I see no real obstacles. GFRC is designed for much lower weight and strong thin-section areas such as between woofers and the uprights next to the woofers. It can be solid tinted. It is ready to be unmolded within 24hrs. The mold itself requires basic woodworking skills and makes countersinking woofers and experimenting with waveguides a relative breeze. Countersinking, for instance, is a matter of jigsawing and gluing up pieces in the mold as opposed to intricate work with a router bit, especially if you wish to very cleanly countersink an oddly shaped flange. Waveguides are a matter of plaster casting a negative using any available model (off-the-shelf waveguide) and positioning it in your mold. I'm a complete novice. But the GFRC tutorials online for countertops, which are remarkably similar to speaker baffles, do not describe it as being that daunting.
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can certainly be done the question is does this provide additional benefits over just using fiberglass resin with the glass mat. I would think with very thin walls the additional dampening from concrete would be in compromised but testing would tell us. this might be a good question in the cabinet material measurement thread
Wouldn't it be better to go the whole hog, and cast the whole speaker in one piece. Perhaps best for smallish speakers used on the ground floor..
Thiel CS6 used concrete baffles for a while. I think the CS7 did as well. Some online discussions say they stopped because of cracking in shipping.
https://www.stereophile.com/floorloudspeakers/218/index.html
"the front baffle, which is cast from concrete"
https://www.stereophile.com/floorloudspeakers/218/index.html
"the front baffle, which is cast from concrete"
Also the shipping costs were prohibitive (especially when considering International Orders).
Basic GFRC use is great for getting one side uniform (the side you spray enamel on) that's forward facing to the listener, the problem is getting the other side (internal to cabinet) uniform for contact with the cabinet and the drivers and also insetting the connectors at just the right depth for making those mechanical connections.
Basic GFRC use is great for getting one side uniform (the side you spray enamel on) that's forward facing to the listener, the problem is getting the other side (internal to cabinet) uniform for contact with the cabinet and the drivers and also insetting the connectors at just the right depth for making those mechanical connections.
celestion Kingston. Oddly was not on the market for very long was cast using 'alpha-crystal' which was basically an aggregate. Probably resin and rock like the kenwood turntables.
Irving M. Fried was moderately obsessed with a British critic's (John Crabbe, of HFNRR) plastered-concrete bass horns. Fried said they were 14 feet; they look more like 11 to me. When I say plastered concrete, I mean that the concrete mixture was troweled on, rather than cast.
Link to scans of Crabbe's article:
https://theartofsound.net/forum/showthread.php?15101-2-3-4-5-way-horn-build/page12
I was never tempted to attempt this.
john
Link to scans of Crabbe's article:
https://theartofsound.net/forum/showthread.php?15101-2-3-4-5-way-horn-build/page12
I was never tempted to attempt this.
john
Attachments
If you search GFRC you'll find that it's come a really long way in the last 20 years. It's a different animal than traditional concrete cast. Much lighter and far less susceptible to cracking. And, of course, this is being contemplated for diy. Not for production. So shipping weight is not a factor.
Again, the disclaimer. I've never worked with fiberglass or concrete. I've mixed the bags for sidewalk repairs.... that's about it.
The advantage I'd expect over fiberglass as mentioned would be working with water based materials vs resin/epoxy based. Mess, toxicity, and cleanup, including the toxicity of any finish work like sanding/shaping.
Also I don't think resin/fiberglass sheet is intended for thick/dense projects such as a poured casting like this. This is what I'd expect a GFRC baffle to look like..... Casting a baffle only instead of the whole speaker just greatly simplifies the mold and allows for adjustments in cabinet volume and design.
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And the easily made basic parts needed for a mold for the baffle above. The edge round can just be off the shelf corner molding. Some means of vibration may be necessary.
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GFRC is apparently far stronger in tensile breaking strength than traditional concrete cast.
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This is just daydreaming. I might bring the question to a diy countertop idea sharing forum if I can locate one and see what the thoughts are.
Again, the disclaimer. I've never worked with fiberglass or concrete. I've mixed the bags for sidewalk repairs.... that's about it.
The advantage I'd expect over fiberglass as mentioned would be working with water based materials vs resin/epoxy based. Mess, toxicity, and cleanup, including the toxicity of any finish work like sanding/shaping.
Also I don't think resin/fiberglass sheet is intended for thick/dense projects such as a poured casting like this. This is what I'd expect a GFRC baffle to look like..... Casting a baffle only instead of the whole speaker just greatly simplifies the mold and allows for adjustments in cabinet volume and design.
