Radical Speaker Cone Failures?

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thermionic

Well-known member
Joined
Jun 3, 2004
Messages
1,671
Hi,

I should preface this by saying that I'm a goody-two-shoes, in that, in the 30+ yrs I've been tinkering with audio equipment, I've never knowingly blown a driver. I've always felt the signs of impending destruction to be blatant and have adjusted the gain accordingly. Hence, I do not consider myself an expert in loudspeaker failure modes. I have seen a few blown drivers - always manifested in the form of a siezed or damaged coil. I've seen / witnessed the chatter effect of worn surrounds many times. One great area of satisfaction for me has been replacing foam surrounds early, before damaging the coil, to see the driver have a new lease of life (one has to get one's kicks where one can in this business...)

Anyway, a couple of weeks back I attended a party in a small, private venue. The speakers used (in conjunction with powered subwoofers) were these large main studio monitors, consisting of a Scanspeak-type HF dome + ATC mid driver (think along lines of a Boxer or ATC 300 kind of scale) and a pair of 15" Gauss bass drivers. The monitors came from a famous studio. They weigh a ton, supposedly had input from Roger Quested and, to my ears, have always sounded good. Ideal for a small, private bar.

It was a hot evening. About 1am, 2 hours into the party, both HF drivers failed... (I should add that this isn't an installation of mine - and the *limiters* were switched to bypass....). As the usual engineer wasn't there, muggins got called upon to inspect damage. The x-overs confirmed the issue to either be with the amps, or speakers. This author did not feel popular, with about 70 party-goers standing around whilst he fumbled around amp rack with a maglite...

Without a load of tools, all I could do was cite HF amp failure. Both channels had gone  - it'd be odd to blow both tweeters at once, right?

This is the weird part: upon inspecting the monitors, one of the 15" Gauss drivers had completely torn its cone. What's odd is that it had not only detached about 200-degrees from the centre dust cap, but also from the surround...the cone thus flapping, like a narrow strip....

How on earth could a cone detach from both the dust cap and surround? Heat? Certain parties wondered if riff-raff had gotten into party and caused vandalism, as this had happened before. I wish I had a photo.

You could see that the cone was torn - it was not a clean break along the glue lines.

According to the engineer who looks after the installation, both tweeters were blown - not the amps.

What makes me curious is that the coil in the Gauss driver felt perfect - like new. The dust cap and 160 degrees of remaining cone could push in and out, feeling the same as the undamaged speaker...

Have you ever seen a cone detach at both sides, i.e. dust cap and surround? Melted glue? Vandalism? Where would you point the finger?
 
I have seen that before but only in a speaker that was in storage for a long time in a non temp controlled environment. The foam surround rots or the paper cone  gets damp and when you run it after a long time of sitting there boom. But I doubt this was the case here.  As for the tweeters it's odd that both would pop unless there was something with the amp that caused them both to pop. I had similar issues a while back with a studio I tech for but it was all their clients fault playing the music(if you could call it that) at ungodly painful volume levels.
 
MagnetoSound said:

Hmmm.. Right under our noses, during the party. It sneaked out from a hole, scaled the soffit mounts and withstanding 120+dB levels, gnawed the LF cone... Could be  ;D
 
Thanks, Pucho. These cones looked like new. The surrounds were in good condition. Had the amp nuked the tweeters, it wouldn't put DC out of both channels... Most likely, if something failed, one channel would go DC.

Anyway - I only know what their tech is telling me...secondhand info...
 
Hi Justin,

That's a really weird one.

Heat, humidity and vibration on the glue? Once it starts to go it shakes itself apart?
I'm just speculating but it has been very hot and sticky here, and imagine it to be even more so 'down South'

Stew
 
The paper was torn - there were jagged edges around the dust cap. There wasn't much evidence of anything peeling off around glue lines. I probably shouldn't have mentioned it. Just like someone had reached in and tried to pull the cone out, tearing it from dust cap and surround edges.
 
I was going to go with tw@t, or vandal!

Dan - is there something you want to share? have you had a bad murine experience?

 
thermionic said:
According to the engineer who looks after the installation, both tweeters were blown - not the amps.

What makes me curious is that the coil in the Gauss driver felt perfect - like new. The dust cap and 160 degrees of remaining cone could push in and out, feeling the same as the undamaged speaker...

Have you ever seen a cone detach at both sides, i.e. dust cap and surround? Melted glue? Vandalism? Where would you point the finger?
I've seen that a lot!... Typical case of loudspeaker fatigue. Studio monitors are not good for continuous high-SPL operation.
The typical 15" woofers in studio monitors have a very compliant suspension, contrary to most PA speakers; continuous levels of LF and VLF produce extreme cone excursion.
Regarding the tweeters, they are neither capable of sustained high-SPL operation.
Basically you've experienced a typical case of aging speakers submitted to strenuous conditions.
 
pucho812 said:
did anyone push the dust caps in? drives me crazy when they do that. For the life of me I could never understand why anyone would do such a thing

you come and explain that to our one and a half year old.  ???
 
Kingston said:
pucho812 said:
did anyone push the dust caps in? drives me crazy when they do that. For the life of me I could never understand why anyone would do such a thing

you come and explain that to our one and a half year old.  ???
;D you got me there. I hate to say that is different but it is as they are 1.5 years of age but, I am referring to adults, well atl east they are adults physically not sure about their mental which would explain a few things.
 

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