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In Reply to: RE: Perforated speaker cabinets posted by Bill the K on June 23, 2024 at 04:42:45
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.
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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.
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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.
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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?
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