Greetings!
I have a question about wall construction of cabinets. First, the ultimate goal is to beef up my existing cabinets without loosing too much internal volume, but before I do that, I was wondering if anyone had experience with lining the interior of a cabinet with 3/8" thick drywall?
My current cabinet is minimally braced. While I would love the idea of adding more internal bracing panels, getting them inside the cabinet would be very difficult since the only orifice is the 15" speaker cutout.
This is the current internal bracing of my cabinet. Not shown is the 3/4" by 1-1/2" braces that run on all corners of the cabinet. They join the main panels together. All panels are 3/4" MDF. Internal braces are hardwood. Those shown are either 3/4" by 2-1/2" (actual dimensions) or 3/4" by 1-1/2".
The thought I had was use construction cement to attach a layer of sheetrock to each MDF subdivided panel. To keep loss of internal volume of the cabinet to a minimum I was thinking of using 3/8" household drywall or sheetrock.
Additionally, I was thinking of adding a layer or two of the 050" thick self-stick rubber roofing sheet available at the lumber store (Poor Man's Damplifier Pro). This stuff has foil paper on one side and pull-off paper on the other. It comes in rolls 6" wide.
The end sandwich would be three layers of different density material, but I have no idea if this is a valid mechanism to reduce cabinet resonance or to what degree.
I have an accelerometer, so in theory it is possible to test this approach, but I don't want to waste time if there is prior art to show that it is a poor or even bad approach.
I am interested in your thoughts on the subject and perhaps alternatives that might yield better results.
Thanks!
I have a question about wall construction of cabinets. First, the ultimate goal is to beef up my existing cabinets without loosing too much internal volume, but before I do that, I was wondering if anyone had experience with lining the interior of a cabinet with 3/8" thick drywall?
My current cabinet is minimally braced. While I would love the idea of adding more internal bracing panels, getting them inside the cabinet would be very difficult since the only orifice is the 15" speaker cutout.
This is the current internal bracing of my cabinet. Not shown is the 3/4" by 1-1/2" braces that run on all corners of the cabinet. They join the main panels together. All panels are 3/4" MDF. Internal braces are hardwood. Those shown are either 3/4" by 2-1/2" (actual dimensions) or 3/4" by 1-1/2".
An externally hosted image should be here but it was not working when we last tested it.
The thought I had was use construction cement to attach a layer of sheetrock to each MDF subdivided panel. To keep loss of internal volume of the cabinet to a minimum I was thinking of using 3/8" household drywall or sheetrock.
Additionally, I was thinking of adding a layer or two of the 050" thick self-stick rubber roofing sheet available at the lumber store (Poor Man's Damplifier Pro). This stuff has foil paper on one side and pull-off paper on the other. It comes in rolls 6" wide.
The end sandwich would be three layers of different density material, but I have no idea if this is a valid mechanism to reduce cabinet resonance or to what degree.
I have an accelerometer, so in theory it is possible to test this approach, but I don't want to waste time if there is prior art to show that it is a poor or even bad approach.
I am interested in your thoughts on the subject and perhaps alternatives that might yield better results.
Thanks!
The fact is that by using different materials which have different resonances,you'll end in choosing one which will have its own resonance shifted outside the audible range . For each one you'll have to consider also : rigidity ,weight and damping , applied also to the lengths and dimensions of the project / box . Looking at the picture , the braces seems well done ,as they break in the middle of the panels . I tried lead ,but with little boxes ,so it may not work in a bigger box . Maybe Loren ...you should focus in cutting stationary waves , and I would avoid putting the big reflex ports in the front.
Here is a little more information: Each panel is asymmetrically divided by braces, which should help further brake up compound resonances. The ports are already located in the front and changing that would not be trivial. It can be done, but is not a simple matter. However, I do not understand why it would work to have them located anywhere else but the front baffle.
Here is my reasoning, which I hope you might help find the flaw. I think that the ports reinforce and cancel the wave front from the woofer based on the desired frequency of resonance. If the ports are located at a different panel, then the distance from the port to the woofer changes and impacts the phase relationship of the port/woofer and some degradation would result. Is this not the case and why? Additionally, firing the ports to say the rear would then fire into the corners where the cabinets face and create a corner horn. That would seem to complicate the predicted behavior. At least that would be my concern. Is that based on solid ground?
