I think it comes down to this - at least with smaller woofers - with a battery and careful clamping you could be right with the placement. With shims, you know you're right. I'm a lazy SOB, but I'm careful, so I used the battery method and kept checking my work to ensure it was properly centered. Another six CX100 woofers successfully repaired, and my bedroom surround system now has B&O speakers in place.

Audiofriends wrote:

Dear Sir,

 

Why doesn't the 8"MSN fit? Can you tell the exact size witch doesn't fit? The 8"MSN has been uses >100x for these speakers without any problems. It's true that our website is out of date (.nl - .com is a clone of it). It's originally a hobby-site from 1998 and that can been seen. But can you tell me one supplier that does give all the sizes like we do, and the compliance? (http://www.audiofriends.nl/pdf/foamsurrounds.pdf). We are busy with a webshop, and are very active on Ebay. Actually we have been rather to busy to bother about the style of our website.

Dear Fred

You may call me Soren

Thank you for a very good and detailed reply, you are right about the 8" MSN, it does fit the S80, I got a little mixed up with my dimensions and suppliers, my opologize. And thank you for joining the forum its good to have expert advise at hand.

If infected with the BeoVirus and loves restoring vintage B&O, what you do, is to get your restored items as close to the original as possible, and thats why we get picky about dimensions and quality, only as an exception do we use items that comes near to or are altered to fit originals.

Back to shimming.

Dmacri wrote: "I'm a lazy SOB, but I'm careful, so I used the battery method and kept checking my work to ensure it was properly centered."

Shimming is a 5 min. job that gives you a secure way of knowing, where in all other ways you can only hope. So why skip a 5 min. job and maybe destroy or damage an item that is imposible to replace.

 

Soren - I also found that no matter how clean I thought I had the speakers, on at least two of them I had some left over old adhesive that rolled down the face of the cone as I was gluing the rings in place. I would have hated it if they fell into the voice coil gap. I have no idea where they came from.

I do shim larger speakers, like the woofers in my RL140s, I just don't think the risk outweighs the reward for these smaller woofers.

I agree that the best way to go is to shim, I just believe in some instances, using a battery is an acceptable alternative.

Hello Leslie,

Well, globally there are about 5 methods:

1. Shimming (see: http://www.youtube.com/watch?v=lp1kjymypQc&feature=related)

2. Cloth pegs (see [url]http://www.audiofriends.nl/pdf/refoaming.pdf[/url)

3. With low testsounds (see http://www.youtube.com/watch?v=g6F6hudpIAg)

4. Don't really center, let the spider center the cone (see: http://www.audiofriends.nl/123-EN/Centre%20midrange.pdf)

5. Not really centering, just pust the cone a few times downwards to see it is free.

1. The shimming on this 10? inch Cerwin Vega is okay but:

The shims has to be equally and the middle of one shim has to come right on the middle of the narrow split of the ring that holds the voicecoil (don't know the word in EN). The split is a weak point, so the shim may not bend this a little outwards. Especially with 'strong' visitcards / film.

Further, there are very much look-alike dustcaps for Cerwin Vega on the market (I have them to, never sell them), but not for every speaker(!). So you might have to put a larger dustcap from other material on the cone. Well that's not good, because the higher frequenties of the woofer (just take a two-way speaker and cover the tweeter, and play a sweap (carefully(!)(http://www.audiofriends.nl/archief/testsignalen), takes a lot of 'high' frequencies with the dustcap (if it's not a textile like with Tannoy dualconcentric). So with an other dustcap this changes to. With a small woofer the cone also gets heavier by the first partly cut dustcap remains, extra glue and larger dustcap. Efficiency gets lower.

Also, but no very often, the middlepool isn't a straight cilinder, but for instance a kind of mushroom ('T') to make a egal magnetic field between the middle pole and the upper poleplate. Shims than can't be used. Also the shims must actually fit perfect (thickness), because otherwise the magnetic field will be different on different sites (the voicecoil then be a little tilt). If there's no other way: just use the old dustcap. Make a little mark with a pencil were you cut. than place it back with using a little glue.

2. Cloth pegs. See manual. For most woofers >5 inch very good.

3. Well, I don't know. I don't know if anywone has experienced some with speakers, but often, if you make the woofer rather work like on Youtube, the wires to the cone drags the cone a little with high amplitude. That's not what I want. Also often the force to drag the surround over the glued frame may the tough. The frequenty drags the foam in a direction, but also disforms the foam because of the force. The amplifier goes of and the disformed foam comes again in it's old direction and pushes the voicecoil in an other way.

I have to say I haven't used this way, it may work fine in practice. But what if the surround is mounted on the back of the cone en the outer lip comes somewhat up? My clothpeg method doesn't have a problem then.

4. Most times for midranges. You have to be sure the spider holds the cone right in the middle.

5. Well, I don't like this. Can give underbenieth:

There may be some faults in spelling etc. Opinions etc. are welcome.

So, for a 4 inch Beovox CX50 etc. I would prefer type 4.

Best regards, Fred

Hello everybody,

I have uploaded a long item yesterday, but I don't know if Beoworld want to place this. I need to use URL's of my own, and that may be seen as advertisement. So I made a PDF to avoid advertisement with my opinion about shimming etc. Can be seen were the other pics ets. also come from. It seems that I can't insert a link anymore.

Best regards, Fred

 

Audiofriends wrote:

Hello Leslie,

Well, globally there are about 5 methods:

This is good Fred, with your permission, I will post this in a Wiki about refoaming on the new forum, will check for spelling and send to you for revision and OK, before publishing.

I'm still for shimming 😁