Jesmonite / Alphacrystal : Has anyone made DIY speakers using it?

[NAT.D.BERG]

Hey,

I was recently tempted by some Celestion Kinstsons on ebay and, in researching them, found that the 'amazing new substance' they were made of can be bought at an art/craft store near me.. and is called Jesmonite.

Here's a link with the reference to the Kinstons at the bottom:



http://www.tersus.co.uk/applications2.html


I am interested in making some AlphaCrystal/Jesmonite heads for my Kef 107s but does anyone have any experience in using the stuff?

All tips are welcome..

Nat

[sreten]

http://www.tersus.co.uk/products.html

Hi,

there is some info here, "jesmonite" is a brand name of some water
based products that appear to be an alternative to polyester resin.

I suspect the "alphacrystal" part is a type of filler used.

What is wrong with the current 107 heads ?

/sreten.

[NAT.D.BERG]

Hello Sreten

It is : "a mineral filled, acrylic polymer prepared as a water-borne solution said to be safe, easy to handle and environmentally friendly'" to quote a Celestion Kingston review from the day - probably a re-quote from Celestion's blurb.

Basically I want to combine several urges into one project: to craft/sculpt something, cure a case of upgrade-itus, to get involved in some kind of audio-DIY project that doesn't involve electronics and sitting at a table soldering, have a more unique hifi..

I have also been reading about Celestion Kinsgtons in more depth and they sound like they would be fantastic.

The Kefs don't quite disappear as I'd like them to but I love their styling and don't want to part with them for that reason alone.

A tweeter upgrade is first, as recommended by many owners, but I'm thinking far ahead and of making Celestion Kingston-style heads to further improve detail and perhaps imaging..

Who knows what they would sound like but I'm sure it would be fun to try unless Jemonite is a pig to work with.. don't want to waste money on it within reason.

[sreten]

http://www.canonburyarts.co.uk/jesmix.html

Hi,

Also see the above. Have you considered modding the 107 heads ?

/sreten.

[NAT.D.BERG]

That's the place.. not far from me.

I have considered modding them but I'm not sure what I could do. There might be room for some simple cross-bracing but then I don't want to change the size of the cavity too much.

They are an interesting design in themselves in a way in that they have these external cavities up the side walls that are filled with a kind of silicon rubber. They are made of just a plastic though, not particularly rigid except by the virtue of having relatively small flat areas.

One thing I plan to do is to make the crossovers external which may free up some room to stiffen the head with something inside.

I would be surprised though if no-one has tried DIYing speakers with this Jesmonite stuff seeing as Celestion got such good results from it. It's fairly cheap too by weight (adding the weight of the liquid to the powder).

Hmm..... Think I might have to have a chat with the people at Cannonbury Arts and jump in at the deap end.

As an aside, I have also found that Aerolam (used in Celestion SL600s and SL700s and also in the Pink Triangle Anniversary turntable) is also an art-orientated material and readily available to all - now it's called Hexalite and used as a rigid platform for mosaics.. Just goes to show that these fantastic and mysterious materials manufacturers boast about (and justify their high prices with) are out there for all of us to use! Long live DIY!

[sreten]

utilizes aircraft grade, polypropylene honeycomb core material that is epoxy bonded to a durable outer shell of thermoformed ABS plastic.

Hi,

Hexalite seems to describe the honeycomb construction, not material.

Aerolam by this definition is a aluminium "hexalite". Hexalite may not be aluminium.

Post some photos of the head units - I may have some ideas.

But note the following :

One way of building a head unit a la BBC principles is to make it soft,
damped and heavy, such that damped resonance modes are below
the operating frequency of the head unit. Consequently the cabinet
is operating in "breakup" mode, but due to the mass and frequencies
involved actual output is relatively low and relatively uncoloured.
For the above case making it stiffer would actually make it worse,
as the main modes would be moved into the operating region
and be less well damped.

The above is something you can only do it a 3-way. Incidentally if you
are following the above principles, the bass cabinet is made light and
stiff and braced to raise the main modes above its operating range.
Consequently for this cabinet structural damping is minimal.

4th order L/R acoustic slopes (not lower) help with the above principles.

/sreten.

[NAT.D.BERG]

That was an unfortunate typo I'm afraid.. Hexlite (no 'a' in the middle) is what I meant:


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