Running 4 speakers from a 2-channel amp

Just an update in case anyone is interested
I listened to the Concertos and didn't like them much at all. The bass was weak and muffled, they didn't image well, lacked detail, and were very much "in the box." The had a lot of cosmetic damage as well. I compared them to some Quad 12L's, which were in mint condition and at half the price of the Concertos. Originally, i just wanted to use the Quads as a comparator, but I wound-up buying them as a temporary fix until I find something better. Since then I've come to like the Quads more and more, though best within a certain range of genres. I still think of them as temporaries, and I'm looking for some SF Minimas to try next.

In the meantime I bought the very first Japanese version (different mains power) iDecco in Japan, directly from the distributor before they reached the market here. This is an amazingly good unit. I'm using this mainly to listen to flac files streamed from my iMac to my Quads, and it sounds warm and extremely detailed.

I also picked-up a second set of NS-1000x's, a rare walnut set in the best condition I've ever seen these speakers in. I'm thinking of keeping this set for replacement parts, so that I'll always have NS-1000x's in good shape around. The full set here in Japan costs about as much as two used so-so conditioned beryllium tweeters do overseas.

AL - I would never connect speakers in series but I believe DF doesn't suffer - at least with woofers in series within the same box. It appears that each woofer sees impedance of the other woofer in series (JBL wrote paper on that - that is incorrect) but in reality EMFs are in opposite phase and cancel. If amp's output impedance is zero - it looks like two woofers are connected in parallel in opposite polarities (EMFs cancel). Connecting woofers in series makes sense only when they are identical (for cancellation). Connecting speakers boxes in series will be a mess.

More info here: http://www.cartchunk.org/audiotopics/SeriesSpeaker.pdf

or here: http://www.monstercable.com/mpc/stable/tech/A2538_Wiring_Woofers.pdf

Thanks Kijanki . . . A good explanitation of why it can be appropriate to wire speakers in series under certain circumstances. It should be noted the main assumptions/limitations . .

First, it makes the loudspeaker performance more variable with manufacturing tolerances, so in i.e. the D'Appolito array mentioned the effective tolerance for the drivers themselves must be better than for the parallel connection to get the same average results. And for a professional sound reinforcement application, there's one-quarter the statistical redundancy in the event of driver damage.

Second, it assumes that the driving source (amplifier) have essentially a zero output impedance. Although one wouldn't expect to see an SET or OTL amp for this kind of application, series volume controls should definitely be avoided, especially because they introduce enough frequency-response variations of their own.

So for something like putting four pairs of identical outdoor speakers on a single receiver ... The series/parallel scheme works great, provided they're hooked directly to the (typical solid-state) amplifier.

Kirkus - I remember seeing large bass guitar stacks that had a lot of small (about 10") speakers (10-12). They must have been connected serial/parallel to obtain any drivable impedance.

I've read on this forum that before SS popularity speakers/drivers had very high impedance (16 or even 32ohm). Maybe it was to match better with tube gear but it could be for other reasons. Lower impedance allows to squeeze more power from SS amps.