DIY Refoaming Speakers - The definitive ?

Greetings to all. I have refoamed speakers over the years and read up on the various techniques to accomplish the job. It all comes down to 4 ways of centering the voice coil, thee most important part of the process. Some use the "cone push and set" by hand as promoted by the kit sellers, some cut the dust caps and shim, some use the battery method and then there is the signal generator @ 30Hz. This prompts a question. What is the definitive Number One process? I tend to believe that the signal generator @ 30Hz is the top of the food chain, however, I wonder why 30Hz seems to be the "magic bullet" tone setting for all speakers? Shimming has always worked for me provided the voice coil is working in the first place. The battery method raises concerns in terms of potential frying the coils, and the batteries or both !!? A standard AA Battery emits 1.5 Volts, but my Electronics guru (82 yrs of age and still shocking) stated that it would be risky using this process because voice coils are activated in millivolts, thus the difference in voltage and a lack of resistance could burn the coils. Yet others have stated they have hooked up batteries for 4 hrs continuous with no problems? Grey areas remain which only raise more questions for those less informed. My objective is to fill in some of the blanks that exist. I recall a Physics Professor commenting on the battery method which described horizontal and vertical planes of alignment !!?? Even with such an experts advice, the comments still seemed speculative. There has to be expert first hand knowledge of the facts underlaying the 4 methods used to center voice coils. AK is the place to be for such knowledge and information. My objective is to tighten up the loose ends surrounding each process. I thank you all in advance for contributing to this thread.

There are so many different types/brands of foam surrounds available it can be difficult to decide on which is the correct one for the speaker. A thick foam is not necessarily better than a thin flexible one and may very well be inferior and restrict the movement of the cone. One with a very wide edge on the metal side of the cone is not better than one with a narrow edge. The width of the "roll" is different from one kit to another and there is little information about which is correct except for the vintage ARs on the Classic Speaker forum.
I buy my kits from Rick Cobb AKA looneytunes on e-bay. M _Sounds is very popular with many who do their own refoaming. There are experts here on AK that will be along to offer their advice.

I know there are more veteran re-surrounders out there. Regarding your question which addresses methodology only, we have only used the shim method mostly because we usually have drivers of questionable quality. Because of the questionable quality, we are hesitant to use the "feel" method. We intend to try the 30 cycle method on the next refoam. Using a battery (for more than an instant) makes me rather nervous since even 16 ohms is a very small DC load.

This seems to be double posted, the earlier at 10:24

When I use test tones I usually don't use 30 hertz, but 200 or 400 depending on driver size, this way it is more clear when the driver is not centered. Then afterwards I will cycle it with low frequencies.

Regarding the battery method - just makes no sense to me. At least with a test tone, 30hz, 200hz or whatever, the coil is moving in and out around a natural mid point. The ability to adjust volume ensure's you aren't overextending anything. In the case of a battery the cone is extending as far as it can forward, or as far as it can backward. Just stresses the spider and to me makes it difficult to glue the surround to the frame at a good neutral position. My experience anyway.

I think it just boils down to personal choice as I have seen all the methods described above to work well with many individuals.

The real dilema is wheather to cut open the dust cap which many do not want to do for reasons of added expense and work. I rather like looking under the dustcap so I can sweep/clean the VC gap area clean and make sure the VC has not been subjected to compression or the smell of burt VC wire. Also some vented voice coild can get debris in the gap from the sponge they use to filter the air going into the VC- it can crumble and end up in the gap for sure- especially on some of the older JBL drivers and others!

So pick yuour poison carefully!
DC

30hz test tone so far for all of my surrounds and i have been using surrounds from Rick cobb. I am not an expert, but so far i have done 3 sets of ola's, 2 sets of boston a60's, 1 set of baby advents, 1 m&k vx7 and 1 set of epi 100's.

A AA battery has worked fine for me many times.

I'm the best refoamer in the world and I just do it by feel.



