Posted by 22L (A) on April 28, 2007 at 16:35:09

I have a set of 988's being driven by a Unico 80wpc. I listen to some rock music and it does fine at fairly loud levels. The other day just for fun and to see how they would do I put in some Metallica. I didn't have the volumn any higher than normal but one of the speakers cut out. I imediatley shut it down. I have played other music since then including some slightly more mellow rock(Radiohead, Tonic, Coldplay) and it seems fine. I am nervious though. Is the ghost of Cliff Burton after my Quads?

• Re: What may be the cause of a Quad 988 cutting out? - monk1 13:59:53 04/29/07 (0)
  In Reply to: What may be the cause of a Quad 988 cutting out? posted by 22L on April 28, 2007 at 16:35:09:

  Without knowing how large your room is, it is possible the amp may have been driven into clipping. Sustained clipping would trigger the protection circuitry and shut down the speaker. I used to play a lot of rock music on my ESL63 USA Monitors in a small room (~350 sq ft) at fairly loud (90+ dB-SPL) levels using amps that ranged in 50 - 140 W/ch output. I've never shut them down. However, I have witnessed shut downs in slightly larger rooms when driven by a Bryston 4B.

  To see if the protection may be shutting down one speaker prematurely, you can compare the two speakers' thresholds using a mono signal for both speakers. This should reveal any gross discrepancies.
  
  
  

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• Re: What may be the cause of a Quad 988 cutting out? - kentaja@yahoo.com 21:46:50 04/28/07 (0)
  In Reply to: What may be the cause of a Quad 988 cutting out? posted by 22L on April 28, 2007 at 16:35:09:

  Gary has given a good description of what has occurred to the speaker. The ionization detector will engage the protection circuit when charge migration between the diaphgraghm and stator plate occurs. The protection circuit was doing its job. In addition to the ionization detector, the speaker has a zener clamp protection circuit to preven any stator-to-stator over voltage conditions or arcing.

  There should be no damage to the speaker. For pop/rock type music about 95-98dB is about all it will do. This varies from speaker-to-speaker and will be largely dependent on the bass content of the music.
  
  

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• Probably, from the ... - Gary Jacobson 18:59:14 04/28/07 (0)
  In Reply to: What may be the cause of a Quad 988 cutting out? posted by 22L on April 28, 2007 at 16:35:09:

  ...description you give here, before and after, we can conclude that the most likely event was that the ionisation detector (an antenna) in the speaker picked up some indication of the speaker beginning to arc and shut it down. This would be a sudden cut off, not even a second of gross distortion. It is not unusual for each speaker to have a slightly different cut off point, but, of course in stereo they will be receivingdifferent signals and in th is case, one was too loud.

  Regards,
  Gary Jacobson
  
  

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