Do DCR ports have to be identical?

[unknownuser]

The common method for designing a DCR enclosure is to design a ported one with two ports, then add a divider at 1/3 the distance from the bottom of the enclosure, and put a third, identical port through it.

My question is, do the ports have to be identical, or can they just have the same tuning frequency?

My current design would require three 3x40" ports (or something like that) to keep down port noise at maximum output, and that's going to take up A LOT of volume. From my understanding, these ports all act differently, and would be moving different amounts of air at different frequencies. If I could identify which ports are doing what, I could prioritize on the port size, and the ports that don't need to be 3" ID won't be, and I can save some internal volume.

Does anyone here know if this will work, and/or which ports operate over what range? (The vented enclosure this was designed from was tuned to 23 Hz)


(Originally posted by: Kyle)

[Wolf]

> The common method for designing a DCR
> enclosure is to design a ported one with two
> ports, then add a divider at 1/3 the
> distance from the bottom of the enclosure,
> and put a third, identical port through it.

> My question is, do the ports have to be
> identical, or can they just have the same
> tuning frequency?

The third wouldn't have the same tuning frequency as either of the modeled ports would have. Each port is a successively lower frequency in implementation. Also, as you go lower in frequency, the ports air-movement becomes larger. If you want a subwoofer with DCR, it'll be HUGE, or undoable due to excessive port length/volume. There really isn't a modeler for DCR port-air-speed AFAIK.
Later,
Wolf