Woofer trouble, resoldering voice coil wire to cone?

muovimies

Super Member
I'm in the process of refurbing a set of old speakers, they are a 70s budget affair with a 1" Heco dome tweeter and a 7" Heco woofer. Putting them back together after repainting the front baffles etc. I run into some trouble.

The woofer on the other speaker distorts unless played at really low volume. It happens mostly on low frequencies but also higher up at certain frequencies, 1kHz being one. I found out that if I gently press on the second point where the voice coil wire attaches to the cone, the distorting resonance goes away. Pressing anywhere else on the cone, or the other attachment point doesn't produce similar change. It does seem to help at bass frequencies too, at least some of the "gurggling" goes away but at those frequencies the cone is moving so much it's impossible to keep a steady pressure.

There's no mechanical noises or voice coil scraping or anything when moving the cone by hand, so I'm thinking there's a bad contact there, but resoldering it seems tricky. I already tried but didn't manage to do anything other than make a mess. I'm also a bit baffled by the symptoms, if it was a bad contact you'd think it would sort of come and go and not be so precise and predictable... am I overlooking something, anything else I should check?

I recall these speakers being fine when I last used them less than a year ago and I didn't bother hooking them up before going through the restoration (cosmetic, the cross-over has been recapped earlier already, and I resoldered every contact just in case), which is a bummer because I put two days of elbow grease on them, if counting the waiting time for things to dry etc... which is probably already more than these speakers deserve, at least if you go by what they sell for second hand over here, but I do like them.
 
Well it didn't make any sense as it sounded more like a mechanical problem so I went over it again and found a very small washer which had gotten loose and was rattling against the cone underside. Problem solved.
 
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