[OSIB16]

I’m going to be doing some experimental modifications to BEOVOX CX100 speakers where I will remove the lower woofer, and replace with a identical size Passive Radiator, and will also install another Passive Radiator at the rear panel of the speaker.

My question is… Is it a bad idea to ‘pack tight’ the entire speaker with wool wadding, including lining the walls with open cell foam? Or will that restrict the Passive Radiators from working?

[corndog71]

First of all, you don’t need to line the box with foam.  Ideally you would use No Rez but there are cheaper solutions.  Its more about reducing the resonance of the walls of the box.  Foam won’t do that. 

As far as stuffing the box with poly fill or other it shouldn’t be packed right.  Leave a cavity from front to back in your planned arrangement to allow some direct air flow to the passive radiator.

[OSIB16]

First of all, you don’t need to line the box with foam.  Ideally you would use No Rez but there are cheaper solutions.  Its more about reducing the resonance of the walls of the box.  Foam won’t do that. 

As far as stuffing the box with poly fill or other it shouldn’t be packed right.  Leave a cavity from front to back in your planned arrangement to allow some direct air flow to the passive radiator.

Thanks for the tips. What is the cheaper solution to No Rez that you are referring to?

[richidoo]

If you remove one of the woofers you change the load on the crossover filters which changes the filter target frequency. If you remove a woofer you have to redesign the crossover.

Stuffing the box solid with damping material is rarely a good idea. Stuffing damps cone motion and converts detail to heat. A little goes a long way. Lining the wall with 1" owens corning 703 rigid FG board is similar concept to no rez but cheaper and I assume less effective?

Passive radiator uses pressure energy from powered woofer to drive it. The more PRs you add the more energy needed to move them. Removing weight only raises the resonant freq which defeats your purpose in supporting the woofer. Try one PR first. Can add another easier than removing one. 

[OSIB16]

It is possible to replicate the crossover of the smaller BEOVOX CX50 speaker by performing some quick soldering to my CX100.