Has anyone ever used polymer concrete (ie. epoxy and stones/gravel/sand forming a very strong composite, also called synthetic marble) as a speaker enclosure?
I'm not a mechanical engineer but I think it should make a great material for subwoofer enclosures. It weighs alot (about 2200kg/m^3 depending on a lot of factors) and due to its structure it dampens vibrations very well (someone even said its "acoustically inert"). These sound like good properties for a subwoofer enclosure. I did some quick calculations and with some element requiring very small enclosure (like P.audio TM-10 which would work well in a 15l reflex) and with a cube of inner size of 25x25x25cm and 5cm thick walls (overkill) you'd need around 60kg of polymer concrete which translates to around 2,7 liters of epoxy (rest is granite gravel/stones/sand). So finished subwoofer would weight like under 80kg. Doesn't sound too bad, light enough to be carried by two people. I'm pretty sure you could make it with way thinner walls, this was just a simple calculation.
Is there any reason why polymer concrete would not make a good enclosure? Would it be considerably better than MDF? Please enlighten me. It might be "overkill" but I sort of like these kinds of "because I can" projects 🙂
I'm not a mechanical engineer but I think it should make a great material for subwoofer enclosures. It weighs alot (about 2200kg/m^3 depending on a lot of factors) and due to its structure it dampens vibrations very well (someone even said its "acoustically inert"). These sound like good properties for a subwoofer enclosure. I did some quick calculations and with some element requiring very small enclosure (like P.audio TM-10 which would work well in a 15l reflex) and with a cube of inner size of 25x25x25cm and 5cm thick walls (overkill) you'd need around 60kg of polymer concrete which translates to around 2,7 liters of epoxy (rest is granite gravel/stones/sand). So finished subwoofer would weight like under 80kg. Doesn't sound too bad, light enough to be carried by two people. I'm pretty sure you could make it with way thinner walls, this was just a simple calculation.
Is there any reason why polymer concrete would not make a good enclosure? Would it be considerably better than MDF? Please enlighten me. It might be "overkill" but I sort of like these kinds of "because I can" projects 🙂
Look here: Luidsprekers - Terrazzo Art Fidelity - Outstanding in Sound and Design - TAF Oss. Has been succesfully been done for ages...
regards,
Eelco
regards,
Eelco
Hi,
Polymer concrete has been used extensively in the machining world. Google: polymer concrete and epoxy granite.
Regards,
Polymer concrete has been used extensively in the machining world. Google: polymer concrete and epoxy granite.
Regards,
Hyvok,
Did you ever move ahead with your plans to try polymer concrete? I recognise that this material has other properties which granite and stone do not have, and which may be beneficial for audio applications.
Curious,
Luca
Did you ever move ahead with your plans to try polymer concrete? I recognise that this material has other properties which granite and stone do not have, and which may be beneficial for audio applications.
Curious,
Luca
Hyvok
I have used polymer concrete to make a treble/mid range enclosure some years ago. It works well.
The main advantage of polymer concrete is that is has about 4 times the compressive strength of ordinary concrete and many times more tensile strength ( ordinary concrete has no real tensile strength which is why reinforcing is added ).
You can drill concrete but a neat hole will only be obtained using a diamond drill which is very expensive. I built a wooden mould, soaped the insides and then poured the concrete into the mould. Inside the mould I added templates shaped like the speaker frames and poured the concrete around the templates.
The concrete I used was 15% polymer and used granite aggregate.
Don
I have used polymer concrete to make a treble/mid range enclosure some years ago. It works well.
The main advantage of polymer concrete is that is has about 4 times the compressive strength of ordinary concrete and many times more tensile strength ( ordinary concrete has no real tensile strength which is why reinforcing is added ).
You can drill concrete but a neat hole will only be obtained using a diamond drill which is very expensive. I built a wooden mould, soaped the insides and then poured the concrete into the mould. Inside the mould I added templates shaped like the speaker frames and poured the concrete around the templates.
The concrete I used was 15% polymer and used granite aggregate.
Don
Don, I'd love to see pics of how your polymer concrete enclosures turned out.
I have poured old-fashioned concrete into the space between two cylinders for a loudspeaker, and I want to create more complicated shapes the next time I make a woofer 'box'...
I have poured old-fashioned concrete into the space between two cylinders for a loudspeaker, and I want to create more complicated shapes the next time I make a woofer 'box'...
What a coincidence! I have been reading info on the web for a week about polymer concrete for speaker cabinets! Then I finally find this thread and Luca just bumped it today after 3 years quiet! 😀
I have a sealed 2 way in a 17 liter plywood box that is vibrating too much noise, and smearing 100-300Hz. I want to try a epoxy granite box. This thread is really the only discussion I have found anywhere related specifically to using polymer concrete in loudspeaker cabinets, so I hope it gets some traction.
