The Workbench

Re: Review: sellers of loudspeaker foam rings

Søren Mexico — Wed, 29 Feb 2012 14:16:37 GMT

Audiofriends:

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

Re: Review: sellers of loudspeaker foam rings

Audiofriends — Wed, 29 Feb 2012 04:27:26 GMT

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

Re: Review: sellers of loudspeaker foam rings

Audiofriends — Tue, 28 Feb 2012 17:08:02 GMT

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

Re: Review: sellers of loudspeaker foam rings

dmacri — Sun, 26 Feb 2012 15:43:27 GMT

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

Re: Review: sellers of loudspeaker foam rings

dmacri — Sun, 26 Feb 2012 15:41:10 GMT

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.

Re: Review: sellers of loudspeaker foam rings

Søren Mexico — Sun, 26 Feb 2012 12:25:19 GMT

Audiofriends:

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.

Re: Review: sellers of loudspeaker foam rings

dmacri — Sun, 26 Feb 2012 09:31:07 GMT

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.

Re: Review: sellers of loudspeaker foam rings

Leslie — Sun, 26 Feb 2012 04:39:06 GMT

Btw, I did 4 pairs Penta's (32 midrangers) and they all sound great!

Not to mention all the CX's....

Re: Review: sellers of loudspeaker foam rings

Leslie — Sun, 26 Feb 2012 04:36:54 GMT

I wonder why I don't read anything about shimming methods on Audiofriends and Goodhifi's website and maybe others as well.

Have been watching a video on Youtube to see what shimming cones exactly means! Very interesting for these large drivers, still I'm not convinced using this method on small drivers like CX50/100's, Penta's midrangers. Larger speakers okay, but the small ones?

Fred, your comment please as a hobbyist?

Re: Review: sellers of loudspeaker foam rings

Audiofriends — Sun, 26 Feb 2012 03:04:11 GMT

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.

The 8"MSN isn't a 'special surround' like sometimes claimed bij other company's, but a standard on. Special made surrounds are expensive by making a special mould. We have made some for popular speakers like the 8"VF for the Vifa M21WG.

The size of the S40 (by customers)

A = 160

B = 179

C = 199

The size of the S80 (by customers):

A = 160

B = 182

C = 202

Size C of the 8"MSN = 194

Further isn't there any supplier that askes as many data to the customer as we do. It might be not plesant for the customer, but we need for instance the innerdiameter of the gasket. Other suppliers don't bother about this. The 8"MSN should fit perfectly, and I like to know why you think it doesn't fits.

A data base might be welcome for the customer (if you mean the sizes of the speakers) but isn't good for the seller, for he will give away a lot of information to other sellers. I have a database ofcourse, from my customers. So if you want a database you will have to get you hands out of you pockets and do it by yourself I'll guess.

You almost can't find surounds that fit exactly, couse they need a new mould then, and 3D drawings like we did on the 8"VF. Then the surrounds might be exact as before, but it's no guarantee. Also often the new surround must not be exactly like befor if for instance size C surrounds is the same as the size C frame. Than you don't have a possibility to center the cone right.

'A good Surround supplyer IMO should have a website where we, with the B&O model type and number, can, find the correct surround for our drivers, with the dimensions for control' - See Ebay and our PDF-list. As far as I know (I haven't seen any proof) there aren't anywere in the world exact fitting B&O surrounds (if you mean than special made like original). Waist of time to search for it.

Best regards, Fred

Re: Review: sellers of loudspeaker foam rings

Søren Mexico — Sat, 25 Feb 2012 21:24:29 GMT

Stonk:

I have used Fred's foam rings for some CX's and they were superb.

I've been on a lot of web sites offering surrounds, but to find a surround that fits exactly, is a lot of work searching, mostly the sellers offer the most populars, and finding one that offers the correct one is imposible, their websites with dimensions (if they have them) are badly set up, and many times they offer: fit for Beovox S80, S40, S50, S120 or whatever, an 8" driver in the diff. models isn't the same, the 8 " MSN from AF just doesn't fit into a S80 driver, it will fit the cone but never the basket.

