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jonnycat 14th September 2012 11:16 PM

Adhesive for felt dust cap + paper cone?

I am replacing the original aluminum dust cap in an old Altec 600B driver (paper cone) with a felt one I acquired locally. I cut away the aluminum cap and left a small rim at the original glue line as you can see here:

The nice fellow I got the dust cap from suggested that I use Elmer's glue, but I thought I might ask here to see if anyone had another suggestion (I don't know how well I can expect Elmer's to adhere to the old adhesive/aluminum rim).

I know I've seen online companies sell repackaged "special" glue for this purpose, but I would imagine an appropriate adhesive is generally available without buying it from a speaker company. Maybe gorilla glue?

Thanks for any suggestions you can offer me on this.

jonnycat 15th September 2012 02:53 PM

I'm posting a followup to this message. I did a test of some wood glue on the old aluminum dust cap, and I was able to peel it off after it dried.

After doing some research online, I came across a suggestion to use an adhesive called "E-6000", so I will pick some of that up locally today and do a little test with that product.

Joe Roberts 15th September 2012 03:28 PM

Use it as is without a dust cap. A flat felt dust cap will have no sonic effect.

Just don't use them in your metal shop!

jonnycat 18th September 2012 04:02 PM

You know, Joe, I wouldn't have thought people would run a driver without a dust cap, but after doing some reading about drivers on this site it seems that there are people who do just that! Apparently, some high-end guitar amp speakers make an attempt to approach this by using the thin "screen" type dust caps.

In any case, since this was all I have right now, I stuck it on with the E6000 product, and it is still curing (takes a few days to fully set up).

I'll post a picture when it's all done.

Joe Roberts 18th September 2012 05:11 PM

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I have seen lots of old speakers with no dust cap whatsover.

Part of my point was that a felt disc is like no dust cap sonically.

Adding a hard material domed dust cap can enhance HF output and the aluminum dome on the 600B was intended to do just that. That is the earliest aluminum dome speaker I know of.

Very thin and easy to mess that dome up. A lot of 600Bs have a sticker on them saying "Do not touch dome." It is almost as fragile as an Altec compression driver diaphragm.

I have one good "modern" speaker" that has no dustcap. It is a GIP 18" field coil driver optimized for "full range" use, although I'd use the term lightly. This unit has a short extension of the voice coil former which acts like a whizzer, adding a bit of tizz around 9k.

However, being a field coil unit, if some metal junk gets attracted to the gap, I can de-energize the magnet and vacuum it out!

jonnycat 18th September 2012 05:23 PM

Aye, it was indeed a very thin piece of aluminum, which was likely what lead to it's demise (it had a tear in it). I harvested this driver from an old Baldwin organ tone cabinet, where the speaker was on the top, pointing up. The grill cloth was torn, so I'm guessing someone used the cabinet as a table at some point, and the inevitable occurred.

I am going to use this for a low-watt guitar amp I am building, so hopefully the felt cone will still work (my ear is not trained to be very discerning in these matters).

Joe Roberts 18th September 2012 05:34 PM

It will work just fine, especially for guitar. Do not worry about these relatively minor details and crank it up!

jonnycat 18th September 2012 11:34 PM

Hey thanks Joe, I appreciate it. It didn't turn out looking very good, but this was my first time cutting into a speaker, and I learned a lot.

I was pretty nervous about the procedure, but now that I've gotten my feet wet it really isn't all that difficult, and if I decide in the future to play around with the driver it won't be too hard to cut out this dust cap and play around with other options.

I like the "set" of the E6000 adhesive, as it is really thick and stays in place without running. I still have to let it set up for a few more days before I plug it in, but here is how it turned out:

It's not going to win any beauty contests, but I'm happy enough with the results.

Joe Roberts 18th September 2012 11:40 PM

What are you talking about...excellent job!

That is not what I was thinking by a felt dustcap. That is more like a standard paper dustcap.

Either way, should be fine, especially for guitar use. The 600B is a stout speaker and won't easily break up into a buzzsaw tone like an old small magnet Jensen, but it will sound good.

jonnycat 19th September 2012 01:08 AM

Hey thanks Joe, I appreciate it! You're probably right about the cap being paper, I was thinking it was felt that had been treated to be really stiff, but it's probably way too stiff to be felt.

It might not be optimal, but it's going to sound a lot better than the noise that the aluminum one made with the little tear in it!

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