I have built speakers from Trex decking material which has very low resonant freq, so I thought it would be good. But man it was awful. And very difficult to glue even with West System epoxy. I threw it in the dump after only one listen. Yuk. But that is like plastic version of MDF, so I expect rock loaded epoxy to be much harder, stiffer and self damping.
I think it has been done before, rumors on web suggest that Aerial, Wilson, Vapor have used it. Any other mfgs used this type of box?
It is the SOTA material for machine tool frames. These tools cut at high speed, eg audio midrange freqs. They use this instead of metal to damp vibrations that would compromise the quality of the cut when vibration from the tool impact travels through the ringing metal and bounces back to affect the position of the cutting tool. Where millionths of an inch matter. These tool frame also have to be able to support the tools which weigh tons. So it can't be too compliant, stiffness is as important too. Seems like it should be a perfect speaker material. Being a composite of high Q stone with low Q epoxy, and high stiffness and high mass. Hmmmm....
What's not to like? (Literally, do tell!!)
Rich
I have a sealed 2 way in a 17 liter plywood box that is vibrating too much noise, and smearing 100-300Hz. I want to try a epoxy granite box. This thread is really the only discussion I have found anywhere related specifically to using polymer concrete in loudspeaker cabinets, so I hope it gets some traction.
I have built speakers from Trex decking material which has very low resonant freq, so I thought it would be good. But man it was awful. And very difficult to glue even with West System epoxy. I threw it in the dump after only one listen. Yuk. But that is like plastic version of MDF, so I expect rock loaded epoxy to be much harder, stiffer and self damping.
I think it has been done before, rumors on web suggest that Aerial, Wilson, Vapor have used it. Any other mfgs used this type of box?
It is the SOTA material for machine tool frames. These tools cut at high speed, eg audio midrange freqs. They use this instead of metal to damp vibrations that would compromise the quality of the cut when vibration from the tool impact travels through the ringing metal and bounces back to affect the position of the cutting tool. Where millionths of an inch matter. These tool frame also have to be able to support the tools which weigh tons. So it can't be too compliant, stiffness is as important too. Seems like it should be a perfect speaker material. Being a composite of high Q stone with low Q epoxy, and high stiffness and high mass. Hmmmm....
What's not to like? (Literally, do tell!!)
Rich
Just have to figure out a technically satisfying shape for the speaker and a way to make the mold reusable (as it might turn out good).
Acryl 60 acrylic modifier
An alternative to epoxy/concrete might be Acrylic modified concrete.
I built a house by dry stacking 12" block and applying surface bonding cement.
I used Acrylic modifier called Acryl 60 in the surface bonding cement.
This additive made the surface bonding cement change from gritty, sandy and hard to apply to smooth as cake icing.
I of course used as little as possible and imagine if you used straight Acryl 60 and no water the concrete would be very different.
just a thought.
Dave
An alternative to epoxy/concrete might be Acrylic modified concrete.
I built a house by dry stacking 12" block and applying surface bonding cement.
I used Acrylic modifier called Acryl 60 in the surface bonding cement.
This additive made the surface bonding cement change from gritty, sandy and hard to apply to smooth as cake icing.
I of course used as little as possible and imagine if you used straight Acryl 60 and no water the concrete would be very different.
just a thought.
Dave
Rich,
The usual disadvantages:
More expensive.
More work.
Heavier, so more expensive/difficult to move.
For most, the disadvantages (literally) outweigh the advantages.
That stuff looks cool Dave. The datasheet says it can be used with plaster also, which doesn't shrink.
Thanks pekk, I saw those at a show, they sounded good.
Yeah, most people may not see the value, but DIYers who use expensive low distortion midrange drivers will be more excited about it because a noisy box smears the sound and reduces the value of their driver "investment." Lots of high end mfgs have moved away from wood, the others use very thick MDF.
It won't cost too much more than traditional construction, and the small price premium would be good value if it works. Resin is the most expensive ingredient, ~$50-100 for a pair of 2ways. Aggregate, thin plywood shell for casting into, some 18mm plywood scraps for screws, that's it. Cancel the MDF, baltic birch and laminating glue.
The benefit of this stuff is in the midrange where eliminating resonance in the passband is difficult with wood construction. So the weight penalty would be limited to a smallish box. Anything under 50 pounds would be fine with me. I think an MDF box with as good midrange resonance control would weigh at least as much.
I would not use it for bass box because I think traditional methods and materials are adequate for bass. Hardwood ply is stiff enough for close bracing to push resonance above the working bandwidth, <500Hz.
Thanks pekk, I saw those at a show, they sounded good.
Yeah, most people may not see the value, but DIYers who use expensive low distortion midrange drivers will be more excited about it because a noisy box smears the sound and reduces the value of their driver "investment." Lots of high end mfgs have moved away from wood, the others use very thick MDF.
