[tbrooke]

I have a pair of the original subwoofers that I have been happy with for a long time - I use them with my RM30s - I noticed some buzzing and a popping that makes me think they may need some work - I looked on Parts Express and noticed that they had several subwoofers with 2 drivers and I started thinking that instead of replacing or refoaming the passive radiator just use 2 active drivers. One forward facing and one downwards facing --

Will this work? - I guess I could try it and find out but I thought I'd ask

[GeorgeAb]

Personally, I would inspect and repair. If you wanted to experiment, rather than using actives in place of a passive radiator I would first try going fully sealed. Another thought is if it is happening in just one of the pair that you could swap out parts from problem unit to assist in troubleshooting. 

A passive radiator makes use of the backwave (adding power output) while maintaining the speed and control of a sealed enclosure. The amount of resistance the passive provides to the active is the tuning portion. Use of an active in passive mode (no electrical power) in place of a passive radiator likely would have a different amount of resistance. I believe the key is tuning the passive to the active's output to get extension while maintaining control.   

Usually the failure mode is the foams get holes in them. They can be replaced https://www.simplyspeakers.com/speaker-foam-edge-repair-kit-fsk-15a.html. If the spiders are rotted out I would find a new passive.

[Jstower]

I agree with George, I would leave them the way Brain designed them. Vmps subwoofers were and are great. If you wanted to upgrade I  would upgrade the 12” drivers to Dayton #295-464 or look for something similar. Good luck

[ST86]

The active driver and its T/S parameters are matched to the size (internal volume) of the box, along with the passive's parameters and tuning (added mass). Replacing the passive with another active driver will likely cause a mismatch with the driver parameters and box size, unless you find two active drivers that will play nice together in that box volume.

I suggest repair or replace whatever is buzzing with same components.

Regards,
Ed