2. digital
  3. 163272-135704

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!
128x128howaanders8

Showing 4 responses by erik_squires

erik_squires
16,472 posts
 
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.
erik_squires
16,472 posts
 
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
erik_squires
16,472 posts
 
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.
erik_squires
16,472 posts
 
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
More to discover