This does not match my experience. I trialled both the 8351B and 8361A and found the 8361A to be vastly superior, even at 1.5m and identical SPL. I did not expect this given that both Genelec and others here have stated that the primary benefit of the 8361A over the smaller 8351B is SPL (but also a slightly improved low end frequency response and slightly longer listening distance). However, I also took into account the feedback of others here, who stated that the speaker sounded much bigger and delivers substantially greater bass response than the 8351B. This was absolutely my experience and so why the 8351B was returned. In terms of actually why, the question of how some of the SPL available to the 8361A could be traded for greater LFE extension interests me. Perhaps I might also add that I'm someone who enjoys the process of tinkering with things to increase knowledge and understanding whilst also exploring the potential of optimising their performance (even if this results in no or minimal gain).
As I've done my best to communicate, the speakers are fabulous. I'm always smiling when listening to them... They were absolutely worth the time it took to save for them and I would never this of them as a waste. I have never stated that I wanted to squeeze a subwoofer out of them. I did mention the benefits of a sub as well as not wanting one, but never that I wanted to turn the 8361A into a sub; rather, I wanted to explore safely trading some of its SPL for greater LFE.
Not once have I said that the points raised are unhelpful. Please re-read my comments. In fact, I would have hoped you would have come to the opposite conclusion! I'm expressed my gratitude for the responses I've received several times now and have changed my thinking on multiple occasions and shared this with you all.
Perhaps my determination can be explained by mostly feeling misunderstood, despite repeated attempts to address this, and not being convinced that what has been shared necessarily means that I cannot continue to explore the overarching question I raised. Furthermore, whilst my -18dB example was extreme, I also provided a -10dB example. If -10dB is also extreme, what about something lower? In the absence of evidence to the contrary, I am happy to accept that ported speakers are not ideal for trading SPL for LFE based on the feedback of multiple individuals here. However, this does not necessary mean I cannot to some degree trade SPL to improve LFE in a manner that is safe and brings measurable benefits. It seems more about getting the balance right and thanks to some of the feedback here, I've more of an idea now about how to achieve this than I did before.
I'm going to take a break for now as I'm exhausted from all this. Nevertheless, I am deeply grateful for everyone's feedback. Thank you.