tournedos wrote:

This may create a false sense of confidence and lead to disappointment once you try to do some bigger bass drivers from say, M and S series or RL140 without shimming.

We have had this discussion several times (and I love it). Before my first attempts to refoam I did my homework, reading up on driver constructions and materials, I also took into consideration that we are mostly refoaming drivers of 20 + years.

One of my concerns is this, if a speaker starts sounding bad, many people dont bother to find failures, they just buy a new one and put the old one in the garbage, or (lucky for us) leave it in the attic or the garage, after some years someone find it or the owner cleans up his spaces and put it up for sale.

What happens, during this time, to the drivers with a bad surround, stored in a bad environment.

Here a drawing of a driver, the gap in the voice coil is shown too big, in reality it is (for some driver types) only 2 to 3 strands of hair (depending on your hair type, mine is 0.04 Mm)

This is the way you will see, and think about, the driver when you are going to fit a new surround. TOTALLY WRONG, see next pic.

This is the way you will have to imagine your driver, the way its placed in the cabinet and stored

Without the surround there is no support for the top of the cone, the only thing that gives it some support is the spider. Let the speaker be stored for some years without use, what happens ?? The down force from the cone will force the spider in the direction of the blue arrows, there is no way to avoid it, Its the law of nature, Newton and Einstein will confirm this. The ambient where the speaker is stored will help a lot to deform the spider, hot, cold, humid, dry, not to speak of air pollution from when you wash your car, paint or clean the floor in your garage.

THIS IS ONE ( 1 ) OF THE REASONS FOR SHIMMING. 

Nearly all speaker repairers recommend some "play in time" for a repaired driver, the new surround has to settle they say, not right, the spider will after a long down time deform and get stiff, the play in time is more for the spider than anything else, it take some time before it gets flexible and comes back to its natural position again (if ever). This is maybe the reason why Mika doesn't like his CXs

Shimming gives you 10 min. extra job per driver and it is easy, so why not do it.

Now tell me if I'm wrong😂

Søren Mexico wrote:

Now tell me if I'm wrong😂

Yes: it's millimeters, not megameters 😁

My CXs came straight out of use (most of the original surrounds were still in one piece, although barely) and the problem was definitely with the replacement surrounds. They were so hard material that I remember wondering how they ever could work the same way as the originals. I guess I should've aborted the mission at that point. Frankly I'm not a big fan of CXs in general, they sound somehow irritating to me - which is why I've loaned them out 😁

tournedos wrote:

Yes: it's millimeters, not megameters 😁

Mm. is the correct way in Mexico😁

It takes much more than 10 minutes to carefully remove the dust cap, to source a new dust cap and to glue the new one in place.

Additionally, when removing the dust cap, there is a high likelihood that debris (paper from the cap, pieces of glue etc) ends up between the voice coil and the magnet. This means the shimming method is at least as likely to cause trouble as the battery method.

Personally I agree with Soren and would NEVER re-foam a speaker without shimming it.

You'll get away with it more easily on the likes of a CX50/100 driver because of the driver's short travel but try it on the likes of a the 10" sub driver from a pair of MS150s, for example, and it is highly likely to go wrong due to this driver's long travel and very (very!) small magentic gap.

As ot the extra time involved in "removing, sourcing and fitting a dust cap" it takes barely 5 minutes more to remove and re-fit the dust cap. As to sourcing it, surely you order it at the same time as the foam surrounds?!

tournedos wrote:

Søren Mexico wrote:

Now tell me if I'm wrong😂

My CXs came straight out of use (most of the original surrounds were still in one piece, although barely) and the problem was definitely with the replacement surrounds. They were so hard material that I remember wondering how they ever could work the same way as the originals. I guess I should've aborted the mission at that point. Frankly I'm not a big fan of CXs in general, they sound somehow irritating to me - which is why I've loaned them out 😁

On the odd occasion that I need to, I buy new replacement drivers from B&O. Other than that, I simply sell the speakers "for spares or repair" and let someone else "get off" on the process.

Generally, deciding whether to attempt a DIY refoam job or not should include a personal evaluation of your own general DIY skills.
What may seem an easy task for some people (let alone the foam surround sellers), could easily end in tears
and loss of money for others with less refined skills and practice.
The CX drivers are not the most difficult ones to work with but still, I would advice anyone considering
the attempt, to practice on some other drivers first.

I get a lot of refoam jobs in here, mainly B&O but occasionally others, and several of them show the results of failed DIY attempts (*sigh*).
Some can be rescued but many are over the edge and it's really a shame. Most 6½, 8 and 10 inch drivers are no longer available
and for them it's even more of a headache to get the owners loved speakers working as intended again since only
very few spares come up for sale and many owners, unaware of the repair possibilitym threw out the bad woofers.
The CX drivers are more plentyful and actually still available from B&O, not particularly cheap but at
least available, but it's still a waste of money and time if you fail a refoam job with a damaged
driver as the result.

There are so many things, that can go wrong. Just drop a piece of debris from the old surround around the magnet center piece
and you're in trouble. Glue in the wrong places, wrong glue that's impossible to shift,,distorted metal basket from dropping driver on the floor,
shorted speaker wires to the metal housing of the CX drivers because the owner used scissors to remove insulation and twisted wires to
solder tags due to lack of a soldering iron, brown packing tape put across the cone to hold everything in place while the araldite set...
You wouldn't believe it.
Just a few days ago, a nice white pair of Beovox CX100 was brought in. The owner had decided to attempt a refoam himself
but didn't get far. Actually, while removing the old surround frmo the first driver (by just pulling it as stated on some foam sellers websites),
he managed to pull the coil away from the spider, leaving the cone and coil just hanging in the flex wires.
He stopped at this point since it didn't quite look like on the website.

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I have said it so many times before; Good refoamers are worth their cost.
BTW; So are good surrounds. I don't use the dutch ones either. Very kind customer service but I've returned too many
surrounds that didn't fit.

Martin

Can only echo the last two comments: foam material is tricky to get right, as are foams that actually fit.

I started out a skeptic about reshimming and the Dutch foams alike (still have them here) and ended up getting different foams and reshimming after getting a hold of a speaker to practice on. It's not easy. Did a capable job though I'd suggest that good professionals really do earn their money...

But you don't need to completely remove the dustcap.  Many people cut most of the way around and bend the cap back on the small piece remaining, acting like a hinge. Once shimmed and refoamed, fold the dustcap down again and glue in place.  Some will approve of this, others will frown.

I can see that refoaming the smaller CX100's/CX50's is by far easier and appreciate all of the comments.  I can well believe and accept that the larger drivers are a much bigger job that necessitates finer tolerances - having said that, 'simply speakers' in the US regularly refoam drivers without shimming and just use the 'rub' method - no batteries involved either.  I watched their video presentation on refoaming Bose drivers.  I also bought their glue which seems to be 1st class.

I'm glad this has been discussed here as it shows there are many ways of doing the same job and I've certainly picked up some good information to bear in mind for my next refoaming job.

Dave.

Meaning that if you don't have the skills then keep your hands off especially if you wanna do the shimming part as well? I did about a hundred if not more, refoaming CX100's and Penta drivers, all from the "Dutch" Good Hifi and never encountered any problems with their foamrings! In fact, with proper instructions anyone with two left hands can do that (CX100's and Penta drivers)!