From what I understand, the Portfolio models with the upgraded sound system have an extra subwoofer built in them that the Alpine system doesnt. Where exactly is that?

Thanks

 

The largest visible speakers in my 2009 XKR Portfolio Convertible are in the doors. I don't know if a subwoofer might be hidden under the rear seats; if there is one, you can't see it. I believe there is no subwoofer in the trunk. The owner's handbook doesn't mention a subwoofer. See this link to Bowers & Wilkins website and their description of the 2009 XKR Portfolio sound system.
http://assets.bowers-wilkins.com/med...ss_Release.pdf
My other car is a 2007 Lexus LS460 with the Mark Levinson sound system and to my ears both have excellent sound quality (except when the top is down in the Jag - then the exhaust note is music to my ears).

 

In my 08 portfolio, to me, it sounds like there is a woofer within the dash or front of center console.

 

It's located below the glove box, facing up, covered by a hush panel.