Dynaco A25XL woofer trouble - can it be repaired?

[Dun]

I‘ve just bought a pair of A25XL‘s for next to nothing. One seems to be working fine and sounds wonderful but the woofer on the other has some serious issues and I really want to know if it's possible to repair it. I've looked at all the very helpful A25/A25XL repair threads here and elsewhere for clues but my issue seems to be different. I should mention that I have no direct experience with repairing speakers but I have some with DIY electronic builds/repairs.

The symptoms of the patient:

Produces a very faint sound overall and a lot of rattling when I play bass-heavy stuff (at low volume). The same happen when I connect the amp directly to the woofer. The cone does not seem to move at all.

I measure 8.6 ohm resistance across the woofer terminals (and the tinsel leads) with the woofer removed from the circuit

I don‘t see any cracks in the cone or rubber surround but it kind of looks like there is more glue (yellow color) exposed at the cone/surround border on one side of the cone than the other side (see picture). Could the culprit be a tiny opening between the cone and the seal? Is there anything else I could check?

Many thanks in advance!

 

[RTally]

Has the cone separated from the rubber surround in that area? If so, that is a problem, but not likely the major problem.

Look under the cone at where the voice coil former joins the cone. That is the area between the spider and the back of the cone. Is the former connected all the way around to the cone? Is the spider connected to the former all the way around? You can gently lift the cone away from the magnet to better inspect, but don't lift too far.

Spread your fingers around the dust cap and gently push in the cone. Does it move easily and soundlessly or is there noise, like scratching? If you hear anything, that means your voice coil is not properly engaging the gap in the magnet.

 

[Dun]

Thanks for the tips!

Has the cone separated from the rubber surround in that area? If so, that is a problem, but not likely the major problem.

Thee picture attached to my first post shows the cone/surround border on one side. There seems to be more glue exposed between cone and surround on that side of the cone than the other, but I don't really see an opening there.

Look under the cone at where the voice coil former joins the cone. That is the area between the spider and the back of the cone. Is the former connected all the way around to the cone?

I'm not sure how to see the juncture between the voice coil former and cone? Through the dustcap? Sorry - I'm a complete beginner here

Is the spider connected to the former all the way around? You can gently lift the cone away from the magnet to better inspect, but don't lift too far.

The spider seems to be connected all the way around. However, it looks like there are cracks that have been glued in a previous repair - see pic 1 & pic 2. It's not a rupture. Also, there is some kind of discoloring around the coil area in one spot - see pic 3.

Spread your fingers around the dust cap and gently push in the cone. Does it move easily and soundlessly or is there noise, like scratching? If you hear anything, that means your voice coil is not properly engaging the gap in the magnet

I'm not able to push the cone in at all - it's all the way in no matter how the woofer is positioned (I'm not applying much pressure here). I can push the cone cone up from behind but never down. I guess this is abnormal behavior.

PIC1:
I
PIC2:
PIC3:

 

[RTally]

I'm not sure how to see the juncture between the voice coil former and cone? Through the dustcap? Sorry - I'm a complete beginner here

Hey, we gotta learn sometime and somehow. You are asking good questions and responding with good info. Keep it up.

It looks like the spider is smack-dab against the cone. I have not yet pulled a woofer out of my Dynaco's so I do not know how they look, exactly. However, most woofers I've seen have the spider attached to the voice coil (VC) former, not the cone. In your case, the former is not visible, but you are looking in the right place.

The spider seems to be connected all the way around. However, it looks like there are cracks that have been glued in a previous repair - see pic 1 & pic 2. It's not a rupture. Also, there is some kind of discoloring around the coil area in one spot - see pic 3.

That discoloration looks like a glue drip, not what I would expect to see if the VC had overheated. Maybe someone tried a repair and botched it, and was messy enough to drip glue on the cone.

I'm not able to push the cone in at all - it's all the way in no matter how the woofer is positioned (I'm not applying much pressure here). I can push the cone cone up from behind but never down. I guess this is abnormal behavior.

Major problem there. The cone should easily move in and out. Since it cannot move in and based on the surround seeming to be attached very high up the cone, I would surmise that your VC and former is messed up, badly. It could be that the VC former has detached from the cone or has broken up in the gap. Bummer, either way.

Short of removing the cone and rebuilding the driver, you may just want to buy a replacement woofer. Find a direct replacement instead of just using a driver that fits. Do a search for the part number on your driver. ebay often has Dynaco woofers for sale. There may be someone here who has one for sale. If you subscribe to AK, you can post in AK Barter Town. Subscribing is $25 and it supports the site and allows you to buy and sell on BT.

 

[Dun]

OK, that's really a shame. I think I'll open it up, have a look and try to learn something. Thanks a lot for your help.

I heard somewhere that it's not a good idea to replace only one woofer?

It's a bit surprising that my 25XL has the SEAS 25 TV-EW woofer model which is the one normally found in the A25 model. According to some the A25XL's should have a different woofer (25 F-EW H085).

