2014 M4 Harmon Kardon bass high pitch dash rattle please help (with video)

[yoyoyoyoyoyoyoyoyoyy]

I have a 2014 M4 with HK system and have fiddled and fiddled with frequencies and settings. In general terms I have the bass on full and the treble quite high. I like bassy punchy music and do like the volume around 75% (very loud)

It seems recently that a deep low bass tone of around 40hz really makes the system sound incredibly poor. I am aware this is a relatively well known thought (I mean that the HK system isn't all that incredible - and I have searched and searched for posts).

But I feel, I MUST be able to rectify my rattle/frequency issue - the video (needs to be on high volume) shows just one song that begins with a bass note (around 25hz to 75hz that to me, sounds like a tweeter is trying to produce the bass and is flapping around? It's so annoying (and very embarrassing with passengers as it sounds Sh..!)

Any thoughts or recommendations then please let me know. I guess I will need to remove the door card and disconnect each speaker to hear which area/trim/speaker is to blame.

Fading front 100% and left 100% indicates that side of things
I have tried Logic on and off - no different
I can turn the bass down or fade to rear to reduce the noise but is always there.
Low volumes absolutely fine (noise only occurs when volume is above say 50/60%/loud)
Does happen with MP3 Ipod playing and DAB radio

Many thanks

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