I don't think it would be practical to domestically ship a large enough slab to be useful as an OB. You are more or less local, Bill, so you could have something made on a custom basis and pick it up in person.
I think we are either doing a small-ish general-purpose 4-or-5-sided box that people can use in a speaker build or doing a much more ambitious project that would be designed for a specific set of drivers only, like a speaker kit.
It might be possible to make a 2-box set with one box nesting inside the other. The smaller box would be used for the midrange and tweeter, and the larger for a woofer, of a 3-way system.
Keep the suggestions coming!
MFG Notes
Make slabs from lightweight concrete for the boxes. Pearlite is a possible filler candidate.
These may be joined to form an air tight seal using current adhesive and cast in-place pocket screw insert technologies. Celebrate the joints with kerfs.
For egg-shapes, of course, cast as one piece.
Dip concrete in polyurethane bath to finish to a hard, impermeable surface.
Note: Tarrasa must be ground to a finished surface before dipping/coating/sealing.
For the baffle panel(s), form from a reinforced thermo-plastic that may be CNC to specification for driver mounting. Press in flange nuts after machining.
Regards,
WHG
Make slabs from lightweight concrete for the boxes. Pearlite is a possible filler candidate.
These may be joined to form an air tight seal using current adhesive and cast in-place pocket screw insert technologies. Celebrate the joints with kerfs.
For egg-shapes, of course, cast as one piece.
Dip concrete in polyurethane bath to finish to a hard, impermeable surface.
Note: Tarrasa must be ground to a finished surface before dipping/coating/sealing.
For the baffle panel(s), form from a reinforced thermo-plastic that may be CNC to specification for driver mounting. Press in flange nuts after machining.
Regards,
WHG
An example on youtube, (bendy concrete coffee table).
https://www.youtube.com/watch?v=5HbsmFgdz0g
Making a U shape by laying up a laminate of materials and then forming should be possible. My main thought for this is to allow surface detail to be laid out sparsely, first, then fibre reinforced concrete poured... Alternatively, thin concrete or cement, then impress the stones, then add fibre concrete, then form. Would required aggressive polishing to to reveal the finish.
https://www.youtube.com/watch?v=5HbsmFgdz0g
Making a U shape by laying up a laminate of materials and then forming should be possible. My main thought for this is to allow surface detail to be laid out sparsely, first, then fibre reinforced concrete poured... Alternatively, thin concrete or cement, then impress the stones, then add fibre concrete, then form. Would required aggressive polishing to to reveal the finish.
These guys are producing Terazzo loudspeaker enclosures for some 30 years now.
https://www.taf-oss.nl
As I understand it, the internal cavities are made by polystyrene fillers/cut-to-shape- blocks, that are melted away once the walls have hardened.
It should not to be too hard to do it yourself.
Transportation costs for make on demand will be a deal breaker, I suppose.
Good luck,
Eelco
https://www.taf-oss.nl
As I understand it, the internal cavities are made by polystyrene fillers/cut-to-shape- blocks, that are melted away once the walls have hardened.
It should not to be too hard to do it yourself.
Transportation costs for make on demand will be a deal breaker, I suppose.
Good luck,
Eelco
Thanks guys, but I am NOT looking for info on HOW to make the concrete enclosures, tips about mold making, or what material to use. There is already an expert terrazzo concrete guy who will handle that. I also know that we are not the first people on the planet to use this material for speakers...
I AM simply looking for input on the SHAPE and SIZE of whatever is made.
Should it be a small, conventional general-purpose BOX with removable front and possibly rear baffles that the user would then supply when they build it up for their own project?
-or-
Should it be something that is not easy to make by the DIYer like a spherical enclosure for a midrange and tweeter that would sit on top of another cabinet, possibly part of a kit (driver choices fixed and crossover already developed)?
-or-
Some other shape or sized enclosure like an open baffle, U-/M-frame, and that kind of thing?
I AM simply looking for input on the SHAPE and SIZE of whatever is made.
Should it be a small, conventional general-purpose BOX with removable front and possibly rear baffles that the user would then supply when they build it up for their own project?
-or-
Should it be something that is not easy to make by the DIYer like a spherical enclosure for a midrange and tweeter that would sit on top of another cabinet, possibly part of a kit (driver choices fixed and crossover already developed)?
-or-
Some other shape or sized enclosure like an open baffle, U-/M-frame, and that kind of thing?
I can envision a spherical midwoofer+tweeter enclosure. I would probably go with a 5" or 6" midwoofer and the standard 4" diameter tweeter flange, placed as close together as possible. In that way it can be used with a wide variety of MW and T drivers, including some waveguided tweeters. The idea of casting in a small waveguide is a good one, too.
To accommodate the larger sphere size, it could be supplied as two halves that are then joined together or can be assembled/disassembled repeatedly. If the two haves are nested, it would reduce the shipping size to just over half the size of the sphere.
