
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. 🙂
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. 🙂
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?
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.
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".
after thinking a bit more about it the term to search for on the web is "snubber".
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!
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!
I'm thinking impedance correction circuits might benefit from it. A speaker being a logarithmic device in resistance. A diode the same. Maybe there's some connection there.
If there's really big inductors, diodes prevent current peaks when paralleled in reverse with inductor... but then in a audio circuit, I think it's not a very good idea!
The only sensible use of diodes, which are inherently non-linear and a potential source of distortion, is some sort of protection circuit. Are there any relays, LEDs or similar in the circuit? It would be nice to see a circuit diagram.
peranders said:
Possibility. I remember seeing a crossover schematic years ago where the HF crossover coil was actually a transformer with a zener (or may have been two zeners) across the secondary winding. I believe that when the level increased to operate the zeners, it changed the effective inductance and raised the crossover point as aform of protection.
Cheers
Graeme
Strange,
The only things I can grasp is protection of reverse voltage on
bipolar electrolytics. (OR)...
Using diodes to clip the signal sent to the HF driver may be another
solution.
Clipping the signal to the tweeters should be ok since they are
already crossed over and the total energy absorbed by the voice
coil can only contain higher harmonics of the already high frequency.
/ Mattias
The only things I can grasp is protection of reverse voltage on
bipolar electrolytics. (OR)...
Using diodes to clip the signal sent to the HF driver may be another
solution.
Clipping the signal to the tweeters should be ok since they are
already crossed over and the total energy absorbed by the voice
coil can only contain higher harmonics of the already high frequency.
/ Mattias
"Beam me up"
Yeaah, That is why the high end guys have such a airy crisp
treble. Just add some higher harmonics, like a high level exciter...
/ Mattias
Yeaah, That is why the high end guys have such a airy crisp
treble. Just add some higher harmonics, like a high level exciter...
/ Mattias
Are you thinking of surge protection devices such as Raychem Poly switches (PTC's)? I think they would fall in the category of varistors.
http://www.circuitprotection.com/02Databook/multimedia/03.C12_loud_(118-121).pdf#search='raychem%20%20speaker%20protection'
(Sorry, I can't capture then entire url.)
http://www.circuitprotection.com/02Databook/multimedia/03.C12_loud_(118-121).pdf#search='raychem%20%20speaker%20protection'
(Sorry, I can't capture then entire url.)
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