Gluing questions

[rbmcginnis]

Hello all:

I am starting my speakers after 7 years of accumulating parts.

The panels are 40" x 19". I am using 3m 9485pc transfer tape to glue spacers (.060") which are made from long zip ties.

My question is about gluing the middle spacers - Do I glue them just to the stator, or to the stator and mylar? I know this is a basic question, but I cannot find the answer.

I am also planning to mechanically stretch the mylar and heat shrink to remove the final ripples. Any opinions on this? The stretch table should put a lot of tension on the mylar.

Thanks all.

[Calvin]

Hi,

before one could give a possible answer You should supply us with more information about Your conncept and the to use materials.

jauu
Calvin

[I_Forgot]

Originally posted by rbmcginnis
Hello all:
The panels are 40" x 19". I am using 3m 9485pc transfer tape to glue spacers (.060") which are made from long zip ties.

Have you tried that tape with the nylon zip-ties and the diaphrgam film? There aren't many adhesives that will stick to nylon.

My question is about gluing the middle spacers - Do I glue them just to the stator, or to the stator and mylar? I know this is a basic question, but I cannot find the answer.

It depends on how you are going to support the drivers in some sort of frame. Most people support the drivers by the insulators, however there is no reason why you can't support the driver by one or both of the perforated metal stators. The diaphragm will have to be glued to the insulators on at least one side, and that side's insulators will have to be glued to the stator. You can do whatever you want on the other side, however, gluing to polyester film that is under tension is "iffy" and it's best to glue it to the insulators on both sides, and for both insulators to be glued to their respective stators.

I am also planning to mechanically stretch the mylar and heat shrink to remove the final ripples. Any opinions on this? The stretch table should put a lot of tension on the mylar.

If you do a good job mechanically stretching the film, there won't be any wrinkles to try to remove with a heat gun. If you manage to get sufficient tension on the film mechanically, a heat gun won't be able to take out any wrinkles that there may be, but there shouldn't be any because the thing is under tension. Any wrinkles at all will probably render the speaker unlistenable, so set your goal to be zero wrinkles with very high mechanically applied tension.

I_F

[rbmcginnis]

OK, thanks for the information.

I plan on taping all spacers to the stators. The transfer tape works well with the mylar and nylon. Very good shear strength. I will do one more test before assembly. I like the ties because they are narrow.

I will use three around the perimeter of each stator and one every 5 inches to obtain a DS ratio of about 70. My question is: do the ones spaced every 5 inches need to be taped to the mylar. Or, does the mylar just float on the internal spacers? I expect that they do not, but I am not positive.

You have an intersting point about only securing the mylar on one stator; I still plan on supporting it with both stators for added strength.

[Bazukaz]

Hi,
I don't think it is a good thing that ties are narrow. The diapraghm tension should be quite high , and i wonder if narrow area would hold it properly. I wouldn't trust double sided tape that much.You should test it first , with membrane tensioned on something, before going to final assembly.

Regards,
Lukas.

[rbmcginnis]

Let me explain.

I am using three strips side by side. This gives me about 1/2" of surface around the perimeter.

This is no normal doublestick tape. I taped mylar to two wooden blocks and could not shear them apart. I expect the strength with the nylon strips will be a bit less, but quite strong.

I like the thin strips as spacers in the middle of the stator.

By the way, no one has answered the primary questions of gluing the middle pieces to the mylar.

[Mutley666]

From my limited understanding of ESL construction (I have read the esl cookbook but not got round to building one as yet), I would imagine that gluing the middle space to mylar membrane would be essential. If the mylar is not glued to the centre spacers would this not cause noise as the mylar vibrates backwards and forwards touching the nylon spacers?

As I said, I'm just guessing here as I have not built and ESL (yet)

[I_Forgot]

I would glue/tape them because if they aren't secured, any non-flatness in the stator will make an air gap which will buzz like a cicada when you play music. Secure is always better.

As far as the adhesive performance goes, a quick stick it and pull test isn't the whole story. Your speaker will have very high tension on the film and it will be applied for years. The adhesive on the tape may creep due to the constant pull provided by the diaphragm. The only real test for that is to make a driver and see if it lasts. Typically what happens is the adhesive creeps into the air space between the insulator and stator reducing tension on the diaphragm ("gee, it worked last week, but now the diaphragm slaps against the stators unless I lower the bias voltage") and/or causing leakage between the diaphragm and stator draining the bias from the diaphragm.

I have been using double sticky tape to hold my dust covers which are tensioned using only a heat gun (they are much less critical than the diaphragms). I find that I have to reshrink the dust covers every few monnths because they loosen up due to adhesive creep, I think, or maybe just the diaphragm relaxing.

Maybe the tape will work. I haven't tried it, so I can't say for sure. I have used Scotchgrip 4693 contact cement and it sticks to the polyester diaphragm as permanently as you can get (years) with no creep. I don't know how well it would work on nylon. I suspect it would be OK. I think nylon is a low surface energy material like polyester, and surface energy seems to be the key to getting adhesives to bond.

I_F

[BillH]

Hi, rb.

I also can recommed the 4693 contact cement. It's available from mcmaster and is considerably cheaper than a good quality double sided tape. I had to take the diaphragm off one panel that was attached with 4693 and it was stuck for the long term.

Have you considered using acrylic sheet for the spacers? It's also available from mcmaster. One piece of acrylic wouldn't tend to 'roll' with a tensioned diaphragm attached as three zip ties might.

[Few]

I'm having a hard time finding the Scotchgrip 4693 on McMaster-Carr's website . Can you provide a link? Also, I've seen 4693 and 4693h; are they the same material?

Thanks.