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Ever hear the "Maggie Scream"?

Ok, so I got a bit dramatic in my title. However, the phenomenon is real. It's happening to my Magnepan 1.6's, which are biamped at 200 wpc. So, 400w into each speaker.
When I power down the system, about 20 seconds later, there is a pronounced, but not loud, electronic sound, which starts out high pitch and slowly drops until very low, then dies. Like the speaker itself is powering down.
The sound is from the SPEAKER (I know someone is going to say, 'are you sure it's the speaker, and not some other piece of electronics?') Has anyone else encountered this phenomenon, and what is it? Is this the amps powering down?
I'm assuming I'm not hurting the equipment this way; I've had this sound in the speakers for months.
douglas_schroeder
loontoon
301 posts
 
Dude, It's not your speakers!!!!

To produce a signal requires a voltage and I assure you the Maggies have NONE.

It sounds to me like capacitor discharge from your amp. And no it should not make noise.

loon
bill_k
911 posts
 
I recently had a discussion with an owner of some Piega
ribbon speakers that experienced the same problem that
you're describing. I noticed that you have Outlaw power
amps, and that happens to be the same brand of amps that
he uses! I'd be pretty certain that the sound is that of
your Outlaw power amp's power supply discharging. You
might contact Outlaw to see what they have to say. Some
Adcom GFA amps were also known to behave this way.
Without (expensive) relay protection designed in an amp's
output stage, this seems to be a pretty common occurance.
jvogt
212 posts
 
I have 1.6's and I've never heard such a thing.

My suspicion is that it's the power amp.
kkm
124 posts
 
It's your electronics, to prove to yourself, unplug speaker wire then power down, if it screams, its possess.

Most likely, it could be the sound of your caps discharging?

To see if its your pre, turn off the pre first, then wait and listen, if nothing, then turn off your amp and listen. What you are hearing shouldn't be harmful unless it is really loud. LEt us know what you find out.
mezmo
516 posts
 
Yea, sounds like the amps. I know that there was a batch of Bryston amps that went out at some point that had a muting switch that went bad after a couple of years. That is, when you power it down, there is normally a mutiung switch that cuts off the feed to the speakers first, so that any stored power in the amps doesn't bleed into the speakers (creating such unpleasant sounds as the one's you're talking about) as the stored power is dissipated. When the muting switch went, you'd get all sorts of wonderful sounds just after shutdown -- kinda like somone was tearing your speakers in half. Pretty alarming. It was a common enough problem that folks who knew Bryston immediately knew what was up and, being Bryston, it was fixed immediately, no questions asked (with a relatively simple replacement of the muting switch). Not that I'm sure that's what you're dealing with, but it sounds awfully similar.
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