Why would these need to be applied with a trowel vs roller brush? I have that product and plan to use it in a study on construction methods. I'll be using a Peerless 830970 firing into the box as a sound source. Once the cabinet radiation is measured, I'll cut a hole for an SB15 in poly and Al, and test stuffing materials by measuring how much radiates through the "dummy" SB15.
To gain an even thickness.
Way back when... I tried rollers and brushes and could not get the layer thickness I wanted and I could not get it even.
Guessing from your image I think you are envisioning a coating on the inside, I'm not. My plan is to use two layers of wood with the rubbery stuff between, so the entire box is two layers. Please clarify if I'm wrong...
Thanks for the tip on thickness, I'll look at the trowel. I assume it would be finest tooth trowel I could find? Obviously my tile trowels won't fly!
No, I'll be doing a constrained layer. I'll start with typical construction as in the pic, and compare MDF vs various grades and thicknesses of ply (also taking suggestions on what else to use), then I'll move on to lining damping material on the walls (can't remember what I have but it was a top performer over at diyma when they did this sort of experiment), then coating the inside with AcoustX and mix of caulk and glass microspheres, and lastly some constrained layer stuff. When I do CSL I want to check both wall construction and bracing and see how they differ.
Augerpro:
We're talking 40 years ago... so forgive me if the memory is a bit dim...
I just picked up one of the grouting trowels used for floor tiles. I remember looking at the various ones in the hardware store but I'm not sure if I picked the finest or the medium.
There was none of this visco-elastic stuff around back then. So I ended up with the clear silicone used on bath tubs. About 8 tubes of it, for two speakers, if I recall.
I did several tests on scrap wood and found, as in the video, a thinner layer actually worked better. We didn't have accelerometers back then either, but I did find that a small condenser mic mounted on double sided tape gave me a good enough peek at the results on my scope.
I can't be sure, but I seem to recall my results where almost the same as in the video. A much shorter and lower amplitude ring time when the panels were struck.
Needless to say, I will be very interested in your results.
We're talking 40 years ago... so forgive me if the memory is a bit dim...
I just picked up one of the grouting trowels used for floor tiles. I remember looking at the various ones in the hardware store but I'm not sure if I picked the finest or the medium.
There was none of this visco-elastic stuff around back then. So I ended up with the clear silicone used on bath tubs. About 8 tubes of it, for two speakers, if I recall.
I did several tests on scrap wood and found, as in the video, a thinner layer actually worked better. We didn't have accelerometers back then either, but I did find that a small condenser mic mounted on double sided tape gave me a good enough peek at the results on my scope.
I can't be sure, but I seem to recall my results where almost the same as in the video. A much shorter and lower amplitude ring time when the panels were struck.
Needless to say, I will be very interested in your results.
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That would be a valid concern.
But I'm thinking that with a little planning you could avoid most of that. For example to recess the woofer, make the inside layer opening the size of the basket and the outer layer opening the size of the frame so that the screws actually go into the inner layer... no routing required. Also a corner joint technique like the image I posted eliminates any need for re-cuts or routing.
and... even more careful in my case since I'll be hiring a local cabinet maker to pre-cut the wood for me. Living in an apartment is not conducive to the use of table saws and routers.
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I used a lot of those drivers (with the factory XO). The drivers weren’t great (compared to today) and the XOs were really bad. I have at least a handful of the tweeters to give away.
dave
I have only used the construction adhesive polyurethane Sikaflex (for boat building). I believe it's a different product. Like other construction adhesives it has a heavy consistency so it doesn't sag/run on vertical surfaces. I just don't think it would roll.
I have also used Locktite PL Premium poly sealant (for home repairs) and I can't image it rolling or even being easy with trowel application - it's sort of like applying runny taffy - sticks to tools, fingers, etc.
You have something different. If it rolls, that would be great. Interested to hear how it and your study work out.
notes
A toothed trowel application provides some control of uniform thickness (the tooth depth determines thickness, however the results are not exact).
my experience with polyurethane sealants/adhesives in a caulk gun tube is they have a limited shelf life as they absorb moisture right through the paper tube and cure. wrap tube in plastic.