 

[RTally]

OK, that's really a shame. I think I'll open it up, have a look and try to learn something. Thanks a lot for your help.

I heard somewhere that it's not a good idea to replace only one woofer?

It's a bit surprising that my 25XL has the SEAS 25 TV-EW woofer model which is the one normally found in the A25 model. According to some the A25XL's should have a different woofer (25 F-EW H085).

I would remove the dust cap first to see if anything obvious is wrong with it. If the VC former is detached, you should be able to see it with the dust cover removed.

 

[WaynerN]

Thanks for the tips!



Thee picture attached to my first post shows the cone/surround border on one side. There seems to be more glue exposed between cone and surround on that side of the cone than the other, but I don't really see an opening there.



I'm not sure how to see the juncture between the voice coil former and cone? Through the dustcap? Sorry - I'm a complete beginner here



The spider seems to be connected all the way around. However, it looks like there are cracks that have been glued in a previous repair - see pic 1 & pic 2. It's not a rupture. Also, there is some kind of discoloring around the coil area in one spot - see pic 3.



I'm not able to push the cone in at all - it's all the way in no matter how the woofer is positioned (I'm not applying much pressure here). I can push the cone cone up from behind but never down. I guess this is abnormal behavior.

PIC1:
I
View attachment 1377037 PIC2:
View attachment 1377038 PIC3:
View attachment 1377039

That is not an A25XL woofer. I know because I own 2 sets of them.

 

[WaynerN]

This is the woofer:

 

[WaynerN]

I believe you have a woofer for the A25. Not designed for the A25XL cabinet (sure it will fit) but cabinets are different sizes between the 2 models. That is why you got them cheap, they have the wrong drivers in them.

 

[Pete B]

This is the woofer:

View attachment 1378419

What is the SEAS number on that woofer?

 

[WaynerN]

Its not the 25 TV-EW, other then that, I don't remember and I'm not going to open one up to look.

 

[Dun]

I believe you have a woofer for the A25. Not designed for the A25XL cabinet (sure it will fit) but cabinets are different sizes between the 2 models. That is why you got them cheap, they have the wrong drivers in them.

OK thanks for the tip, I didn't suspect that

 

[Dun]

I would remove the dust cap first to see if anything obvious is wrong with it. If the VC former is detached, you should be able to see it with the dust cover removed.

It doesn't look obviously detached. Maybe it's an obstruction below that is preventing the cone from moving.

 

[WaynerN]

How do you know its an A25XL?

 

[Dun]

Height of the cabinet is just under 20 inches and it has a 3-position knob in the back

 

[RTally]

Height of the cabinet is just under 20 inches and it has a 3-position knob in the back

According to this website, the A-25 and A-25XL have the same size cabinets:
http://home.indy.net/~gregdunn/dynaco/components/speakers/

The A-25XL is the same as an A-25 but with updated drivers and a 3 position tweeter control instead of a 5 position switch. Sounds like you have the A-25XL

See, also, http://audiokarma.org/forums/index....aco-a25-a25xl-or-both-which-is-better.300022/

 

[Dun]

OK, somehow I had the idea that the A25's were quite small and the A25XL's much bigger.

But it turns out I misremembered and the knob is actually a 5-position so I definitely have an A25. Sorry for this confusion. It will be easier to find a replacement woofer.

If anyone needs the official sizes for various models, here's a link to an old brochure from Dynaco (although the XL is not listed):

http://www.preservationsound.com/wp-content/uploads/2012/07/Dynakit_Specs.jpg

 

[WaynerN]

According to this website, the A-25 and A-25XL have the same size cabinets:
http://home.indy.net/~gregdunn/dynaco/components/speakers/

The A-25XL is the same as an A-25 but with updated drivers and a 3 position tweeter control instead of a 5 position switch. Sounds like you have the A-25XL

See, also, http://audiokarma.org/forums/index....aco-a25-a25xl-or-both-which-is-better.300022/

They are not. The info on Greg Dunn's site on cabinet size is incorrect.

The 2 speakers have nothing in common. Different woofers, different tweeters, different cabinet size, different cross-over, different level control (3 or 5 position).

 

[WaynerN]

OK, somehow I had the idea that the A25's were quite small and the A25XL's much bigger.

But it turns out I misremembered and the knob is actually a 5-position so I definitely have an A25. Sorry for this confusion. It will be easier to find a replacement woofer.

If anyone needs the official sizes for various models, here's a link to an old brochure from Dynaco (although the XL is not listed):

http://www.preservationsound.com/wp-content/uploads/2012/07/Dynakit_Specs.jpg

The A35 (or A35XL) are much larger.

 

[RTally]

They are not. The info on Greg Dunn's site on cabinet size is incorrect.

The 2 speakers have nothing in common. Different woofers, different tweeters, different cabinet size, different cross-over, different level control (3 or 5 position).

If you have a tape measure and an A-25XL, how about measuring it and posting the measurements for posterity. And post a picture of the back so we can see the model number. Nothing like having a historical record.