Downward firing subwoofer

The higher the Q rating of the Passive the easier it responds to the active driver. So a light cone, return spring and surround would add to a higher Q (Quality). Those types of passive are to blend the lower and upper octave of the driver. In other words they are more sensitive to MASS weight change.

In a heavy construction PR it may take ounces to change the Q. I suspect your current PR and driver are matched to hit a certain LOW point then roll off quickly. That is a good reason to use a PR,

In one with higher sensitivity (Q) it may only take a thumbnail of soft putty to change the Q and blend the upper and lower ranges of your sub..
Its a talent but well worth the effort to mechanically tune YOUR subs to YOUR main speakers to your room and YOUR amps..

THAT PR can do just that....:-)

It can also remove the challenge of tuning correctly to remove boom (too much mass on the PR) OR not enough mass to hit the bottom octave at -3-6db. That is the difference in a port vs adj PRs vs closed port IB design. You can hit 20hz at +1db vs 20hz at -6db via DSP and EQ. A 100 watt plate amp vs a 1000 watt plate amp..

If you know what your doing. It actually cost less to drive that kind of setup to.. A LOT less amp as long as they have 100@8 ohms or so on the dampening if your a real BASS head.. 100 watts a 8 ohms for plate amp will rattle the house with the PRs tuned.... Oh yea!!

I would just replace the sub, sell old one if you can. Just don't buy another downward firing sub, I don't like them.

It would be a problem due to the impedance load on the amplifier in the sub as well as mess up the sound of the bass from the subwoofer. If it is a passive unit with no built in amplifier then you would just mess up the tuning, double active driver subs usually have a larger box than a single driver sub.

Just try it and see what happens.

then buy a puppy.