Hi i am building fullrange speakers 3 Way With 15 10 and a horn bass reflex . . I would like to make them heavy and free of resonances, after building is it possible to pour lets say about 10 mm of self levelling concrete into the cabinet, one surface at a time.
Amy thoughts maybe others tried.. Things to be aware of.
Amy thoughts maybe others tried.. Things to be aware of.
10mm of concrete may crack easily and rattle unless reinforced with mesh.
You may be better off looking for Durrock at the home supply stores.
Durrock is a concrete board used as a tiling surface.
It can be cut with a Skil saw with a concrete blade and glued to the wood.
You just need to choose an adhesive that bonds to both well.
If going the pour route, I would nail metal mesh to the wood and then pour.
You may be better off looking for Durrock at the home supply stores.
Durrock is a concrete board used as a tiling surface.
It can be cut with a Skil saw with a concrete blade and glued to the wood.
You just need to choose an adhesive that bonds to both well.
If going the pour route, I would nail metal mesh to the wood and then pour.
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Thx for your reply.. I have been thinking about that the vibrations might crack the concrete.. I Will look into the produkt you mentioned or using some kind of mesh.. Did find self levelling concrete That has fibres That Should prevent cracking.. Think This is a matter of learning by doing... I know expensive speakers sometimes uses sort of sandwich materiale to prevent resonances... This must have same effekt if done Well.. No one here tried This..?
Add white PVA (Weldbond) glue to your concrete mix & it is way more resistant to cracking but the tradeoff is it is no longer waterproof. I have used it in speaker construction before & is great! Add fibres or screening all the better, just google for mix ratio as I forget the #'s now or buy an elastomeric tile cement, they are polymer fortified & give where regular does not but here regular tile cement is around 8$ a bag & the polymer stuff get up around 50$ a bag, that is all I use laying tiles on wood floors as it gives & regular cracks & turns to power.
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I built white tops for a small 8" diameter speaker about 40 years ago out of white portland cement and sand. No cracking to this day. Built quite a few.
There's a big diff between premix stuff and making ur own... however concrete shrinks when it cures... otoh there are other materials that are used for similar duty that expand when curing! 😀 They use some of that stuff to repair roadways on bridges and the like...
Vibration will do nothing at all to cured concrete in ur lifetime, unless your mix was very weak, and improperly done, improperly cured.
Remember cement is what holds together aggregate, and that is called concrete (basically). You can pick a whole lot of different stuff for aggregate... and control the % of aggregate when you mix urself...
Read up, there's lots on concrete and cement online, and about commercial additives, not just PVA glue...
There's a big diff between premix stuff and making ur own... however concrete shrinks when it cures... otoh there are other materials that are used for similar duty that expand when curing! 😀 They use some of that stuff to repair roadways on bridges and the like...
Vibration will do nothing at all to cured concrete in ur lifetime, unless your mix was very weak, and improperly done, improperly cured.
Remember cement is what holds together aggregate, and that is called concrete (basically). You can pick a whole lot of different stuff for aggregate... and control the % of aggregate when you mix urself...
Read up, there's lots on concrete and cement online, and about commercial additives, not just PVA glue...
Whatever you use has to be able to adhere properly or you'll risk horrible resonances and buzzing. Another option is floor levelling compound. Also work pointing out that there are many additives available for cement/concrete to enable it to flow and adhere more easily to surfaces. Exterior grade ones tend to be water and freeze proof.... to a degree.
You may want to have a read of this post http://www.diyaudio.com/forums/construction-tips/152459-guide-using-acoustic-concrete.html 🙂
Tony.
Tony.
Thx a bunch guys. . Ill stick With the floor levelling cement and and glue to it also i will prime the inside of the cabinets using god thick primer and add some fine sand so That the concrete Can stick Well and long. . Think ill Photoshop dokument the process and post it here for others With same concrete fetish 🙂
Ringing can be a problem. What about adding sand on top of the cement in the btm of the cabinet. You could go the extra step & hot melt some of the thicker roofing materials to the top of your cement after it has cured well in the bottom of the speaker. A pair of R&L subs I made rang like bells from the excitement of the drivers but when I used my heatgun & welded the tar roll type material to both the inside of the cement cylinder & outside all vibration was gone & the sound was solid with no artifacts.
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Not to discourage Amplidude from going down the concrete path but the acoustic concrete post reminded me of a technique I used when building my 3-way mains back around 1990. The cabinets are a combination of 12" diameter Schedule 40 PVC split in half lengthwise and extended with cabinet grade birch plywood on the sides. For whatever reason I decided some acoustic deadening was needed and chose to use a combination of the foam beads (ghost poo) mixed with a gallon of roof cement. Due to the adhesive properties of the roof cement all I had to do was trowel it on the surface. It also acted as a caulk to fill in any gaps in the transition from the plywood to the pipe. It must have worked well because those speakers are still my mains to this day. I just recently refoamed the woofers and the sound is tighter than ever.
Commercially the Acoustic Energy AE1, an expensive and tiny mini-monitor had "concrete" lined sides. It was done unevenly to create non parallel internal dimensions.
For a start heavy does not necessarily mean resonance free - could actually increase internal resonance due to standing waves set up by the reflection, especially with a reflective material like concrete. Then if you do add 10cm of concrete (and cover it with ant-reflective material) your cabinet will have to be over 10cm higher for the same internal volume - are you really sure this is a good idea? Internal bracing is more effective in reducing both types of resonance without affecting internal volume significantly.
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