Allright , so I was taking apart my subwoofer in my 1993 LS400 the other weekend and here is some interesting stuff that I found.
First off I have a 1993 LS400 with the Nakamichi system.
1) The Subwoofer is an 8" driver
2) The subwoofer is 5Ohm, Thats right its stamped right on the bottom of the woofer, 5 ohm!!
3) the factory amp for the sub is in the driver side of the trunk near the power antenna.
4) To pull out the sub, Unclip the wiring harness which is maybe 6 inches down from the speaker. Then de solder the wires, instead of cutting.

I installed a 4 Ohm earthquake free air sub rated at 125rms and let me tell you that there definately is a difference in the smoothness of the base transition and it seems to be pushing alot more air throughout the cabin.

Just some info that I found out first hand. Hope it helps!

 

That is pretty interesting. Did you use an automarket amp? Also, did you notice any rattles appear?

 

5 ohms...wow!

static911

 

I was leery at first about keeping the factory amp from what I had heard of others frying theirs when running aftermarket speakers. I think that only will happen when you run a speaker with greater ohms than is supposed to be run off the amp. (therefore more resistance)
Well...Anyways, I hooked the speaker up and sealed it with clear non hardening silicone. I put everything back in place and Voila!!
It sounds much smoother than factory, Hits lower, and more importantly I learned how to take a part and put back together one more part of my car!!