We took out the stock drivers, and replaced them with JL 10W6D4 drivers.
We had to play around with the wiring a little on the subs, because they are dual 4-Ohm voice coil drivers.
After playing around with them for a while, we opted to run the coils in parallel, dropping the drivers down to 2-Ohms.
We also blocked off the ports in the AL-III's, they seemed to have a better low frequency response.
The sound from the JL drivers is MUCH better in my opinion. Everything sounds about the same until you get down to 50 Hz or so...
then the JL's really start to stand out. The ultra low frequencies really start to growl, compared to the stock drivers both at high volumes, as well as very low volumes.
It's like a small set of "subwoofers" were added to the room, with out messing up the curve.
The 10W6's might not be the perfect drivers to use here... we are going to look for a pair of 10W3's and try those as well.
The problem with the 10W6's is the power handling. They are rated for 500w RMS, which is about 200w more than the ribbons.
So to balance the highs to the lows using a single amp, we have the bass gain on the preamp set to about 2:00-3:00
If and when he bi-amps them, it won't matter at all though.
These drivers made a huge difference in the lower frequencies, and made the bass come alive in alot of tracks.
A very worth while test you should try and toy around with !!