Speaker noises

[19Seventy7]

I have a pair of Dynatron LS1428 speakers which were used on a Dynatron HFC51, then a Decca RP400, now it's back to the Dynatron.

When I was first using them on the Dynatron, they were fine with the only issues I had being down to connections.

I then used them with a Decca RP400, which worked fine with for a few months, then I turned the record player on one morning and there was a loud "sparking" noise from the speakers, then throughout use. There were no problems the night before.

I checked connections and all were fine.

I then replaced the Decca again with my Dynatron, thinking it may be the record player, but they also do this with my Dynatron.

Any idea's as to why?


Thanks

[camtechman]

Do the main speakers have a foam like suspension and has it started to crumble, as many such speakers did that were from the 1970's ?

If this is the case, the speaker coil will rub against the core, thus causing the noise and will be more noticeable with bass speakers.

[19Seventy7]

I'm not too sure, they've never been opened up, but I've just looked online but can't seem to find any information on them.

Maybe someone on here knows a bit about them?

Thanks

[Nuvistor]

A number of Dynatron speakers have the fronts fabric held on with Velcro or clips. The backs of the cabinet were sealed.
Your speakers may be the same, if the fronts remove easily you can check if they have foam, it surrounds the edge of the cone and attached to the speaker frame.

See post #23 for a photo of a speaker with foam surround.

https://www.vintage-radio.net/forum/...=122692&page=2

[JulietMike]

I believe those speakers have a rubber-roll suspension which could have perished. Easy to remove the front fabric to check.

John

[19Seventy7]

Okay, thank you. I'll check now and keep you updated.

Thanks

[19Seventy7]

I've looked at both speakers and they all seem to be fine.

Both of the speakers have some black powder in them, but I cannot find where from as neither speakers nor tweeters have rotted.

Thanks

[19Seventy7]

Originally Posted by Nuvistor

A number of Dynatron speakers have the fronts fabric held on with Velcro or clips. The backs of the cabinet were sealed.
Your speakers may be the same, if the fronts remove easily you can check if they have foam, it surrounds the edge of the cone and attached to the speaker frame.

Sorry, I never saw your reply until now - apologies.

One of the fronts were held on with nails, the other is just pushed in, the nails have been removed.

There is no foam like that, it's still a foam type material, the best I can describe would be like that of the weatherproofing strips on cars.

Thanks

[Lucien Nunes]

Two types of speaker fault can result in a crackly, crunchy sound. One is the off-centre voice coil problem mentioned, which is most likely what has happened here even if the surrounds look OK. It is a distinctive noise recognisable immediately once you know what to listen for, part way between scraping / crackling / buzzing. The other is less common and tends to be quite vicious, where the pigtail to the coil has a fatigue fracture that breaks the circuit as it vibrates. Both kinds tend to get worse with increasing volume or may be completely OK at low volume, setting in as the cone excursion increases.

A rough and ready way to prove that voice coil rubbing is the problem is to touch the cone with a finger just outside the dome, pressing very gently outwards towards the surround. Pressing in one direction, often upwards, will tend to clear the fault while pressing the other way will worsen it.

[snowman_al]

Don't laugh,
Try turning them upside-down for a few days.
A picture or two might help as well?
Alan

[19Seventy7]

I'll give snowmans idea a try first and see what happens, if nothing changes I'll give Luciens idea a try.

I'll get them photo's to you as soon as my phone charges.

Thank you all for your help, much appreciated.

[19Seventy7]

Here are the images, there is that black powder in both speakers.

[leslie5555]

The foam surrounds seem to be intact, can I ask does the unwanted sound occour only when playing music or when your not playing music?

[Nuvistor]

The black powder looks like like the remnants of foam, I think the Dynatron speaker removable fronts had black foam backing on them.
Perhaps it has disintegrated and as been removed as much as possible by a previous owner.

Edit, Apologies if I sound vague, it’s 40 years since I last saw them.

[19Seventy7]

Originally Posted by leslie5555

The foam surrounds seem to be intact, can I ask does the unwanted sound occour only when playing music or when your not playing music?

It's both, but much more common with music playing.

Originally Posted by Nuvistor

The black powder looks like the remnants of foam, I think the Dynatron speaker removable fronts had black foam backing on them.
Perhaps it has disintegrated and as been removed as much as possible by a previous owner.

Edit, Apologies if I sound vague, it’s 40 years since I last saw them.

I'm not sure of the foam on the back of the fronts, you could be right, but mine doesn't have any.

No problem I wouldn't say you were vague.

Thanks you all for your help.

[BRASSBITS]

The foam that frank in post 14 refers to was between the speaker cloth and the board this was only very thin and will have perished by now.
if you put a finger between the cloth and board you will probably find some remnants of it

[19Seventy7]

Oh okay, I'll check tomorrow, I have it all set up again, to keep the area tidy.

Thanks

[crackle]

Have you had these speakers long, do you know their history?
I wonder if they could have been poorly re-coned in the past.

Another thing to check is the inner suspension by the voice coil, has this come away from the speaker frame.
Does the speaker cone make a scratching noise when you push it with evenly spaced pressure.

Mike

[snowman_al]

InsertNameHere
Can you clarify a couple of things please?
Is it one or both speakers with the 'sparking' noise?
You say it / they make a noise when not playing music sometimes. Now you have the covers off can you watch the cones and see if they are moving in and out with nothing playing. Try different positions of the volume control too.
Do you have other speakers to try to make sure the amplifier or cables are not to blame?
Alan

[Techman]

These Dynatron speakers are not the best, in my opinion. The electronics in the Dynatron systems that they came with are generally capable of better performance when matched to better speakers - I would say that these speakers performance could be described as adequate and acceptable, but could do better.

I've got a pair buried somewhere in the loft and I can tell you that they don't like a lot of "Quo" through them at high volume, even when powered by the original Dynatron system they came with, and are likely to make the noises you describe after such an event