Gordon,
Have you tried using the expanding foam they have in the construction industry? Its primarily used for sealing gaps in masonry such as those around windows, fan ducts and so on but once cured its pretty hardy and resists the elements well. Very lightweight but stable too.
It comes in spray cans so that could be the main sticking point. I guess you could use a hose attachment to direct the stuff into awkward places and then fill out from there. Takes about 30 minutes to set and begins to expand immediately after coming out the can.
Also I'm useless with science but SY is probably the resident boffin on such thing here. I'd recommend emailing him and he'll might surprise you with a of some compound or product that will do what your looking for.
Have you tried using the expanding foam they have in the construction industry? Its primarily used for sealing gaps in masonry such as those around windows, fan ducts and so on but once cured its pretty hardy and resists the elements well. Very lightweight but stable too.
It comes in spray cans so that could be the main sticking point. I guess you could use a hose attachment to direct the stuff into awkward places and then fill out from there. Takes about 30 minutes to set and begins to expand immediately after coming out the can.
Also I'm useless with science but SY is probably the resident boffin on such thing here. I'd recommend emailing him and he'll might surprise you with a of some compound or product that will do what your looking for.
I'm using a two part expanding polyurethane foam that's designed for marine applications. It's the lightest density, but I've done another pour today, and this one's worked pretty well.
I used quite a bit more than what I'd calculated would be needed, and, as desired, it started to rise up out of the enclosure. I slapped a lid on it and held it until the pressure got really high, then let it foam up a bit.
Once cured, I cut the foam level to the top with a saw, and opened the mold up. The pressure has pushed the plastic bag out into the inside face quite well. It's not a trivial job to make one (and I'd obviously need one for every speaker box, as it would be destroyed in the final casting process) but it wasn't too bad.
Pic attached - the two halves of the mold are in the background, yesterday's failure on the front left, today's success on the right.
I used quite a bit more than what I'd calculated would be needed, and, as desired, it started to rise up out of the enclosure. I slapped a lid on it and held it until the pressure got really high, then let it foam up a bit.
Once cured, I cut the foam level to the top with a saw, and opened the mold up. The pressure has pushed the plastic bag out into the inside face quite well. It's not a trivial job to make one (and I'd obviously need one for every speaker box, as it would be destroyed in the final casting process) but it wasn't too bad.
Pic attached - the two halves of the mold are in the background, yesterday's failure on the front left, today's success on the right.
Attachments
Hi sploo,
Have you considered an inflated bladder? Like a balloon only tougher? It could be inflated for the casting then deflated and pulled out thru the speaker hole to use again. Rubber inner tubes, some rubber cement, a schrader valve and a little planning/work could save you tons of foam.
A thought.
Have you considered an inflated bladder? Like a balloon only tougher? It could be inflated for the casting then deflated and pulled out thru the speaker hole to use again. Rubber inner tubes, some rubber cement, a schrader valve and a little planning/work could save you tons of foam.
A thought.
MJL21193 said:
Only after a few pints.
Yeah, it's a good idea, and one of the first I considered. However, the enclosures are carefully calculated using some software I've written (you give it a desired curve, enclosure volume, and info about bracing and driver displacement, and it generates a volume of roughly the right size/shape). If there were a way to inflate a balloon inside the enclosure, and form it to that shape (so it would take that shape once inflated outside the mold), that would be great. However, I felt that getting a balloon to the right size, shape, volume, and to make sure it stayed in the right place throughout a casting process, was just going to be too hard.
BERENO said:could you treat the inside of the mold so that you dont have to use a plastic bag? Something like a lacquer that would not stick to the foam? That might eliminate the need for the bag and pressure. Just a thought
It's a great idea... if you know something that'll do it? I spent some time trying out various waxes and other coatings, all with no luck. I spoke to a guy from where I bought the foam, and he wasn't optimistic I'd find anything. It sticks like "brown smelly stuff" to a blanket!
hmmmm.... well I cant think of anything else. Wax on the lacquer is more like what I was thinking, but if that did not work then I dont know what else to recommend. could you lay strips of wax paper on the inside of the mold covering all the exposed areas? When you take the mold apart, the wax paper would go with the foam. It might take a while, but it would allow for a really good mold.
Another idea would be to drill small holes in the mold so that trapped air can escape from the inside of the mold so that the corners can fill in. Just thoughts.
I can see the potential for this thread to quickly move OT, so maybe you should start a new thread asking for some more ideas...
Another idea would be to drill small holes in the mold so that trapped air can escape from the inside of the mold so that the corners can fill in. Just thoughts.
I can see the potential for this thread to quickly move OT, so maybe you should start a new thread asking for some more ideas...
BERENO said:could you lay strips of wax paper on the inside of the mold covering all the exposed areas?...
I can see the potential for this thread to quickly move OT, so maybe you should start a new thread asking for some more ideas...
I think wax strips would take a very long time to apply. I was wondering if I could get a big balloon (one so large that it could fill the volume without really being stretched much). If it was about the right size then it shouldn't have any creases. That said, the result in a plastic bag isn't too bad - certainly good enough for the inside of a speaker, which would of course be filled with damping material.
I did initially discuss some of this stuff on a thread titled "Concrete Horns". I'm planning to have a chat with some local sculptors about what I'm trying to do - when I get more info, I think it would be time to start a thread, and maybe collect some of what's been discussed into that! Cheers for the interest.
Man, I love that room! Very nice work.
Killing those wall reflections has to make a big difference. No matter what others say about the bass stuff, what you've done has got to help. From what you've written, it seems to.
The very best systems I've heard were in very good rooms - purpose built and treated. They were always very comfortable rooms to be in even without the music playing - comfortable to talk in, too.
I will soon be starting room treatment - tho mine has to be temporary, as I don't own the place. Slightly bigger room but with a window of the same size and in the same place as yours.
Glad to read you got the projector ISF calibrated. I used to do that for a living - makes good great. Never did much HT, mostly broadcast, editing suites, large venue projection - that sort of thing.
I have seen the new JVC DiLA projectors - they rock! Superb images. Video projection has come so very, very far in the past 10 years. Even right out of the box the stuff looks pretty good.
Congrates on the nice room - you've inspired me.
Killing those wall reflections has to make a big difference. No matter what others say about the bass stuff, what you've done has got to help. From what you've written, it seems to.
The very best systems I've heard were in very good rooms - purpose built and treated. They were always very comfortable rooms to be in even without the music playing - comfortable to talk in, too.
I will soon be starting room treatment - tho mine has to be temporary, as I don't own the place. Slightly bigger room but with a window of the same size and in the same place as yours.
Glad to read you got the projector ISF calibrated. I used to do that for a living - makes good great. Never did much HT, mostly broadcast, editing suites, large venue projection - that sort of thing.
I have seen the new JVC DiLA projectors - they rock! Superb images. Video projection has come so very, very far in the past 10 years. Even right out of the box the stuff looks pretty good.
Congrates on the nice room - you've inspired me.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.