Has anyone ever tried pressurizing the inside of an enclosure? It would obviously only work on a sealed enclosure, but by increasing the amount of air inside, wouldn't that be somewhat like increasing the size? Also, would a bit of pressure in the box help control excursion?

Just thinking.

 

I believe pressurizing an enclosure would make it seem to the sub as a smaller enclosure not bigger. It doesnt sense the molecules of air itself it merely reacts to the pressure the pressure of course changes with the air volume and the speaker movement the larger the volume the less pressure is exerted on the sub. If you pressurize the box the sub will have to work too hard and you will damage it. Here are some pics of my GC monitor, box, amps, and power distribution

 

Pressurizing a sealed enclosure would make the enclosure appear smaller to the driver.

It wouldn't work though. If the enclosure is already "charged" with pressure then even when the driver is at rest with no signal the enclosure is attempting to drive it. Some or all of the xmax of the driver would be used up just sitting there. Even if it was made to work with some sort of special dsp there's no sense in it. If you wanted the enclosure to act smaller you'd just make it smaller.

 

If he had said low pressure, then he would be right on both of his assumptions. It would make the box seem bigger and would keep the speaker from "over reaching" as i like to call it. Unfortunatly it would create excess stress like someone else was saying on the cone of the sub. It might not stay at low pressure for very long though, sort of like a balloon over time. It would also change the speakers neutral postion to one sitting farther back, not sure how that would affect it though.

If your looking for "fake volume" you can cram some of that polyurathane cotton stuff in there and it simulates a bigger airspace.

 

I don't think it would be good for the speaker: since the pressure would not be the same on both side of it, there would always be a pression on your sub when it is not playing.

 

How exactly does that work?

 

He's talking about poly-fil. It's the stuff in pillows or stuffed animals. You can buy it at Wal-Mart for nothing. Loosely stuffing a sealed enclosure with polyfill will make the enclosure appear slightly larger to the driver; about 10ish% bigger. You have to be careful though; too much of it and you start rolling off on the low end much to early. I always use it as a tuning aid.

 

Cool. Now, what about sound deadening stuff? Should I line my enclosure with it?

 

Putting the driver in the sealed box reduces the 180deg wave (thickness=stiffness=effectiveness) It would have no purpose but to burn money. Save the dampening for the front doors fore they do not have a enclosure and any reduction for the negative waves would be a bonus.

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and just a note, pressurizing the enclosure, wether positive or negative pressure, will have negative effects on over excursion. the voice coil works both ways, if there is positive pressure the voice coil will reach full out excursion sooner than normal. and just the opposite would happen if there were a vacuum in the enclosure. the VC would bottom out sooner. and as it was mentioned earlier, the likelyhood that you'll have a perfect seal is slim to none. couple hours tops and you'll be back to atmospheric pressure.