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The usual C/CX foam vs rubber question…

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matador43
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matador43 posted on Thu, Jul 22 2021 5:11 PM

Hi alls,

You may find my title a little bit ironic, no offense intended: I know they are many threads on the topic but I've honestly not found a clear answer, not to mention most threads are olds.

I'm in the process of refoaming a pair of C30 speakers. So after looking around for surrounds It seems that two brands raise interest from beoworlders: Goodhifi and Audiofriends. There is an old thread on the Archived Forum where good hifi is pointed as being better, up to the point of the guy from Audiofriend did chime in.
But there is also a recent thread where people is wondering about AF being still in business with answer from a respected member of the forum comforting the OP. Prices are the same more or less.

Then there is the Foam or Rubber point. The answer I've found are or passionate (it was foam then it must be foam) or size dependent. I've also recently come across a thread where a woofer of a C30 or C40 was shown with a surround that did look like rubber to me and was told as original legit by Dillen. To be honest I believe that a speaker refoamed (by me) will loose part of his qualities, I expect that. So if changes will be marginal I would go with the easier to install and longer to last. 

Then I could cross the question like AF Foam vs GHiFi Foam.

Right now and wouldn't talk about shimming or not. one step at the time…

Thanks to everyone helping.

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Dillen
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Dillen replied on Thu, Jul 22 2021 6:23 PM

C and CX models use different drivers with different surrounds.
The C surrounds look a little like rubber, but are in fact a kind of coated foam. They tend to last longer than foam, - but not forever.

For CX50/CX100 I would always use foam.
After losening up a little, the new foam surrounds will end up performing very close to the original surrounds,
whereas the T/S parameters if using rubber surrounds will remain far away.

I would also use foam for the C models.

Martin

matador43
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Thank you Martin, will do with foam then.
Any supplier you would recommend, between those two or others? 

Dillen:
The C surrounds look a little like rubber, but are in fact a kind of coated foam. They tend to last longer than foam, - but not forever.

When decomposing they do look like foam again!

 

Beobuddy
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Audiofriends is still in business. Very knowledgeable man. 

Always trying to reproduce surrounds as close as possible to the original, when it comes to dimensions, material, thickness of it and response.

matador43
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Hi guys,

Refoaming completed! I would not say it was difficult but I would not say it was easy either. It's always tricky to manipulate those things when you think the precision you believe it's involve in their crafting. Honestly, I did it because it was a small driver and that was try or trash, but I think I would not do it on a bigger driver.

Original driver.
 

Work in progress.
 

Ready to re-foam.
 

Kit delivered.
 

Half glued.
 

Ready to go!
 

 

Unfortunately I find them sounding quite average. Maybe a poor repair, maybe by design (I believe they're different design than C40 and obviously CX's) or maybe just because they're competing with a pair of S45-2 as front. 

But they're beautiful!

matador43
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Hi,

Don't wanna do any bad taste sorcery but I wonder if "theoretically", sealing the backside port could improve the bass rendition?

I dont understand acoustics and this why I ask. Also seeing that following installment of that speaker were sealed.

Thank you.

 

Dillen
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Dillen replied on Wed, Aug 11 2021 2:23 PM

The woofer has a ventilated magnet on purpose.

In Beovox CX100 the woofer is ventilated and the midrange is closed (they are not two identical drivers, as many people seem to think).

Martin

matador43
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Dillen:
they are not two identical drivers

Yes distinguished by the hole in the back right,

Thank you Martin, I will not touch them then and carry on with their "flat" rendering.

Svenni
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Svenni replied on Thu, Aug 12 2021 3:30 PM

Isn't the hole on the back just to wall mount them?

Beoplay A2
Beoplay Earset
Beoplay H6 (Gen 2)
Beoplay S3 (pair)
Beoplay S8
Beovox CX50 (2 pairs)

Beovox RL 6000

Noah
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Noah replied on Thu, Aug 12 2021 3:41 PM

I think they are talking about ventilation on the back of the driver, not the speaker cabinet. There are 2 holes on the back of the cabinet, one for the din input and one for wall mounting. 

-Noah M. 

RL 60.2, Beogram 5500, Beomaster 5500, Master Control Pannel 5500, Audio Terminal Remote, H9i, Beovox s45.2, Beosystem 2500 , Beogram 1602, Beolink 1000 remote. 

Looking for: Beocenter 8000, Beosound Century 

matador43
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RIght, It's the hole in the magnet.

But on C30 there is no "hole" for wall mounting. There is a "grid" in which hooks take place. 

Noah
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Noah replied on Thu, Aug 12 2021 5:58 PM

Oh got it. I was thinking that the whole cx/c line had them. My mistake. 

-Noah M. 

RL 60.2, Beogram 5500, Beomaster 5500, Master Control Pannel 5500, Audio Terminal Remote, H9i, Beovox s45.2, Beosystem 2500 , Beogram 1602, Beolink 1000 remote. 

Looking for: Beocenter 8000, Beosound Century 

cooldude
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I have reconditioned several pairs of CX's a few years back.  Mostly with new surrounds from GoodHifi.

Besides the foam rot, It is almost imperative to replace the caps in the crossover. I have done it with all mine.

They originals are getting really old and are often still looking ok, but were out of specs, which muffles the sound.

Also new surrounds need a bit of a workout to loosen up.  

 

 

matador43
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cooldude:

It is almost imperative to replace the caps in the crossover. I have done it with all mine.

They originals are getting really old and are often still looking ok, but were out of specs, which muffles the sound.

Thank you for your advice. According to the service manual, on C30 it's just one capacitor per speaker, worth trying!

6.8 microfarad, hope it's not too much exotic! 

Dillen
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Dillen replied on Thu, Aug 12 2021 9:27 PM

matador43:

cooldude:

It is almost imperative to replace the caps in the crossover. I have done it with all mine.

They originals are getting really old and are often still looking ok, but were out of specs, which muffles the sound.

Thank you for your advice. According to the service manual, on C30 it's just one capacitor per speaker, worth trying!

6.8 microfarad, hope it's not too much exotic! 

Bipolar axial.
In C30 it may not be quite as important as in larger and more elaborate models, but see if you can find some with specs as close to the original as possible.
Or grab a set from Beoparts-shop.

Martin

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