High Frequency Oscillation hurt resistors in Magico A5 crossovers


Hi,I am looking for help understanding how HFO could blow crossover resistors in Magico A5 speakers. Equipment playing at the time of the incident is as follows...
Magico A5 speakersHegel H30 mono blocksHegel P30 preamp (lt and rt inputs on the Aux inputs from the laptop and Dragonfly Cobalt)
Dell laptopAudioquest Dragonfly CobaltAmazon Hi-res streaming
I was listening to Amazon music at a very moderate level when the application said there was an update available.I instinctively clicked accept while music was paying. It was only off for a few seconds to update and when complete and I restarted music the A5 tweeters were not on. These happened simultaneously and there was no audible noise what so ever indicating a potential issue. After multiple source tests and tweeter test, I was certain the tweeters were fine and it was an electronic issue. The cross overs were removed and sent to Magico and that was when I was told that HFO blew the resistors.
Can anyone explain how/why this happened so I can ideally avoid it happening again?
Thank you!
howaanders8
Begs the question: How did Magico explain it?
Resistors are rated for power applied not freak "update" events. 
"Resistors blown from high frequency oscillation" is all I got. Suggested that I have Hegel tested till I reminded them it was mono blocks and it happened simultaneously to both speakers. This stuff is way over my head.
The trite explanation you received sounds like it was from a low tier employee.  You should request that an explanation be provided by someone in a position of responsibility who can explain or at least try to explain what has caused their product to stop working.

Are they fixing it under warranty?  

Strikes me a bit odd for a passive resistor to blow before the tweeter itself, but perhaps they designed it that way on purpose to protect the tweeter -- resistors are usually a lot cheaper to replace than tweeters.  

But, I know nothing about Magico speakers and their crossover design, so the above is just speculation. 



I have no idea why extremely high frequency energy was emitted by the download process, but, Magico's explanation of what happened to the crossover is reasonable.  There is no way it is a failure of the Magico crossover operating under normal circumstances.  A lot of high frequency energy must have gotten through in order for resistors in both speakers to be fried.

I don't know how you have tested the tweeters independently, but, you are fortunate that they survived the ordeal.  In a way, the resistors acted as fuses.

From your experience, updating software while playing the system appears to be something to avoid.  I hope your problem is confined to that situation and it is not a problem waiting to happen again.
Not entirely sure about warranty at this point. Would be nice to know what caused it however?
Wow very unfortunate. Sounds a bit of a lame excuse since music has LOTS of high frequency and a download? You were lucky as others have pointed out the tweeters are ok. 
Actually, music played at any volume that the speaker was designed to handle rarely contains enough high frequency material to damage a tweeter.  

Most often tweeter damage is caused by amp clipping -- the clipped signal basically becomes square waves which generates much more high frequency energy than was present before clipping.  Another culprit from days of old was when one fast-forwarded an open reel recording without muting or reducing the volume. And if an amplifier went bad and started oscillating, that too could damage a tweeter.  

Have to say that I've never seen a program software update generate high frequency noise. Usually the program simply stops running during the update and then restarts after the update is completed. But, then I'm not a computer expert and don't use your particular setup, so its hard to say exactly where the HF noise came from. The OP did say he was listening at "a very moderate" level which seems a polite way of saying it was fairly loud. Maybe the resistors were already pretty hot and it didn't take much to push them over the edge.  

Good luck with your inquiries. It would be interesting to have a more complete answer. 

How about a quick Google search on what is ’high-frequency oscillation’ in audio (Parasitic oscillation). It’s straightforward, real, and distractive. If you are using a PC as a source, you never know what it is sending out, best to turn-off the amps when you are doing updates.
misstl has a point maybe they’re fuses in operation. Still, I would hope to get something in writing.
Good point that using a computer for source is dirty AND dangerous. Especially today with so many alternatives.
Yep.  Makes sense to me.  What sent your amp into oscillation is the question.  This is one of the potential problems with very high bandwidth electronics.  If they can reproduce FM signals, you won't hear it, but your speaker wills smoke, one way or another.

I'd actually reach out to Hegel, as they may be better able to help you.

Best,

E
The trite explanation you received sounds like it was from a low tier employee.
Maybe it was EBM.

