What is the coating on the Dayton DC28F silk dome?

[keithostertag]

This past weekend I went to the Parts Express warehouse sale and one of the things I bought was a discounted pair of Dayton DC28F silk dome tweeters. I didn't look closely, and when I got home found that one of them has the coating mostly missing/peeled off. I'm told that to repair it requires purchasing a replacement diaphragm assembly.

What is this coating, and what does it do? I mean, is there something special about it that gives a particular sound? Is it semi-permeable?

I wonder (and may try) if just painting on nail polish or some other coating will be sufficient, but I don't know what the properties of the coating are or the technology behind the design. Is the dome more than just a dust cap?

So I'm curious- anyone know what this coating is and how it works to give this tweeter its popular sound?

An externally hosted image should be here but it was not working when we last tested it.

 

[zman01]

Mu guess is that this coating would have some damping properties - IIRC the coating is soft and slightly sticky. Nail polish would make the dome more hard and rigid - so likely not the right choice of coating.

 

[TMM]

Some kind of polymer coating. Good luck ever getting the same frequency response as the non-damaged one unless you intentionally strip it off both tweeters and apply your own polymer recipe to both. Honestly just get the replacement diaphragm.

 

[twinter]

1" fabric dome tweeters have an anti-phase resonance mode in the dome center between 12 to 15 kHz. The coating damps this resonance and significantly impacts the related frequency response curve. Quite a bit of work goes into the development and application of coatings for high performance fabric dome tweeters.

 

[chris661]

If they were brand new I'd expect a warranty to cover that!

Chris

 

[keithostertag]

Thanks! Still lots to learn... Yea, I probably will just buy a replacement diaphragm, but I think before then I will do some testing and experimenting to see what I can learn, just for fun...

 

[Zvu]

Mix mouse glue and petroleum benzine. Take little brush and apply the mixture on the dome. Be quick when applying, it evaporates fast. When it evaporates, put some signal through it.

Measure before and after and post here. Use the other tweeter as reference.

 

[Cal Weldon]

Anything about the angle the tweeter should be at when coating? You don't want it going through the fabric i assume?

 

[Zvu]

No problem if it goes through - just don't soak up the fabric so much that it starts dripping. You can always add some more if the coat seems too thin. If you don't press it too much you're hardly going through fabric.

 

[keithostertag]

Very interesting! Are the other common solvents I could use besides petroleum benzene? Like naptha, or regular mineral spirts?

 

[Zvu]

I had this - it is medical grade so it's pure. I'm guessing that other stuff could do it but why experiment when this recipe works and you can get medical petroleum benzine in any pharmacy/drugstore.

 

[drewmc]

I think what he is referring to would be callled petroleum ether in the US.

 

[Zvu]

It looks like this.

 

[keithostertag]

Thanks! That's the CAS number for naptha, very common here in the USA.

 

[Zvu]

You're welcome.

I figured you'd manage to use some of the data from the bottle. I took a pic so in worst case scenario you could show it to someone in the drugstore - because benzene is highly cancerogenic, benzine not.

Try it on piece of paper first to see how thick layer remains after applying.

 

[ilardi]

What is mouse glue? Is it the glue used in mouse glue traps?

Terry

 

[Zvu]

Yes

 

[bentoronto]

Mouse glue... yes, sure feels like it if, heaven forbid, you make the mistake of touching the dome. These are great tweeters and with a sharp slope crossover, you can try to hand them as much of the sound spectrum as you can. BUT be very careful not to let anything (such as wood chips) fall on them.

While fun to experiment, probably unlikely to match the stock version well enough. The replacement domes are reasonable priced.

B.

 

[Patrick Bateman]

It's a $19 tweeter. Save yourself a lot of time and hassle, throw it in the trash and buy a new one.

 

[Zvu]

It's a $19 tweeter. Save yourself a lot of time and hassle, throw it in the trash and buy a new one.

It would be polite to read what was written on the previous page and then comment.

Thanks! Still lots to learn... Yea, I probably will just buy a replacement diaphragm, but I think before then I will do some testing and experimenting to see what I can learn, just for fun...