Isn't that a prerequisite to isolate the outside of the box from vibration?
No scott... Constrained layer is not about isolating lateral vibrations. It is about stiffening and damping the entire wall of the cabinet so that it does not vibrate and produce it's own sound aside from the woofer. (as in "Boxyness")
Watch the video... he demonstrates the principle with two pieces of flexable material. When your flex them together the inner panel has to flex on a smaller radius than the outer one. As you can see in the vid, this ends up with more motion at the ends by the inner panel. By bonding the flat surfaces together with an elastic material you do two things: first you stiffen the overall assembly and second, you create a counter force against flexing, due to the different radii of the panels and the pull back of the elastic layer.
The two panels are so tightly bonded by such a thin layer that anything that would shake the inside panel would also shake the outside one. Constrained layers is not vibration damping, it's materials damping in that you are not preventing the whole panel from vibrating, you are preventing it from flexing.
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. However, box within a box and isolated sounds like an option.
Nothing stops the others from responding if they wish.
What I will not have is another one of your stupid inquisitions with you nit picking some small thing and spending the next 3 days grilling me over it.
We are talking about constrained layer construction... not isolated boxes.. they are two different things.
Okey Dokey ... back to the iggy bin you go.
If you want to talk about something else .. like isolated boxes ... start your own thread, don't try to hijack this one.
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I'm sorry to those reading this. Yes, I'm being very direct with a few people. But I've noticed that there are a small number of users here who seem to want to come into a thread and do nothing but stir the poop and get people off on a tangent, hijacking the thread.
I came here with generosity in mind. I've helped quite a number of people with technical issues and repairs, even offered up schematics and plans from my own repository without asking anything in return. AND I've always been very careful to keep my responses on topic.
But I will confess I have very little patience for people who seem to think they can divert every discussion in their own interests. Isn't that what new or different threads are for?
I asked a simple question about Constrained Layer box construction and I am genuinely interested in anything that contributes to that topic.
The rest of it... not so much.
I came here with generosity in mind. I've helped quite a number of people with technical issues and repairs, even offered up schematics and plans from my own repository without asking anything in return. AND I've always been very careful to keep my responses on topic.
But I will confess I have very little patience for people who seem to think they can divert every discussion in their own interests. Isn't that what new or different threads are for?
I asked a simple question about Constrained Layer box construction and I am genuinely interested in anything that contributes to that topic.
The rest of it... not so much.
Having extensive experience with all types of enclosure damping, I prefer to damped the enclosure structurally rather than just dampen the panels. Structural damping involves damped braces and joints. I do CLD the baffle and the back panel as these are large enough to make a difference, but everywhere else is just structural. Side panels don't seem to benefit by CLD.
The best damping material that I have found is 2K polyurethane - the soft stuff, shore hardness A I believe. It dries even in large panel sandwiches because it cures without air or moisture. It is quite expensive though, but works great. I mix in a lot of glass beads to increase the damping.
The best damping material that I have found is 2K polyurethane - the soft stuff, shore hardness A I believe. It dries even in large panel sandwiches because it cures without air or moisture. It is quite expensive though, but works great. I mix in a lot of glass beads to increase the damping.
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Thank you @gedlee.
Interesting comment. I would tend to agree that some internal bracing will still be necessary. If nothing else it makes a stronger box.
But a question, if I may... You mentioned that back and front work well with CLD and you still use bracing for the sides. That's fine, makes sense to me. But I've noticed that on smaller, bookshelf sized, speakers the side panels are often bigger than the front or back. Does that affect your strategy?
Also can you expand a bit on why you feel structural bracing is better?
Interesting comment. I would tend to agree that some internal bracing will still be necessary. If nothing else it makes a stronger box.
But a question, if I may... You mentioned that back and front work well with CLD and you still use bracing for the sides. That's fine, makes sense to me. But I've noticed that on smaller, bookshelf sized, speakers the side panels are often bigger than the front or back. Does that affect your strategy?
Also can you expand a bit on why you feel structural bracing is better?