..
And the easily made basic parts needed for a mold for the baffle above. The edge round can just be off the shelf corner molding. Some means of vibration may be necessary.
...
GFRC is apparently far stronger in tensile breaking strength than traditional concrete cast.
....
This is just daydreaming. I might bring the question to a diy countertop idea sharing forum if I can locate one and see what the thoughts are.
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Quit dreaming. Or speculating. Do not take it personally.
Bad idea, see below.
Fiberglass is lung cancer toxic, and cement is ground so fine that it will pass through a sieve with 40,000 holes per inch.
I would not use either material indoors without a respirator.
There is a place called Auroville in Puducherry in South India, they used lots of concrete reinforced with chicken mesh (hexagonal mesh), and did some creative work.
Also, lots of buildings in Chandigarh.
So many things are possible...including the casing for water pumps intended for large volumes of water to be pumped.
You need a thickness of at least 25 mm, in my opinion, and that stuff is heavy.
Acoustically, it is absorbent, so your speaker performance will be terrible, compared to other materials.
You can try aluminum composite panels, very popular for building cladding, if you wish to experiment.
Bad idea, see below.
Fiberglass is lung cancer toxic, and cement is ground so fine that it will pass through a sieve with 40,000 holes per inch.
I would not use either material indoors without a respirator.
There is a place called Auroville in Puducherry in South India, they used lots of concrete reinforced with chicken mesh (hexagonal mesh), and did some creative work.
Also, lots of buildings in Chandigarh.
So many things are possible...including the casing for water pumps intended for large volumes of water to be pumped.
You need a thickness of at least 25 mm, in my opinion, and that stuff is heavy.
Acoustically, it is absorbent, so your speaker performance will be terrible, compared to other materials.
You can try aluminum composite panels, very popular for building cladding, if you wish to experiment.
Some years ago, I had an idea to make some concrete speakers for the backyard/garden area. The enclosures would be open on the front, so that a baffle could be attached or removed. The concrete enclosure would be permanent outside. I suppose a removeable baffle made with GFRC would be as dead solid, but with a bit more durability.
Running speaker cable that far was another obstacle that put that idea on hold. Wireless speakers, or battery powered amps might make it a more viable option today.
Now . . . if I can only catch up on the other 1001 projects I have . . .
😉
Running speaker cable that far was another obstacle that put that idea on hold. Wireless speakers, or battery powered amps might make it a more viable option today.
Now . . . if I can only catch up on the other 1001 projects I have . . .
😉
concrete audio (the german company) F-1, I can't find a sound review but the aesthetic mid-century masterpiece,
Read up on FRC...and I think that as a dense composite material, the acoustics would be like a brick wall.
Try looking for information on the net.
Try looking for information on the net.
Elipson, a French company, used to build in the 60s and 70s spherical loudpseakers made of "Staff", a savant mixture of plaster, cement and fiber if I remember well.
These were quite popular some decades ago, used also in airports & Co although intented for HIFI, so many were built - Google is your friend. The main attraction was of course their spherical form. Can't remmeber much more, sorry, nor how they sounded as was quite young the last time I came across some, but they have their followers.
Claude
These were quite popular some decades ago, used also in airports & Co although intented for HIFI, so many were built - Google is your friend. The main attraction was of course their spherical form. Can't remmeber much more, sorry, nor how they sounded as was quite young the last time I came across some, but they have their followers.
Claude
I know what FRC is, I'm just not understanding what you are claiming about the acoustics. Is there a more technical mechanism you are thinking about, when you say "brick wall?"
Over here in the nineties we had Terrazzo Art Fidelity. The man behind those speakers, Koos Schenk, did know concrete and used a filer that had good damping qualities. Most mineral fillers don’t, so you end up with resonating enclosure walls.
While very promising, the production also was quite laborious and in the end Schenk started to explore other (concrete) horizons. But to my opinion his implementation stood out from others experimenting in this direction.
While very promising, the production also was quite laborious and in the end Schenk started to explore other (concrete) horizons. But to my opinion his implementation stood out from others experimenting in this direction.
I've used tinted epoxy reinforced with 2 layers of FG mat, cast into MDF molds to make bookshelf speakers about 20 yrs ago. Wall thickness was 15mm IIRC and the cabinets were totally inert. The biggest challenge was getting the air bubbles out and drilling holes for threaded inserts. One box required 2 gallons of epoxy which isn't cheap.