It might be mentioned that the SP-5500, unlike the 5500X or any other sansui speaker of the era I've seen images of yet, incorporated a massive, full width of the cabinet horn loaded midrange and this may be responsible for the raves about it?
Unlike so many of Sansui's offerings of the era that had configurations like 4 way, 6 speaker etc it would not have suffered from the imaging difficulties you get from voicing octaves across so many drivers.
I recently scored a minty pair of SP-1200's for $20 at a thrift and started researching these, the 1200 is a 3 way 5 speaker design. They sound okay but lack impact and even within their element (classical, etc) are not impressive. Well built tho and the treated cloth surrounds suggest they may outlast most original owners. A neighbor has a similar larger set, they are 4 or 5 way? Woofer, mids, a little horn mid, tweeters and a super tweeter IIRC? It's damn cloudy if you get right in front, can't pinpoint the material at all. He's proud of them though, so I don't want to make him feel bad and have him over to hear my home brew three ways with huge JBL gold tweeters, Focal mids, and Veritas woofers. All surplus I threw together with infinity crossovers and damn the luck if it didn't work out great.
I'll have to hide those when I sell the SP-1200's on CL, prospective buyers will ask me to switch the speaker selector. Umm, we don't want to disillusion our dream for vintage now do we?
The SP-5500's look interesting tho- ever since I tried horns in a car setup-good sized ones, that extended down to around 400hz- not just tweets- I love horns. The way the detail jumps out at you and the imaging they are thus capable of is amazing. In the car I was able to give them their own channel with adjustable crossover to the above and below band drivers, using an a/d/s 8 channel amp. I would guess Sansui's engineers got them to work with the others well, since their response is so much more sensitive it can be a bear.