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Christowp 2nd May 2011 04:05 PM

Mission 770 scratchy sound
 
Friends

I have recently bought a pair of mission 770 speakers and am experiencing some problems. I get a scratchy sound from one of the speakers at a certain point of listening: this is at reasonable volume and with a variety of music. Its irritating and is more prevalent on one channle. Not sure iots the driverr or crossover or just age.

Not ready to retire them as they are really nice and have potential in a second system. Cabs look good and drivers seem to be in good nick

Please advise or provide tips I might try to restore them to normal use

Thanks
Christowp

Andy Bartha 2nd May 2011 07:11 PM

Disconnect the scratchy speaker from the amp and carefully push on the cone to see if you can feel the voice coil rubbing. Slowly and carefully push the cone in the full travel and if you can feel and hear the voice coil rubbing you know it is the driver. If you feel and hear no rubbing then the problem is else where and you will have to pull the driver to inspect the cross over and driver. Considering how old those speakers are there is a good chance the problem will be in the cross over if you do not fell or hear any rubbing.

Christowp 2nd May 2011 07:19 PM

Missions 770 scratchy
 
Thanks Andy

Will try that when I get home from work tomorrow - Christowp

Christowp 5th May 2011 07:11 AM

Scratchy speakers: Mission 770
 
Andy

Drivers clear and no noise or vibration when moving them: will check crossovers and also replace fuses over the weekend

Thanks

CR :)

Andy Bartha 5th May 2011 07:00 PM

You may want to think about replacing the capacitors in the cross over while you have them out. They are very old to say the least and there is a good chance they are electrolytics. Swapping them out for newer much better quality can only help. The inductors wouldn't hurt either but the caps are most important.

digits 6th May 2011 07:23 PM

A scratchy sound developing is often because of amplifier bias setting trimpots drifting with age.

Cal Weldon 6th May 2011 07:25 PM

Maybe swap the speakers around to confirm you aren't hearing static on your volume pots.

rasquire 5th June 2011 09:32 AM

Hope I can help...
 
Dear Christowp,

I hope I can help you because I have registered solely for that purpose! I have owned a pair of beautiful Mission 770s since 1982. I bought them in Cambridge, England, near where they were made. This was with my first pay cheque from Cambridge University.

The right speaker started making a scratchy sound 2 weeks ago. Given how old they are, I wondered if "this is the end". However, I have just flicked the solder and glue blobs on that woofer and behind the driver (which is semi-transparent) I could see a small washer "dancing around" and buzzing against the solder on the inside. I picked up the entire speaker in its housing, inverted it and the washer went up the wire and stayed there. No more scratchy sound.

Obviously a more permanent fix may be needed, but for now I am enjoying unblemished sound.

I really hope you have the same issue -- very easy to fix.

Warmly for tropical north Queensland,

Richard.

Christowp 8th July 2011 11:19 AM

Mission 770
 
Dear Rasquire

Thanks for your reply: just received speakers from speaker compnay: soldering was loose on both bass drivers. This was re done and sound is really good now, no more scratching. Tech feels the internal wiring is unneccesarrily thick and inflexible.

Until next "injury" I am enjoying good clean and detailed sound again.

rEGARDS

Christo


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