When you spoke of considering "rigidity, weight, and damping" when selecting the material, what does that really mean with the material that I have proposed? What I am trying to grasp is if the combination I proposed is a good one or a bad choice and why. Can you elaborate on that some more?
Thanks for your input and I really appreciate your thoughts and opinions.
I know. That thought keeps looming in my mind. I would do that if it wasn't for all the complex cuts involved with the design.
In your mind, what would that exoskeleton consist of?
I hate starting over, cabinet construction drawing looks OK, and OP wants to work on it with=out losing internal volume so adding to exterior makes sense.
Anything that creates a discontinuity makes walls less resonant, to what degree I haven't ever managed to quantify ( maybe one day i'll buy some test equipment ) but I have had subwoofer boxes on which I could mount my Turntable
Anything that creates a discontinuity makes walls less resonant, to what degree I haven't ever managed to quantify ( maybe one day i'll buy some test equipment ) but I have had subwoofer boxes on which I could mount my Turntable
Thanks! Seems like sheetrock has a place.
I am considering working on the inside of the cabinet because I designed for an internal volume of 6 cubic feet, but when I did an analysis I found the actual volume was 6.7 cubic feet, so I have some wiggle room.
Nevertheless, it is far easier working on the outside of the cabinet and plywood would be a better material to attach veneer to. My veneer is not paper backed.
The ports do reinforce the front wave near the system's resonance frequency. However, they'll do that even if they're rear mounted. By moving the ports to the rear you'd be increasing their distance from the listener by a small fraction of a wavelength. The resulting phase shift will be minor.
The advantage to pointing the ports to the rear is that high frequency port resonances and turbulence in the port will be less intrusive if they're aimed away from the listener. Many find that the small change in phase relationship between woofer and port is minor compared to the advantages of rear mounted ports.
Having said all that, I can certainly understand why you'd want to work with the enclosure as it is. If the ports aren't making any offensive sounds then moving them won't make any difference.
Few
After further reading I think what I am after is called constrained layer damping.
Sheetrock would not be a good inner material for that type of construction because it needs to be flexible, like rubber, to absorb shear energies and convert the pressure waves into heat.
So it would appear that a sandwich of MDF-rubber-MDF would be a better choice.
Someone mentioned Green Glue, I am guessing that would take the place of the rubber in the center layer?
Sheetrock would not be a good inner material for that type of construction because it needs to be flexible, like rubber, to absorb shear energies and convert the pressure waves into heat.
So it would appear that a sandwich of MDF-rubber-MDF would be a better choice.
Someone mentioned Green Glue, I am guessing that would take the place of the rubber in the center layer?
But you said that you had only the woofer hole to access the interior.
why don't you take the classic route that is bitumen sheets + felt/damping material ? Other way is to follow Norman Bates' suggestion to put dry sand in between..but it's not doable with a finished cabinet .Me thinks that rubber must be used only in cone suspension ,nowhere else .At the opposite , like Dave said ,you could build an exoskeleton with metal sheets ..it could result a very heavy cabinet ,depending on the thickness of steel ,and could also be braced externally...with long metal bars !
why don't you take the classic route that is bitumen sheets + felt/damping material ? Other way is to follow Norman Bates' suggestion to put dry sand in between..but it's not doable with a finished cabinet .Me thinks that rubber must be used only in cone suspension ,nowhere else .At the opposite , like Dave said ,you could build an exoskeleton with metal sheets ..it could result a very heavy cabinet ,depending on the thickness of steel ,and could also be braced externally...with long metal bars !
Sand is an interesting idea. The issue I see with sand is the Kellogg's Factor. That is, "Some settling of contents may occur."
I can see settling being a big problem with the top horizontal panel.
As you said, a finished cabinet is not readily modified. I am leaning toward making changes on the inside if I can. If I remove any panel, the bottom would be the least destructive. That gives me an opening that is 18.5" by 18.5" and not likely to cause cosmetic effects that require a lot of rework.
Applying constrained layers to the inside would be doable if I limited that to the sub-panels divided by the internal braces already installed.
There is also the possibility of simply applying rock wool to the same internal sub-panels. I have no idea how well that might work.
It all boils down to converting as much of the internal pressure waves into heat as possible, no?
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