Here's the reply from Harman.
Hi Chris
I am sorry to hear of your concerns regarding the Harman Kardon system on your Discovery 4 HSE which were passed to us from our Consumer Division.
We have discussed your concerns with our technical team who have advised that the subwoofer performance is source dependant (music/program content) and its performance may not be as noticeable on certain tracks/broadcasted material. When the subwoofer is properly integrated into the system, you should ‘feel’ it as much as ‘hear’ it as it will be somewhat acoustically transparent due to the low frequency wavelength produced. The subwoofer in our system has a relatively narrow bandwidth and is tuned to perform at frequencies primarily below 60Hz, being seamlessly integrated with the four door bass speakers. If your CD has limited spectral content below this frequency then the subwoofer and subwoofer level control will also have limited impact.
Your primary line of communication should be through your Land Rover dealership; if you remain unhappy with the performance of your Harman Kardon system you could request they contact the central Land Rover Technical Services Department for further investigation.
Kindest regards
Kay
I felt that was a load of techo jibba-jabba which I didn't understand so posed my question again a little more clearly:
Hi Kay,
Thanks for your reply, but I'm none the wiser and nor is the Land Rover technical that I've spoken to.
To clarify: how is the sub woofer control meant to work? Previously when you turned it up you got more bass and when you turned it down you got less, this isn't happening with the Logic 7 system not just for me but for all the people I've spoken to with it installed in their HSE Discovery 4's and I have also posed this question on
www.disco4.co.uk where they confirm what I'm saying.
We're looking for a means to separately adjust the sub-woofer which is there in the control screen but doesn't actually work - how can we achieve this?
I'd appreciate it if you didn't say "Go back to Land Rover" as I've already been to Land Rover and they don't know why it's not working but say it must be something to do with the Logic 7.
Many thanks
Chris
I've still not heard anything and that was 4 days ago.
For me it has become a bit of a issue as playing Madonna's "Nobody's Perfect" track the kids and myself don't get the lovely buzz in our chests that we so enjoyed in the Freelander or any of the tracks that we enjoyed being vibrated to.
The system is far from Premium 
You're a funny man Mr. BBDisco3...if you're ever in Surrey be sure not to look me up. 
