Yury, I can't see anything you have proposed that will really achieve any improvement over a conventional cylinder vent from PVC of reasonable size with flares on both ends. The rippled foam will create extra turbulence and result in poor performance. Your solutions that are meant to reduce port volume will actually do the opposite. The only ways I know to make vents as small as possible with reasonable performance are:
* flares with a good radius on both ends
* smooth flow throughout with minimal bends
* dimples as used by B&W to improve aerodynamics on the flares
* methods to extend the effective length of the vent, such as using a downfiring vent with a clearance less than the diameter of the vent
A shelf vent allows a larger cross section at the cost of a very long vent, which can more easily be accomodated. However they generally dont have flares and hence the area would often need to be greater for equivalent performance. Also the walls are thicker than a PVC vent. Hence the overall volume is much greater.
* flares with a good radius on both ends
* smooth flow throughout with minimal bends
* dimples as used by B&W to improve aerodynamics on the flares
* methods to extend the effective length of the vent, such as using a downfiring vent with a clearance less than the diameter of the vent
A shelf vent allows a larger cross section at the cost of a very long vent, which can more easily be accomodated. However they generally dont have flares and hence the area would often need to be greater for equivalent performance. Also the walls are thicker than a PVC vent. Hence the overall volume is much greater.
Yury,
So you are trying to make smaller vents with the same level of performance. This is not much different to minimising port noise, you are just making more compromises. However, if you can't get rid of vent noise, then you might as well go sealed, since you can't then use the extra output. From vented you expect 6db more output, however what is the point if you can't use it without port noise?
My point is that if your designs aren't suitable to reduce port noise, they won't allow you to make your ports smaller. In fact it looks as if you are making them bigger rather than smaller.
The physical length and effective length of vents is different. If a vent that fires horizontally is close to the floor then the floor extends the effective length of the vent, hence the actual physical length can be shorter.
If you make the vent downfiring, you would normally allow approx the diameter of the vent as the clearance under the sub to avoid changing the tuning. However, if you make the clearance less than the diameter, it will then extend the effective length of the ventj. Using this method you can get 2 - 4 Hz lower tuning due to the increased effective length. Hence the port is not as long, and takes up less box volume. Or you can then use a larger diameter vent to reduce port noise.
This is one technique that requires experimentation to get it right. You could just as easily get inferior performance if not done right.
So you are trying to make smaller vents with the same level of performance. This is not much different to minimising port noise, you are just making more compromises. However, if you can't get rid of vent noise, then you might as well go sealed, since you can't then use the extra output. From vented you expect 6db more output, however what is the point if you can't use it without port noise?
My point is that if your designs aren't suitable to reduce port noise, they won't allow you to make your ports smaller. In fact it looks as if you are making them bigger rather than smaller.
The physical length and effective length of vents is different. If a vent that fires horizontally is close to the floor then the floor extends the effective length of the vent, hence the actual physical length can be shorter.
If you make the vent downfiring, you would normally allow approx the diameter of the vent as the clearance under the sub to avoid changing the tuning. However, if you make the clearance less than the diameter, it will then extend the effective length of the ventj. Using this method you can get 2 - 4 Hz lower tuning due to the increased effective length. Hence the port is not as long, and takes up less box volume. Or you can then use a larger diameter vent to reduce port noise.
This is one technique that requires experimentation to get it right. You could just as easily get inferior performance if not done right.
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