The Workbench

Re: Refoaming Beovox CX50 and CX100

Søren Mexico — Mon, 20 Feb 2012 17:48:11 GMT

Agent00soul:

This drawing does not apply, since the surround is slightly above the frame in rest and isn't pulled very hard against the frame when connecting the battery. There is no chance that the position could change as much as 5 mm. If you had said 0.5 mm, then I could agree.
I have now done a pair of CX100 and a pair of CX50 with the battery method. All six drivers still work perfectly.

Take a 0.5 Mm wire and then a 5 Mm and look at it, then maybe you will learn what the difference between 0.5 and 5 Mm is.

Just measured a 8" driver with an old 1.5 V cell, the cell i checked before testing, it showed 1.22 V, I got a pull of 3.4 Mm, and that with an old battery taken from an emergency flashlight, where it has been for about a year. What happens with a fresh battery with 1.6 V ?? you tell me.

The measurement was done on a 8" Beovox 3702 bass driver with new surround, without surround the pull will be a little longer.

Re: Refoaming Beovox CX50 and CX100

Agent00soul — Mon, 20 Feb 2012 16:01:49 GMT

This drawing does not apply, since the surround is slightly above the frame in rest and isn't pulled very hard against the frame when connecting the battery. There is no chance that the position could change as much as 5 mm. If you had said 0.5 mm, then I could agree.
I have now done a pair of CX100 and a pair of CX50 with the battery method. All six drivers still work perfectly.

Re: Refoaming Beovox CX50 and CX100

riis — Mon, 20 Feb 2012 15:54:19 GMT

Dillen:
2. If white glue is what we in Denmark call woodworkers glue, it will be
nothing but trouble and I simply cannot see how anyone can recommend it.
It hardens completely, becomes brittle and will not bind to the metal basket.

I have refoamed a couple of CX 100's and used the white glue from Good HiFi. This glue looks, smels and feels like ordinary woodworkers glue, but maybe it is not. I'm not a chemist. I would like to find a suitable glue in Denmark to reduce the shipping costs.

Dillen:
Speaker cement is very easy to work with, it settles reasonably well within
10 hours and completely within about 24 hours or so.
It has an incredibly strong bond to almost any material and remains just
slightly flexible and elastic

Can I buy the speaker cement that you mention in Denmark? If so under what name?

/riis

Re: Refoaming Beovox CX50 and CX100

dmacri — Mon, 20 Feb 2012 12:26:59 GMT

That makes sense. I guess I've just been lucky up until now, however I have used shims on larger diameter speakers in the past. I should always use shims to be safe.

Re: Refoaming Beovox CX50 and CX100

Søren Mexico — Mon, 20 Feb 2012 12:08:07 GMT

What happens to the surround using a battery you can see on this drawing, a 5 Mm pull will allso pull the outer edge of the surround away from its natural rest position by +-5 Mm

Re: Refoaming Beovox CX50 and CX100

dmacri — Mon, 20 Feb 2012 07:48:05 GMT

I am refoaming three CX100s this week. I really had a tough time getting the old adhesive off the frames. The cones were not too hard to clean off this time. Now I'm at the point of deciding to use the battery method or to shim? It seems to me the spiders help hold the voice coils in place and there is not enough movement to the cone to throw it off, so a battery may be all that's needed. Any opinions?

Re: Refoaming Beovox CX50 and CX100

Medogsfat — Mon, 21 Nov 2011 06:54:02 GMT

You only need to remove the dustcaps & shim to glue down the outer edges of the new foam rings, the rest of the work can & should be done prior to this. Leave them in place until you do this to save them being exposed for any length of time.

Chris.

Re: Refoaming Beovox CX50 and CX100

dmacri — Mon, 21 Nov 2011 06:43:23 GMT

My concern about the shim method is that you leave the voice coil fully exposed during the time the dust cap is off. Whenever I tried this, I worried I would have something fall in, no mater how clean I kept the area I was working in. I liked the idea of keeping the dust cap intact and letting electo-magnetism do the work for me.

Re: Refoaming Beovox CX50 and CX100

Søren Mexico — Sun, 20 Nov 2011 23:54:55 GMT

My kind of man, shimming is it, then you know where you are, without shimming it will allways be guess work, and you get a chance to clean and check under the dustcap. Good pics

Re: Refoaming Beovox CX50 and CX100

stevepe — Sun, 20 Nov 2011 23:18:46 GMT

Hi All,

I hope it's OK to revive this thread with some additional perspective. I just completed a re-do on one of my C75's woofers. It was rubbing after a refoaming job. (confirmed with the low Hz test tone), so I "faced my fear" and cut the center cap off that bad boy. Fortunately, I was able to cut away the tacky glued outside edge fairly easily with a razorblade. (No new surround needed!)

The shims held things in place nicely, and I have to say that it wasn't tough. The non-shimming methods usually/often work, I know, but I'm firmly in the shimming camp, now. I really like not wondering how well centered it is, and not having to be so fussy with the clothes pins, etc. Worth the trouble, IMO, to cut the cap and re-glue it. ( But I have really good "up close" vision)

I'm liking the the cut and fold back the cap method. Less stuff to buy.

Steve

Re: Refoaming Beovox CX50 and CX100

mipe — Wed, 12 Oct 2011 08:59:22 GMT

just got hands on new surroundings for my b&o cx100, i found 8 pcs, incl. glue, i gave $42 incl shipping ;) http://mynerdstuff.blogspot.com/2011/10/bang-and-olufsen-cx-100-loudspeaker.html

Now, i will try this refoam guide, and make a small 'amateur diy' movie to show if i succed

Re: Refoaming Beovox CX50 and CX100

mipe — Sun, 18 Sep 2011 16:22:16 GMT

thanks, great strategy, i will try to do so ;)

I am going to repair my old defect b&o beovox cx100:

http://mynerdstuff.blogspot.com/2011/09/bang-and-olufsen-beovox-cx100-foam.html

Re: Refoaming Beovox CX50 and CX100

Paul — Sat, 23 Jul 2011 16:04:48 GMT

Hi is there any diffrence in sound when refoaming the cx with rubber instead of a foam one?

Re: Refoaming Beovox CX50 and CX100

Dillen — Sat, 15 Jan 2011 16:13:23 GMT

Finding surrounds that actually fits, both the sizes, lip angle(s) and cone height
can be difficult.
Many of the sets offered are generic surrounds, guaranteed to fit everywhere
and they are rarely as good as advertized.

2mm is not the whole world and your speakers will be fine and will provide for many years of
listening pleasure, I'm sure.
However, it is a fact that the foam should be at rest when the cone is the same.
Any pre-tension in either direction is bound to cause distortion since the cone
will be easier to move in one direction than the other or it will have a dead spot somewhere near the center.
Very easy to see if you have a good signal source, a microphone
and a scope or, even better, a distortion meter.
No moot and no mysteries. Pure physics.

Martin

Re: Refoaming Beovox CX50 and CX100

Craig — Sat, 15 Jan 2011 15:39:03 GMT

Glad to see you refaoming went well.

Craig