Dynaco A25 SEAS 25F-EW H336 Woofer problem / blown

[pfigueroa]

Hi everyone,

This is my first post, so thank you all for your time solving doubts and questions from rookies like me.

I recently bought a pair of Dynaco A25 speakers. When I was checking them, I noticed that one of the woofers was making a slight buzz. The next day, this woofer stopped working. I read some AK posts with tips, so I verified:

1) At first glance, everything seems correct in the suspension and foam. No cuts or degradation. But when I lightly pressed the diaphragm, it doesn't move at all, it's completely blocked. The other woofer moves softly and without any problem.
2) I checked the resistance, and it seems fine: 6 ohms (the nominal impedance is 8 ohms, but I read that in this case a DC resistance of 6 ohms is normal.
3) I connected a mobile phone with a jack / RCA cable and it sounds. I'm not sure if the sound is as loud as it should be, but it sounds.
4) According to some AK publications, I checked the cables that pass through the woofer frame. The insulators are very damaged, so it is very likely to have caused a short issue.

Could someone confirm that the buffer is blown? Or also could be a connection / crossing problem likely? I guess if it was a woofer issue due to a short, the woofer wouldn't sound at all, and the resistance would be 0, or I am wrong?

If it is certain that the woofer is blown, does anyone know where I can find a replacement for this SEAS 25F-EW H336 woofer?

Thanks in advance.

 

[infullview]

Welcome to AK. I don't know if this is the case, but it's possible the magnet structure has move and is pinching the voice coil. This happens on some speakers and you have to detach and re-glue it. Not sure if this problem ever existed on SEAS woofers.

 

[pfigueroa]

Thank you infullview. I will search references about this pinching in SEAS drivers, and check if that is the problem.

If anyone else has references about this issue, I would be grateful.

 

[WaynerN]

Thank you infullview. I will search references about this pinching in SEAS drivers, and check if that is the problem.

If anyone else has references about this issue, I would be grateful.

I have seen this with the H086 tweeter used in the A25XL, but not the H087 tweeter or woofer of the A25. If the terminals on the woofer have fallen apart, the OP can send me a PM and I will return photos of the repairs that I have done to mine, tho he will have to source new terminals as Radio Shack has bit the dust.

 

[GeirH]

A bit late to join in, but anyway:

The magnet issue is rare, but seems to be caused by weak bonding between the magnet and steel pole/top plate. It mostly seems to happen with early ferrite-equipped Seas drivers (mid-70s) when subjected to shock, e.g. if the speakers are dropped on the floor. I've had it happen to a 13F-GM midrange driver. It can be fixed, but it's far from easy to do (I wrecked mine trying). You'll essentially have to take the entire driver apart, removing the spider/cone/surround/wires from the chassis.

If you're not successful in repairing the magnet, a couple of alternatives from Seas are possible:

The Seas CA25RE4 (H250) is pretty much a drop-in replacement for the 25F-EW. It has a coated cone, though, so it won't look quite like the original. It is an old driver too, so it won't be easy to find.

The A26RE4 (H1411) is a modern equivalent, that is still being sold.

Both drivers have 4-layer voice coils, and roll off nicely above 1500 Hz, so they can be used in a 2-way speaker without crossover, just like the A25.

- H -

 

[GeirH]

I forgot to point out that the Dynaco A25 was built with the 25TV-EW woofer, and not the later 25F-EW. I have explained the differences between the two here.

- H -