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Styrofoam is closed cell, so it won't be possible to impregnate it as such.

Orchorsol wrote:Styrofoam is closed cell, so it won't be possible to impregnate it as such.

Yes that is another problem, I was thinking as a last resort of pulling a vacuum on it. But that has its own problems too. I have read that given time water can percolate into the spaces between the cells as happens at sea where styrofoam sometimes ends up wet and eventually becomes waterlogged after long periods.
Looks like coating it is the easiest way out though. How to build up a thick hard coat? Fiberglass, carbon fiber or just plain old paper applique like they did in the old days?

"I already have the styrofoam all carved up and its 18"X13"X6"..."
You said you are making a "horn" inside a box... I'm trying hard to imagine what an 18"x13"x6" horn would even look like or what it would be used for?
Have you carved out the center of the horn or just this rectangular shape?

Daithi wrote:

Orchorsol wrote:Styrofoam is closed cell, so it won't be possible to impregnate it as such.

Yes that is another problem, I was thinking as a last resort of pulling a vacuum on it. But that has its own problems too. I have read that given time water can percolate into the spaces between the cells as happens at sea where styrofoam sometimes ends up wet and eventually becomes waterlogged after long periods.
Looks like coating it is the easiest way out though. How to build up a thick hard coat? Fiberglass, carbon fiber or just plain old paper applique like they did in the old days?

Now, I'm really puzzled that you are worrying about waterlogging... are you using this underwater?

Curt A wrote:"I already have the styrofoam all carved up and its 18"X13"X6"..."
You said you are making a "horn" inside a box... I'm trying hard to imagine what an 18"x13"x6" horn would even look like or what it would be used for?
Have you carved out the center of the horn or just this rectangular shape?

Two chunks of styrofoam which when joined together make up a single piece 18"X13"X6" are fitted inside a box to make a traveling gramophone. A cavity between the two halves is carved in the shape of a horn much like the horn in an HMV 101 portable, and the cavity is lined with hard plastic or paper applique because styrofoam absorbs sound and therefore is unsuitable as a horn material.

Curt A wrote: Now, I'm really puzzled that you are worrying about waterlogging... are you using this underwater?

No, water logging is not an issue. However my initial idea was to impregnate the styrofoam to a depth of ¼ inch so as to provide mass to the horn sides since as mentioned earlier raw styrofoam is unsuitable as a horn material having as it does very little mass and being sound absorbent.
The comment about water logging was simply an observation that styrofoam can be made to absorb liquid under some circumstances such as in the construction of boats and surfboards.

Got it... I think... I think this idea would work to harden the hollowed out portion: brush white glue, like WeldBond glue directly onto the styrofoam. It will dry hard and no paper or other material would be needed...
Weldbond is a universal adhesive that bonds most anything. It is non-toxic, nonflammable and free of fumes. Weldbond is created without animal by-products and environmentally friendly. ... Weldbond can be used in various applications as glue, bonding agent, sealer or primer.

Good luck on your project. Please keep us posted on your progress...

Curt A wrote:brush white glue, like WeldBond glue directly onto the styrofoam. It will dry hard and no paper or other material would be needed...

Good luck on your project. Please keep us posted on your progress...

Thanks Curt. I will be using something like that weldbond. I'm looking for something that will set hard but not too hard to avoid cracking after a long time. So my mind is not totally made up yet.
Rest assured that I will be posting updates but currently progress is glacially slow due mostly to indecision on my part. You can find a thread on the project in the crapophone subforum under the search terms HMV Peli Peliphon.

Are you still planning to use the plastic pipe as the core of your horn? If so, you could fill the box with spray foam insulation after building the pipe core, which is denser than styrofoam sheets and it will form and fill around anything you put in the box with no cutting.
https://www.greatstuff.dupont.com

Curt A wrote:Are you still planning to use the plastic pipe as the core of your horn?

I will only be using the largest piece at the mouth of the horn and the smallest pieces for the tonearm horn transition. Tapering PVC pipe proved to be beyond my skill set and pay grade. When I realised this I switched to styrofoam. My original intention was to do exactly as you suggest. I have found a nice dense styrofoam to work with so I'm happy with my current plan but I would have loved to use the PVC pipe. In readings I have learned that some of the best horns were made from ¼ inch Bakelite. Hard PVC pipe is the closest modern material to that in my view. Its dense and tough and relatively passive to sound.