Hacking Scanspeak Aperiodic Variovent 290001

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It can be opened, although I would not suggest you do this. The Variovent is not intended to be a method of tuning an enclosure: it operates as a pressure relief aperture to modify the response of a sealed enclosure by reducing stored energy. Early commercial speakers using the device often used more than one fitted to the enclosure rear panel.
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Using Oatey floor drains from your local hardware to me are just as effective for this purpose. Fill with open cell foam of your desired thickness, and make foam larger in diameter for more snug fit and less flow.
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I would love to see a picture. Also cause I dont know what is open cell foam. Shouldnt one use thin layers for adjustment? Or maybe just add layers of cloth for that?
That is the type of device. You can get the steel faced for showers etc like you show there, or the all plastic one piece version.
Open cell foam is like egg crate, or the typical seat cushion foam. You can blow through it as it is not solid like memory foam, or foam with a solid surface embossed or finished, or even that of an exercise mat. Best example I have to help you visualize is that of a soft natural aquatic sponge or a synthetic car wash sponge. Stiff foam is not a good option either because it will not compress.

Anyway, I usually cut 1-2" thick foam in a square about a half inch larger than the diameter of the vent. This way, it will need to be compressed to fit, and hold itself in place. The smaller the foam, the more leaky and vice versa.

You can substitute cotton carpet padding, kraft felt, poly or wool batting, and various fibrous damping/stuffing if you have an inner screen to keep it in there snugly. SS uses a thin felt disc at the exit and fiberglass or knauf fiber internally. If you use fiberglass, the felt would keep the fibers detained.

The reason I prefer the foam is for consistent density and repeatable performance.
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The Variovent is not intended to be a method of tuning an enclosure:
True, but I have a feeling the original poster didn't mean the word "tuning" the way you tune the box with a port. You can model different loss/leak factors in WinISD (or other programs) and he is probably trying to vary the leakage my modifying the stuffing of the vent.
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Hello All,

I did some experiments with this sort of stuff.

Yes you can tune an enclosure by adding resistance to a port.

I drilled a 2 inch diameter hole into a sealed 3/4 inch thick enclosure. (add more holes as needed)

I stuffed Dacron stuffing into a gym sock and placed the cotton/Dacron "plug" into the drilled hole.

Then I ran some impedance sweeps with plugs with increasing amounts of Dacron.

The impedance curves could be tailored from impedance peaks that looked like a sealed box to a much lower and wider impedance curve. More Dacron stuffing was more resistance.

Little or no stuffing looked more like a BR curve with two humps like Alice the camel.

Just for fun



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