4th Order Bandpass with Passive Radiator ?

[audioaction]

About a month ago I saw an ad in stereophile(or one of the other hifi magazines) for a sub woofer. The add clearly showed a cut away drawing of the sub, it looked to be a 4th order bandpass with a 10 or 12 inch sub, but instead of a port it used a passive radiator. Does any know what kind of sub this is or if there is anything speacial to making one(like would you calculate the volumes like a 4th order and tune the passive radiator just like a port) I think it was something like 14" cubed and about $1500

[kelticwizard]

Originally posted by audioaction
it looked to be a 4th order bandpass with a 10 or 12 inch sub, but instead of a port it used a passive radiator. Does any know what kind of sub this is or if there is anything speacial to making one(like would you calculate the volumes like a 4th order and tune the passive radiator just like a port)

If you saw a cutout and it simply had a passive radiator where the port would be, there would be little problem, I would think.

I have the original paper by Laurie, (man's name in England) Fincham, who is the "F" in KEF. He popularized the bandpass, and I think that KEF is about the only major hifi company that uses them.

Anyway, in his original paper, the test bandpass had a passive radiator instead of a port. So it is nothing new. I believe the bass rollosff ight be a bit steeper with the Passive Radiator, though.

[GM]

BP designs are no different than any other vented design WRT the vent type, so yes, you can substitute the vent with a PR, though I recommend two to cancel out any vibrations. There are some design considerations when using PRs, but it's all straightforward.

I don't keep up with comsumer audio, so I'm not familar with the unit.

GM