A big thanks to Holliswhy for bringing over LC and a big thanks to LC for bringing over the M51.
We started off with the M51 naked with USB out of the Mac Mini (running Audirvana Plus) into the M51.
Quite a bit of time was spent getting used to this sound and I remember towards the end I said to the boys that 'it didn't sound right'... to which LC replied 'how? does it not sound right'... Too bad, I am no good at describing how I felt so kept quiet. The worse track was when Hollis played 'At The Drive - Fahrenheit' (The boys were getting sick of female vocals by this stage). It sounded horrible and unlistenable.
We then got a process together by picking one track each:
1/ HW > Eagles (Hell Freezez Over) - Hotel California
2/ LC > Lana Del Rey (Born to Die) - Video Games
3/ B4 > Lisa Wahlandt (The Music of Stan Getz and Astrud Gilberto) - How Insensitive
Hotel California was definitely a good track for the purpose of this exercise. The naked M51 playing first up had boomy bass to the point that HW and LC was almost going to carry the C1s out into the lounge for me. (I was aware of my poorly laid out cluttered study but was honestly not prepared for such poor performance).
We then dressed up the M51 with the AP2 and replayed the same three tracks.
It didn't need to go very far at all, we waited for the bass to kick in on Hotel California and it was brutally obvious how such a tiny device on the whole scheme of things can make such a huge difference. In LC's words "It was like we were in a different room". What was originally thought to be room related acoustic issues (yes they still exist) was very much augmented by the AP2. Please be aware that it was NOT a blind test and would the results be any different if it was? (we can try that next time heh?)
Afterwards, we also played with a 6db then a 10db attenuator (16db would not lock on the m51).
Best I let the man LC describe what he heard.
On a separate note (probably should be in the M51 thread), this unit really is something. I just need to find a way to cut it into half to fit into my rack (and spray paint it black):