I think that a sphere would have some nice acoustic properties (smooth baffle step transition). How to integrate that with a bass unit would take some thinking. I did have the idea that a sphere could be put above a large rectangular pedestal/box with a large (e.g. 15" or 18") driver firing upwards and the sphere almost nestled into it. If you keep below the frequency where you start to get interference between driver and sphere this might work well. Thoughts?
Member
Joined 2009
Paid Member
There are a few ideas you can find....
I quite like the 'rough' look for concrete speakers, it's a design choice of course. See image of 'Brutus' full range. Nice size too.
I like this stuff too, I'd have this in my house (it looks non-trivial to make): Concrete Audio
I quite like the 'rough' look for concrete speakers, it's a design choice of course. See image of 'Brutus' full range. Nice size too.
I like this stuff too, I'd have this in my house (it looks non-trivial to make): Concrete Audio
Attachments
Last edited:
I think that is a photoshopped image. I don't see any fasteners (e.g. screws) in the driver on the right.
I have seen the Concrete Audio site before. They did a lot of shows up until mid 2016 and then nothing is listed after that.
Last edited:
Well, with a 6" midwoofer it could be used as a satellite until 90 Hz or so. A carefully placed assembly of subs a la Geddes/Welti or built in subs could do the very low end. Deep bass then could finally work with instead of against the room.
For a more conventional approach such a sphere unit could be placed on top of a B&W 801 style enclosure, but preferably a bit more rounded at the angles. I do not see any immediate advantages with an up firing woofer, but might be overlooking those.
For a more conventional approach such a sphere unit could be placed on top of a B&W 801 style enclosure, but preferably a bit more rounded at the angles. I do not see any immediate advantages with an up firing woofer, but might be overlooking those.
For now I think I will focus on a conventional rectangular box that the DIYer is familiar with. It will probably be provided without front and rear baffle. I am hopeful that blank MDF or similar baffles could be provided to fit front and rear that the DIYer could modify as needed for drivers, port, binding posts, etc. since this is familiar territory for most loudspeaker builders and it would allow the most flexibility in terms of what can be built with the cabs.
I exchanged a couple of emails with the terrazzo guy and he has used glass microspheres and other fillers that reduce the density of the material. We are now trying to decide what size cabinets would make sense to make. We could make two that could nest in a single shipping box/crate so that they could be shipped together if the DIYer wanted both sizes.
I exchanged a couple of emails with the terrazzo guy and he has used glass microspheres and other fillers that reduce the density of the material. We are now trying to decide what size cabinets would make sense to make. We could make two that could nest in a single shipping box/crate so that they could be shipped together if the DIYer wanted both sizes.
Mode Diversity Preferred
Internal standing wave modes are focused into a single set of frequencies due to the common radius of a sphere. An egg-shape will diversify these and spread acoustic energy in the back chamber over a larger, harmonically unrelated set. WHG
Internal standing wave modes are focused into a single set of frequencies due to the common radius of a sphere. An egg-shape will diversify these and spread acoustic energy in the back chamber over a larger, harmonically unrelated set. WHG
That's right. You can try to address this by modifying the interior space to include a bullet shaped object behind the magnet of the driver to redirect/reflect sound and adding stuffing or, as you mention, change the internal shape by making it a teardrop shape. Both of these approaches were used by B&W.
I was more thinking about the smooth radiation pattern of the driver-in-sphere as shown by Olson and others in the low to mid frequency "baffle step" transition region.
Anyway, something like that will be down the road a bit...
Concrete N... one pour. I tried to figure it out on this years Munich event but the sales guy was well trained and revealed nothing 
No demo which was a disappointment.
Concrete Audio
//
No demo which was a disappointment.Concrete Audio
//
Superior Outside as Well
While not demonstrated by Olson, two spheres of differing [R] and morphed together, provide a smooth diffraction surface for both drivers of a 2-way satellite unit . WHG
While not demonstrated by Olson, two spheres of differing [R] and morphed together, provide a smooth diffraction surface for both drivers of a 2-way satellite unit . WHG
Ah, interesting. So assuming we can describe this loosely as an "egg" shape, where on the surface do you thing would the drivers best be located? On the larger round end or on the "side" with the larger driver towards the larger end and the smaller (e.g. tweeter) towards the smaller end?
One issue that comes along with any enclosure that doesn't have any flat surfaces is how to stand it up as a loudspeaker. Your "egg" or my "sphere" will roll away unless there is a stand included that cradles it or some portion of it, or there are three of four struts cast into it that can be used to stand it up on top of something... any thoughts on that?
Oslon only took it as far as the sphere. An eggshape or even better, The B&W shape keep the semisphere front but have a better trailing side.
dave
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.