Bass reflex vs Passive radiator question

Hi Guys,
Having no exposure to Passive Radiator, was wondering if it sounds more open & less boxy sounding. Yes have heard some well designed BR speakers but there's at time less open sounding. Sorry for my English, difficult to put it in words.

Many thanks
 
Using a passive radiator (PR) brings two advantages:
  • With low tuning frequencies in small enclosures, a BR port becomes impractically long. A PR obviously doesn't, all you have to do is add some mass to the cone.
  • In 2-way systems, a BR port shows resonances in the port itself, which present themselves as unwanted sound output at mid frequencies. A PR doesn't do this and is a better choice.
There are some disadvantages too, higher cost being the most important one. About your statement about the sound of 'well designed' BR speakers, you'll have to explain that better. Well designed BR systems do their job fine. Not so well designed systems don't.
 
A couple of points, to add to the above:

The much bigger area of the ABR (Auxiliary Bass Radiator), compared to a port and its associated "tunnel", may allow transmission of unwanted internal mid-range rubbish (in addition to that passing through the driver cone).

An ABR completely avoids any "chuffing" associated with a ported design operating at high spls.
 
Thank for the advice Gents. Re passive radiator assuming that it an 8 inch woofer can we not us a passive 8 inch radiator too ? If I not mistaken its all about adding weight on the cone to achieve the tuning frequency. Keithj01 commence on mid range rubbish got me curious. If the box is made large enough with appropriate stuffing would this be a none issue ?

Thanks again
 
You can model in WinISD but you need to manually enter the PR parameters. Rule of thumb is to use a PR twice the area of the main driver but others have shown it can be done with less. For an 8” driver I would start by modelling the SB 29NRX PR and see how it goes.