Hello Tang,
That is an interesting question. Now with Al's suggestion that I comment, I will try to answer it.
I sold my Mini IIs over two years ago so my aural memory may be a bit vague. Al and I have discussed for years the effect of subwoofers with mini monitors. We have different opinions on the subject. I attempted two times to integrate subs in my system with the Mini IIs and was not successful. I owned two JL Audio F110 subs and later tried a REL sub on Al's raised sub platform. Perhaps the problem was my room, or there was simply an incompatibility issue with the integration attempts. I always heard trade offs. Coherence was a problem, and the subs seemed to detract from the clarity of the Mini IIs. One does not read many instances of the Mini II being used successfully with subs. In fact I asked Alon Wolf about getting a pair of Magico Subs for my Mini IIs, and he suggested getting a bigger speaker like my Q3 and selling the MIni II. The gap between the midrange and sub is just too great, IMO, and that of Magico.
Al seems to like a slightly richer sound with a fuller lower midrange/upper bass than I do. I prefer overall clarity and coherence and am willing to sacrifice the lower registers somewhat. I've never really heard a mini/sub system where I don't hear the subs. In some sense, this describes the differences between the sounds of our two systems, both then with the Mini II, and now with the Q3. We have slightly different preferences, even though as one audio buddy mentioned to me the other day, we both use the BSO as one of our references. We may hear the same system or live performance, while sitting right next to each other, and yet we hear or focus on different things, and prefer different things.
My memory tells me that the Mini II is more extended than Al's mini speakers, both his first pair , and then his two Ref 3A models. I was very satisfied without subs for the music I listened to at the time. With the Q3s, I now listen more to larger scale classical that the Mini IIs could not portray as well. I also used to ask Al to turn off his subs at times when listening to his system because I liked the purity of that sound more when listening to smaller scale music like string quartets. I no longer do that because his system sounds different and much better now with the new gear and zero toe-in, but I suspect he also found my requests a bit tiresome.
Another factor is that Al openly discusses his preference for being able to adjust the bass output level for various recordings. He enjoys this adjustability to suit his listening pleasure while I prefer to hear the recording as is.
So, Al and I have some differences regarding our opinions about subs with mini monitors. My experience is quite limited. I think Al has more knowledge and experience combining the two. In fact, we first met when I contacted him after reading about his system being mini-monitor based,as was mine. I reached out to him and we discovered that we live just 15 minutes from each other. The rest is history, as they say.
Having written that, here is how I would describe my memory of my system with the Mini II versus his current system with mini-monitor plus two subs: I preferred my old system with Mini IIs to Al's old system, especially when he had only one REL sub with his old gear. My system was more resolving with fewer compromises. However, it was not as extended, it had a smaller sound, and the stage was not nearly as deep, but for the music I listened to, it sounded very convincing and right to me. It did have lots of dynamics and was incredibly coherent and resolving. Al's system was not as smooth sounding and suffered from some high frequencies sharpness or brightness which may have been caused by his digital or his older speakers. I don't really know.
We have both moved on from those older systems. I have fuller range Q3s now and can play and enjoy large scale jazz and classical. My system is now much more capable. His new speakers are also much better than what he had and they are now better integrated with his two new JL Audio subwoofers. His digital is much better sorted out, and his electronics are very good. I thoroughly enjoy both systems now, and I think he does as well, though I suspect we each prefer our own system over our good friend's.
The two systems do sound different and they reflect their owner's current tastes and preferences. They do sound similar in many respects, but I would say the tonal balance is what differs most. Al was over the other night listening to my system and he preferred my MSL Sig Gold/SME V-12 combination while I preferred my new vdh Master Sig/3012R combination. I would describe the primary difference as one of tonal balance where the MSL/V-12 is slightly fuller, richer sounding in the lower midrange to upper bass. It is a more ripe sound, which is what I hear in Al's system. I find the vdh/3012R to be more timbrally accurate, more dynamic, and slightly cleaner sounding, though I also very much like the other combination for what it offers, which is why I so enjoy going to visit Al and hearing his system.
I enjoyed my time with the Mini II (boy, that channels MikeL's language
) and I learned a lot from those speakers. They were excellent, and I think a classic design. They were also beautiful to look at and extremely well made. Al's Ref 3 and JL subs are now really singing, but I now don't really know whether I would prefer them to my Mini II. Overall, the systems I think sounded pretty similar, but Al's can now portray large scale music better than my Mini II based system could. A direct comparison between the two speaker combinations in the same system would be fascinating in the hands of a set up expert. I am not sure I could fully optimize either speaker to hear them at their best. Jim Smith did take my Mini II very far and given its limitations in extension and number of drivers, it sounded excellent on all music except larger scale classical, jazz and heavy rock. Al's system now sounds excellent and convincing on those genres, though perhaps the tonal balance is slightly different, and it is not as pure in the Mini II's sweet spot, but that is based on a rapidly failing memory.
I hope that answers your interesting question.