Doug

Done all 4 ways myself. Tend to use the battery method mostly - choose the polarity to push the cone up to make it easy to first glue the surround to the cone and make sure its centered, then to keep it up and make it easy to apply adhesive to the back side of the outer edge of the surround, then reverse the polarity to pull the surround down onto the frame for clamping. Never had a problem with the battery method damaging VCs.

cubby01 said:

Regarding the battery method - just makes no sense to me. At least with a test tone, 30hz, 200hz or whatever, the coil is moving in and out around a natural mid point. The ability to adjust volume ensure's you aren't overextending anything. In the case of a battery the cone is extending as far as it can forward, or as far as it can backward. Just stresses the spider and to me makes it difficult to glue the surround to the frame at a good neutral position. My experience anyway.

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Isn't the test tone 30hz or 200hz basically introduced voltage anyway....so why wouldn't the introduction of a small 1.5v source be any different? I struggled to center my VC by feel on my first refoam, after using a AAA (or AA same voltage) I never had another issue with any further refoam jobs.

Oh, and with all due respect to the 82 year old gentleman (and I am serious) speakers are subjected to much more than mere millivolts.

It's volts AC.

Doug

30 Hz test tone worked for me

I've only done a refoam once. I used the 30 Hz test tone method using Rick Cobb's refoam kit. This method worked very well for me. I just ordered another set of foams from Rick to refoam the 12" woofers and passive radiators on my JBL L150A's and I intend to use the same method since it worked well for me prior.

I really appreciate the 30Hz CD Rick sent me. I use it to rattle the plaster against the studs in my apartment with my four stacks of Advents.

My friends are impressed with that.



Doug

Doug G. said:

I'm the best refoamer in the world and I just do it by feel.



Doug

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I'm beginning to feel that may be as good as any other method. I'm beginning to think many of us don't trust ourselves and want some verification and crutch to validate whichever club we belong in.

Really, if it's quiet it should work. Unless the driver is damaged beyond refoaming to begin with.

CUlater said:

Done all 4 ways myself. Tend to use the battery method mostly - choose the polarity to push the cone up to make it easy to first glue the surround to the cone and make sure its centered, then to keep it up and make it easy to apply adhesive to the back side of the outer edge of the surround, then reverse the polarity to pull the surround down onto the frame for clamping. Never had a problem with the battery method damaging VCs.

Click to expand...

That's all I ever do.
I use the battery to mechanically see if there are alignment problems in the first place.

I don't even bother reversing polarity.
Once I disconnect the battery the cone drops.

Then I press the cone in and out as it is drying to make sure there is no rub.

Never heard of keeping the battery connected for four hours.

What is definitive is what makes you feel comfortable.

It should be evident each method works by the number of fans of each. So professors and academic debates aside, whatever turns you on.

Push and try for me.

It doesn't bother me that different people like different methods.

I've successfully replaced the surrounds on one pair of speakers, so I believe I qualify as an expert...

I don't understand how the "shim" method could be superior to any of the other methods listed. First, it causes the most (potential) damage to the speaker from removal of the dustcap alone. Then, too much tension on one side of the surround after the adhesive cures will negate the spacing once the shims are removed. The push and feel method may prevent scraping, but it doesn't facilitate a centered VC in the gap. I wouldn't trust the battery method (personally).

As I mentioned before, I am an expert...I've used the 30 Hz tone method for 100% of the woofers I've re-foamed, and have experienced 100% success using this method.

nrenter, you are correct re the shim method but incorrect re the push and try or feel method.

With a good spider, the VC is already centered at the top and we only have to ensure that the former is parallel to the pole piece all the way down. If you push on the cone in different places all around the outside edge and there is no rubbing, you can be sure the VC is parallel to the pole piece.

Doug

Maesto here, I am stuck with 4 toddlers this weekend, cant sit down to thank you fast enough without some munchkin trying to poke a new dent in my dust caps. Will get back too you's all in a bit. Thanks for all the great info. To Doug, "the best refoamer in the world" Would you mind elaborating on how you developed your technique for the rest of us "not so greatest in the world" refoamers? Your confidence is what we all aspire to have, but it lacks details from the "hands on" knowledge you attest to have, but the collective "we" may all be lacking. Back to you all soon, and many thanks.