I need to replace my OEM stock 8" subwoofer in my 2007 Lexus ES350. I am looking at a Polk Audio db840 8-Inch Single Voice Coil Subwoofer with 4ohms. Would that work for my system? Looks like the factory sub is 2.5 dual ohms. Does that mean 5 ohms total? Thanks!

 

I gonna go on a limb and say they are in parallel not in series, so 2.5 each. I'm sure someone here can confirm

 

I'll agree that it was probably wired in parallel.

What is your goal in replacing the OEM sub? Is the old one broken? Then get a factory replacement. I've seen them on Ebay. More bass? Just picking a sub at random to drop in there may not provide as much bass as the factory model. Or even worse, a very bad frequency response in the bass region. You need to know details like the Qts and sensitivity of the factory model so you can plot the response of both (OEM and replacement) subs in some simulation software.

 

I believe the sub is blown & the cone is split. Anyone know the part number or where I can get a factory replacement? I totally agree in keeping with the factory replacement, then I can be sure it will sound good

 

Factory replacement will cost upwards of $200. This is a better option - http://www.ebay.com/itm/07-LEXUS-ES350-SUBWOOFER-86160-33730-/370991733541?pt=Car_Audio_Video&hash=item5660d49b25&vxp=mtr

 

Another option is to disconnect it and get a dedicated amp and sub, and that will also give you a better base sound overall...

 

This. Or if you don't want to do that, the sub you put in the original spot has to be a free-air sub.

 

No it doesn't.

Some speakers labeled as "free air" have a Qts in the .600 to .800 range while other car subs have a Qts higher than 1.000 which would work better in free air applications. I've used subs with a Qts as low as .500 in free air. You can go lower as long as you have extra excursion to spare but the bass may bet a little boomy.

 

Has anyone successfully reinforced (or insulated) the rear upper deck in the ES 350 to prevent rattling from the stock subwoofer?

I think it has enough bass for my needs, just got to get rid of the damn rattles.
Thanks!