I’ve had a pair of Spendor Classic 4/5 in a 4.5m x 4.5m room, some of which is a window bay and chimney alcoves. Overall they worked really well, and gave surprising presence and bass response (at times), even well out into the room when being listened to, say 50cm from any wall, 2 metres apart, 2 metres from the listening position, angled in. They disappear, image amazingly and were utterly coherent.
Weirdly, in the smaller bedroom next door (4m x 3.3m), they sounded a bit lost and lacked weight! Room acoustics I guess.
In the end, and after lots of agonising over it, I sold them and decided to upgrade to the Spendor Classic 3/1’s (due for delivery mid-March), which are a different beast. Ported and go a fair bit lower in the bass. When I first demoed them, I found them a bit much for the room and found the smaller speakers were a bit more involving in some ways. However, after keeping the 4/5’s for a while longer, I continued to feel dissatisfied with the level of scale and bass on offer (tried a sub, didn’t get on with it). While a sub added bloom, depth, and to a degree, scale (although the latter felt a bit artificial), it was a pain to integrate well, and I felt I was always faffing, depending on the track in question.
Regardless of following all the setup guides (admittedly by ear, without dsp), I was subtly aware of the sub at times. Coupled with the extra cables, clutter etc, I gave up on the idea. Yes, I am sure (a pair) of perfectly integrated subs could give great results. But I had neither the inclination, floor space or patience to go down that route.
So I then re-demoed the 3/1’s and gave them more time, but paid particular attention to playing with positioning, and tried them in other rooms in the house, and ended up preferring them, as an all-rounder, with more convincing scale and depth, better tone and texture of bass compared to the 4/5s with a sub, yet retaining (most) of the smaller speakers' other virtues. I think a lot of the initial feeling of ‘these may be too much for the room’ was as a result of not giving them a fair chance, and therefore not getting acclimatised to them (having been so used to the limited bass response of a ls3/5a type speaker, which was the norm of what my brain was used to).
Of course, ls3/5a types will always win out on imaging, coherence, disappearing, midrange speed, flexibility of positioning, but I also think that slightly bigger speakers of the same ilk (e.g. the 3/1s or the Graham ls6 etc) can get nearly there in those attributes, but have a significant advantage in the area of scale and depth, making them more adept all-rounders.
Bass extenders mentioned in this thread are an interesting one - would love to hear them...but they're certainly pricey, and I suspect I would have been left thinking ''why didn't I just buy bigger speakers?''. However, without hearing them, I am no authority on the subject.