It won't cost too much more than traditional construction, and the small price premium would be good value if it works. Resin is the most expensive ingredient, ~$50-100 for a pair of 2ways. Aggregate, thin plywood shell for casting into, some 18mm plywood scraps for screws, that's it. Cancel the MDF, baltic birch and laminating glue.
The benefit of this stuff is in the midrange where eliminating resonance in the passband is difficult with wood construction. So the weight penalty would be limited to a smallish box. Anything under 50 pounds would be fine with me. I think an MDF box with as good midrange resonance control would weigh at least as much.
I would not use it for bass box because I think traditional methods and materials are adequate for bass. Hardwood ply is stiff enough for close bracing to push resonance above the working bandwidth, <500Hz.
When I used polymer concrete to make a mid/treble enclosure I bought the polymer as an additive and mixed it with ordinary concrete adding about 15% by volume. Additives such as this are used in construction to make a strong mix for grouting in bolts etc.
If your mix contains any cement then you will need to add the right amount of water to chemically activate the cement.
The big advantage of polymer concrete is that it has tensile strength. Ordinary concrete, cement and blocks etc do not really have any tensile strength and can crack easily.
It is no more difficult to place in a mold than ordinary concrete if you make the mix just workable. As with ordinary concrete you need to put lots of soap on the inside walls of the mold to avoid the concrete sticking.
I do not have any pictures of the enclosures I made and I gave the enclosures away, with the speakers in them, some years ago when I upgraded to a better speaker system.
I also built a polymer concrete bass cabinet to sit below the mid/treble enclosure. However I did not detect much improvement in the bass and reverted to a wooden bass cabinet for ease of moving around.
Don
If your mix contains any cement then you will need to add the right amount of water to chemically activate the cement.
The big advantage of polymer concrete is that it has tensile strength. Ordinary concrete, cement and blocks etc do not really have any tensile strength and can crack easily.
It is no more difficult to place in a mold than ordinary concrete if you make the mix just workable. As with ordinary concrete you need to put lots of soap on the inside walls of the mold to avoid the concrete sticking.
I do not have any pictures of the enclosures I made and I gave the enclosures away, with the speakers in them, some years ago when I upgraded to a better speaker system.
I also built a polymer concrete bass cabinet to sit below the mid/treble enclosure. However I did not detect much improvement in the bass and reverted to a wooden bass cabinet for ease of moving around.
Don
Not sure if this is of any value because it doesn't really make it any easier to build speakers, but I did find out that the quartz countertop materials like Caesarstone, Silestone, etc, are made of 93:7 stone:resin, just like the homemade epoxy granite mentioned above, except they have much higher proportion of stone:resin than DIY. This makes them more dense, should ring at lower freq.
So I went a-knock, knock, knockin on the sample countertops at the local home warehouse and found that some of the quartz samples do ring sharply at high frequency despite the resin binder, but Silestone brand seems especially dead sounding, and it is very popular brand worldwide.
The appeal of using countertop material is WAF. It's pretty enough for a woman's kitchen, aka her household sacred altar. It is smooth and shiny right from the start, no painting. If you and she together pick the right color, then you are 5% on the way to her approval of your DIY speakers. 😉 There are a couple of decent looking black colors that would look pretty cool.
It is not as difficult to work it as I first thought. I found some tools to make the cutting and shaping pretty easy, like Cyclone V1 on this page:
Diamax | Diamond Tools | Polishing Pads | Diamond Blades | Core Bits | Discos de Corte. Wet saw for rent at most home centers. Order a piece of raw counter top slab from the homecenter.
I intend to sit down with the kitchen designer at homedepot next week to see if he will order 10 small pieces from the contractor. Doubt it!
So I went a-knock, knock, knockin on the sample countertops at the local home warehouse and found that some of the quartz samples do ring sharply at high frequency despite the resin binder, but Silestone brand seems especially dead sounding, and it is very popular brand worldwide.
The appeal of using countertop material is WAF. It's pretty enough for a woman's kitchen, aka her household sacred altar. It is smooth and shiny right from the start, no painting. If you and she together pick the right color, then you are 5% on the way to her approval of your DIY speakers. 😉 There are a couple of decent looking black colors that would look pretty cool.
It is not as difficult to work it as I first thought. I found some tools to make the cutting and shaping pretty easy, like Cyclone V1 on this page:
Diamax | Diamond Tools | Polishing Pads | Diamond Blades | Core Bits | Discos de Corte. Wet saw for rent at most home centers. Order a piece of raw counter top slab from the homecenter.
I intend to sit down with the kitchen designer at homedepot next week to see if he will order 10 small pieces from the contractor. Doubt it!
Why do high end speaker companies rarely show a frequency response plot or a harmonic distortion plot? These are all things they obviously have and used to refine their speakers. The Estelons look very nice and probably sound nice too - but when there is a lot of fluffy prose describing the speaker virtues and no data - I get the sense that people who can afford this stuff are buying the image and brand and not the performance. I mean even Ferrari shows you the acceleration, braking, and skid pad G's.
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