"Very moderate" meant low volume that you could easily talk over jsyk.
I have emailed Hegel as well and am awaiting a reply.
+1 to this.  Look to your electronics, unlikely the PC put out high frequencies, but maybe it put out something that in combination with your electronics, cables and speakers started a high frequency oscillation.
erik_squires10,415 posts01-14-2021 4:51pmYep. Makes sense to me. What sent your amp into oscillation is the question. This is one of the potential problems with very high bandwidth electronics. If they can reproduce FM signals, you won't hear it, but your speaker wills smoke, one way or another.

I'd actually reach out to Hegel, as they may be better able to help you.

Best,

E

You should have bought the monitor out of your platinums LOL much better than 
Magico.
That's monitor audio platinum Gen 2
RF oscillation is independent of the actual music, if any.  Once it starts it's a runaway, self maintaining process. Unless you have a scope on the speaker terminals you'll never know it's happening.
@havocman
You should have bought the monitor audio
The monitor audio plastic tweeter diaphragm would melt like a candle, LOL
Do you live near area 51 ?
Post removed 
@ricred1 
Newton's third law : For every action, there is an equal and opposite reaction. My comment was a reaction to a silly remark involving your speaker. Didn't see you complain then 😶
I'm not sure what the plastic tweeter reference is about, but the best AMT's have phenomenal resistance to overloading.  They will survive power bursts that would make almost any dynamic tweeter turn into a projectile.

Best,

Erik
Enough ladies... I was simply looking for an explanation to my problem. Thanks for everyone who took my inquire seriously.
Wouldn't be a 2020/21 audiogon thread if at least two participants didn't actively search for ways to fight with one another.  I wish I could say that I found such behavior entertaining, but honestly it just sucks the joy out of this place.

Anyway, at least you got some useful information out of the group. And thank God those resistors were there and were not over-rated. Please do provide further updates if you get any additional information.
I think the LF > HFO etc has been covered adequately.  A schematic of your crossover would help. Anyway, with updates, components are reset, turned off, turned on.  It is reasonable that the +5V PS voltage to your USB DAC was also reset.  The switch mode PS used are 200-300 kHz.  The voltage has to settle.  And the ripple, particularly with Dell products is already quite bad.  The dragonfly has some PS filtration, but it is not great.  Being as this happened during a reset, and that is the way resets work, it is my best guess.  I would not expect your speaker engineers to shed and light on something like this. 

This may happen again for no fault of your own.  How can you avoid this?  Get an outboard PS/USB and forget the laptops poor voltage source.  Not only will you add protection, you should experience better fidelity.

Magico is technologically driven so it’s likely that it’s not the speaker’s faulty design but rather the HFO caused by an external source - also likely caused by running the update while having the speakers engaged.

Seems like the OP has the solution - don’t do software updates while the speakers are engaged - likely a good idea/lesson for us all. But unless the OP has a deep technological curiosity, seems like a potential fruitless rabbit hole to further track down the source of the HFO. I’d expect minimal/no incentive for component manufacturers to spend time/effort to assist you in this endeavor.  
I want to be clear:

Oscillation burning out tweeter resistors or tweeters is not new to Magico.  It is very rare, but it does happen and when it happens it is the electronics which are at fault. If you try to protect the speaker from this, you might as well start trying to introduce surge protectors into the speaker itself.

We can't even get people to use tone controls, can you imagine protection circuitry like this??  :-)

A bigger concern is that honestly not all electronic makers are as careful about protecting their amps from oscillation, and may eschew making the amp stable regardless of load for the sake of high bandwidth.
What kind of speaker cables are you using? Mega capacitance cables can cause high frequency oscillations with some amplifiers. Even more likely if you biwire. HF Oscillations are self-sustaining with ever increasing level once started due to the signal “reflecting” in the cable. With digital audio and high bandwidth amplifiers the chance to trigger this increases. While amplifiers  are often designed to mitigate this, I am not a fan of very high capacitance speaker cables. The effect is similar to a feedback loop you hear when a microphone picks up it’s own speaker but well above audible frequencies.
Wireworld Eclipse 7 Copper I believe. No bi-wires.
Can’t find specific capacitance per foot measurements. Not familiar with the design or layout of your cables. Generally speaking, flat layouts with “positive” and “negative” leads in close proximity increases capacitance. The greater the surface area the +/- present to each other and the closer together the greater the capacitance. The close proximity is typically used to decrease inductive losses at higher frequencies but it comes at the cost of higher capacitance.  It’s Generally accepted that this is a good thing (some might argue that) and capacitance at speaker level has minimal effect unless it gets so high that you drive the amplifier into HF oscillation.