Gluing/stitching materials to cones

[Bret burrill]

I've had bad luck on most forums because people give me a hard time about my ideas. Usually people jump to conclusions about what I'm trying to achieve, and sometimes my ideas are just plain dumb. Please keep an open mind on this one and try to refrain from personal attacks. Thank you.

I'm building a 15" subwoofer from a speaker that sat outdoors for 20 years. I took it apart and the entire inside of the voice coil had a wasp's nest in it, the wasps had long since moved out. I bought some inexpensive components and rebuilt it. It was very hard to find a spider that was small enough in diameter, everything is much larger these days. I'ts stiffer than I wanted but I could spend the rest of my life looking for a better one. The cone is paper with a coating on it and is very rigid, with a foam surround. I got all the original glue off the voice coil and assembled everything yesterday. The gap on this was tight compared to the other subs I built and by some miracle there is no rubbing on it.

Now I want to glue some things to the cone, or stitch them and glue combined. This is mainly for aesthetics, but if these things also stiffen the cone I suppose that would be an added bonus. I'm stuck trying to decide if I should attach things that are very rigid, very flexible, or somewhere in between. I'm thinking that if the objects are rigid, the cone might tear where they are attached. If they are flexible they might vibrate and cause noise, or even break from vibrating.

I'm thinking about two objects radiating out from the dust cap 180 degrees apart, or maybe three objects 120 degrees apart.

I read some older threads about treating paper cones with glue to stiffen them, but couldn't find any where people were attaching things. I'm aware that keeping the cone light is important, so I'm thinking of using very light materials and maybe gluing at intervals to keep the weight down.

I would appreciate your feedback. Thank you. Keep in mind that this is an art-oriented experiment, not an audiophile-oriented one.

 

[Moondog55]

I've been a member here for a long time and I do not recall any personal attacks in that period; although there have been a number of very heated disagreements. So sound quality is a secondary thing here and all you want is a particular "Look"?
Symmetry may turn out to be of great importance and therefore I think equal halves won't work but a trilobal could be OK
Without a rough sketch I'm just pushing air around. Would you by any chance talking about a "Lemon Squeezer" dust cap arrangement?
You realise that it may not sound good so that's a start
Sketch please

 

[brig001]

Is this the sort of thing you are thinking of Wizzer cones: the million dollar question! look at top post

Certainly works on whizzer cones and can’t see why it wouldn’t work on a main cone

Brian

 

[Bret burrill]

I have had good luck on this forum. People here have been helpful. I'm just beat down by life and don't need any more negativity.

Here is a quick doodle. These things would be highly decorative, not just lines like I have drawn. I just can't imagine what shapes I will use until I pick a material. I'm thinking thin aluminum sheet, foam core or who knows.

In doodle "c" the shape is arranged so only small points attach to the cone.

Thanks for your input.

 

[SpeakerBob]

Maybe a soft material like wool (yarn ?) that can be dabbed onto the cone with a paintbrush / glue.

Could use a slightly flexible glue like some of the old fashioned gum type ones.

 

[Bret burrill]

Yes. I have some fancy speaker glue that is flexible/rubbery when dry. I like the yarn idea.

 

[phivates]

If you want to lower the resonant frequency (and sensitivity) then adding mass is the easy way. I think I'll go downstairs and try some modern duct tape, the shiny aluminum stuff, to some throwaway woofers and report back. I have tried mixing epoxy and lead shot, which worked, in a donut right at the voice coil, like Radio Shack did on their Optimus woofers, and AR on the early AR-3.
The yarn idea will look good.

 

[Bret burrill]

Phivates - so the epoxy and lead shot was rigid I take it. Was it on a paper cone? I am surprised it didn't crack or tear the cone where it was attached. This is the kind of info I was looking for.

I'm all for lowering the resonant frequency. I didn't know adding mass would do this. I'd rather not lower the sensitivity, but I suppose like every other aspect of speakers, there is always a trade off.

 

[phivates]

Add mass: lose sensitivity. It's a law unless you add motor strength and that isn't real simple. The lead shot/epoxy donut is only half an inch wide right around the voice coil former, where the paper cone is at its stiffest.

 

[jplesset]

Back when I worked at Infinity (early '70s), we used "perma gum" to lower the resonant frequency. It's rather like putty, stays flexible, and sticks well to the paper cone.

 

[Bret burrill]

Add mass: lose sensitivity. It's a law unless you add motor strength and that isn't real simple. The lead shot/epoxy donut is only half an inch wide right around the voice coil former, where the paper cone is at its stiffest.

Yeah not much flexing in that area.

I looked up permagum. It is sold for applying to refrigerant lines.

 

[Xoc1]

Tannoy HPD drivers had 8 reinforcing ribs attached to the back of the cone in a radial pattern to increase stiffness. They look like paper triangular ribs attached all round with glue. So I would think that something like that could be applied to the front of the cone without compromising the functionality too much, and look fairly radical at the same time!

 

[phivates]

Decades ago there was the RCA LC1A

 

[Moondog55]

Here was I thinking of something that resembled a rose but in stiff paper or felt, just for the "look" of the centre. Might not sound good but it would look great.

 

[kanaddem]

Have you considered papier mache? You may be able to form it directly onto the paper cone and have it stick (depending on the coating of the cone) I'm not sure how sculptural you want to get with this - it's just an idea, I like the idea of whatever weird thing you've got going. Also, have you considered embroidering the cone? Perhaps look up Russian punch needle embroidery? I've only ever seen it done with largish needles, so that may be a no go if you plan on driving this thing at any reasonable SPL.

Sometimes you need something that looks good to just make some noise. I hope it comes to fruition!

 

[afa]

you might be able to use shaped polystyrene foam, Like the Kef B139 and Leak LEAK Sandwich - Wikipedia, or the Yamaha trapezoidal Yamaha Electone E-3 | Rotary speaker on the right. | Enrico Di Pierro | Flickr but only done in a more artistic way
cheers

 

[Bret burrill]

moondog55 - a rose is an awesome idea, I wasn't thinking that wild, but you have got my imagination going.

I had not considered paper mache. I did want to make a sculptural cone out of fiberglass, but I have read all kinds of stuff about glue not sticking well to it.

This one is going to be pretty tame because it is a speaker that is pretty nostalgic to some people and I don't want to go overboard. I would be willing to get crazy with a pyle or something along those lines.

 

[Bret burrill]

OK I thought I would let you all know, this endeavor has led me to building a vacuum forming machine. I will post pics if I ever make something cool.

 

[pinkmouse]

Look forward to seeing them!

 

[Moondog55]

Another option perhaps; or an addition to; have you thought about 3-D printers in this application?
Some of the stuff a nephew of mine has been playing with looks like it might be applicable to fancy dust caps
No personal experience just a passing thought.