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Dynaco A25 bad re-foam or woofer problem?

strat68

strat68

Member
Youtube link below says it all but I got a pair of dynaco a25's for $95 yesterday and it was a public meet up thing so I couldn't test them. On one the voice coil rubs which you can hear while testing with the hand pressure method. My question is what likelihood is it being a bad re-foam job? The other speaker is fine and physically they are in excellent shape. Should I get a surround kit and rip the existing one out even though it looks brand new. Or could it be a larger issue with the woofer? Thanks, if you listen to the video with headphones you can hear the hand movement test.

 
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Butyl rubber surrounds -not foam surrounds -have never seen a foam kit for these and wouldn't think of refoaming them .Because of the slightly odd basket size it's usually pretty obvious if someone does a close 'nuff replacement and both of your woofers look original.
 
It is actually a smaller issue with the woofer. The voice coil is not moving properly in the VC gap in the magnet. Get a replacement woofer and that will fix the problem. VC could be mis-shaped, bent from over excursion or burned up enough to cause rubbing.

Be aware there are 2 distinctly different woofers used in the A24, Scanspeak and SEAS. Check your to be sure what you get is a match. I've done this as I have a woofer that was rubbing.
 
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Thank you both. Regarding the surround- I knew it wasn't foam I just blurted that and should have said surround. Still the guy says he was the original owner from 1970, and regardless that surround doesn't look 45 years old to me. Hence why I thought it was a bad refurb.. OK, blue shadow- you're advising a new woofer, I suppose I should pull them out tomorrow and post some pics before I start looking for folks selling part-outs. I have not seen them since it's barely 24 hours since I got them. Hopefully, someone can advise me in that regard. Thanks again.
 
Here's a weird piece of advice for you. The drag on the VC can come from cone sag. After years, they can do that. My suggestion would be to remove the offending woofer and turn it upside down from it's original position. See if that fixes things. A cheap, no frills solution, and it just might work out for you. Might get you a couple more years of use. It happened to some Missions I have. The biggest problem you may run into is removing the woofer. They can be a real chore on A-25's.
 
^^^ This, but what you might want to try first is just turning the whole speaker upside down, or on either side and try the speaker (gently) on same music or material that you heard the rubbing on - turn up volume slowly and carefully so that you don't permanently damage the voice coil further (although it could be already).

Whichever position the speaker is in that the woofer works best in should then be marked as up on the woofer frame and then you can orient it so when you take it out. The position may also need to be checked in an odd position (angled for example, so you might have to set up two large objects (like concrete bricks but be careful with the veneer - cover bricks' edges with towels) to prop up the speaker at odd angles.
 
All good suggestions from blue, sine and mech.. Start with the simplest fix and work your way towards, more complex $$$ solutions.
 
There is another common problem with Dynaco woofers which I have experienced twice. On the backside where the speaker wires are connected there is a grommet that breaks loose. When it does, it slides down the tinsel and rests up against the back of the woofer cone. The result is the grommet starts to vibrate against the cone causing the woofer to sound like it is buzzing. Again, turning your speaker upside down will lessen the effect or eliminate it entirely. From there, you need to remove the woofer and slide the grommet (which may be hard to see at first glance) back into position at the speaker terminal. I used a dab of silicone to keep it into position. Please post back and let us know how you made out.
 
I'm sure the 180 rotation must have worked for somebody at some time, but the lighter the cone assembly the less likely it is to work, and the A25's cones are relatively low mass, but who knows, you might get lucky, and it doesn't cost anything. Checking the leads is always a good idea. It is much more likely that your woofer's voice coil has been damaged by overheating or "bottoming" against the magnet (or both) because of over-extension. Start looking for a functioning replacement if the 180 trick doesn't work.
 
Well, maybe its rubbing from cone sag, but with all the units that I have repaired, I've really never seen it. Look thru the screen dust cap of the woofer with a strong flashlight and see if there are signs of something getting hot. My number one guess is that some "smoked" these, running way to much power, or too much clipped power, and the VC heated up, warped and now scrapes.

eBay is a great place to look for a replacement. The model number will be on a label in the back. It is made by SEAS.

'ner
 
An occasional fault, not seen much in vintage woofers, is a loose spider partially detaching from the frame. But if careful physical movement by finger or hand senses a VC rub, then the voice coil is suspect, as well as a shifted magnet if there is any evidence the speakers have been dropped or damaged.

Edit: farmhand beat me to it by a minute while I was typing. :thumbsup:
 
Pics after woofer removal. Wondering about the grommets mentioned above. There are two grommets where the wire leads touch the paper. I don't think the grommets are an issue. But I am curious if they are out of place. They were both fastened to the cone and as you see in the pics I started peeking it back.20151101_200132.jpg View attachment 644015
 
I'm hoping someone with a raw Dynaco driver will chime in on this one as I cannot remember what was actually on the back of the woofer cone itself, in other words, what should be there and what shouldn't. It's been a few years since I repaired the problem on mine and my memory is short. Have you tried playing the speaker while you have it out of the cabinet?
 
Oh, your terminals have fallen apart! Very common with this woofer. It is the other model that I was expecting, but this is a SEAS woofer. Pretty low power handling tho.

The washers on the flex wires are actually the coined over part of a semi-tubular rivet. If that is what was making your "scratching" noise, then a simple repair of the connections is all you need to do to fix it. Here is a picture of how to fix.

IMG_0276.JPG

Wayner
 
WaynerN said:
Oh, your terminals have fallen apart! Very common with this woofer. It is the other model that I was expecting, but this is a SEAS woofer. Pretty low power handling tho.

The washers on the flex wires are actually the coined over part of a semi-tubular rivet. If that is what was making your "scratching" noise, then a simple repair of the connections is all you need to do to fix it. Here is a picture of how to fix.
Click to expand...

Wayner, thanks. Note the magnet difference, is your example pic a ceramic version and mine and AlNiCo?? In my pic above, the closer grommet was pulled away from the paper by me, there is one point that is stuck and I am afraid to force it. My terminals are loose, but a google image search suggests that my terminals look as they should for that magnet type- i.e. no red/black screw terminals. (Another view attached).

In any case holding the speaker by the magnet and pushing the cone in and out I am hearing the scraping (rotating in all directions) and the grommets are not rattling so it was probably fried as suggested above. I will try and play the speaker unmounted as vintageman1 suggests to observe.
20151101_200044[1].jpg
 
I forgot that you have an A25, I have A25XLs. so your woofer is correct for your speaker. I had a brain fart. The black and red terminals on my speakers are the ones that I added to repair the terminals. My stock terminals looked like yours.

'ner
 
So it looks like the woofer is toasted. Any recommedations for a replacement? I.e. is there a modern replacement and worth it to get 2 so they match? Or should I wait for an old one to pop up on the famous auction site :)
 
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