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I am wondering about cabinet panels with little holes filled by granite balls. I feel it should be quite rigid and non reflective. Should be non resonant too.May not be too expensive. This should be easier to make than panels with fillings.Will this sound better too I wonder.
Bill
Follow Ups:
The simplest way to control panel damping is constrained layer damping which is 2 layers for each panel glued together with a glue that never totally hardens. The panels can be the same material or different ones. A simple one going back over 50 years to the old IMF Monitor speakers is to finish a wood(MDF today) panel with Formica(or similar material) with the non setting glue.
Rigidity in this case would usually be bracing perpendicular to the walls, preferably close together, say 4 to 6 inches.
I think Q Acoustics has a dual panel with a gap filled by a fluid I think. I am thinking of perforations stuffed with dampeners. Easy to build and experiment. Maybe good for budget bookshelves. Maybe a wild idea. It would also work like semi open baffle variation. Sorry for the craziness.
Cheers
Bill
I'm totally aware of Q Acoustics cabinets. Rockport also uses constrained layer damping and probably a few others. I mentioned IMF because they did it 50 years ago. And, of course, in the 60s there were thw Wharfdale cabinets that were two layers with a middle layer of sand.
And some mildly controlled craziness is cool and fun.
It seems unlikely to me, at least at low frequencies where box volume tunes the cabinet.
Transmission loss is dominated by stiffness below resonance, damping around resonance, and mass above resonance. The holes will reduce stiffness, and the granite will increase mass, so it should help above the resonance frequency and hurt below. Damping is hard to guess without knowing the specific panel material and installation method.
Typical panels resonate at a few hundred Hz. Of course the are multiple resonances above the first one, but the same rules apply to them too.
I hope that is helpful.
!
The Mind has No Firewall~ U.S. Army War College.
I've tried it and compared it to panel to panel bracing. Bracing was more effective, and resulted in a lighter weight cabinet.
!
The Mind has No Firewall~ U.S. Army War College.
The answer is to use both. The bracing raises the resonant frequency of the panels. The constrained layer damping reduces the intensity and duration of the resonances.
I didn't find constrained layers with bracing to work any better than bracing alone. Raising the panel resonant frequency is a side effect of bracing, but in and of itself doesn't reduce panel vibrations. No matter what the panel resonance frequency if the internal pressure isn't enough to cause the panel to vibrate it doesn't matter. Adequate bracing alone accomplishes that. So does mass, and mass doesn't raise the panel frequency, it lowers it. Knowing how these different methods compare requires building cabs of the same dimensions of each configuration and then measuring the results. That's not something the average builder is going to do, but since I make my living designing speakers it's something I had to do to be sure of which delivers the best result.
!
The Mind has No Firewall~ U.S. Army War College.
What you need at minimum are two materials with very different sound velocities bonded together.
Hello Tom, the Hilti smoke caulk IS the 3rd {the glue} this caulk Never dries and is quite expensive.
The Mind has No Firewall~ U.S. Army War College.
except every thing I've read says it's better to raise resonance. Plus some very well received speakers use constrained layer damping such as Q audio(Fink designed) and Fink speakers> And the Fink company is considered one of the best out there having produced a ton of award winning speakers for decades.
Yes, a lot of places say that. But it's not raising the resonance that stops the panels from vibrating, it's making them stiffer. When you make them stiffer it also raises the resonance, but that's just a byproduct. If raising the resonance was what really mattered we'd make all of our speakers from eighth inch plywood. And yes, constrained layer is one way of doing it. It's just not the way I prefer to use, based on having compared all the options.
You realize that raising the resonance and stiffer are the same thing?
Granite is about as reflective as it gets.
Various other materials. Soft balls of various densities may offer different sounds.little cones projecting out could produce interesting multi horn sound. I think there is good scope for research.
Cheers
Bill
I'm not sure what you're getting at, but where panel stiffness is concerned that's most easily achieved with bracing, while damping internal reflections is easily accomplished with a variety of materials, ranging from Type 400 fiberglass to open cell foam to polyester or cotton batts.
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