Can someone please explain?

[BeltwayBandit]

I have a triode mode KT88 amp and two different speakers I listen to.  One pair is a wonderful 2Pi speaker from pi speakers and the other set is a MLTQWT made from a Fostex FE207e.  Both with sensitivities in the 95-97 db range.

A couple of weeks ago I had friends over and we were A/B swapping the speakers and one of my guests said - "It's too bad you can't play them both - they both have characteristics that I like."

So - yesterday I hooked up the two speakers in series just for giggles to see what it would sound like.  The room came alive.  I was hearing notes not heard before, sound stage was deep and discrete with instruments clearly placed.  It was truly like being in a jazz club. 

What is happening?  Are the two speakers voices canceling out distortion?  Is it a simple addition of 3db?  Is the amp happier with a higher load?

Any thoughts would be appreciated.

[Grainger49]

That is interesting and very surprising.  I wouldn't have tried it for fear that the two speakers would have had drastically different responses that would have destroyed the soundstage. 

You have proved how wrong my first thoughts can be.  And now you have a happy combination.  (sounds like an entree at a Chinese restaurant)

[BeltwayBandit]

Part of me thinks that speakers may have more of a "voice" than we may all appreciate.  Perhaps it's adding different drivers with drastically different construction materials - who knows.  Very interesting indeed.

[braubeat]

single ended tube amps seem to like higher impedance speakers. sounds like you have a fortunate combination.