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Old 23rd February 2014, 03:59 AM   #1
gassit is offline gassit  Australia
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Default M Distorts in MMMMT

One of the Mark Audio Woofer No.6's in my DIY MMMMT cabinet distorts noticeably even at a medium-level volume.

There is no visible damage at the front, so it looks like I'll have to open the back of the cabinet and have a peek inside. What should I be looking for in the drive unit -- a dry or loose soldering joint in the attached crossover wires or something in the woofer itself. Pics, if available, would be a great help.

Thanks in advance for any suggestions.
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Old 23rd February 2014, 11:10 AM   #2
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Reproduce a modest amount of cone excursion using your fingers, a few mill. If there is grating sensation, the speakers blown.
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Old 23rd February 2014, 07:40 PM   #3
chrisb is offline chrisb  Canada
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I'd open the enclosures if possible to check for something that might be intermittently touching the one cone. If the driver has a braided/litz wire lead from the terminal block to the voice coil, those can sometimes come into contact with the moving cone or pleated suspension spider.
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Old 23rd February 2014, 08:01 PM   #4
tinitus is offline tinitus  Europe
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sometimes, forcing it to a non linear motion may show that it rubs to one side only
a perfectly linear motion may not reveal this
but it may be enough to cause a problem when playing

or, maybe it could be out of allignment such that it has got non linear Xmax

maybe a loose litz wire, loose surround or spider

or simply a very poorly connected speaker wire, or partly broken terminal
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Old 23rd February 2014, 10:16 PM   #5
jimbro is offline jimbro  United States
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I've heard of mounting screws being too tight causing problems with MA drivers but you'd think it would have shown up sooner.
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Old 24th February 2014, 12:14 AM   #6
gassit is offline gassit  Australia
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Lorienblack: I tried your "test" and there is indeed a grating sensation -- I can feel the driver is rubbing against something. BTW when you say the driver is blown, what has physically happened and can it be repaired?

Chrisb, tinitus and jimbro: I won't be able to open the back of the cabinet to see if any of your diagnoses are correct until later in the week; so please stay tuned.

Everybody: thanks for your replies-- for a novice like me, they were really helpful.
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Old 24th February 2014, 07:57 AM   #7
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Sounds like the voice coil is coming into contact with the magnet assembly, usually that means the driver is toast.

Sometimes, tuning the driver around 180 degrees can solve the problem, gravity lends a hand so the part of the speaker that was at 12 O'clock spins round to sit at 6 O'clock. Chances are slim with such a light driver, but it's worth a punt.
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Old 2nd March 2014, 07:03 PM   #8
gassit is offline gassit  Australia
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Hello everyone.

I took off the back of the speaker cabinet yesterday.

The fault turned out to be a poor connection to the driver in question.

Re-soldered it and everything sounds great now.

Thanks again for all your help!
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Old 2nd March 2014, 07:21 PM   #9
chrisb is offline chrisb  Canada
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It's always a relief when it's something that simple
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Old 2nd March 2014, 08:49 PM   #10
gassit is offline gassit  Australia
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You're telling me!
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