David, ALL speakers (except sealed acoustic suspension ones) have a vent of one sort or another that lets the air out (and in) from the back of the speaker. There are also infinite baffle types that have the rear not enclosed at all...
Surprised you (or anyone) can be a professional audio engineer and not know that. It is not an "acoustic ambiguity" but a failure of logic and analysis.
Bass Reflex designes tune the port with a tube so that the vent reinforces or smooths the resonances of the woofer, and some designs have a front port and some have rear-facing ports. There are various advantages and deficits to the two designs. Some have passive radiators in the front, and some on the back.
Passive radiators do not allow the air to pass in and out, but the diaphragm moves in the same manner. Mackie studio monitors are among the modern speakers that use passive radiators.
Look up and study speaker enclosure design if you want to know more. I learned this and a lot more as a teenager figuring out what speakers I liked and wanted, and we didn't even have an internets to access at the time.
On Feb 7, 2013, at 9:19 AM, David Breneman wrote:
> This raises a question for me. When I was in high
> school I bought (on the strong recommendation of a
> friend, who actually loaned me some of the money) a
> pair of "Ultralinear"brand speakers. These had two
> bass "elements." A 10" woofer and a 10" "passive
> radiator" which was another 10" speaker cone sealed
> into the same airtight box as the woofer. When the
> active speaker went out, the passive one went in,
> and vice versa. That seemed totally nuts to me even
> as a 17 year old, but the speakers sounded fine so I
> lived with the acoustic ambiguity. Is there any kind
> of sound engineering behind such a design? Or was it
> just eye candy engineering?