The one substance I really want to try....
is called 'Hebel" blocks.. It would probably have to be built "in situ" , but maybe the Hebel panels might be usable. Hebel is a liteweight aerated cement product, in blocks or panels.
http://www.hebelaustralia.com.au/default.asp
is called 'Hebel" blocks.. It would probably have to be built "in situ" , but maybe the Hebel panels might be usable. Hebel is a liteweight aerated cement product, in blocks or panels.
http://www.hebelaustralia.com.au/default.asp
Advent used to have a couple of speakers that had expanded foam cabinets and perforated aluminum grills. The outer layer of the foam was much denser and harder than the internal layer, and the boxes were not much lighter than wood, though I think they were cheaper to manufacture. I owned a pair of them (an Advent II maybe?) and thought they sounded sweeter and less boxy than standard Advents, but they were also dramatically less easy to integrate into the average decorating scheme, since they were white with silver grills. This was ok in the 70s, maybe, but probably less popular later.
The later Bozaks -- made in Taftville, not Norwalk, and using conventional drivers -- had regular appearing cabinets but the actual enclosure was half of a sonotube (the cardboard tubes used as forms for poured concrete columns) built into the box with the gaps filled with poystyrene foam. I have a pair of these, but can't comment on the sound because a part of the midrange contouring circuit was fried, leading to a dead short in both midranges.
I can't find any information about component values and so I suppose I have to unwind the coils, and reproduce them. What a pain. Anyone know what happened to the people who worked there -- I think the designer was named David Luchs -- I sure would like to find out the values of the coils.
The later Bozaks -- made in Taftville, not Norwalk, and using conventional drivers -- had regular appearing cabinets but the actual enclosure was half of a sonotube (the cardboard tubes used as forms for poured concrete columns) built into the box with the gaps filled with poystyrene foam. I have a pair of these, but can't comment on the sound because a part of the midrange contouring circuit was fried, leading to a dead short in both midranges.
I can't find any information about component values and so I suppose I have to unwind the coils, and reproduce them. What a pain. Anyone know what happened to the people who worked there -- I think the designer was named David Luchs -- I sure would like to find out the values of the coils.
Blackpool Rock
WS Slater makes a very tasty sucrose composite. It likely doesn’t have any purpose related to speaker building, but they will extrude batches with customized lettering embedded in the core.
http://www.slaters-rock.co.uk/
WS Slater makes a very tasty sucrose composite. It likely doesn’t have any purpose related to speaker building, but they will extrude batches with customized lettering embedded in the core.
http://www.slaters-rock.co.uk/
at one of those gift stores like sharper image or brookstone there was a novelty shelf system that used INFLATED speaker enclosures, made of the same kind of transparent plastic sheet material they use for beach balls and other things. not hi-fi. probably not even lo-fi. but a conversation piece nonetheless.
/andrew
/andrew
Here's the full griff...
Dave, many thanks.
OK. The top and bottom are each made of two sheets of 19mm MDF. One piece fits inside the smaller half-ellipse, the other inside the larger half ellipse. The angle aluminium and MDF make a frame (seen from the front) to which the aluminium can be folded round and secured. You now have a box, but the gap between the aluminium sheets is unfilled. The original design that 7N7 worked to was slightly different (read "not as good"), so I can't give filling details that are tried and tested, but I would be inclined to drill a hole in the MDF to squirt the foam in. The foam is that stuff people use for bodging houses.
The shape of the box is very rigid, and doesn't cause reflections (satisfying 7V's reservations). The traditional "knock" test sounded good. The front panel is boringly flat (makes it easier to mount the loudspeaker), but should have profiled edges to reduce diffraction.
For the mathematical whizzes amongst you. I did an Internet search to calculate the perimeter of an ellipse. There are approximations and an exact series that converges frighteningly slowly. In the end, I made a pair of aluminium templates, used them to mark out the MDF. Carefully cut the MDF and measured it with a steel tape measure. That's how impractical the formulae were! (Bear in mind that a 1mm error in 400mm was not acceptable.)
Dave, many thanks.
OK. The top and bottom are each made of two sheets of 19mm MDF. One piece fits inside the smaller half-ellipse, the other inside the larger half ellipse. The angle aluminium and MDF make a frame (seen from the front) to which the aluminium can be folded round and secured. You now have a box, but the gap between the aluminium sheets is unfilled. The original design that 7N7 worked to was slightly different (read "not as good"), so I can't give filling details that are tried and tested, but I would be inclined to drill a hole in the MDF to squirt the foam in. The foam is that stuff people use for bodging houses.
The shape of the box is very rigid, and doesn't cause reflections (satisfying 7V's reservations). The traditional "knock" test sounded good. The front panel is boringly flat (makes it easier to mount the loudspeaker), but should have profiled edges to reduce diffraction.
For the mathematical whizzes amongst you. I did an Internet search to calculate the perimeter of an ellipse. There are approximations and an exact series that converges frighteningly slowly. In the end, I made a pair of aluminium templates, used them to mark out the MDF. Carefully cut the MDF and measured it with a steel tape measure. That's how impractical the formulae were! (Bear in mind that a 1mm error in 400mm was not acceptable.)
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