What we need is a supplyer that specialize in B&O, just like Soundsmith, where we can order our cantilevers, and can see on the web, which cantilever fits which model.

A good Surround supplyer IMO should have a website where we, with the B&O model type and number, can, find the correct surround for our drivers, with the dimensions for control, some same model types has different drivers and the supplyers should pick up on this when a buyer tells him that the one for F.eks S45 do not fit his S45.

The Supplyer would get a lot of help from the forum if he would take on the big workload it would be to build a database, and deliver first class items.

There are good supplyers out there but non who has it all.

Re: Review: sellers of loudspeaker foam rings

Stonk — Sat, 25 Feb 2012 19:27:39 GMT

I have used Fred's foam rings for some CX's and they were superb.

Re: Review: sellers of loudspeaker foam rings

Audiofriends — Sat, 25 Feb 2012 18:52:06 GMT

Audiofriends:

Dear Sir,

With Google I came to this item and I would like to give a feedback. I have checked my mail till 3 august 2011 back (NL is blocked on Ebay), but I can't find someone witch has bought these items (must be the 4"AS-5 or 4"A-2) and later on bought one again. That should also be impossible if you mentioned the problem, because if a surround gets waisted at what reason whatever we provide normally a free surround with free shipment. If we made a mistake about that please contact us, you will get the money of the extra surrounds back. If you ordered bij Ebay with an EN-account: you can't order one surround, Ebay doesn't give the possibility.

Further the original surrounds are from foam, so the new ones need to be as much as possible as the original material. If foam gets pressed to hard, it's actually not really foam anymore. It often has become a hard, stiff, material with a smooth surface, witch also makes sounds of it own. If the basematerial is right (such as with original Tannoy surrounds) it may be a thin, not hard and supple surround. But then the material get's heavier per square inch and a bit like rubber. Also not the right material if you want to keep the surround (and sound) as much as original. If you look in the book of Vance Dickason it's clear.

The surrounds can mute the vibrations (resonances) of the membrane at the edge. If the surround is very thin and very hard pressed, this is not like original. Actualy, the surround will give his own sound. With a hard pressed surround the efficiency may be higher, just like the difference between cloth and foam surrounds at the Bose 802. But hard thin pressed or medium pressed hasn't to do something with the foam quality itselves. Only the hard thin one gives a more louder noise (efficiency) at higher frequencies but often will have a sound (high Fs) of is own, because it has become a kind of hard plastic, and isn't foam anymore like original. The Fs will be higher, the lower frequencies of the midrange will be (compared with the higher frequenties) less loud. If the surround is made from heavier material the efficiency may be lower and the Fs lowers.

I'm sorry about the centeringproblem. Have you mounted the surround just in line with the cone? Sold surround are always checked before shipping. And why didn't you tell it to me? I have a lot of PDF's for all kind of problems, especially in Dutch. Further I would be very pleased to see the two different refoamed speakers. And I can send you some testsignals, especially for the midrange, so you can hear if there is any difference and if I'm right with the above story.

Best regards, Fred

I wander if someone hase some decent feedback. Jokes are fine.

Best regards, Fred

Re: Review: sellers of loudspeaker foam rings

Audiofriends — Sat, 25 Feb 2012 18:44:53 GMT

See www.audiofriends.nl/bw for pics. I have also a manual for the passive radiator on if I'm right the Redline 60.

These ones are propably used by the topicstarter: real foam like it should be.

Best regards, Fred

Re: Review: sellers of loudspeaker foam rings

Audiofriends — Sat, 25 Feb 2012 18:18:44 GMT

Hello,

Just to introduce me. If you want I have plenty photo's of refoamed B&O speakers, but I don't know actually if I may from Beoworld. I wander if the topicstarter has photo's of his repaired surrounds. The surrounds may not be disformed, we always send in a cardboard box.

I'not really a salesman, but a hobbyist, have a website with lots of do-it-yourself information since 1998.

Best regards, Fred