Stacked Bookshelf Speakers -- Perplexing Nirvana?

I lived in the Bay Area, CA, but for two years I have been working in Beijing (!) which turned out to be a home audio desert. Perhaps due to the high density of living, people generally only listened to music via earphones or in their cars. So over time I brought over assorted electronics and a pair of cheap old Monitor Audio Monitor 2.5 bookshelves. Recently I acquired locally a pair of so-called full-range single-driver Fostex F120A (alnico) 10-liter ported boxes and ended up stacking them on top of the Monitor 2.5 which are on the floor.

Well, the F120A frequency response is dome-shaped, and the old 2.5's frequency response is bowl-shaped. While muting one or the other by remote control to compare their sound, I discovered an almost perfect balance by playing them both at the same volume. The F120A's driven by Bel Canto S300iu give an extremely transparent, zero-time transcient "on-stage" sound, but short on highs and lows, while the 2.5's driven by a very nice 300B SET provide an extremely musical, acoustically rich experience, but quite lean in the midrange. By combining, I can dial-in the sound perspective and degree of involvement, but usually keep the two sources balanced.

I have owned Quad ESL63 driven by ARC D70II, Monitor Audio Studio 20 driven by Quad 909, Quad 12L Active Monitors, etc., but I think this bizarre setup may be the best and truest I have heard. Naturally, I'm perplexed and somewhat unhappy with the situation!

My next quest would be for something simpler or more "normal". Next month I will visit California and try the Focal Pro Twin 6 Be (active pro monitors) and old-school Morel/Renaissance Duet, both bookshelve speakers that I _might_ be able to lug back to Beijing. Other candidates are the Monitor Audio Gold Signature GS-LCR (used as stereo pair) and ELAC floorstanders. Unlike American-made audio which are exorbitant in China (if available at all), both ELAC and Monitor Audio are nicely discounted.

Trying the Fostex turned out to be a surprise educational experience -- a "serendipitous discovery" for me. I have to say, hearing Gilels playing Beethoven's Pathetique Sonata, especially the longs runs, is glorious and so luxurious. I am fortunate to have attended many solo, small ensemble, and vocal concerts and now, listening to recordings of these fine artists and performances really takes me back to the live experience.

The stacked bookshelf speakers cost less than $1K together. The electronics are in the $5K range combined.

Equipment: Quad 99CDP, Bel Canto S300iu, Pureaudio 300B SET (vintage German input 6DJ8, rest are current Chinese tubes), Audience AU24 interconnect, Canare 4S11 star-quad speakerwire.

Recordings used: Baltimore Consort "On the Bank of the Helicon"; Claude Bolling's Greatest Hits; Rachel Podger's Bach unaccompanied "Chaconne"; William Christie's Fischer solo harpsichord; Kathleen Battle and Christopher Parkening "Pleasures of Their Company"; Gilel's Beethoven. Etc.

-- William
By combining, I can dial-in the sound perspective and degree of involvement, but usually keep the two sources balanced.

Perhaps you have two poor speakers (bowl and dome) that happen to complement eachother and also compensate for a floor placement (not the best place for a bookshelf). How is the imaging?

FWIW: If this is creating nirvana then I agree with your thought that it is "perplexing" - by rights it really should not and it suggests something is badly wrong with the setup or room acoustics => I'd try to find the root cause as to why this makes an improvement.
As my mother used to say: "If you are happy, I am happy." ;-)

Wchang, I don't doubt your observations one bit, and I think your analysis is correct.

This is rather interesting situation, as in a way it's a direct comparison of a high waveform-fidelity system vs. a poor waveform, but better frequency response, system.

The single-driver Fostex alone would preserve the original waveform exceptionally well as it doesn't even have wizzer cone, but adding the Monitor Audio speakers to the mix must inevitably destroy the waveform fidelity. On the other hand adding the Monitor Audio speakers improves the frequency response, and as this real-world example illustrates the in-room frequency response matters more.

Funny, I've run two pairs of floor standers (Vandersteen 2aSig and Dynaudio 72 side by side, and really liked the sonics too. No imaging to speak of, but very satisfying.
Thanks for the replies. The Monitor 2.5 were eBay $250 oldies with very fast gold dome tweeters but the mid/woofers aren't quite so quick. So the highs complement the F120A nicely while the mids compromise the overall transcent response and "waveform fidility" -- but fortunately the old 2.5 mids are fairly recessed to begin with. The lows from the 2.5 are not as tight as from later model metal cone M.A.'s but aren't too bad -- a slightly relaxed bass.

I expected the imaging to go to hell but so far so good. Then again, I don't have a great reference pair in Beijing.